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Composites Part B : Engineering
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ISSN (Print) 1359-8368
Published by Elsevier Homepage  [3184 journals]
  • Modification on glass fiber surface and their improved properties of
           fiber-reinforced composites via enhanced interfacial properties
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Dengxun Ren, Kui Li, Lin Chen, Sijing Chen, Mangui Han, Mingzhen Xu, Xiaobo Liu For fiber reinforced composite laminates, properties of laminates can be significantly affected by interfacial properties. In this work, a kind of phthalonitrile containing aromatic ether nitrile linkage (PEN-BAPh) was applied to modify glass fibers (GFs). Cured PEN-BAPh on GFs surface were investigated by Fourier transform infrared spectroscopy (FT-IR) and Ultraviolet–visible spectroscopy (UV–Vis). Scanning electron microscope (SEM) and thermogravimetry (TGA) testing were also applied to confirm the modification. Then, modified fiber-reinforced phthalonitrile-based resin composite laminates were fabricated. As the results indicated that all of the composite laminates showed improved flexural strength, flexural modulus and glass transition temperature (Tg = 296.8–299.6 °C). Improved interfacial adhesion was also studied via interlaminar shear strength (ILSS), impact strength test and monitoring the fracture surfaces. Stable dielectric constants, relative low dielectric loss and outstanding thermal stability (T5% > 350 °C) were obtained for designed composite laminates.Graphical abstractImage 1
       
  • Improvement effect of fiber alignment on resistance to elevated
           temperature of ultra-high performance concrete
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Huanghuang Huang, Rui Wang, Xiaojian Gao This paper investigated mechanical properties of ultra-high performance concrete (UHPC) after exposure to elevated temperatures ranging from 200 °C to 800 °C. Two casting methods were applied to prepare UHPC specimens containing randomly distributed or aligned steel fibers. X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) were utilized to evaluate the microstructure degradation of UHPC with high temperatures. Experimental results indicated that compressive strength, flexural strength and toughness were significantly reduced by 83.4%, 82.5% and 84.6% for UHPC specimens with randomly distributed steel fibers after exposure to 800 °C. The alignment of steel fibers can positively alleviate the degradation of mechanical properties of UHPC, inducing an increase of 33.8%, 72.4%, 43.9% and 58.8% for the residual compressive strength, flexural strength, toughness and deflection at post-cracking peak point, respectively. According to microstructure measurements, cement hydration products were badly decomposed by high temperature exposures with the occurrence of coarsening pore structure in cement paste and worsening the interface between cement paste and steel fibers, subsequently causing the mechanical performance degradation of UHPC specimens. Although the tensile strength of fibers was notably reduced by high temperatures, the fibers still performed bridging effects on cracks in UHPC. This is the main reason that the fiber alignment can significantly improve the residue mechanical properties of UHPC after exposure to high temperatures. Therefore, the high temperature resistance of UHPC can be improved by optimizing the orientation of steel fibers.
       
  • Surface modification of polyethylene fiber by ozonation and its influence
           on the mechanical properties of Strain-Hardening Cementitious Composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Zeyu Lu, Ran Yin, Jie Yao, Christopher K.Y. Leung Polyethylene (PE) fibers are widely used to develop high strength Strain-Hardening Cementitious Composites (SHCC). Unlike Polyvinyl Alcohol (PVA) fiber, which has relatively low tensile strength and strong bond with matrix, the high tensile strength of the PE fiber is not fully utilized in the system, due to the hydrophobic nature of the fibers. In this study, a promising fiber treatment method by using ozone and ozone-derived hydroxyl radicals is developed to modify the surface properties of PE fibers, aiming to improve the fiber/matrix interactions and then the tensile performance of resulting SHCC. Firstly, feasibility and mechanism of ozonation are revealed by competition kinetic technology, and the XPS results indicate that only hydroxyl groups can be introduced to the PE fiber by optimizing the ozone (O3) concentration and treating time, and surface roughness of the PE fiber is also increased due to the etch effect from ozonation. For the tensile performance of SHCC, compared to the composites with pristine fibers, PE fibers treated with O3 for 30 and 60 min can improve the ultimate tensile strain of SHCC by 1.3 and 2.5 times, respectively. This significant enhancement in deformation capacity of SHCC is attributed to the increased chemical bond and frictional bond after fiber treatment, as the results from single fiber pullout tests show that the fiber/matrix frictional bond is increased from 2.35 MPa (pristine PE) to 3.13 MPa (O3 (30 min)/PE) and 3.38 MPa (O3 (60 min)/PE). The research outcomes provide a novel way on surface treatment for PE fibers to improve the tensile performance of SHCC.
       
  • A robust bi-layer separator with Lewis acid-base interaction for high-rate
           capacity lithium-ion batteries
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Muhammad Waqas, Shamshad Ali, Dongjiang Chen, Bismark Boateng, Yupei Han, Mei Zhang, Jiecai Han, John B. Goodenough, Weidong He Poly(vinylidene fluoride-hexafluoropropylene)-lanthanum oxide//poly(vinylidene fluoride-hexafluoropropylene)-hexagonal boron nitride (PVH–LaO//PVH-BN) bi-layer separators are developed through a two-step blading approach. La2O3 in the PVH matrix enhances the Li+ conduction by providing extra Li+ conducting pathways owing to the Lewis acid-base interaction of La atoms with the PVH chains, leading to a high lithium-ion transference number of 0.72 and ionic conductivity of 7.5 × 10−4 S cm−1 at room temperature. Moreover, the strong interfacial interaction between h-BN and PVH in the bi-layer separator enhances the thermal and mechanical stabilities of the separator. Batteries based on lithium iron phosphate and the bi-layer separator deliver a discharge capacity of 158 mAh g−1 at 0.5 C after 100 cycles and a rate capacity of 81 mAh g−1 at 10 C after 1500 cycles.Graphical abstractPVH-LaO//PVH-BN bi-layer separators are prepared through a two-step blading approach. The as-prepared separator owns interconnected microporous structure with high porosity, robust thermal and mechanical stability, high tLi+ number with enhanced ionic conductivity, and capable to suppress dendrite growth. Batteries based on LFP and PVH-LaO//PVH-BN separator deliver excellent cyclic performances and high rate capabilities at room and elevated temperatures.Image 1
       
  • Atomization of cellulose nanocrystals aqueous suspensions in fused
           deposition modeling: A scalable technique to improve the strength of 3D
           printed polymers
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Shadi Shariatnia, Akshaj Veldanda, Suleiman Obeidat, Dorrin Jarrahbashi, Amir Asadi 3D printed polymer parts remain too low in mechanical performance that inhibits their industrial applications. We introduce a novel and scalable technique to enhance the strength of 3D printed polymer parts. We incorporate cellulose nanocrystals (CNCs) between adjacent layers of polymer with the aid of an atomization process integrated within a fused deposition modeling printer to spray aqueous suspensions of CNC during the printing process. CNCs act as nano-stitches between the polymer layers and thus improve the interlayer adhesion and ultimate strength of the printed parts. We show that spraying aqueous suspension of CNC with 0.5–1 wt% concentrations increase the interlayer strength of acrylonitrile butadiene styrene (ABS) parts by 44%, tensile strength by 33%, tensile modulus by 20% and the toughness by 33% in both longitudinal and transverse directions. Increasing CNC concentration above 1 wt%, however, results in CNC agglomerates between layers, which negatively affects the interlayer adhesion and reduces the ultimate strength. Non-toxicity of CNC and water and hydrophilicity of CNC leverage the scalability of this method.
       
  • Benzimidazolyl-substituted cyclotriphosphazene derivative as latent
           flame-retardant curing agent for one-component epoxy resin system with
           excellent comprehensive performance
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Jianwen Cheng, Jun Wang, Shuang Yang, Qianqian Zhang, Siqi Huo, Qiaoxin Zhang, Yefa Hu, Guoping Ding Epoxy resin (EP) is inherently inflammable and most flame retardants used now unavoidably deteriorate other properties of EP. Moreover, the components of EP system tend to be formulated as one-component system for large-scale industrial production instead of being blended just before use. In order to overcome these issues, benzimidazolyl-substituted cyclotriphosphazene (BICP) was synthesized and utilized as latent flame-retardant curing agent for EP. According to the curing and rheological behavior studies, BICP maintained chemically inert towards EP at room temperature and could rapidly cure EP when heated. The combustion test results indicated the outstanding flame retardancy of EP/BICP thermosets. With 10.7 wt% addition of BICP, the limited oxygen index (LOI) of EP/BICP-12 thermoset was as high as 33.5% and UL94 V-0 rating was achieved; the peak of heat release rate (pk-HRR), average of heat release rate (av-HRR), total heat release (THR) and fire growth rate (FIGRA) of EP/BICP-12 thermoset were decreased by 69.8%, 33.2%, 34.7% and 71.8%, respectively, compared with those of the neat EP thermoset. Most attractively, other properties of the EP/BICP thermosets were not impaired despite of the enhancement of flame retardancy. Compared with the neat EP thermoset, the EP/BICP thermosets showed comparable mechanical properties and improved dielectric properties. Especially, the Tg values of EP/BICP thermosets (except for EP/BICP-8 sample) were around 190 °C, 34 °C higher than that of the neat EP thermoset. All these results demonstrated that EP/BICP system with remarkable comprehensive performance has the potential to achieve wider application in key fields.
       
  • Self-constructed nanodomain structure in thermosetting blend based on the
           dynamic reactions of cyanate ester and epoxy resins and its related
           property
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Song Chen, Li Yuan, Zehao Wang, Aijuan Gu, Guozheng Liang A new strategy to obtain nanodomain structure in thermoset/thermoset blends was developed via different dynamic reactions of cyanate ester (CE) and epoxy (EP) resins in the presence of zinc (II) acetylacetonate and glutaric anhydride. The resulting polymer systems show high mechanical property mainly attributed to EP nanophase and the excellent interfacial interaction between EP nanophase and CE matrix. Owing to the broad glass transition, the polymer systems display thermally activated triple shape memory effects in the temperature ranges of 150–225 °C. Moreover, the systems exhibit thermal self-healing behavior resulting from the transesterification and possible reactions between the residual cyanate ester and epoxy groups, and a 78–83% recovery of fracture toughness for the resulting polymers can be achieved after the first healing schedule of 200 °C/2 h.Graphical abstractImage 1
       
  • Effects of microstructure and pore water on electrical conductivity of
           cement slurry during early hydration
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Kaiqiang Liu, Xiaowei Cheng, Jingxue Li, Xianshu Gao, Yan Cao, Xiaoyang Guo, Jia Zhuang, Chunmei Zhang In this study, inductance-type electrical conductivity measurement (IECM) was performed to study the electrical conductivity of different formulations of cement slurry. Low-field nuclear magnetic resonance, in situ X-ray micro-tomography, and environmental scanning electron microscopy were used to investigate the effects of the microstructure, pore characteristics, and pore water of cement slurry on its electrical conductivity. Experimental results showed that the pore characteristics and ion concentration governed the initial electrical conductivity of fresh cement slurries. The sedimentation stability of fresh cement slurries increased the number of interconnected pores, and the initial electrical conductivity increased from 16.8 mS/cm to 19.4 mS/cm. When the CaCl2 accelerator content was 2 wt%, the initial electrical conductivity of the fresh cement slurry increased to 26.9 mS/cm, while the electrical conductivity rapidly decreased with the formation of hydration products. With increasing hydration time, large amounts of hydration products were formed in the pores, which changed the microstructure and pores of the cement slurry from connected large volume pores to many small volume pores and subsequently changed the distribution of pore water. The experimental results revealed that the connected porosity of the cement slurry was proportional to the electrical conductivity. An exponential relationship was found between the electrical conductivity and the evaporable water content, whereas a linear relationship was found between the electrical conductivity and the free water content.
       
  • Preparation of low-κ polyimide resin with outstanding stability of
           dielectric properties versus temperature by adding a reactive
           Cardo-containing diluent
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Xiuting Li, Peiyan Zhang, Jie Dong, Feng Gan, Xin Zhao, Qinghua Zhang High stability of low-κ value in a broad temperature region is a critical property for low dielectric constant polymer materials especially when they are served in some harsh conditions. However, most polymer dielectrics always exhibit a significant variation in dielectric property at around Tg or sub-Tg due to the local segment or chains motion, thus, low-κ polymer dielectrics are limited to a relatively narrow working temperature region. Herein, we described a series of novel crosslinked polyimide (PI) thermosets by blending a reactive Cardo-containing diluent into the PI oligomer, the dielectric constants of which were greatly reduced from 3.4 to 2.5 and were surprisingly stable over a temperature region of -150-250 °C. Meanwhile, the cured blended thermosets exhibited a 32–139 °C increase in Tg compared to the pristine PI. Detailed analyses have illustrated that the significantly reduced κ value, highly stable dielectric property and superior stability of these blended samples are originated from the synergistic effects of the large free-volume of Cardo-containing diluent, looser molecule packing resulted from the TR reaction and the highly crosslinked network. This desirable combination of facile processability, attractive dielectric behavior and excellent thermal stability makes them potential utilization in aerospace, microelectronic industries and other harsh environment applications.Graphical abstractImage 1
       
  • Effect of plasma modification of polyethylene on natural fibre composites
           prepared via rotational moulding
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Panikkassery Sasidharan Sari, Sabu Thomas, Petr Spatenka, Zoya Ghanam, Zdenka Jenikova The potential use of plasma modified polyethylene (PPE) as a matrix for natural fibre composite has been studied. Rotational moulding technique was employed for the manufacture of composite. Coconut fibre (coir fibre) was selected as the reinforcement and the effect of chemical treatment on fibre also being studied. In fact, the interfacial interaction between coir fibre and PE was analyzed systematically by creating four different types of interfaces (PE/natural fibre, PE/bleached natural fibre, PPE/natural fibre and PPE/bleached natural fibre). Water absorption, scanning electron microscopy and mechanical measurements were carefully carried out to understand the level of interactions between coir fibre and the polymer matrix. The mechanical properties of the PPE coir fibre composites were compared with unmodified PE coir fibre composites. PPE/bleached coir fibre composite showed lower water absorption due to better fibre/matrix interaction. SEM images revealed that a strong interfacial interaction between natural fibre and polymer matrix is possible with plasma modified PE matrix. Finally, it is very important to add that this is the first attempt to demonstrate that Rotational moulding could be successfully applied to plasma modified PE as the matrix and coir fibre as the reinforcing. This work will open tremendous possibility for the application of Rotational Moulding of natural fiber composites.
       
  • An efficient method to extract a mode I cohesive law for bonded joints
           using the double cantilever beam test
    • Abstract: Publication date: Available online 17 September 2019Source: Composites Part B: EngineeringAuthor(s): S. Abdel Monsef, A. Ortega, A. Turon, P. Maimí, J. Renart Cohesive Zone Models (CZM) are widely used for modeling bonded joints. The main difficulty concerning the use of CZM is the obtention of the interface cohesive law. To measure the cohesive law of bonded joints, experimental methods have been developed which are tedious and expensive because they require the use of additional measurement techniques in addition to the basic test outputs (load and displacement) to measure the J-integral and the crack opening displacement, essential parameters that obtain the cohesive law. In this work, a method is presented to obtain the cohesive law directly from the load-displacement curve of a DCB test. The method combines a model based on Dugdale's condition with an inverse method. The method is compared to the measurements from other authors who used the aforementioned more costly existing methods, and a good agreement between them is obtained. The method presented reduces the instrumentation needed during the test and it is very useful when testing under extreme conditions requiring the use of environmental chambers.
       
  • Coaxially aligned MWCNTs improve performance of electrospun
           P(VDF-TrFE)-based fibrous membrane applied in wearable piezoelectric
           nanogenerator
    • Abstract: Publication date: Available online 17 September 2019Source: Composites Part B: EngineeringAuthor(s): Chaoxian Zhao, Jin Niu, Yangyang Zhang, Cong Li, Penghao Hu Polymer-based piezoelectric nanocomposites are much promising in self-powered wearable application. In this work, flexible MWCNTs/P(VDF-TrFE) fibrous membranes were prepared via electrospinning. The introduction of coaxially aligned MWCNTs improves the mechanical-to-electrical output of 18.23 V and 2.14 μA of peak values in 3 wt% loading piezoelectric nanogenerator (PENG). An output power density of 6.53 μW/cm2 was obtained at 10 MΩ load resistance under the test condition close to practical use of 20% strain and 1 Hz external stress. In application test, tiny movement on the device could instantly light LED bulbs or LCD screen. The PENG also represents high stability during more than 20,000 cycles.
       
  • Insight into the dispersive mechanism of Carboxylated Nanofibrilllated
           cellulose for individual montmorillonite in water
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Chuan Sun, Zhiqiang Fang, Famei Qin, Kaihuang Chen, Jingyu Wang, Zixian Ding, Xueqing Qiu Carboxylated nanofibrillated cellulose (CNFC) has emerged as a promising green dispersant to prepare stable aqueous individual montmorillonite (MMT) suspensions. Nevertheless, its underlying dispersive mechanism remains elusive. Herein, we attempt to unveil the dispersive mechanism of CNFC for individual MMTs in water by characterizing the interfacial interactions between the two components using a quartz crystal microbalance with dissipation monitoring (QCM-D) and an atomic force microscopy (AFM). Both electrostatic repulsion and steric hindrance contribute to the excellent stability of homogeneous individual MMT suspensions, and their individual contributions are dependent upon the dosage of CNFC dispersant. The electrostatic repulsive forces dominate over the van der Waals forces that trigger the aggregation of aqueous individual MMTs when the dosage of CNFCs is 2 wt% (based on individual MMTs). With increasing dosage of CNFC dispersant, the electrostatic repulsive forces between individual MMTs tend to be level off while the steric hindrance gradually becomes a dominant factor that influences the dispersion stability of aqueous individual MMT suspensions. Finally, the effect of the CNFC dispersant's dosage on the optical and mechanical properties of nanocomposite film made with CNFCs and CNFC-dispersed individual MMTs is investigated. Understanding the dispersing principle of CNFCs for individual MMTs in water could pave the way to extend the applications of MMT in numerous value-added fields such as high-performance nanocomposites and flexible electronics.Graphical abstractIlluminate the disperse mechanism of Carboxylated Nanofibrillated as a green dispersant dispersing individual Montmorillonite at different dosage by AFM.Image 1
       
  • Decoupled effects of bone mass, microarchitecture and tissue property on
           the mechanical deterioration of osteoporotic bones
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Pan Liu, Xiaoxiao Liang, Zhenzi Li, Xiaobin Zhu, Zuoqi Zhang, Lin Cai Based on the theory of composite mechanics, a three-pillar framework “bone mass-microarchitecture-tissue property” instead of “bone mass-bone quality”, is proposed to quantitively characterize the mechanical deterioration of osteoporotic cancellous bones related to the three aspects, and accordingly the individual and integrative influences of bone mass, microarchitecture and tissue property on the mechanical properties of cancellous bones are investigated via the μCT-based finite element method (FEM) simulations of bone samples from healthy and ovariectomy-induced osteoporosis mice. Comparisons among the healthy, mild osteoporotic and severe osteoporotic bones clearly show that the healthy bones have a larger bone volume density and an optimized architecture exhibiting longitudinal superiority able to more efficiently resist the daily loadings which are commonly along their longitudinal direction, while osteoporosis does not only significantly reduce the bone volume density but also greatly deteriorate the microarchitectural topology, resulting in a distinct reduction in the magnitude of effective Young's moduli and a breakdown of the longitudinal superiority as well. Furthermore, through modeling in silico we decoupled the three major factors to probe into their individual effects on the mechanical deterioration of osteoporotic bones. It was found that sole bone loss would exponentially decrease the effective Young's moduli of cancellous bones, microarchitecture plays a dominant role in defining the anisotropic characteristics of bones such as the longitudinal superiority; and change of tissue property seems having a slight and linear influence on the effective Young's moduli of cancellous bones.
       
  • Cationic starch-grafted-cationic polyacrylamide based graphene oxide
           ternary composite flocculant for the enhanced flocculation of oil sludge
           suspension
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Ying Chen, Gongwei Tian, Boyin Zhai, Huili Zhang, Yuning Liang, Hongbao Liang In this study, a novel, highly efficient and environmentally friendly ternary composites flocculant, namely, cationic starch-grafted-cationic polyacrylamide/graphene oxide (CS-g-CPAM/GO), was synthesized by ammonium persulfate initiation polymerization and condensation reaction. First, CS-g-CPAM was polymerized with cationic starch (CS), acrylamide (AM) and diallyl dimethyl ammonium chloride (DMDAAC), and CS-g-CPAM/GO was then synthesized by condensation reaction. The influence factors of graft polymerization were investigated, including total monomer concentration, initiator dosage, monomer mass ratio of mAM: mCS: mDMDAAC, post-polymerization temperature and post-polymerization time. The chemical structures and morphologies of the samples were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric and differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The CS-g-CPAM/GO was used to flocculate the oil sludge suspension, the effects of CS-g-CPAM/GO dosage, temperature and pH value on the flocculation performance were investigated, and the flocculation mechanism of CS-g-CPAM/GO was also analyzed. The results show that CS-g-CPAM/GO has outstanding flocculation effect, and CS-g-CPAM/GO flocculates oil sludge particles by adsorption bridging and charge neutralization in acidic and alkaline conditions.Graphical abstractImage 1
       
  • Gravity-driven and high flux super-hydrophobic/super-oleophilic
           poly(arylene ether nitrile) nanofibrous composite membranes for efficient
           water-in-oil emulsions separation in harsh environments
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Shuangjiang He, Yingqing Zhan, Yulong Bai, Jiaxin Hu, Yunzhao Li, Guiyuan Zhang, Shumei Zhao Nanofibrous membranes with super-wetting feature exhibit promising application for oil/water emulsion separation, but achieving durability and high separation efficiency in harsh environments remains challenging. Herein, we developed a facile and effective strategy to prepare super-hydrophobic/super-oleophilic nanofibrous composite membranes, which perfectly integrated the two processes of electrospinning and fixing hydrophobic TiO2 nanoparticles to the surface of interconnected poly(arylene ether nitrile) (PEN) nanofibers using EVO-STIK serious glue. As a result, the constructed super-hydrophobic PEN/P–TiO2 nanofibrous composite membranes (WCA = 165 ± 2.4°) exhibited excellent separation efficiency (99.75 ± 0.12%) under gravity drive, with extremely high separation flux of 6853.65 ± 274 L/m2·h for surfactant-free emulsions and 3531.62 ± 231 L/m2·h for surfactant-stabilized emulsions. More importantly, the obtained PEN/P–TiO2 nanofibrous composite membranes showed stable super-hydrophobic feature and oil/water emulsion separation performance in harsh environments such as strongly corrosive solutions, physical damage, and high/low-temperature systems. Therefore, the super-wetting nanofibrous membranes with easy-handling, durable, and efficient oil/water separation performance could find potential application for emulsified oil-water separation system in harsh environments.Graphical abstractImage 1
       
  • Preparation, characterization, in vitro bioactivity and rBMSCs responses
           to tantalum pentoxide/polyimide biocomposites for dental and orthopedic
           implants
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Syed Asadullah, Han Wu, Shiqi Mei, Deqiang Wang, Yongkang Pan, Dongliang Wang, Jun Zhao, Jie Wei Polyimide (PI) may become a promising biomaterial for dental and orthopedic application due to its high mechanical strength, good biocompatibility and bio-stability as well as modulus of elasticity similar to the bone of human body. In this study, bioactive tantalum pentoxide (Ta2O5, TO)/polyimide (PI) composites (TPC) were fabricated by blending modification through a process of cold-pressing and sintering. The results revealed that the compressive strength, thermal stability, surface roughness, hydrophilicity and surface energy of TPC were significantly enhanced with the increase of TO content. Moreover, apatite mineralization of TPC in simulated body fluid (SBF) was obviously improved, in which TPC with TO of 50 wt% content (TPC50) displayed the best bioactivity. Furthermore, the cellular responses (adhesion, proliferation and differentiation) of rat bone mesenchymal stem cells (rBMSCs) to TPC were obviously upregulated with the increase of TO content. The results demonstrated that the TO content in the composites remarkably affected not only physical-chemical properties but also the cells behaviors. It can be suggested that TPC50 with improved surface properties and bioactivity as well as good cytocompatibility would have great potential and prospect for dental and orthopedic applications.
       
  • A stable, ultrasensitive and flexible substrate integrated from 1D
           Ag/α-Fe2O3/SiO2 fibers for practical surface-enhanced Raman scattering
           detection
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Jiangtao Xu, Songmin Shang, Shouxiang Jiang Conventionally, the surface-enhanced Raman spectroscopy (SERS) measurement is performed by dispersing noble metal nanoparticles onto the target sample directly or assembling noble metal nanoparticles onto a micro-sized substrate. Despite it is flourishing, this method is not adequate for various samples, mainly limited by either a defined confinement of the test position or the complex extraction process of the target sample on the irregularly shaped surface, besides the costive materials, complex and uncontrollable fabricating processes. Herein, we demonstrate that the α-Fe2O3 thin film is decorated with Ag nanoparticles constructed on SiO2 fibers as a flexible SERS-active substrate, which yields a functional optical enhancement of the signal at 532 nm laser excitation. It shows a high enhancement factor of 4.71 × 105, ultrahigh sensitivity of 10−15 M, and excellent signal stability with a relative standard deviation (RSD) of 1.22% and reproducibility with a RSD of 0.258%.Graphical abstractImage 1
       
  • Synthesis and characterization of gold/silica hybrid nanoparticles
           incorporated gelatin methacrylate conductive hydrogels for H9C2 cardiac
           cell compatibility study
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Bikendra Maharjan, Dinesh Kumar, Ganesh Prasad Awasthi, Deval Prasad Bhattarai, Ju Yeon Kim, Chan Hee Park, Cheol Sang Kim Herein, gold/silica (Au/SiO2) hybrid nanoparticles (NPs) were incorporated into the gelatin methacrylate (GelMA) matrix to construct mechanically strong and electrically conductive GelMA hydrogel for biomedical applications. As-prepared GelMA-Au/SiO2 hydrogels were characterized by field emission scanning microscopy (FESEM), compressive strength test, and conductivity/resistivity measurement. Accordingly, to evaluate the cell compatibility of as-prepared conductive hydrogel, the in-vitro biocompatibility assay was performed in rat cardiomyoblast H9C2 cells. The results showed composite hydrogel possessed enhanced compressive strength and conductive property without compromising the beneficial properties such as porous morphology and biocompatible nature of GelMA hydrogel. After incorporation of hybrid NPs, the compressive strength and Young's modulus of composite hydrogels were increased by two-folds. Similarly, the cyclic compression test showed that the pure GelMA hydrogel loses its mechanical stability from the initial cycles, while GelMA-Au/SiO2 hydrogels were sustained up to 50 cycles. In case of cell viability study, the CCK-8 assay result showed enhanced cardiomyoblast cell adhesion and proliferation on the conductive hydrogels. Moreover, the GelMA-Au/SiO2 conductive hydrogels exhibited an increased cell viability by 15% of pure GelMA hydrogels. Similarly, the confocal laser scanning microscopy (CLSM) results showed uniformly aligned cell growth throughout the conductive hydrogels. Overall, this study presents a novel strategy for inducing electrical conductivity and improving mechanical integrity to the gelatin-based GelMA hydrogel by incorporating bifunctional hybrid NPs for regenerative medicine and tissue engineering applications.
       
  • Impact of nanosilica on the friction and wear of a PEEK/CF composite
           coating manufactured by fused deposition modeling (FDM)
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Leyu Lin, Nicholas Ecke, Miaozi Huang, Xian-Qiang Pei, Alois K. Schlarb Carbon fiber (CF) reinforced polyetheretherketone (PEEK) coating material on a pure PEEK backing was prepared by using FDM technique towards the aim of studying its tribological properties. Two kinds of tribo-tests were conducted. Firstly, the tribological performance of PEEK/CF coating was evaluated by sliding against a steel ring. In a second attempt, nanosilica was fed into the interface of polymer and steel ring, to study the effect of nanosilica on the tribological properties of the coating. The results demonstrate that friction coefficient and wear rate strongly dependent on the siding direction. Both characteristic values exhibit much lower values, when the sliding took place perpendicular to the carbon fibers. Comparative analyses of the worn surfaces reveal that the great friction and wear reduction can be contributed to the effective distribution of shear stress on carbon fibers. More usefully, taking-in of nanosilica into the interface significantly improves friction performance of the coating material. The responsible mechanisms are rolling of nanosilica in the interface and reduction of adhesion between the tribo-pair due to presence of nanosilica. It is highlighted that oriented short CF reinforced PEEK tribo-coatings can be manufactured thanks to the FDM technique and their tribological performance can be further modified with external nanosilica taking-in into the sliding interface. It is expected that the external nanoparticle donator could be integrated into the composite materials through printing with optimized processing which can prevent formation of defects in the composites.
       
  • Excellent energy storage density and efficiency in blend polymer-based
           composites by design of core-shell structured inorganic fibers and
           sandwich structured films
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Yang Cui, Tiandong Zhang, Yu Feng, Changhai Zhang, Qingguo Chi, Yongquan Zhang, Qingguo Chen, Xuan Wang, Qingquan Lei In this study, the ferroelectric polyvinylidene fluoride (PVDF) blended with linear dielectric polymethyl methacrylate (PMMA) is chosen as polymer matrix (named as PMMA/PVDF). The effect of PMMA content and differently structured fillers on the microstructures and electrical properties of PMMA/PVDF-based composites have been investigated. The inorganic 0.5Ba(Zr0.2Ti0.8)O3- 0.5(Ba0.7Ca0.3)TiO3 fibers (abbreviated as BCZT), BCZT embedded with Ag particles (BCZT+Ag), and core-shell structured BCZT+Ag@Al2O3 fibers as fillers were designed and prepared by electrospinning technology. As the insulating Al2O3 shell layer could relieve the dielectric difference between the BCZT and polymer matrix and confine the mobility of carriers provided by Ag, the energy storage density and efficiency are 4.02 J/cm3 and 78.0% for the 3 vol% BCZT+Ag@Al2O3/40% PMMA/PVDF composites at an electric field of 320 kV/mm. To further improve the energy storage properties of the single-layered composites, the sandwich-structured composite films have been designed to improve the breakdown strength. The results show that the energy storage density and efficiency of sandwich-structured composite film with 40 wt% PMMA/PVDF as outer layer and 3 vol% BCZT+Ag@Al2O3/40% PMMA/PVDF as inter layer are 9.6 J/cm3 and 69.8%, respectively, at an electric field of 400 kV/mm. This work presents an effective way to improve the energy storage properties of inorganic/polymer composites.Graphical abstractImage 1
       
  • Insights into the molecular structure and reinforcement mechanism of the
           hydrogel-cement nanocomposite: An experimental and molecular dynamics
           study
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Dongshuai Hou, Jianyu Xu, Yu Zhang, Guoxing Sun The biomedical and industrial application of hydrogels are strongly limited by their poor mechanical properties. In this paper, non-aggregated Ca(OH)2 nano-spherulites (CNS) with diameters
       
  • Stress mitigation for adhesively bonded photovoltaics with fibre
           reinforced polymer composites in load carrying applications
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Yiqing Dai, Yu Bai, Thomas Keller Structural loads, especially in-plane compression, may cause local buckling and debonding of the photovoltaic (PV) cells that are mechanically integrated with structural members and this may lead to degradation in their electrical performance. This paper proposes an approach to mitigate the strains transferred from structural members to PV cells through the partial composite action provided by low-modulus adhesives. Specimens were fabricated by bonding amorphous silicon (a-Si) PV cells to glass fibre reinforced polymer (GFRP) structural components by an adhesive layer of 0.5- or 2.0-mm thickness. Two types of adhesives were used including a two-part rigid epoxy adhesive and a low-modulus silicone adhesive. These integrations were then submitted to in-plane compressive loadings. PV cells bonded by the silicone adhesive showed no damages during loading. While for PV cells bonded by epoxy adhesives, obvious electrical performance degradations were observed, when the strain reached 0.62% or 0.23% for specimens bonded by epoxy with a layer thickness of 0.5 mm or 2.0 mm respectively. Debonding and local-buckling of the PV cells were also witnessed. Theoretical analysis was conducted to understand the strain mitigation of the adhesive as a result of the induced partial composite action. Results demonstrate that such strain differences between the GFRP and the bonded PV cell are dominated by the shear modulus and thickness of the adhesive layer as well as elastic modulus, thickness and length of the PV cell. The theoretical analysis was validated by finite element (FE) modelling and design suggestions are provided accordingly.
       
  • Effect of steel fibers with galvanized coatings on corrosion of steel bars
           embedded in UHPC
    • Abstract: Publication date: Available online 14 September 2019Source: Composites Part B: EngineeringAuthor(s): Liang Fan, Weina Meng, Le Teng, Kamal Henri Khayat Ultra-high-performance concrete (UHPC) is widely accepted for its super-high durability. However, the corrosion performance of steel reinforcing bars embedded in UHPC and the improved protection of UHPC cover to steel bars are seldom studied. Furthermore, whether using steel fibers in UHPC will accelerate or slow down the corrosion of steel bars is of special interest. In this study, the effects of two types of steel fibers with different galvanized coatings (brass and zinc coated fibers) on the electrical resistance of UHPC and corrosion resistance of embedded steel bars were investigated. Electrochemical tests were conducted for 1 year in 3.5 wt % NaCl solution. The tests included open circuit potential (OCP), linear polarization resistance (LPR), Tafel polarization, and electrochemical impedance spectroscopy (EIS). Test results showed that ASTM C876 was not applicable to UHPC to determine corrosion state of embedded steel bars based on the OCP values. This is because the dense microstructure of UHPC can limit the penetration of oxygen and significantly lower OCP values. The corrosion rates in terms of corrosion current densities of steel bars from the LPR and Tafel polarization tests showed a decreasing trend with time, hence indicating that the steel bars were in passive state. Furthermore, chloride was not detected in the UHPC matrix after the electrochemical tests. This proved that corrosion did not occur on the steel bar surface in the testing period. The electrochemical resistance of UHPC matrix, the resistance of passive film, and the charge transfer resistance of the steel bars from the EIS test displayed a long-term increasing trend. However, when the conductive steel fibers increased from 0 to 2%, by volume, the UHPC matrix resistance decreased by more than 40%. It was also found that the fiber type and fiber content did not affect the resistance of passive film and charge transfer resistance of embedded steel bars. Galvanic corrosion did not happen due to uniform distribution of the fibers along the cast specimens. When proper casting method was employed, both brass and zinc-coated steel fibers can be safely used in UHPC for fiber volume up to 2%.
       
  • Design, analysis and fabrication of thick co-cured wing structures
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Zeaid Hasan, Jessica Rader, Alec Olson, Delphine Turpin, Ryan St Onge, Jon Amback Over the past few decades advances in the design, materials, and manufacturing of thermoset composite materials have expanded rapidly. Nonetheless, aerospace structures have not yet adapted many of these technologies. This can be attributed to the risk adverse nature of the engineering community and associated regulatory agencies in this field.One of the technologies that has recently gained more traction in the composites field is the use of unitized co-cure structures. Driving this change is the potential for reducing part count, touch time and labor costs. Most of the work done to date focuses on thinner structures (~0.15 inch in thickness) resulting in a lack of understanding of the behavior of much thicker parts representing wing-like structures.This paper provides insight into the fabrication of a full-scale wing demo made from Cycom 5320–1. The design, analysis and fabrication aspects are discussed and presented. It was shown that utilizing an outer mold line (OML) tooling approach with silicon mandrels provided a final product that achieves the set engineering tolerances. Nondestructive inspection showed no defects or anomalies in the part using the proposed fabrication approach. In addition, a brief discussion on the part warpage was presented and concluded that the amount of warpage detected in thick co-cured structures is less than that observed in co-bonded and secondary bonded parts.
       
  • Review on techniques to improve the strength of adhesive joints with
           composite adherends
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): X. Shang, E.A.S. Marques, J.J.M. Machado, R.J.C. Carbas, D. Jiang, L.F.M. da Silva The use of adhesive joints has increased rapidly in the past decades. Driven by the growing demand for lightweight structures, composite adherends have increased in popularity, benefiting from their high specific mechanical properties and design tailorability. However, composites are typically weak in the transverse direction, which can cause premature failure by delamination. Several techniques, aimed at reducing stress concentrations and increasing the transverse strength of the adherends, are discussed and compared in terms of material arrangement and geometry design. Lastly, a short summary on prominent features of the techniques is given. The paper is intended to provide guidelines for the design of adhesive joints with composite adherends.
       
  • Preparation, microstructure and performance of poly (lactic acid)-Poly
           (butylene succinate-co-butyleneadipate)-starch hybrid composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Linghan Meng, Long Yu, Saud Khalid, Hongsheng Liu, Shaobo Zhang, Qingfei Duan, Ling Chen Poly (lactic acid) (PLA)-poly (butylenesuccinate-co-butyleneadipate) (PBSA)-starch hybrid composites were developed, in which PBSA was used to improve mechanical and thermal properties while starch was used to decrease the cost of PLA and PBSA. To minimize the decomposition of PLA and PBSA during thermal processing, the hybrids sheets were prepared by one-step extrusion through connecting a twin screw extrude with a single extrude fitting a sheet die. The hybrid composites were characterized and observed that: (a) the one-step extrusion technology distributed starch granules into PLA/PBSA matrix homogeneously with minimizing the decomposition of polyester and the energy input decreased about 35% comparing with two-step extrusion, where the tensile properties by one-step were improved about 15–20% and impact strength was increased about 30%; (b) addition of starch granules, as fillers, deteriorated the continuous structure of polyester matrix due to poor compatibility between hydrophilic starch and hydrophobic polymer PLA/PBSA matrix. However, stearic acid acting as a surface modifier increased the compatibility between starch fillers and polymeric PLA/PBSA matrix and further improved the mechanical properties of the hybrids. PLA/PBSA-based hybrid composites filled with 30–40 wt % starch provided an acceptable balance between cost and performance of PLA-based materials.
       
  • Facile construction of one-component intrinsic flame-retardant epoxy resin
           system with fast curing ability using imidazole-blocked bismaleimide
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Qianqian Zhang, Jun Wang, Shuang Yang, Jianwen Cheng, Guoping Ding, Siqi Huo Latent curing epoxy resin (EP) system with satisfactory flame retardancy has attracted rather considerable interest both in academic and industrial communities over the years. Herein, imidazole-blocked bismaleimide compounds were synthesized through the Michael addition reaction of N,N′-bismaleimide-4,4′-diphenylmethane (BDM) with imidazole (IM), 2-methylimidazole (2MI), and 2-ethyl-4-methylimidazole (EMI), respectively, and were simultaneously used as latent curing agent and flame retardant synergist for 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) based EP (DOPO-EP). The storage stability study disclosed that imidazole-blocked bismaleimide compounds kept chemically inert towards epoxy at room temperature, resulting in long pot life over 40 days. When heated, imidazole-blocked bismaleimide compounds underwent retro-Michael addition reaction to regenerate BDM and the corresponding imidazoles. The fast curing ability was thus achieved via chain polymerization of epoxy initiated by thermally generated free imidazoles. Moreover, polybismaleimide component derived from the homopolymerization of thermally generated BDM was incorporated into the cross-linked EP network, resulted in enhanced thermal and charring performance of epoxy matrix. Compared with the contrast samples EP/2MI-BDM and DOPO-EP/2MI thermosets, DOPO-EP/2MI-BDM thermoset exhibited better flame retardancy with remarkably higher limiting oxygen index (LOI) value and UL94 rating as well as lower peak of heat release rate (pk-HRR), average of heat release rate (av-HRR) and total heat release (THR) from cone calorimeter test. The flame-retardant mechanism study revealed the synergistic flame-retardant effect of phosphaphenanthrene and bismaleimide in condensed phase.Graphical abstractImage 1
       
  • Experimental behaviour of damaged masonry arches strengthened with steel
           fiber reinforced mortar (SFRM)
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Nicolò Simoncello, Paolo Zampieri, Jaime Gonzalez-Libreros, Carlo Pellegrino In this paper, the results of an experimental campaign aimed to study the behavior of damaged solid clay brick masonry arches strengthened with steel fiber reinforced mortar (SFRM) are presented. Conditions of damage studied included preloading, horizontal displacement of one of the supports, or a combination of both. After damage was produced, the arches were strengthened with one layer of SFRM at the intrados and retested. The performance of the strengthened arches is discussed in terms of failure mode, and variation in the load carrying capacity, ductility and stiffnesses with respect to unstrengthened undamaged condition. The results show that the SFRM strengthening was able to increase significantly the strength and stiffness of the arches, although in some cases such increase was accompanied by a reduction in the specimens’ ductility. In addition, an analytical formulation for the design and assessment of the capacity of masonry arches strengthened with SFRM was developed. Comparison between predicted and experimental values show good agreement, which allowed validating the analytical method.
       
  • Recycled Stone/ABS particulate composite: Micromechanical finite element
           fracture analysis
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): D. Karimi, A.S. Milani, F. Alavi New stone composite samples, fabricated using nano- to micro-sized recycled granite particles with irregular shapes and random distribution within a ABS matrix, demonstrate a highly nonlinear and complex fracture behavior. To model this behavior, a mixed mode cohesive zone finite element model is identified using the single-leg bending (SLB), in order to represent the granite particles-ABS interfacial debonding. An inverse methodology is then proposed to determine the parameters of the cohesive zone (CZM). A direct method based on J-integral approach is employed to determine the effective parameters of the traction-separation law. A two dimensional micromechanical extended finite element model (XFEM) of the composite is generated using X-ray micro-computed tomography (XMT) to mimic the actual shape of the particles. Finally, the identified cohesive model parameters have been employed to simulate the crack growth within the granite particulates/ABS composite. The comparison of the numerical and experimental results of the SLB test demonstrated the effectiveness of the proposed simulation framework.
       
  • Cavitation erosion of glass fibre reinforced polymer composites with
           unidirectional layup
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): R. Guobys, Á. Rodríguez, L. Chernin Glass fibre reinforced polymer (GFRP) composites are increasingly used in marine applications and can be subjected to aggressive environmental effects, one of which is cavitation. This study investigates the behaviour of unidirectional GFRP composites exposed to cavitation erosion generated using an ultrasonic transducer. Cavitation erosion tests were performed in accordance with the ASTM G32 standard. All specimens were preconditioned to eliminate the influence of water absorption on the mass loss caused by cavitation. The erosion process was monitored with a microscope and the mass loss was measured at regular periods. The tested specimens were scanned with X-ray computed microtomography. The research findings indicated that the erosion process was affected by several parameters including specimen thickness, distance between fibre bundles, bundle shape and distribution. The initiation and development of erosion damage were highly influenced by the surface condition. Cavitation erosion traced parts of fibre bundles located closer to the surface creating trenches and valleys on the surface. The regions with thick epoxy layers above and between fibre bundles were much less susceptible to erosion damage. Several erosion mechanisms were identified and discussed. The research findings also highlighted the difficulties in characterising ultrasonic cavitation erosion of GFRP composites using acoustic impedance and mean erosion depth.
       
  • Full-degradable composites reinforced by the low temperature treated
           cotton fabrics with enhanced strength and interfacial bonding
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Ran Li, Junfeng Wei, Shi Xu, Quan Zhu, Wanshuang Liu, Yiping Qiu, Qiuran Jiang The improper disposal of vast discarded cotton fabrics results in environmental pollution and waste of valuable cellulose resource. Full-degradable composites were hence developed from biodegradable matrices, poly (lactic acid) (PLA) and cellulose acetate (CA), with the reinforcement of the cotton fabrics treated by a low-temperature alkali/urea treatment. This treatment could provide cotton fabrics with a compacter structure, 18.4% enhancement in tensile strength, roughened fiber surface and raised hydrophilicity. After the treatment, the composites displayed 9.7–10.1% enhancement in tensile strengths, 36.3–66.5% rise in tensile moduli, 24.7–39.62% increment in flexural strengths and 42.4–52.1% improvement in flexural moduli. Compared to the PLA composites, the treated cotton fabric/CA composites displayed higher improvements in their properties due to better interfacial bonding between fabrics and the hydrophilic CA matrix, which was proven by a 42.8% increment in peeling strength. The stronger interfacial adhesion also prevented the invasion of microorganism and feculence, and reduced the degradation rate of the CA composites in soil. However, the hydrophilic nature made the CA composites more vulnerable to degradation in water. Considering the low cost, saved resource, less pollution, and acceptable properties for applications, the approach developed in this work possesses the potential to promote an environmentally friendly and sustainable reuse process for discarded cotton fabrics.Graphical abstractImage 1
       
  • Green fabrication of graphene oxide/epoxy nanocomposite and its
           application in diamond abrasive tools
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Rui Wang, Jianhua Zhang, Shaoyun Chen, Lixin Wu, Dongxian Zhuo, Xiuyan Cheng In order to improve the wear resistance and service life of the epoxy resin (EP)-bonded diamond abrasive tools, graphene oxide (GO) was incorporated through a green method without any organic solvents. A curing accelerator, 3-methyl-N,N-diethylbenzenamine (3-MBDEA) acts as a phase transfer agent which rapidly catches GO from water phase to epoxy phase, and the diamond/GO/EP abrasive tools were fabricated via in situ polymerization. The effect of GO on the structure of EP was characterized, and the grinding performances of as-prepared diamond/GO/EP abrasive tools were evaluated in the grinding of concrete. Results show that the service life of the diamond/GO/EP abrasive tools are significantly improved by the incorporation of GO. In the case of the diamond with the size of 50 μm (D50)/GO0.5/EP abrasive tool only with 0.5 wt% GO, its service life increases by 75% compares to that of the D50/EP abrasive tool. The excellent performance of diamond/GO/EP abrasive tools is attributed to the improvement of the wear resistance of EP and the enhancement of the interfacial adhesion between EP and diamond with the addition of GO. This work may provide a potential industrial application for graphene-related materials.Graphical abstractImage 1
       
  • Accurate determination of the “time-zero” of autogenous shrinkage in
           alkali-activated fly ash/slag system
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Y. Ma, X. Yang, J. Hu, Z. Zhang, H. Wang Autogenous shrinkage based on different “time-zero” may result in underestimation/overestimation on the cracking potential of alkali-activated fly ash/slag (AAFS). This study reports an experimental investigation on the “time-zero” of AAFS pastes characterized by different techniques. It is found that the internal capillary pressure in AAFS pastes significantly increased after 5–7.5 h, which is far beyond the final setting time that is normally regarded as “time-zero” for Portland cement. The transition time derived from capillary pressure method directly captures the alteration of capillary stress in AAFS, which matches well with the change of the shrinkage slope. Due to the moisture equilibrium between the specimens and humidity sensor, it is hard to use the measured internal relative humidity to determine the real “time-zero” of AAFS. This research finds that the onset of capillary pressure in AAFS paste provides a more scientific and accurate determination of “time-zero”.
       
  • Effects of ozonized carbon black on fracture and post-cracking toughness
           of carbon fiber-reinforced epoxy composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Seong Hwang Kim, Sang Jin Park, Kyong Yop Rhee, Soo-Jin Park Improving the fracture and post-cracking toughness of carbon fiber-reinforced composites based on thermosetting epoxy matrices are of significant interest in a wide range of applications. Herein, we report the synergistic integration of multi-scale composites by combining nano-scale filler and macro-scale fiber reinforcement inspired by the hierarchy approach. For the nano-scale filler, the carbon black (CB) surface was successfully modified using ozone treatment and thereby achieved highly efficient dispersion and interfacial properties. The reinforcing mechanisms were also analyzed, and the improvements on dispersion and interfacial properties should mainly be attributed to mechanical interlocking effect. For all of the multi-scale composites fabricated, the ozone-functionalized CB content was found to be optimal at 5 wt%, which improved the fracture and post-cracking toughness by 12.5% and 61.9%, respectively, compared with pristine CB.
       
  • Expanded graphite assistant construction of gradient-structured char layer
           in PBS/Mg(OH)2 composites for improving flame retardancy, thermal
           stability and mechanical properties
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Hao Chen, Ting Wang, Yanliang Wen, Xin Wen, Doudou Gao, Ronghua Yu, Xuecheng Chen, Ewa Mijowska, Tao Tang It is a great challenge to improve the flame retardancy of polymer materials by adding eco-friendly magnesium hydroxide (Mg(OH)2) but simultaneously maintain satisfied mechanical performances. In this study, expanded graphite (EG) as a synergist was introduced into poly(butylene succinate) (PBS)/Mg(OH)2 system to investigate the effect of EG on their flame retardancy, thermal stability and mechanical properties. The results showed that only addition of 5 wt% EG into PBS/20 wt%Mg(OH)2 resulted in excellent flame retardancy, including that the LOI was 29.4%, the UL-94 rating reached to V0, and the PHRR decreased by 73%. These flame retarded parameters were comparable or even better than that of PBS/40 wt%Mg(OH)2 composites. More importantly, PBS/20 Mg(OH)2/5 EG presented much better thermal stability and mechanical properties than PBS/40 wt%Mg(OH)2, indicating a balanced improvement on comprehensive performances of PBS. Based on the comparison with PBS/20 Mg(OH)2/5Graphene(Gr) system and the structure analysis for residual chars, the mechanism for improved flame retardancy was attributed to the formation of gradient-structured char layer due to the helpful thermal expansion process of EG together with the decomposition of Mg(OH)2 during combustion, resulting in better barrier action to heat, oxygen and flammable gases via “labyrinth effect”. As far as we know, it is the first report that gradient-structured char layer was discussed in flame retarded polymer systems. Hence, this work provides not only a high-efficient synergist to improve the flame retardant efficiency of Mg(OH)2, but also useful guidelines to design polymer composites with balanced comprehensive performances.Graphical abstractA gradient-structured char layer formed in poly(butylene succinate)/magnesium hydroxide/expanded graphite (PBS/Mg(OH)2/EG) system during combustion, resulted in remarkably improved flame retardant efficiency of Mg(OH)2 as well as a good balance on flame retardancy and mechanical properties.Image 1
       
  • Automated spray up process for Pineapple Leaf Fibre hybrid biocomposites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Mohd Hanafee Zin, Khalina Abdan, Norkhairunnisa Mazlan, Edi Syams Zainudin, Kan Ern Liew, Mohd Nurazzi Norizan This paper investigates the fabrication of hybrid biocomposites of Pineapple Leaf Fibre (PALF)-glass-vinyl ester (VE) utilizing automated spray up process. This method can be applied for components in interior aircraft and automotive industry. In this study, the manual chop spray gun is integrated with industrial robotic arm to produce random discontinuous fibre composite (DFC) from PALF roving (273 tex) and vinyl ester resin. The characterization includes mechanical (tensile, and flexural test), thermal (DMA and TGA) and a morphological analysis (SEM) of the surface fractures from the tensile test samples. For each mechanical result, coefficient of variance (COV) is calculated to measure the variability of the mean distribution. The comparison is made among the glass (100% glass), PALF-vinyl ester (100% PALF), and glass-PALF-vinyl ester (PALF 50%, Glass 50%) hybrid biocomposites on the mechanical strength and consistency of the outcome. The result showed that hybridization increased the tensile strength by 171% compared to PALF-VE composite, reduced the composite density and increase thermal properties compared to PALF-VE and glass-VE composites.
       
  • Hygro-thermo-mechanical modelling of multilayered plates: Hybrid composite
           laminates, fibre metal laminates and sandwich plates
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): F. Moleiro, E. Carrera, G. Li, M. Cinefra, J.N. Reddy A new layerwise mixed model is developed for the coupled hygro-thermo-mechanical static analysis of multilayered plates, addressing hybrid composite laminates, fibre metal laminates and sandwich plates under hygro-thermo-mechanical loadings. This model is based on a mixed least-squares formulation, i.e. a strong form model, with a layerwise variable description for displacements, transverse stresses and in-plane strains, along with temperature, transverse heat flux and in-plane components of the thermal gradient, as well as moisture, transverse moisture flux and in-plane components of the moisture gradient, all taken as independent variables. This mixed formulation ensures that the interlaminar C0 continuity requirements, where the material properties change, are fully fulfilled a priori by all independent variables. The effects of hygrothermal environments in the behaviour of multilayered plates are here demonstrated considering hybrid composite laminates, fibre metal laminates and sandwich plates with different side-to-thickness ratios under a series of hygro-thermo-mechanical loadings. Three-dimensional (3D) exact solutions are used to assess the results by the present model and some further by an alternative weak form model in the framework of Carrera Unified Formulation (CUF). The present model is shown to predict a highly accurate quasi-3D hygro-thermo-mechanical description of the through-thickness distributions of displacements and stresses, temperature and heat flux, moisture and moisture flux, all together.
       
  • Comparative study on solid and hollow glass microspheres for enhanced
           electromagnetic interference shielding in
           polydimethylsiloxane/multi-walled carbon nanotube composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Yan-Jun Tan, Jie Li, Jie-Hua Cai, Xiao-Hong Tang, Ji-Hong Liu, Zong-qian Hu, Ming Wang Herein, solid and hollow glass microspheres (SGM and HGM) were added into polydimethylsiloxane/multi-walled carbon nanotube (PDMS/MWCNT) composites to induce multiple interfaces. The electromagnetic interference (EMI) shielding of the PDMS/MWCNT composites was expectedly enhanced by the multiple reflection and/or scattering at the interfaces between GM and PDMS/MWCNT phase. The EMI shielding effectiveness (SE) of the PDMS/MWCNT composites with 3.0 vol% MWCNT fillers increased from ~40 to ~52 dB and ~46 dB by the addition of 30 vol% SGM and HGM, respectively. The high specific SE value was found in the composites with HGM due to the low density of the samples with HGM. The effect of the diameter and the content of SGM, the content of MWCNT, and the sample thickness on EMI SE of the PDMS/MWCNT/SGM composites were investigated in this work. The high-performance EMI SE were achieved in the composites by balancing the thickness of conductive layers and the amount of multiple reflection and/or scattering interfaces.Graphical abstractHigh-performance electromagnetic interference shielding effectiveness was achieved in polydimethylsiloxane/multi-walled carbon nanotube/glass microspheres (PDMS/MWCNT/GM) composites by balancing the amount of multiple scattering/reflection at interfaces and the thickness of conductive domains between GM particles for the absorption of electromagnetic waves.Image 1
       
  • Strong, stretchable and ultrasensitive MWCNT/TPU nanocomposites for
           piezoresistive strain sensing
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): S. Kumar, Tejendra K. Gupta, K.M. Varadarajan We report strong, stretchable and ultrasensitive thermoplastic polyurethane (TPU) nanocomposites reinforced with multiwalled carbon nanotubes (MWCNT) for piezoresistive strain sensing. Uniform dispersion of MWCNT in TPU matrix offers low percolation threshold (0.1 wt%) and superior electrical conductivity. MWCNT/TPU nanocomposites exhibit different sensitivities and measurable strain ranges depending upon MWCNT concentration. Static stretch experiments reveal nearly linear piezoresistive response up to 15%, 35% and 45% strain with gauge factor (GF) of 22, 8.3 and 7.0 for 0.3, 0.5 and 1.0 wt% MWCNT loaded TPU nanocomposites, respectively. With further stretching, TPU nanocomposites evince strain-dependent GF of 6395, 6423 and 7935 at 35%, 95% and 185% strain for 0.3, 0.5 and 1.0 wt% MWCNT loading, respectively. Furthermore, we observe improvements in tensile strength, yield strength and Young's modulus of 51%, 37% and 23% for 0.1 wt % MWCNT loading and 10%, 83% and 66% for 0.3 wt % MWCNT loading, respectively. Cyclic stretch/release tests for 0.3 wt% MWCNT loaded nanocomposites show good recoverability and reproducibility over 100 cycles up to a strain-amplitude of 50%. Ultrahigh GF of MWCNT/TPU nanocomposites compared to extant work together with their tuneable sensitivity in both small and large strain regimes, enhanced strength and ease of fabrication make them attractive for high performance strain sensing devices.Graphical abstractImage 1
       
  • Construction of intumescent flame retardant and hydrophobic coating on
           wood substrates based on thiol-ene click chemistry without photoinitiators
           
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Tongtong Ma, Liping Li, Qingwen Wang, Chuigen Guo Intumescent transparent coatings consisting of allyl-functionalized phosphonitrile (HABP), trimethylolpropane tris(3-mercaptopropionate) (TMMP) and 1H,1H,2H,2H-perfluorodecanethiol (PFDT) were prepared via photo-induced thiol-ene reactions without photoinitiator, and then fabricated onto wood surfaces to achieve both flame retardancy and hydrophobicity. The effects of PFDT content on the waterproof and fire prevention of the samples were investigated. The chemical structure of the HABP was characterized with FTIR, NMR and HRMS techniques. The surface compositions and transparency of the coatings were characterized by XPS and UV–Vis spectrophotometer. The sample could pass the UL-94 V-0 test and the double bond conversion (DCC=C) of the corresponding coating reached 93.3%. Results showed that the more the coating contained PFDT, the better the coated samples exhibited hydrophobicity and flame retardancy. From a broader perspective, thiol-ene reactions without initiators are showing significant potentialities for rapidly designing functional coatings on wood substrates, which will be develop more functional coatings for other application fields.
       
  • Predicting the stacking sequence of E-glass fiber reinforced polymer
           (GFRP) epoxy composite using terahertz time-domain spectroscopy (THz-TDS)
           system
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Dong-Woon Park, Gyung-Hwan Oh, Hak-Sung Kim A terahertz time-domain spectroscopy (THz-TDS) system was used for measuring and predicting stacking sequence of laminated composites. The THz wave's penetration behavior in emissivity (E)-glass fiber reinforced polymer epoxy composites was analyzed. The relationship between polarization angle of THz radiation to fiber direction of the composites and dielectric constant in THz frequency range was formulated using a two-dimensional transformation matrix. Then, the dielectric constants of arbitrarily laminated composite plates were calculated by combining the transformation matrix via laminating rule. The dielectric constants of the arbitrarily laminated composites were measured and compared with those of the developed theoretical models. It was found that the THz waves could be successfully used to predict the stacking sequence of the laminated composites with 0.25% error.
       
  • Ballistic performance of bioinspired nacre-like aluminium composite plates
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Tingyi Miao, Luming Shen, Qingfeng Xu, E.A. Flores-Johnson, Jianjun Zhang, Guoxing Lu Inspired by the hierarchical structure of nacre, an aluminium alloy (AA) 7075-T651 based composite plate is developed for ballistic applications. The proposed nacre-like composite plates are made of 5, 7 or 9 layers consisting of many ~1 mm thick AA7075-T651 tablets bonded together with toughened epoxy adhesive. Experimental ballistic tests on these composite plates, using a hemispherical nosed steel projectile at impact velocities in the range of 340–450 m/s, were performed. Both the 5-layer and 7-layer plates exhibited a better ballistic performance than their bulk counterparts based on the observation that the measured residual velocity of the projectile through the composite plate was lower than that through the corresponding bulk plate with similar areal density. However, the performance improvement is reduced as the composite plate thickness increases (from 5 to 9 layers) due to the increased likelihood of ductile failure occurring prior to perforation in the thicker bulk plates. The failure pattern analysis of the impacted specimens confirmed that the impact performance enhancement of the nacre-like composite plates can be attributed to the hierarchical structure facilitating both localized energy absorption (by tablet deformation and interlocking) and more globalized energy absorption (by inter-layer delamination and friction).Graphical abstractImage 1
       
  • Tannic acid intermediated surface functionalization of bamboo micron
           fibers to enhance mechanical performance of hybrid GFRP
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Ashangbam Satyavrata Singh, Sudipta Halder, Jialai Wang, Muhammad A. Imam, Peiyuan Chen In this study, tannic acid (TA) mediated surface functionalization of bamboo micron fibers (BMFs) was done through a simple green process and subsequently compared with their counterpart based on silane treatment to use them as reinforcement in the hybrid laminated composite. The surface functionalized BMFs were characterized using XPS to reveal the attachment of the functional ligands. Introduction of TA-treated BMFs (TBMFs) in hybrid glass fiber reinforced plastics (GFRP) improves the σy and E of the composite over GFRP by ~48% and ~55%, respectively. Drastic improvement in flexural properties is also observed mainly attributed to the restriction to microcracks formation and fiber debonding at the inter-ply regions of the GFRP. TA provides a green alternative surface functionalization agent for highly porous natural fibers, making them a low-cost attractive reinforcement used in high-performance hybrid GFRP.Graphical abstractImage 1
       
  • Biomimetic nanocomposite scaffolds based on surface modified
           PCL-nanofibers containing curcumin embedded in chitosan/gelatin for skin
           regeneration
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Azadeh Ghaee, Shadab Bagheri-Khoulenjani, Hamideh Amir Afshar, Hamidreza Bogheiri Recently, nanofibrous-hydrogel composites are luring attention for tissue regeneration applications as they mimic soft-tissues' microstructure. Mostly, the electrospun nanofibers based on synthetic polymers such as Polycaprolactone (PCL) are placed in a crosslinked hydrogels. Due to hydrophobic nature of PCL, integration of these nanofibers with the hydrophilic hydrogels of matrix is not sufficient. In this study, we applied Poly(ethylene glycol) methyl ether methacrylate (PEGMA)-surface-modified PCL nanofibers within chitosan-gelatin hydrogels for skin regeneration applications. In addition, curcumin was loaded into PCL nanofibers due to its great impact on skin regeneration process. Fabricated nanofibrous-hydrogel scaffolds were characterized using scanning electron microscopy (SEM), porosimetery, Fourier transform infrared spectroscopy (FTIR), mechanical compression test, and water uptake studies. Curcumin release was investigated using UV/Vis spectrophotometry. In order to study biocompatibility of scaffolds MTT assay and cell culture was performed using L929 cells. FTIR spectra confirmed PEGMA modification of PCL nanofibers. Results of mechanical test determined that surface modified PCL nanofibers improved mechanical strength and modulus of scaffolds. Porosimetery studies showed proper porosity of scaffolds for skin regeneration from 90.43 to 71.48% and pore size of 101–256 μm. Biological test confirmed proper biocompatibility and good cell attachment to the scaffolds. Taken together, the chitosan/gelatin hydrogel incorporating PEGMA modified PCL nanofibers containing curcumin shows great potential for skin regeneration.
       
  • Lattice structures as thermoelastic strain gradient metamaterials:
           Evidence from full-field simulations and applications to functionally
           step-wise-graded beams
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Sergei Khakalo, Jarkko Niiranen The present work investigates the mechanical and thermomechanical bending response of beam structures possessing a triangular lattice microarchitecture. The validity of generalized continuum models, in general, and the associated dimensionally reduced models for functionally step-wise-graded microarchitectural beams, in particular, is approved by full-field finite element simulations. Most importantly, the necessity of the temperature gradient in the Helmholtz free energy is substantiated. The corresponding strong and weak forms for the associated Bernoulli–Euler and Timoshenko models of functionally graded beams are derived. The effective classical thermoelastic properties of a metamaterial with a triangular lattice microarchitecture are defined by means of computational homogenization. The additional length scale parameter involved in the generalized beam models, and associated to the particular triangular microarchitecture, is calibrated by fitting the mechanical bending responses of a series of lattice beams to the analytical solutions of the corresponding theoretical models. Strongly size-dependent mechanical and size-independent thermal bending responses are observed for both thin and thick beams with triangular lattice microarchitectures. Finally, different lattice beams with varying microarchitectures are introduced and shown to behave as generalized functionally step-wise-graded beams with respect to the higher-order elastic modulus, i.e., the length scale parameter varying in the direction of the beam axis.
       
  • Effect of environmental conditioning on the properties of thermosetting-
           and thermoplastic-matrix composite materials by resin infusion for marine
           applications
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): N.H. Nash, A. Portela, C.I. Bachour-Sirerol, I. Manolakis, A.J. Comer Glass-fibre reinforced polymer (GFRP) laminates were manufactured using Vacuum assisted Resin Transfer Moulding (VaRTM) with a range of thermosetting resins and an infusible thermoplastic resin as part of a comprehensive down-selection to identify suitable commercially available resin systems for the manufacture of marine vessels greater than 50 m in length. The effect of immersion in deionised water and in an organic liquid (diesel) on the interlaminar shear strength (ILSS) and glass transition temperature (Tg) was determined. The thermoplastic had the highest Tg of all materials tested and comparable ILSS properties to the epoxy. Immersion in water, however, caused larger reductions in ILSS properties of the thermoplastic compared to the other systems. SEM showed a transition from matrix-dominated failure in the dry condition to failure at the fibre-matrix interface in the wet and organic-wet specimens. The overall performance of the infusible thermoplastic is good when compared to well-established marine resin systems; however, the environmental performance could be improved if the thermoplastic resin is used in conjunction with a fibre sizing that is tailored for use with acrylic-based resin systems.
       
  • Effects of the graphene nanoplatelets reinforced interphase on mechanical
           properties of carbon fibre reinforced polymer – A multiscale modelling
           study
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Marzena Pawlik, Huirong Le, Yiling Lu Mechanical properties of carbon fibre reinforced polymer (CFRP) are greatly affected by an interphase between fibre and matrix. Coating fibre with nanofillers has been suggested to improve the interphase properties. In this paper, a multiscale modelling framework was developed to investigate how graphene nanoplatelets (GnPs) influence the mechanical properties of CFRP laminate by reinforcing the interphase. At the nanoscale, the Mori-Tanaka homogenisation method was used to determine effective properties of the GnPs reinforced interphase. GnPs reinforced interphase properties at different GnPs orientations, and volume fractions were examined. At the microscale, a 3-D representative volume element (RVE) model based on obtained interphase properties was used to predict the elastic constants of CFRP unidirectional lamina. This RVE model consisted of three phases: carbon fibre, epoxy resin and the GnPs reinforced interphase. The incorporation of GnPs in the interphase increased both longitudinal and transverse lamina moduli. Finally, simulations of the three-point bending test were performed on the macroscale CFRP laminate. The macroscale modelling based on predicted lamina properties was found to reproduce experimentally measured flexural modulus well. It was found that the GnPs coating on fibre has a positive influence on the mechanical properties of CFRP, and the enhancement varied with orientation and local volume fraction of GnPs. In the presence of GnPs coating, 0° and 90° flexural moduli of CFRP laminate increased by 6.1% and 28.3% respectively.
       
  • Experimental study of external bonded CFRP-concrete interface under low
           cycle fatigue loading
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): A. Chalot, L. Michel, E. Ferrier The main problem with carbon fibre reinforced polymers (CFRPs) in reinforcement is the bonding of the reinforcement to the concrete because the failure generally occurs by debonding. In the case of seismic loading, a high level of stress with cyclic loading may appear in the adhesive zone that's why this study focuses on the low-cycle fatigue of a concrete/CFRP interface under a high level of shear stress. It focuses on the influence of the fatigue loading amplitude on the service life (number of cycles prior to failure). This paper presents the results of an experimental campaign conducted on double shear test, an analysis of the failure mechanism, and the development of an analytical model to predict the lifetime of a CFRP/concrete interface. We studied two different CFRPs, one based on a unidirectional textile, composite A, and the other reinforcement based on a bidirectional textile (with a 70/30 ratio), composite B. The results of this study will allow the development of an empirical model based on Wöhler's fatigue law describing the fatigue life of a CFRP-concrete interface as a function of the imposed fatigue loading amplitude. Once validated and enhanced, this empirical model will make it possible to predict and therefore reduce the risk of disbonding.
       
  • Processing cellulose@Fe3O4 into mechanical, magnetic and biodegradable
           synapse-like material
    • Abstract: Publication date: Available online 11 September 2019Source: Composites Part B: EngineeringAuthor(s): Yang Zhang, Jingyu Li, Na Ma, Zhichao Meng, Guoxin Sui Despite of the remarkable progress in effort to fabricate information storage materials in this digital age, it remains a huge challenge to develop the integrated renewable material combining high density magnetic medium, excellent mechanical and biodegradable properties via green and facile method. Synapses on the neurons are a perfect model for efficient mass transport and information transmission by reaction network. Inspired by the morphology of the network structure, we design the synapse-like cellulose@Fe3O4 composites (CFCs). The reactive cores (Fe3O4) are anchored onto the cellulose chains acting as magnetic synapses that impart compact structure for bulk cellulose@Fe3O4 composites (BCFCs) at the interface mediated by hydrogen bonds. Due to the additivity and cooperativity of hydrogen bonds, the BCFCs are prepared via in-situ formation of Fe3O4 NPs on the cellulose chains followed by hot-pressing, leading to high density (∼1.7 g/cm3) magnetic medium, high compressive strength (CS) (∼213.6 ± 3.5 MPa), and excellent biodegradable property. Our work offers a promising strategy to fabricate BCFCs for bio-compatible and military applications, capable to physically vanish at prescribed times once they are no longer needed.Graphical abstractImage 1
       
  • Synthesis of MoS2/MoO3 or P3HT nanocomposites consisting of sandwich-like
           structures via environmental benign supercritical fluid CO2 and its use in
           supercapacitor
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Fitri Nur Indah Sari, Yen-Chun Liu, Jyh-Ming Ting Environmental friendly supercritical fluid CO2 technique has been used to synthesize MoS2/nanobelt MoO3 and MoS2/nanowire Poly(3-hexylthiophene) (P3HT) nanocomposite using commercial MoS2 and P3HT powders, and hydrothermally synthesized MoO3 as the precursor materials. Two unique features are demonstrated. One is that the supercritical fluid CO2 not only transforms the commercial 2H MoS2 into 1T exfoliated MoS2 but also partially oxidizes MoS2 into MoO3-x. The other is that not only nanowires are inserted into layered MoS2 for the first time but also the resulting MoS2/P3HT nanocomposites exhibit a distinctive structure favoring ion transport. More importantly, the unique features lead to reduced electrical resistance due to improved ion and electron transfers. Both MoS2/MoO3 and MoS2/P3HT exhibit significantly improved electrical conductivity with additional redox active sites such that excellent specific capacitance of 39 mF cm−2 and 55 mF cm−2 at 5 mV s−1 in 1 M KCl are obtained for MoS2/MoO3 and MoS2/P3HT, respectively. The results show an enhancement of capacitance by 244% and 423% for MoS2/MoO3 and MoS2/P3HT as compare to exfoliated MoS2, respectively. The MoS2/MoO3 and MoS2/P3HT symmetric cell also show excellent cycle stability up to 114% and 722% after 2000 cycles, respectively.Graphical abstractMoO3 nanobelts and P3HT nanowires were inserted into MoS2 layers for the formation of sandwich-like MoS2/MoO3 or P3HT heterostructures. The resulting single or few layer 1T/2H MoS2, oxygen vacancies MoO3-x, shorten ionic diffusion path between MoS2 layers due to the existence of P3HT, and additional redox active sites from the MoO3 and P3HT all contribute to increase the Csp by 244% and 423% for MoS2/MoO3 and MoS2/P3HT, respectively, as compared to MoS2.Image 1
       
  • Numerical analysis of screw swirling effects on fiber orientation in large
           area additive manufacturing polymer composite deposition
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Zhaogui Wang, Douglas E. Smith Large Area Additive Manufacturing (LAAM) polymer deposition employs a single screw extruder to deliver pelletized feedstock resulting in significantly higher flow rates as compared to conventional filament-based extrusion additive processes. Swirling kinematics in LAAM melt flow that result from the screw rotation generate unique particle alignment patterns within the fiber-filled polymer during deposition processing. This paper investigates the effect of the single screw swirling motion on the resulting fiber orientation in a short fiber polymer composite extrudate. An axisymmetric non-Newtonian viscoelastic flow is simulated with the finite element method, where the flow nearby the extruder screw tip, within the printing nozzle, and a short section of free extrudate compose the flow domain. Fiber orientation tensors within the flow domain are evaluated using the Wang-O’Gara-Tucker Reduced Strain Closure (RSC) fiber orientation diffusion model with the orthotropic fitted closure. The results indicate that swirling kinematics yield a longer flow path for fibers to travel and orientate within the flow domain, yielding orientation tensor results that are notably different as compared to a non-swirl event. The predicted principal elastic constant from the swirling flow and non-swirling flow models exhibit 21% difference, and those from the swirling model using the RSC closure shows a good agreement with reported experimental data for a similar material system.
       
  • Development of carbon coated NiS2 as positive electrode material for high
           performance asymmetric supercapacitor
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Souvik Ghosh, J. Sharath Kumar, Naresh Chandra Murmu, R. Sankar Ganesh, Hiroshi Inokawa, Tapas Kuila Facile synthesis of carbon coated NiS2 composite through one-step hydrothermal process was demonstrated. Three different composites were synthesized (NCC1, NCC2, and NCC3) by changing the stoichiometric ratio of nickel, sulphur and carbon precursor. The particle size and its distribution depend on the amount of carbon precursor and metal sulphides ratio. The carbon coating on metal sulphides significantly augmented the electrochemical properties of the supercapacitor electrodes. It was found that in an optimum ratio of carbon precursor and metal sulphide, the particles were formed uniformly as seen in the NCC2 composites and exhibited the specific capacitance of 2212 F g−1 at a specific current of 2 A g−1 in a three-electrode system. An asymmetric supercapacitor (ASC) device was fabricated with NCC2 as positive electrode and thermally reduced graphene oxide as negative electrode. The ASC device showed high specific capacitance of 184.9 F g−1 at 3 A g−1 and specific energy of 50.35 Wh Kg−1 at a specific power of ~2.26 kW kg−1. It showed ~83% retention in specific capacitance after 6000 charge-discharge cycles. High specific capacitance, specific energy and specific power of the ASC device confirmed that the NCC2 composite could be used as energy storage electrode materials for supercapacitor applications.
       
  • Multiscale stochastic computational homogenization of the thermomechanical
           properties of woven Cf/SiCm composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Ho-Il Choi, Fei-Yan Zhu, Hyungjun Lim, Gun Jin Yun This paper demonstrates a set of two-scale asymptotic computational homogenization formalisms of Cf/SiCm thermomechanical properties and proposes a 3D micro-to-mesoscale stochastic bridging methodology considering the uncertainties of the constituents’ properties and geometries. For multiscale thermomechanical analyses, the thermal conductivity (TC), the coefficient of thermal expansion (CTE) and the elastic stiffness (ES) properties are homogenized at the microscale within the fiber tow. The proposed consistent multiscale bridging method models spatial random fields using the three-dimensional Karhunen-Loève (KL) expansion method with integration with a 3D FE-based computational homogenization model. We compare effects of two different uncertainties (i.e., geometric and spatial material randomness) to statistical variations of the effective thermomechanical properties at the microscale. By comparing with threshold COV values, we determine the thermomechanical properties to be modeled as random fields. At the mesoscale RVEs, we randomize the key twelve thermomechanical properties, perform two-scale computational homogenization and draw statistical variations at the mesoscale.
       
  • Realizing simultaneous improvements in mechanical strength, flame
           retardancy and smoke suppression of ABS nanocomposites from
           multifunctional graphene
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Guobo Huang, Siqi Huo, Xiaodong Xu, Wei Chen, Yanxian Jin, Rongrong Li, Pingan Song, Hao Wang Acrylonitrile-butadiene-styrene (ABS), as one of the most widely used engineering plastics, suffers from the problem of serious flammability and low mechanical strength. To address such an intractable challenge, herein, we report the design of a graphene-based multifunctional additive (Sb-Mo/Br-rGO) via the bromination followed by precipitating antimony molybdenum. The surface functionalization enables Sb-Mo/Br-rGO to homogeneously disperse within the ABS matrix through facile melt-blending. The incorporation of 5 wt% Sb-Mo/Br-rGO leads to a 31% increase in tensile strength and 73% increase in elastic modulus relative to the ABS bulk. In addition to significant enhancement in thermal stability, the inclusion of 5 wt% Sb-Mo/Br-rGO significantly delays the time to ignition of ABS by 12 s, and noticeably reduces the peak heat release rate (PHRR) and total smoke production (TSP) by 45% and 54%, respectively. Such improved performance portfolio is primarily because the mechanical reinforcing and thermal barrier effect of graphene nanosheets, the flame retardant effect of bromine/antimony, and the smoke suppression action of antimony molybdenum. This work provides an innovative methodology for the design of multifunctional additives to create high-performance polymeric materials with high strength and low flammability, thus contributing to improving the quality of life.Graphical abstractImage 1
       
  • Molecular-engineered hybrid carbon nanofillers for thermoplastic
           polyurethane nanocomposites with high mechanical strength and toughness
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Le Li, Lin Xu, Wei Ding, Hengyi Lu, Chao Zhang, Tianxi Liu The development of strong-yet-ductile polymer nanocomposites is critical, but still faces a great challenge. Herein, a hybrid carbon nanofiller consisting of one-dimensional carbon nanotube (CNT) and two-dimensional graphene (G) was molecularly engineered, and the as-prepared G-CNT hybrid nanofiller was then solution-casted with thermoplastic polyurethane (TPU) for the fabrication of TPU nanocomposite films. Due to the formation of unique network structure with multiple interactions of G-CNT hybrid within TPU matrices, the as-fabricated TPU nanocomposites showed simultaneously improved mechanical strength and toughness. With addition of only 1 wt% G-CNT hybrid, the tensile strength and toughness of TPU/(G-CNT) nanocomposite reached 69.5 MPa and 246.2 MJ m−3, 1.9 and 2.9 times over that of neat TPU, respectively. The significant and simultaneous enhancement in mechanical strength and toughness of TPU nanocomposites is attributed to homogeneously distributed G-CNT hybrid and its unique energy dissipations due to factures at different deformation stages upon tensile deformation. The work therefore provides a simple and efficient strategy for fabricating mechanically strong and ductile polymer nanocomposites with molecular-engineered hybrid carbon nanofillers.
       
  • Organic/inorganic hybrid consisting of supportive poly(arylene ether
           nitrile) microspheres and photocatalytic titanium dioxide nanoparticles
           for the adsorption and photocatalysis of methylene blue
    • Abstract: Publication date: Available online 5 September 2019Source: Composites Part B: EngineeringAuthor(s): Xuefei Zhou, Lingling Wang, Xiaocan Liu, Mingzhen Xu, Xiaobo Liu In this work, the hybrid microspheres (B-b-S-P/TiO2) fabricated by immobilizing titanium dioxide (TiO2) on the pre-prepared poly (arylene ether nitrile) (B-b-S-P) microspheres were obtained via sol-gel method. To investigate the comprehensive functionality of B-b-S-P microspheres and TiO2 nanoparticles in dyes wastewater treatment process, four kinds of B-b-S-P/TiO2 hybrid microspheres were fabricated by tuning the content of TiO2 nanoparticles. The achieved microspheres were characterized by several techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) and UV–Vis spectrophotometry (UV–Vis). Results revealed that the B-b-S-P microspheres were efficient in adsorption of MB and the TiO2 nanoparticles were anatase pattern with photocatalytic activity for degradation of MB. The B-b-S-P/TiO2-1 and B-b-S-P/TiO2-2 hybrid microspheres that containing 12.3 wt% and 24.8 wt% TiO2 nanoparticles, respectively, displayed good adsorption efficiency to MB, while the subsequent photodegradations were limited. When TiO2 content was 48.3 wt%, B-b-S-P/TiO2-4 hybrid microspheres tended to aggregate, which not only impeded their adsorption to MB but also decreased the light utilization efficiency in photodegradation stage. As a result, B-b-S-P/TiO2-3 hybrid microspheres containing 40.7 wt% TiO2 nanoparticles made full use of the adsorption advantage of B-b-S-P and photocatalytic superiority of TiO2 nanoparticles. They exhibited the most efficient decolorization performance accompanied by a demethylation reaction.Graphical abstractImage 1
       
  • Functionally graded truncated square pyramid folded structures with foam
           filler under dynamic crushing
    • Abstract: Publication date: Available online 4 September 2019Source: Composites Part B: EngineeringAuthor(s): Zhejian Li, Wensu Chen, Hong Hao Dynamic crushing responses and energy absorption of functionally graded folded structure with foam fillers are investigated in this study. The proposed structure consists of multiple layers of folded truncated square pyramid (TSP) foldcore with foam fillers added inside each unit cells and the interlayer plates to separate each layer of foldcore and its foam filler. The foldcores are folded using pre-patterned thin aluminium sheets. Two types of foam including cubic shape expanded polystyrene (EPS) foam fillers with density of 13.5, 19 and 28 kg/m3 and rigid polyurethane (PU) foam with two shapes. Two sets of functionally graded multi-layer structures are achieved by varying the densities of EPS foam fillers (positively/negatively graded EPS) and varying the shapes of PU foam fillers (positively/negatively graded PU) inside each layer of TSP foldcore. These specimens are then crushed under 1 and 10 m/s. Under 1 m/s crushing, excellent crushing responses as energy absorber are observed for both negatively graded and positively graded multi-layer structures with low initial peak force and low fluctuation in resistance throughout deformation. Under 10 m/s crushing, however, positively graded structures show much more uniform load-displacement response with significantly reduced peak crushing force, increased energy absorption than negatively graded structures. Up to 60% increase in specific energy absorption is shown for folded structure with positively graded PU foam as comparing to the uniform structure without foam filler under 10 m/s crushing.
       
  • Microstructure characterization and thermal performance of reticulated SiC
           skeleton reinforced silica aerogel composites
    • Abstract: Publication date: Available online 4 September 2019Source: Composites Part B: EngineeringAuthor(s): Xinli Ye, Zhaofeng Chen, Sufen Ai, Bin Hou, Junxiong Zhang, Qianbo Zhou, Fei Wang, Hezhou Liu, Sheng Cui The silica aerogel composite reinforced by reticulated SiC skeleton (SiC/CF-Aerogel) was manufactured successfully via the chemical vapor deposition of the SiC coating and sol-gel process of silica aerogel in this paper. The results indicated that the SiC coating was deposited on the carbon skeleton with the induction of silica aerogel in the pores. The mechanical properties were enhanced due to the 3-dimensional reinforcement, which possessed a higher compressive response compared with the pure silica aerogel. Besides, SiC/CF-Aerogel possesses fine adiabatic performance with a thermal conductivity of 0.161 W m−1 K−1 at 700 °C. A physical heat model was proposed to illustrate the heat transfer to better understand the excellent thermal properties. It had a big practical potential for future applications.
       
  • Finite element modelling of the explosive blast response of carbon
           fibre-polymer laminates
    • Abstract: Publication date: Available online 4 September 2019Source: Composites Part B: EngineeringAuthor(s): A. Gargano, R. Das, A.P. Mouritz A finite element (FE) modelling methodology is presented to analyse the dynamic response of carbon fibre reinforced polymer laminates when loaded by the shock wave generated by an airborne explosive blast. An FE model is developed to calculate the out-of-plane deformation of laminates over the entire duration of an explosive blast loading event. The FE model can also predict the initiation and propagation of delamination cracking and ply rupture in laminates. The response of the composite target plates to explosive blast loading was modelled in the FE program Abaqus using an explicit solver. The explosive air blast load was modelled using the ConWep algorithm. The accuracy of the FE model is assessed using experimental data obtained from small-scale far-field and near-field explosive blast tests performed on carbon-polyester and carbon-vinyl ester laminates. The FE model can predict the dynamic deformation of the laminates to within an accuracy of ∼10%. The model can also accurately determine the location and size of delamination cracks and broken plies.
       
  • Deformation-driven metallurgy of graphene nanoplatelets reinforced
           aluminum composite for the balance between strength and ductility
    • Abstract: Publication date: Available online 4 September 2019Source: Composites Part B: EngineeringAuthor(s): Yuming Xie, Xiangchen Meng, Yongxian Huang, Junchen Li, Jian Cao Despite great strengthening potential of graphene nanoplatelets (GNPs) reinforced aluminum matrix composites, sparked with its high performance with extremely low additions of GNPs, the fatal ductility loss of this composites restricts its applications. The key to obtaining the composites with high comprehensive mechanical performance is the uniformly intragranular dispersion of strengthening phase and the ultrafine microstructures. Here, we present a strategy for GNPs reinforced aluminum composites, namely deformation-driven metallurgy. Multiscale nanostructures were achieved with the structure of nano Al2O3 dots-GNPs-aluminum matrix, while the vast majority of GNPs were dispersed inside grains uniformly and formed metallurgical bonding with the matrix. Nano-grained microstructure was obtained by the “negative feedback” controlled low heat input and the isolation of the GNPs during dynamic recrystallization. An enhancement of tensile strength by 317% with only 27% ductility loss was achieved, indicating that the deformation-driven metallurgy could provide a novel design strategy for GNPs reinforced aluminum composites.Graphical abstractImage 1
       
  • Confinement of low-strength concrete with fiber reinforced cementitious
           matrix (FRCM) composites
    • Abstract: Publication date: Available online 3 September 2019Source: Composites Part B: EngineeringAuthor(s): Jaime Gonzalez-Libreros, Mariano Angelo Zanini, Flora Faleschini, Carlo Pellegrino This paper presents the results of an experimental campaign aimed at assessing the effect of varying influencing parameters on the behavior of low-strength concrete prisms confined with fiber reinforced cementitious matrix (FRCM) composites. For this scope, 60 specimens were casted and tested to derive experimental stress-strain curves under monotonic axial loading. The following test variables were adopted: two types of fibers, i.e. carbon and glass fibers; four section geometries, i.e. circular, square and intermediate with two corner radius values (22 and 38 mm); two specimen dimension values, maintaining the same slenderness h/d = 2, but with two height values, i.e. 200 and 300 mm; and lastly, the presence of a pre-existing damage, with two different levels. Stress vs. axial strain and fibers hoop strains were analyzed and results were then discussed in terms of strength gain and ductility, highlighting how carbon and glass fibers jackets improve the confinement of bare specimens. Experimental evidences show how the extent of strength and ductility gains depend on composite type, cross-section geometry and specimen dimension. Also, full strength recovery of damaged specimens was achieved by carbon-FRCM system, whereas this was not possible by means glass fibers-based jackets.
       
  • Co3O4 nanoparticles embedded in 1D porous N-doped carbon nanofibers
           derived from ZIFs for high-capacity sodium-ion batteries
    • Abstract: Publication date: Available online 3 September 2019Source: Composites Part B: EngineeringAuthor(s): Ziwei Yue, Haotian Li, Jingjing Chu, Gaoyang Qu, Chaochao Fu, Xiaowei Li, Ling Li, Xiaoting Li, Wenming Zhang A well-designed material comprising Co3O4 nanoparticles embedded in one-dimensional porous nitrogen-doped carbon nanofibers (Co3O4@NCNFs) is prepared through electrospinning, immersion in a cobalt-containing zeolitic imidazolate frameworks (ZIF-67/ZIF-8) and follows by calcination and oxidation. The resultant sample displays a high discharge capacity of 332 mAh g−1 after 200 cycles at a current density of 100 mA g−1 and an outstanding long-term performance (181 mAh g−1 at 1 A g−1 over 1000 cycles), which is better than the reported high current density for Co3O4-based materials. The excellent electrochemical performance is attributed to the nanostructure comprising Co3O4 nanoparticles homogeneously embedded in nitrogen-doped carbon nanofibers, which can effectively inhibit the aggregation of Co3O4 nanoparticles, accommodate the volume change during charge and discharge processes and provide high electrical conductivity of the electrode. This work provides a facile method to obtain one-dimensional oxide composites with high electrochemical performance using a new metal-organic framework as the sacrificial template.Graphical abstractImage 1
       
  • Solar heat shielding performance of potassium titanate whisker coated
           polypropylene fabric based on a bionic method
    • Abstract: Publication date: Available online 3 September 2019Source: Composites Part B: EngineeringAuthor(s): Songmin Shang, Yuxiang Wang, Ka-lok Chiu, Shouxiang Jiang Inspired by the special whisker-shaped hairs from the Saharan silver ants (SSant), we fabricated a bionic solar heat shielding fabric by coating prismatic potassium titanate whiskers (PTW) with the binder of polyurethane (PU) and polydimethylsiloxane (PDMS) on the polypropylene (PP) fabric. The test results show that the bionic PTW coated fabric can reflect nearly 90% of the solar irradiance, thus effectively reducing the received radiant power. The solar shielding ability of the fabricated fabric is positively correlated with the density of the coated PTW. Under the same conditions, the surface temperature covered by the as-prepared fabric, compared to the uncoated fabric, can be reduced by 21.3 °C. More so, the thermal conductivity, thermal transmittance, the solar heat gain coefficient (SHGC), water repellency and mechanical properties of the coated fabric are also significantly improved. In summary, the bionic PTW coated fabrics possess the similar thermal shielding functions as the silver ant microhairs. This study provides a strategy for bionic designing and development of solar heat shielding fabric.
       
  • Prediction of mechanical properties of carbon nanotube‒carbon fiber
           reinforced hybrid composites using multi-scale finite element modelling
    • Abstract: Publication date: Available online 3 September 2019Source: Composites Part B: EngineeringAuthor(s): Reza Malekimoghadam, Ugo Icardi The mechanical properties of unidirectional carbon nanotube (CNT)‒carbon fiber (CF) reinforced hybrid composites are scrutinized. Due to lack of comprehensive model, a 3D multi-scale model considering debonding damage is developed, covering from nano-to macro-scale. Considering three different configurations of grown CNT's on the fiber surface, the interfacial behavior is investigated. The results reveal that: (Ⅰ) an extraordinary influence of CNT's on the fiber-matrix interfacial properties, particularly in the composites containing axially and randomly oriented CNT's, (Ⅱ) considering two hybrid systems, composites with CNT's‒coated fibers demonstrate outstanding improvements in the interfacial behaviors than those with CNT's in matrix, (Ⅲ) the pronounced effect of non-bonded interphase region on the interfacial properties, while no influence on the Young's moduli is observed, and (Ⅳ) the presence of CNT's augments the transverse Young's modulus, however, it exhibits negligible effect on the longitudinal direction. The outcomes are consistent with experimental data and can be utilized in designing of CNT‒CF multi-scale composites.
       
  • Industrial-waste agave fibres in flame-retarded thermoplastic starch
           biocomposites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Guadalupe Sanchez-Olivares, Sebastian Rabe, Ricardo Pérez-Chávez, Fausto Calderas, Bernhard Schartel Flame-retarded biocomposites of thermoplastic starch and natural fibres are successfully processed according to state-of-the-art extrusion and injection moulding. Using agave fibres and henequen fibres recovered from local industrial waste is a convincing contribution to sustainability. A systematically varied set of biocomposites is investigated comprehensively, e.g. electron microscopy is used for characterizing the morphology, rheology for the melt viscosity, tensile and impact resistance for the mechanical properties, thermal analysis for the pyrolysis, UL 94 burning chamber and oxygen index for the flammability, and cone calorimeter for the fire behaviour. Achieving sufficient mechanical properties was not the goal in our pre-competitive study but may be tackled by adding compatibilizer in future. The combination of well-dispersed natural fibres, aluminium diethylphosphinate (AlPi) and a special silicone synergist (Si) is proposed as promising innovative route for V0-classified biocomposites. The flame-retardancy modes of action in the gas phase (fuel dilution and flame inhibition) and in the condensed phase (charring, protective layer formation) are discussed in detail, as is the role of combining the ingredients. This work is a convincing proof of principle of how to prepare industrial-waste fibres biocomposites, to apply the synergistic combination of AlPi and Si for future flame-retarded technical polymer materials that are based on renewable resources and compostable.
       
  • NIR light manipulated “paper art” for customizing devices with
           sophisticated structure from DA-epoxy/graphene composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Miao-Jie Jiang, Yu Zhang, Gang Wu, Si-Chong Chen, Li Chen, Yu-Zhong Wang Irreversible covalent network in thermosets brings great difficulty to their reprocessing. Especially, customizing devices with sophisticated architecture still remains a challenge. Herein, a novel “paper art” strategy is developed for preparing epoxy-based components or devices with specifically designed structure by introducing dynamic Diels-Alder network and well dispersed Graphene in epoxy matrix. The physical or chemical transitions such as glass transition, reversible dissociation/reconstruction and irreversible dissociation of DA network are spatially and temporally controlled by NIR-triggered in-situ photothermal conversion of GE and therefore served as “folding”, “bonding” and “scissoring”, which are three fundamental operations of “paper art”, respectively. Thus, by setting up the program of these NIR light-manipulated fundamental operations, epoxy resin composite-based devices with designed hierarchical architecture are facilely prepared.Graphical abstractImage 1
       
  • Electrical, thermal and rheological properties of low-density
           polyethylene/ethylene vinyl acetate/graphene-like composite
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Sohrab Azizi, Claudiane M. Ouellet-Plamondon, Phuong Nguyen-Tri, Michel Fréchette, Eric David Composites of low-density polyethylene (LDPE), ethylene vinyl acetate (EVA), and a graphene-like material were explored for their electrical properties for use in high-volume low-cost conductive applications. A graphene-like material, obtained from hybrid clay-sucrose carbonization, was investigated as an alternative filler with advantages over conventional graphene technology. The electrical properties of the composites as synthesized by the solvent–casting technique were studied using broadband dielectric spectroscopy. The percolation threshold was identified for both as synthesized and annealed composite samples. Due to charge transport and electrode polarization, the sub-percolating composites exhibited low frequency dispersion particularly at elevated temperatures. Composites of LDPE/EVA/graphene-like above the percolation threshold exhibited a higher rheological storage modulus and thermal stability which indicates an alignment between the electrical, thermal and rheological properties.Graphical abstractImage 1
       
  • Enhanced mechanical property and flame resistance of graphene oxide
           nanocomposite paper modified with functionalized silica nanoparticles
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Zhi-Ran Yu, Shi-Neng Li, Jing Zang, Ming Zhang, Li-Xiu Gong, Pingan Song, Li Zhao, Guo-Dong Zhang, Long-Cheng Tang Graphene oxide (GO) paper with outstanding integrated multiple functionalities (good mechanical performance, thermal stability and flame resistance, etc.) is strongly needed for numerous potential applications in cutting-edge fields. In this work, we report a facile and green process to fabricate GO-based nanocomposite papers via introducing functionalized silica (f-SiO2) nanoparticles. The results reveal that addition of f-SiO2 produces simultaneous improvements in mechanical strength, stiffness and flame resistance for GO paper. With incorporation of 10 wt% f-SiO2, the tensile strength, elastic modulus and toughness of the GO/f-SiO2 nanocomposite papers can be increased by about 51%, 317%, and 69%, respectively. Various characterizations disclose that hydrogen bonds and covalent interactions between GO sheets and f-SiO2 mainly contribute to the effective load transfer and energy dissipation between them, and thus leading to the improvements of mechanical properties. Based on the structural observation and analysis, the improved flame resistance of the GO/f-SiO2 papers should be attributed to the formation of rGO/SiO2 protective char, which are derived from the decomposition and redeposition of the grafted silane molecules and inorganic SiO2 and thermal reduction of GO into rGO. Our results suggest that the mechanical and thermal properties of GO papers can be tuned by introducing inorganic/organic f-SiO2, providing a new route for the rational designing and development of mechanically flexible and flame-retardant GO-based nanocomposite paper materials.
       
  • Hybrid vibration control of a flexible composite box cross-sectional
           manipulator with piezoelectric actuators
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): L. Malgaca, M. Uyar Robotic arms can be produced from composite materials with different cross-sections due to their lightness and high strength properties. The flexibility of robotic arms affects the vibration behavior of robots in engineering applications. The suppression of vibrations increases the dynamic performance of flexible robots. In this study, hybrid vibration control of a smart composite box manipulator (SCBM) is investigated numerically and experimentally. Hybrid vibration control is achieved using passive control (PC) and active control (AC) techniques. The single-axis epoxy glass SCBM has a layer orientation of [0/90/0/90]. The PC is achieved with a trapezoidal velocity profile. Experiments are conducted to verify the simulation results. For AC, the PID control with displacement and strain feedbacks is applied to the SCBM, which is driven with the cases in the PC for further reducing residual vibrations. Simulations are performed by embedding the hybrid control method into the finite element solutions in ANSYS. Controller gains are initially found by the tuning methods and then optimized according to the maximum actuation voltage. The residual vibrations of the composite manipulator have been successfully suppressed for different payloads. The effectiveness of the hybrid control technique on residual vibration results is investigated.
       
  • Ultra-robust wide-range pressure sensor with fast response based on
           polyurethane foam doubly coated with conformal silicone rubber and CNT/TPU
           nanocomposites islands
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Jaehyuk Lee, Jaehyung Kim, Yujin Shin, Inhwa Jung Highly durable piezo-resistive pressure sensors with excellent repeatability and fast response were developed. The developed sensor have a characteristic of coated with silicone rubber, which has widened pressure measurement range and improved response time. The sensor is capable of measuring pressures lower than 100Pa and higher than 200 kPa and can measure oscillating pressure well above 50 Hz. The sensor showed high repeatability and durability and operated normally after 1000 cycles at 360 kPa applied pressure. The sensor was made by coating polyurethane foam with silicone rubber and further dip-coated with MWCNT dispersed TPU ink. The use of TPU as a binding material helped MWCNT strongly attach to the foam skeleton and reduced the interfacial electrical resistance. As a result, low hysteresis (6.4%) was achieved. By controlling amount of silicone rubber impregnated, the sensitivity can be controlled from 0.013 kPa−1 to 0.032 kPa−1. These sensors were used for measuring both subtle pressures such as the pulse and large pressures such as the pressure beneath a heel. Additionally, wide range of pressure distributions were measured using the array sensors. The economic value of this sensor is tremendous because it can be used in a wide pressure range where high repeatability and fast response are required.Graphical abstractImage 1
       
  • Experimental and analytical study on strengthening of reinforced concrete
           T-beams in shear using steel reinforced grout (SRG)
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Tadesse G. Wakjira, Usama Ebead The use of steel reinforced grout (SRG) has emerged as a promising technique for the strengthening and retrofitting of reinforced concrete (RC) structures, however, the experimental evidence on its application for shear-critical RC beams is rather limited. Accordingly, this study focuses on the structural performance of SRG-strengthened RC beams critical in shear. At this aim, an experimental investigation has been conducted on eleven RC T cross-section beams. Eight beams were strengthened with different types of SRG (different for the density, namely 1.57 and 3.14 cords per centimeter) comprised of ultra-high tensile strength steel fabrics, and three, which were unstrengthened, were used as reference specimens. The test parameters investigated were as follows: (a) steel fabric density, (b) bond scheme, and (c) amount of internal shear reinforcement within the critical shear span, SRG/stirrups interaction. The experimental results revealed the high potential of SRG system for the strengthening of shear-critical RC beams. It has significantly improved the shear capacity and deformation characteristics of the strengthened beams. The percentage increase in the load-carrying capacity over the reference beam of up to 71% was observed. In addition, an analytical model based on the simplified modified compression field theory (SMCFT) has been proposed to predict the shear capacity of SRG-strengthened beams. The SMCFT-based model has resulted in an accurate and safe prediction of the shear capacity of the SRG-strengthened beams with an average ratio of Vth/Vex of 0.92 and a standard deviation of 4.07%.
       
  • Lightweight Fe@C hollow microspheres with tunable cavity for broadband
           microwave absorption
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Zhiming Deng, Yue Li, Hao-Bin Zhang, Yu Zhang, Jia-Qi Luo, Liu-Xin Liu, Zhong-Zhen Yu Lightweight and high-performance microwave absorption materials with wide effective bandwidth are highly required due to the increasingly severe electromagnetic radiation. It is now still imperative to elaborately tune the constituents and microstructures of absorbers for improving microwave absorption capability over wide frequency ranges. Herein, sulfonated polystyrene@Fe(OH)3@polydopamine (SPS@Fe(OH)3@PDA) microspheres are firstly synthesized with ferric sulphate and dopamine as precursors of Fe(OH)3 and amorphous carbon, and then thermally annealed at 600 °C to generate lightweight Fe@C hollow microspheres. The thermal annealing effectively decomposes SPS templates to gases, and carbonizes the PDA shell to amorphous carbon, which also reduces the ferric irons to magnetic Fe nanoparticles via the carbothermal reduction reaction. Interestingly, the microwave absorption performances of the Fe@C hollow microspheres are obviously improved by increasing the cavity sizes. The Fe@C hollow microspheres with the largest cavity of 780 nm exhibit the broadest effective absorption bandwidth of 7.5 GHz and the superior maximum reflection loss of −37.7 dB. These outstanding performances are attributed not only to the favourable synergistic effect of dielectric and magnetic losses, but also to the optimized hollow structure enhancing the attenuation capability and improving impedance matching. This work provides an efficient approach for designing and fabricating high-performance and broad-band microwave absorbers with tunable peak frequency.Graphical abstractLightweight Fe@C hollow microspheres are constructed by synthesizing SPS@Fe(OH)3@PDA microspheres followed by thermal annealing at 600 °C. The Fe@C HS with the largest cavity of 780 nm shows the broadest effective absorption bandwidth of 7.5 GHz and the superior maximum reflection loss of −37.7 dB.Image 1
       
  • Damage detection in self-sensing composite tubes via electrical impedance
           tomography
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): A.J. Thomas, J.J. Kim, T.N. Tallman, C.E. Bakis Fiber reinforced polymer composites are widely used in the automotive, aerospace, and energy sectors owing to their high specific stiffness and strength. With their increasing use, there arises the need to continuously monitor the health of these composites. Current methods of health monitoring in filament wound composites include embedding optical fibers and piezoelectric sensors during the manufacturing process. These methods, in addition to making the manufacturing process difficult, introduce weak spots in the structure. Alternatively, nanofiller modification of the matrix imparts conductive properties to the composite which can be coupled with imaging modalities such as electrical impedance tomography (EIT) for damage localization. To date, however, EIT has been limited exclusively to planar structures such as rectangular coupons. Because such simple shapes are hardly representative of many real composite parts, this work explores the potential of extending EIT to complex shapes for damage detection. Specifically, non-planar multiply connected domains are considered (i.e. carbon black-modified glass fiber/epoxy composite tubes). Our results show that multiple through-holes as small as 7.94 mm can accurately be detected on a tube with length-to-diameter ratio of 132.4 mm-to-66.2 mm (aspect ratio of 2:1). Further, it was observed that the sensitivity of EIT improved with decreasing tube aspect ratio. EIT was also successful in detecting sub-surface damage caused by low-velocity impacts. These preliminary results indicate that the combination of self-sensing via piezoresistivity and EIT has much greater potential and broader applicability for composite structural health monitoring (SHM) than the prevailing, planar geometry-centric state of the art suggests.
       
  • Process optimization and stochastic modeling of void contents and
           mechanical properties in additively manufactured composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Easir Arafat Papon, Anwarul Haque, Sameer B. Mulani The effects of process parameters (print temperature, bed temperature, and print speed) on dimensional accuracy, void contents, and mechanical properties are experimentally investigated for the additively manufactured short carbon fiber reinforced composites. Such studies are carried out at bead, lamina, and laminate levels to identify the process-microstructure-property relationship. Different dimensional parameters such as height, width, and deposition-alignment are monitored for different process parameters at the bead level and its effects on lamina, and laminate are studied in a multi-level manner. The various sources of uncertainties in fused filament fabrication (FFF) based additive manufacturing (AM) are identified, and their adverse effects on microstructure and performance are analyzed. Utilizing the experimentally extracted data for dimensional variability and mechanical property at each level, physical models were adopted to accurately quantify the uncertainty. A non-intrusive polynomial chaos (NIPC) based uncertainty analysis was introduced to improve the computational efficiency and reliability of the physical models. The classical lamination theory (CLT) is used with a slight modification to account for different kinds of voids of short fiber reinforced composites manufactured by FFF. The adjusted process parameters for 5% carbon fiber reinforced polylactic acid (CF/PLA) composite showed minimum dimensional variability and maximum structural performance at a print temperature of 220°C, bed temperature of 80°C, and print speed of 20 mm/s. The maximum dimensional accuracy, minimum void contents, and improved mechanical properties support these optimized processed parameters. These optimized parameters may be related to the viscosity of the material to identify the same parameters for other material systems. The NIPC accurately predicted intra-bead, inter-bead and interfacial-bead voids contents with the overall void contents in the range of 20–26%. All these predicted void contents were incorporated in the CLT to predict the stochastic load distribution of the laminate. The stochastic model closely predicted the laminate properties in terms of axial load distributions which were validated by experimentation of [00]s, [900]s, [450]s, [00/900]s, and [±450]s laminate testing.Graphical abstractImage 1
       
  • Primary and secondary pyroelectric effects in macro-fiber composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Krystal L. Acosta, Siddhartha Srivastava, William K. Wilkie, Daniel J. Inman Materials like the Macro-fiber Composite (MFC) are employed in energy harvesting applications utilizing the piezoelectric effect. However, energy harvesting using the pyroelectric effect in MFCs is an unexplored topic. This paper takes strides in understanding the thermal micromechanical interactions that MFCs experience due to this effect and leads to a better understanding of how MFCs behave in thermal environments. In this work, the pyroelectric coefficient (primary and secondary) are estimated for P1 and P2 Macro-fiber Composites (MFCs) using micromechanical modeling and experimental techniques. The coefficient of thermal expansion (CTE) is estimated using micromechanical theory for both MFC types which is consequently used in the modeling of the pyroelectric coefficient. Secant based moduli are used to better approximate the properties of components of MFCs in the regime of linear elasticity. Two experiments are conducted to measure the pyroelectric coefficient under different boundary conditions. In the first experiment, the thermal expansion of the MFC is constrained in a Kevlar envelope, while in the second experiment, the MFC is epoxied onto a metal shim allowing restricted deformations. Thermal experiments were conducted in an altitude chamber where the resulting average pyroelectric coefficient is calculated for both experiments.
       
  • Novel 3D printing filament composite using diatomaceous earth and
           polylactic acid for materials properties and cost improvement
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Salonika Aggarwal, Shelly Johnson, Daniel Saloni, Marko Hakovirta There are a large variety of different materials currently used for producing 3D printing filaments. In this paper we are investigating the utilization of diatomaceous earth as a potential component for polylactic acid based 3D printing composite materials. The results clearly show that with only minor deterioration of the basic mechanical properties of the 3D printed material at least 10 wt% of the polylactic acid usage can be reduced and replaced by diatomaceous earth. Our thermal analysis also shows nucleation and chain mobility phenomena in the presence of diatomaceous earth particles. The results also show that we are able to engineer 3D printing surfaces with diatomaceous earth protruding from the composite structure and thus allowing us to create high surface area on the 3D printed objects surface. With this research we have shown for the first time an opportunity for cost reduction compared to using pure polylactic acid filaments and a pathway to immobilizing chemical sensing, antibacterial and antiviral agents on 3D printed objects for many applications such as biomedical.
       
  • High performance aramid pulp/carbon fiber-reinforced polybenzoxazine
           composites as friction materials
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Witchukorn Lertwassana, Tewarak Parnklang, Phattarin Mora, Chanchira Jubsilp, Sarawut Rimdusit The objective of this work is to develop aramid pulp/carbon fiber-reinforced polybenzoxazine composites as high performance friction materials. Effects of aramid pulps and carbon fibers on thermal stability, mechanical properties, and tribological performances of the composites are investigated. Aramid pulps could enhance friction coefficient and friction stability of the composites, while thermal stability, mechanical properties, and wear resistance of the composites are improved with an addition of carbon fibers. The composites exhibit high thermal degradation and glass transition temperatures, high and stable friction coefficient, and good wear resistance. The developed polybenzoxazine composites could be applied as non-asbestos organic friction materials.Graphical abstractImage 1
       
  • Effect of adhesive properties on the bond behaviour of externally bonded
           FRP-to-concrete joints
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Jia-Wei Shi, Wen-Hai Cao, Zhi-Shen Wu The influence of adhesive properties on the bond behaviour of externally bonded fibre-reinforced polymer (FRP)-to-concrete joints is the focus of this paper. First, FRP-to-concrete double-lap shear specimens were tested with different types of bonding adhesives. The test results indicate that when softer adhesives are adopted, the peak load, interfacial fracture energy and FRP effective bond length increase while the peak shear stress decreases. Then, a finite element (FE) model including the adhesive layer was proposed to further investigate the influence mechanism of the adhesive properties. A numerical parametric study indicates that the adhesive tensile strength, ultimate strain, elastic modulus and thickness all have varying degrees of impact on the bond behaviour of FRP-to-concrete joints. Finally, a bond-slip model that considers the adhesive elastic modulus is proposed based on experimental and numerical results. To validate this model, a comprehensive test database that includes 128 FRP-to-concrete joints with different adhesives was collected. The proposed model has been shown to have a higher accuracy and lower dispersion than the existing models for the prediction of the peak loads of FRP-to-concrete joints with different adhesives.
       
  • MOF-derived formation of nickel cobalt sulfides with multi-shell hollow
           structure towards electrocatalytic hydrogen evolution reaction in alkaline
           media
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Caiyun Wu, Yunmei Du, Yunlei Fu, Wensi Wang, Tianrong Zhan, Yanru Liu, Yu Yang, Lei Wang In this work, nickel cobalt bimetallic sulfide with typical multi-shell hollow sphere structure behaved superior electrocatalytic activity towards hydrogen evolution reaction (HER), which have been prepared through a easy method included solvothermal step, calcination step and in-situ sulfurization step. The composition and structure of the obtained nickel cobalt bimetallic sulfide are controlled through adjusting the sulfurization temperature and dosage of sulfur source. The as-prepared Ni–Co-S multi-shell hollow microspheres (abbreviated as Ni-Co-S) behaves superb HER properties in alkaline medium and Ni-Co-S-340(60) performs the most superior property, in which reflected the lowest overpotential (129 mV vs. RHE) at the current density of 10 mA cm−2 and the smallest Tafel slope (96.1 mV dec−1) among all the synthesized samples. The superior electrocatalytic performance of the obtained Ni-Co-S-340(60) for HER is owing to the unique multi-shell hollow structure derived from the intrinsic porous character of Ni-Co-BTC MOF precursor in one hand. And in the other hand, introducing highly active NiCo2S4 into NiS2 would enhance its elctrocatalytic activity because of the strong interfacial effect between NiS2 and NiCo2S4.Graphical abstractImage 1
       
  • Degradable, reprocessable, self-healing PDMS/CNTs nanocomposite elastomers
           with high stretchability and toughness based on novel dual-dynamic
           covalent sacrificial system
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Chi Lv, Jinke Wang, Zhongxiao Li, Kaifeng Zhao, Junping Zheng Synthesizing materials that possesses degradability, reprocessability and self-healability simultaneously without compromising stretchability and toughness is considered a huge challenge. In this paper, a pioneering dual-dynamic covalent sacrificial system is exploited for the fabrication of PDMS/CNTs nanocomposite. In the network structure, aromatic disulfide bonds and imine bonds act as sacrificial units and semi-permanent crosslinking points, respectively. The unique design endows the nanocomposite elastomers with high elongation at break (up to 1420%), high toughness (up to 5000 kJ m−3) and good tensile strength (up to 1.10 MPa). Moreover, these mechanical properties can be regulated by varying the chemical composition and CNTs content. Additionally, the nanocomposite elastomers exhibit excellent self-healing efficiency (12 h, 95% of toughness) at ambient temperature and the ability to be processed multiple times. More importantly, the nanocomposite elastomers can be degraded controllably by three ways, achieving the complete recycling of CNTs and PDMS. We believe that our design strategy will provide a new way for the development of green stretchable tough materials used in a sustainable way.Graphical abstractImage 1
       
  • Tunable CoNi microstructures in flexible multilayered polymer films can
           shield electromagnetic radiation
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Injamamul Arief, Yudhajit Bhattacharjee, Om Prakash, Megha Sahu, Satyam Suwas, Suryasarathi Bose This paper highlights the outstanding electromagnetic shielding efficiency achieved by constructing layer-wise assembly of polymer films containing CoNi (cobalt-nickel) micro flowers, rods, and microspheres. Following a hydrothermal approach, various CoNi microstructures were synthesized from their metal salt precursors using wet chemistry followed by dispersing them in a PVDF matrix along with conducting multiwalled carbon nanotubes (MWNT) and subsequently hot-compressing them into thin flexible films (of thickness less than 1 mm). Few films were also prepared by dispersing only MWNTs in PVDF to construct a layer-wise assembly following an approach wherein a reflector spacer (PVDF/MWNT composites) is sandwiched between n (n = 0,1,2,3) absorbers (PVDF/CoNi/MWNT composites). The film thickness was adjusted in such a way that the total thickness of each assembly is ca. 0.9 mm. This strategy wherein a reflecting layer is sandwiched between the absorbing layers resulted in an excellent total shielding efficiency (SET) of −41 dB. By careful control of different layers in this layer-wise assembly, we managed to facilitate significant magnetic losses coupled with conducting losses. Therefore, this paper offers a replacement of conventional metallic shields with unique CoNi-based polymer composites for suppressing EM radiation.
       
  • Using in-situ observation to understand the leaching behavior of Portland
           cement and alkali-activated slag pastes
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Zijian Jia, Ruilin Cao, Chun Chen, Yamei Zhang This paper presents the leaching behavior of hydration products and unhydrated particles in Portland cement (PC) and alkali-activated slag (AAS) systems with a new in-situ observation method. After leaching in NH4Cl solution, obvious decalcification can be found in unhydrated C3S and C2S in PC, while the unhydrated slag keeps stable in AAS. The Ca in the gel of AAS is more vulnerable to leaching than that in PC due to the lack of phases with buffering capability like portlandite. In addition, the Mg–Al layered double hydroxide, which mainly exists in the dark rim of AAS, is not stable in NH4Cl solution. The in-situ observation method proposed in this study provides a new methodology to investigate the leaching behavior of different phases directly and helps to understand the effect of leaching on cementitious materials from a new perspective, it can therefore be used to instruct the design of durable cementitious systems.
       
  • Novel light-driven and electro-driven polyethylene glycol/two-dimensional
           MXene form-stable phase change material with enhanced thermal conductivity
           and electrical conductivity for thermal energy storage
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Xiang Lu, Haowei Huang, Xinya Zhang, Pengcheng Lin, Jintao Huang, Xinxin Sheng, Li Zhang, Jin-ping Qu Novel light-driven and electro-driven polyethylene glycol (PEG)/two-dimensional MXene composite (PEG@MXene) with enhanced thermal conductivity and electrical conductivity as form-stable phase change material (FSPCM) is first obtained via the simple vacuum impregnation by employing MXene as the supporting skeleton as well as thermally conductive and electrically conductive filler and PEG as the phase change working substance. Fourier transform infrared spectroscopy (FT-IR) indicates that no chemical reaction occurred between PEG and MXene during adsorption process, but X-ray diffraction (XRD) results show the crystalline regions of PEG was decreased by the incorporation of MXene. The differential scanning calorimetry (DSC), polarizing microscope (POM), as well as XRD results demonstrate that the MXene nanosheets act as heterogeneous crystal nuclei and promote the crystallization of PEG. The melting and freezing latent heats of PEG@MXene are as high as 131.2 and 129.5 J/g, respectively, the relative enthalpy efficiency is 80.3%, and the thermal conductivity and electrical conductivity are 2.052 W/mK and 10.41 S/m, respectively. The obtained PEG@MXene has excellent light-to-thermal conversion, electro-to-thermal conversion and thermal energy storage performance. All these results demonstrate that the obtained PEG@MXene will have a great potential application for thermal energy storage.Graphical abstractImage 1
       
  • Modification of halloysite nanotubes with supramolecular self-assembly
           aggregates for reducing smoke release and fire hazard of polypropylene
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Sheng Shang, Xiao Ma, Bihe Yuan, Gongqing Chen, Yaru Sun, Chuyuan Huang, Song He, Huaming Dai, Xianfeng Chen A novel nano-clay flame retardant (HNTs@MEL-PA) is prepared by modifying halloysite nanotubes (HNTs) with supramolecular self-assembly technology using melamine (MEL) and bio-based phytic acid (PA) as the building blocks. Transmission electron microscopy images and Fourier transform infrared spectra show that the surface of HNTs is successfully decorated with MEL-PA supramolecular aggregates by hydrogen bonding. The feasibility of using HNTs@MEL-PA as a flame retardant for polypropylene (PP) is explored. Compared with PP/HNTs composites, the dispersion of HNTs@MEL-PA and its interfacial interactions with PP matrix are greatly improved. Heat release of PP is decreased in a certain degree and its smoke release is greatly reduced by HNTs@MEL-PA. With the addition of 15 wt% HNTs@MEL-PA, total smoke production of PP is decreased from 15.7 to 10.2 m2, indicating the greatly improved fire safety. Flame retardant and smoke suppression mechanisms of HNTs@MEL-PA are proposed based on thermal decomposition results and the analysis on char residue.Graphical abstractImage 1
       
  • Effect of comingling techniques on mechanical properties of natural fibre
           reinforced cross-ply thermoplastic composites
    • Abstract: Publication date: 15 November 2019Source: Composites Part B: Engineering, Volume 177Author(s): Habib Awais, Yasir Nawab, Adnan Amjad, A. Anjang, Hazizan Md Akil, M. Shukur Zainol Abidin Continuous natural fibre reinforced thermoplastic composite materials not only offer low weight and better strength than short fibre reinforced composites but are also biodegradable and eco-friendly. The impregnation of resin into the reinforcement is considered as a major concern during the fabrication of thermoplastic composites. Therefore, intermediate materials known as comingled fabrics were developed to assist the fabrication of continuous fibre reinforced thermoplastic composites by aligning the polypropylene fibres alongside the reinforcement natural fibres (jute, hemp and flax) using weaving and knitting techniques. Cross-ply composite panels were fabricated using hot press compression moulding method. The novelty of this work is the simplified methodology to develop the comingled fabrics and the effects of comingling on the mechanical properties of composites. The effect of the comingling technique on the tensile, flexural and impact properties of composites is explained in this research work. Knitted comingled composite specimens exhibit superior mechanical properties than woven comingled composite specimens. The experimental results have shown 14%, 7% and 3% increase in tensile strength, 25%, 20% and 13% increase in flexural strength and 37%, 54% and 44% increase in impact strength of knitted comingled specimens of jute, hemp and flax respectively.
       
  • Influence of stearic acid in zinc based Maleated-EPM ionomer: A novel
           approach towards recyclability
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Sanjay Pal, Kinsuk Naskar In recent decades, the relevance of recyclability and reprocessability of cross-linked elastomers has increased rapidly, especially taking into account that cross-linked elastomers constitute a great mass of non-recyclable and non-biodegradable waste. This research article highlights some key impacts of using stearic acid at different dosage levels in zinc-based maleated ethylene propylene (M-EPM) ionomers. As inferred from several experimental analysis, a relatively small amount of stearic acid (7.5–10 phr) is sufficient to yield similar properties as one would obtain from the high dosage of conventional ionic plasticizer (10–30 phr) in zinc-based M-EPM ionomer system. All samples were easily prepared by a general rubber processing equipments like internal mixer, two-roll mill, electrically heated hydraulic press, etc. Additionally, 7.5–10 phr of stearic acid can make Zn based M-EPM ionomer reprocessable at high temperature (≥150 °C), exhibiting a typical thermoplastic behavior. Samples were studied using general characterization techniques such as, ODR, DMTA, FTIR, AFM, and TEM analysis. A phenomenal ten-fold rise in the tensile strength, and a significant improvement in the hardness (Shore A) values were observed after the addition of 7.5–10 phr of stearic acid in zinc-based M-EPM ionomer system.
       
  • Damage characterization of adhesively-bonded Bi-material joints using
           acoustic emission
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Milad Saeedifar, Mohamed Nasr Saleh, Sofia Teixeira De Freitas, Dimitrios Zarouchas The aim of the present study is to characterize the damage in bi-material steel-to-composite double-lap adhesively-bonded joints using Acoustic Emission (AE). Two different structural adhesives, a ductile (Methacrylate-based) and brittle (Epoxy-based), were used to bond CFRP skins to a steel core. The fabricated joints were loaded in tension while damage evolution was monitored by AE. Due to the difference in the fracture nature of the adhesives “ductile vs. brittle”, different damage mechanisms were observed; including cohesive failure within the adhesive layer, steel deformation, failure at the adhesive/adherends interface (adhesive failure) and delamination in the CFRP skin. To classify these damages by AE, the AE features of each damage mechanism were first obtained by conducting standard tests on the individual constituents. Then, these AE reference patterns were used to train an ensemble decision tree classifier. The best parameters of the ensemble model were obtained by Bayesian optimization, and the confusion matrix showed that the model was sufficiently trained with the accuracy of 99.5% and 99.8% for Methacrylate-based and Epoxy-based specimens respectively. Afterwards, the trained model was used to classify the AE signals of the double-lap specimens. The AE demonstrated that the dominant damage mechanisms in the case of the Methacrylate-based were cohesive and adhesive failures while in the case of the Epoxy-based they were CFRP skin failure and adhesive failure. These results were consistent with the Digital Image Correlation, Fiber Optic Sensor and camera results. This study demonstrates the potential of AE technique for damage characterization of adhesively-bonded bi-material joints.
       
  • Strong and transparent PMMA sheet reinforced with amine functionalized BN
           nanoflakes for UV-shielding application
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Ankita Bisht, Vijayesh Kumar, Palash Chandra Maity, Indranil Lahiri, Debrupa Lahiri Polymer composites with suitable reinforcement can offer UV-shielding ability and strength simultaneously. Such material systems are being researched for many commercial applications, including window shields and automobiles. However, the inherent challenge is retaining transparency, while using reinforcement for adequate strength and UV-shielding. In this study, boron-nitride nanoflakes (BN) were reinforced in poly(methyl-methacrylate) (PMMA) to synthesize a strong and transparent sheet for structures for UV-shielding purpose. BN nanoflakes were amine functionalized and added for a range of content (0.1–3 wt%). Uniform dispersion and strong interfacial interaction led to efficient load transfer from matrix to reinforcement, thus increasing strength and modulus by 155% and 148%, respectively, with 2 wt% BN. UV-B and UV-C shielding properties improved as compared to PMMA for all composition. Addition of 0.5 wt% BN to PMMA offered improvement in blocking UV-wavelength by 325%, along with high transparency of ~65% to visible light.Graphical abstractImage 1
       
  • Machining behavior of multiple layer polymer composite bearing with using
           different drill bits
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Alpay Tamer Erturk, Fahri Vatansever, Eser Yarar, Sedat Karabay The aim of this work is to investigate the drilling behavior of multiple layer orthotropic polyester composite reinforced with woven polyester fiber and PTFE particle. Drilling ability of the synthetic polymer composite bearing material was examined using a drilling system with different drill bits, feed rate, and spindle speed parameters. The investigation was performed by changing the tool and composite interface. Drilling experiments were carried out on two orientations of the composite structure using three types of drill bits. Results show that the tribomechanical behavior of the drilling operation is affected at different levels by tool geometry and coating. This multiscale behavior is related to the intrinsic friction properties of tool design and coating nature that influence the tribologic contact at the interface between the cutting tool edge and composite surface. The ANOVA was used in the evaluation of experiment results. The best results of thrust force, torque, and surface roughness were obtained with HSS Co bit. Drilling of perpendicular direction requires lower thrust force and torque values than the parallel direction to fiber lamination.
       
  • Graphene type dependence of carbon nanotubes/graphene nanoplatelets
           polyurethane hybrid nanocomposites: Micromechanical modeling and
           mechanical properties
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Amir Navidfar, Levent Trabzon Micromechanical modeling and mechanical properties of polyurethane (PU) hybrid nanocomposite foams with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) were investigated by means of tensile strength, hardness, impact strength and modified Halpin–Tsai equation. Three types of GNPs, with varied flake sizes and specific surface areas (SSA) were utilized to study the effect of GNP types on the synergistic effect of MWCNT/GNP hybrid nanofillers. The results indicate a remarkable synergetic effect between MWCNTs and GNP-1.5 (1:1) with a flake size of 1.5 μm and a higher SSA (750 m2/g), which tensile strength of PU was improved by 43% as compared to 19% for PU/MWCNTs and 17% for PU/GNP-1.5 at 0.25 wt% nanofiller loadings. The synergy was successfully predicted using a unit cell modeling, which the calculated values agree with the experimental results.Graphical abstractImage 1
       
  • A mechanistic criterion for the mixed-mode fracture of unidirectional
           polymer matrix composites
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): J. Jamali, M.J. Mahmoodi, M.K. Hassanzadeh-Aghdam, J.T. Wood A mechanistic fracture criterion has been developed to predict the mixed mode through thickness (translaminar) fracture behaviour of unidirectional (UD) polymer composites. This criterion is energy based and is able to predict the toughness of UD composites. The prediction requires only UD composites constituents and interfacial properties. In order to develop the criterion, the through-thickness fracture behaviour of bulk polymer (epoxy) and UD composite (glass fibre epoxy) along with their fracture surface have been investigated. The fracture testing of glass fibre epoxy and neat epoxy under various in-plane loading is performed using compact tension shear (CTS) fixture. The loading ranges from pure mode I to different mixed mode I/II ratios and pure mode II. To consider the energy absorbed during the plastic deformation of reinforced matrix, the fracture surface morphologies of glass epoxy and neat epoxy were investigated which show an increase by the increase in the shear mode. This effect was included in the developed criterion as well. Consequently, the predictions from the criterion show very good match with the CTS experimental results.Graphical abstract(a) Simplified fracture surface morphology of UD composite. Comparison of the size of plastic region in front of crack tip in unreinforced (b) and reinforced (c) polymer. Criterion prediction and experiments comparison of (d) pure epoxy (e) UD composite.Image 1
       
  • Construction of SiO2@UiO-66 core–shell microarchitectures through
           covalent linkage as flame retardant and smoke suppressant for epoxy resins
           
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Wenwen Guo, Shibin Nie, Ehsan Naderi Kalali, Xin Wang, Wei Wang, Wei Cai, Lei Song, Yuan Hu The SiO2@metal organic framework (Universitetet i Oslo-66, UiO-66) core–shell microspheres were constructed through covalent linkage between amine groups in UiO-66-NH2 and epoxy groups on the surface of silica. The morphology and size of the SiO2@UiO-66 core–shell microspheres could be simply controlled by tuning the ratio between UiO-66-NH2 and epoxy terminated silica (E-SiO2). As observed by TEM, the SiO2@UiO-66 hybrids showed better dispersion state within epoxy matrix compared to either E-SiO2 or UiO-66-NH2. The incorporation of SiO2@UiO-66 hybrids slightly promoted the thermal degradation of the resultant epoxy composites but improved residual yield. The dynamic mechanical analysis results indicated that the SiO2@UiO-66 hybrids slightly increased the glass transition temperature and the modulus. The SiO2@UiO-66 hybrids exhibited higher efficiency in reducing the heat release rate and the smoke production rate compared to either E-SiO2 or UiO-66-NH2. The influence of the component ratio in SiO2@UiO-66 on flame retardancy of the epoxy composites was also studied by cone calorimeter. Specifically, the SiO2@UiO-66 hybrid with medium ratio (SiO2@UiO-66-2) exhibited maximum reduction in peak heat release rate (−31%), total heat release (−23%) and total smoke production (−16%). The char residues were investigated by the Fourier transform infrared spectra, scanning electron microscopy and X-ray photoelectron spectroscopy, which demonstrated that the enhanced flame retardancy of EP/SiO2@UiO-66-2 was attributable to the continual morphology and high thermal resistance originated from the presence of the silicon and zirconium complex. These favorable characteristics including high flame retardant efficiency and good smoke suppression make SiO2@UiO-66 hybrids promising for flame retardant polymers application.
       
  • Multi-walled carbon nanotube and carbon nanofiber/ polyacrylonitrile
           aerogel scaffolds for enhanced epoxy resins
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Akram Dourani, Majid Haghgoo, Masood Hamadanian Despite the unique characteristics of carbon nanostructures such as carbon nanotube (CNTs) and carbon nanofibers (CNFs), their practical applications are limited because of their extremely low solubility and poor dispersion characteristics. To obtain composites with favorable electrical, thermal and mechanical properties, a network of nanofiller/polyacrylonitrile (PAN) aerogel was prepared by non-solvent and thermally induced phase separation (NIPS/TIPS) method and used as a scaffold to create epoxy nanocomposite. Compared with the conventional mixing, this method brought about a considerable increase of compressive strength (about 500%). Furthermore, an electrical percolation threshold as low as 0.0028 and 0.019 vol % was observed for CNT/polyacrylonitrile/epoxy nanocomposites (CNT/PA/E) and CNF/polyacrylonitrile/epoxy nanocomposites (CNF/PA/E), respectively. To the best of our knowledge, this small amount of percolation threshold has not yet been reported for CNT and CNF based nanocomposites. Such intriguing performance can mainly be related to a three-dimensional nanotube and nanofiber network structure in the resin matrix.
       
  • Experimental characterization and microscale modeling of isotropic and
           anisotropic magnetorheological elastomers
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Mostafa Asadi Khanouki, Ramin Sedaghati, Masoud Hemmatian In this research, a systematic study is conducted on the sample preparation, characterization and microscale modeling of magnetorheological elastomers (MREs) with isotropic and anisotropic particle distributions. Different MRE specimens with silicone rubber as the matrix material and varying content of carbonyl iron particles as magnetizable fillers are fabricated. The quasi-static properties of the samples are characterized experimentally using an advanced rheometer equipped with a magnetorheological device. The elastic response of the MREs at zero magnetic field is first investigated theoretically and experimentally. A microscale modeling approach is then used for predicting the response of the MREs under an external magnetic flux density. The approach is based on the idealized distribution of particles inside the matrix according to the regular lattice models or chain-like structure for isotropic and anisotropic dispersions, respectively. Several lattice types are proposed, and performance of each lattice is compared with their counterparts. Detailed explanation is provided on the behavior of the proposed lattices and changes in the properties of the MREs are described from the microstructure point of view. The results for different lattice models are then compared with the experimental measurements for both isotropic and anisotropic MRE samples.
       
  • Highly efficient Cu-phthalocyanine-sensitized ZnO hollow spheres for
           photocatalytic and antimicrobial applications
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Hanan H. Mohamed, Inès Hammami, Sultan Akhtar, Tamer E. Youssef This work is focused on in-situ synthesis of a novel composite of Zin oxide (ZnO) and Copper Phthalocyanine (CuPc) as an efficient solar light photocatalyst for water purification. The results of these analyses confirmed the successful preparation of CuPc-sensitized ZnO composite. SEM and TEM analyses revealed the spherical shape of pure ZnO with a bit of agglomeration. Interestingly, the ZnO particles showed the hollow structure when prepared in the presence of CuPc. It is suggested that CuPc takes over the function as structure modifying agent for the formation of hollow spheres of ZnO. The prepared CuPc/ZnO composite was highly efficient and reproducible solar light photocatalyst as compared to pure ZnO, demonstrating the sensitization role of CuPc. In addition, the inhibitory activity of the synthesized nanomaterials was assessed against two multi-drugs resistant bacteria, B. cereus and P. aeruginosa. The results showed a clear inhibitory zone around the pathogenic strains indicating the presence of antibacterial activity against bacterial strain. Antibacterial activity was also investigated in liquid medium in the presence of different nanomaterials under solar light irradiation. The best results were obtained for CuPc/ZnO with better reduction in the number of viable cells. The CuPc/ZnO nanocomposite exhibited bactericidal and not bacteriostatic mode of action. Hence, CuPc/ZnO composite could be considered as a possible alternative for antibiotics. Thus, the current study provides the multifunctional green nanomaterials for water remediation under natural conditions.Graphical abstractImage 1
       
  • Hybrid carbon fiber-carbon nanotubes reinforced polymer composites: A
           review
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Muhammad Razlan Zakaria, Hazizan Md Akil, Muhammad Helmi Abdul Kudus, Faheem Ullah, Fatima Javed, Norlin Nosbi As a result of its impressive 3D network structure form, a great deal of interest has thus been generated among the science community on the hybridization of carbon fiber (CF) and carbon nanotube (CNT). Although there had been a large amount of studies conducted on this novel hybrid material, there are however, limited reviews being published on their fabrication methods and performances in polymer composites. For this reason, apart from collectively introducing and discussing the advantages and limitations of the hybrid CF-CNT based on various fabrication methods such as those of chemical vapour deposition, electrophoretic deposition, electrospray deposition and chemical functionalization, this study had also examined and compared the detailed performances of each of the hybrid CF-CNT reinforced polymer composite based on their fabrication methods through its mechanical, electrical and thermal properties.Graphical abstract[Image 1]
       
  • A review of coir fiber reinforced polymer composites
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Adewale George Adeniyi, Damilola Victoria Onifade, Joshua O. Ighalo, Akorede Samson Adeoye Natural fiber reinforced polymer composites play important roles in the production of eco-friendly materials because of their high modulus, meticulous strength and reduced carbon footprint on the environment. Coconut (cocos nucifera) is cultivated extensively in tropical countries for its fruits whereas the husks and shells are mostly disposed as waste. These portions of the coconut plant serve as potential resource for natural fibers which are used to reinforce polymer composites. This work gives an overview of current knowledge of coir fiber and coir fiber reinforced polymer composites. The preparation and production of different matrices reinforced with coir fibers and the mechanical structural and thermal properties of these composites have been studied by several researchers and are elucidated in this review. The major treatment techniques used to modify coir fibers were also discussed.
       
  • A review on recent advancement of electromagnetic interference shielding
           novel metallic materials and processes
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Dimuthu Wanasinghe, Farhad Aslani The demand for new materials in the field of electromagnetic interference shielding has increased dramatically in the last few decades due to the advancements in the electronics industry. To meet these growing demands, many new materials are being investigated to replace traditionally used metal sheets. Some of the promising materials being researched are polymer-based composites due to their low specific weight, ease of fabrication, and low cost. Some researchers have also looked into the modification and synthetization of new metal-based shielding materials. One of the significant disadvantages of modifying metallic materials is the reduction of their electrical conductivity that adversely affects the shielding effectiveness. Hence, the modifications carried out should be able to maintain the shielding effectiveness at high values while eliminating the shortcomings of metal sheets. In this review article, novel metal-based materials are analyzed for their shielding effectiveness. While some of the materials reviewed in this paper are merely metal-based composites, others consist of more complex additives including metal oxides and carbides. Apart from the shielding effectiveness, this article analyses the variation of other important properties such as electrical conductivity and mechanical properties for a few of these materials.
       
  • Surface-coating engineering for flame retardant flexible polyurethane
           foams: A critical review
    • Abstract: Publication date: 1 November 2019Source: Composites Part B: Engineering, Volume 176Author(s): Haitang Yang, Bin Yu, Pingan Song, Cristian Maluk, Hao Wang Flexible polyurethane foams (FPUFs) have been extensively used in furniture, carpet, automobiles, etc., due to their superior thermal insulation, low bulk density and superior chemical resistant properties. Unfortunately, they are extremely ignitable and flammable, and release a large amount of combustion heat accompanied by plenty of smoke and toxic gases upon ignited, thus posing a potential threat to lives and property. The minimization of their fire hazards is usually realized by the addition of flame retardants, and the creation of flame retardant coating. As compared with the former approach, the surface coating strategy has gained much more interests because it improves the flame retardancy of FPUFs without compromising mechanical properties. To date, several surface-coating approaches, including in situ deposition, sol-gel process, plasma technique and layer-by-layer (LBL) assembly have been developed for improving the fire safety performance of FPUFs. This review focuses on the recent advances in flame retarded FPUFs by employing the surface coating approaches. This work also summarizes the design of intumescent and non-intumesecent fire retardant coatings applied to the fire protection of FPUFs by depositing (nano)coatings on their surfaces. Special attention will be paid to the FPUFs treated with flame retardant nanocoating via the LBL assembly. Moreover, this work further compares the advantages and disadvantages of these surface coating methods, and finally presents some future research opportunities on flame retardant FPUFs materials.Graphical abstractImage 1
       
 
 
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