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Composites Science and Technology
Journal Prestige (SJR): 1.702
Citation Impact (citeScore): 6
Number of Followers: 222  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0266-3538
Published by Elsevier Homepage  [3182 journals]
  • Fabrication of well dispersed poly(vinylidene fluoride)/expanded
           graphite/ionic liquid composites with improved properties by
           water-assisted mixing extrusion
    • Abstract: Publication date: Available online 9 November 2019Source: Composites Science and TechnologyAuthor(s): Jun Tong, Wei Li, Ling-Cao Tan, Hai-Chu Chen Poly(vinylidene fluoride)/expanded graphite/ionic liquid (PVDF/EG/IL) composites are fabricated by a one-step melt mixing extrusion especially with water injection. It is found that the IL helps the EG to be exfoliated and dispersed well in the PVDF matrix especially with water injection, which is confirmed by the results of the scanning electron microscopy micrographs and Wide-angle X-ray diffraction. Thus, the PVDF/EG/IL composites especially with water injection exhibit much higher electrical and thermal conductivities than the PVDF/EG composite. The PVDF/EG/IL composite with loading of 4 wt% EG prepared with water injection exhibits electrical conductivity of about 8.9 × 10−9 S/m, which is almost 6 times higher than the one prepared without water injection and 3 orders higher than the PVDF/EG composite. And the enhancements in the thermal conductivities are 107.7% and 132.8% for the PVDF/EG/IL composites prepared without and with water injection, respectively, which are much higher than those of the PVDF/EG composite. Moreover, the introduced IL especially with better dispersion caused by water injection induces the formation of polar crystals due to the ion-dipole interaction between the ammonium ions of the IL and the C–F dipoles of the PVDF chain.
       
  • Nanocomposite enhanced radiation resistant effects in polyurethane
           Elastomer with low fraction of polydoapmine nanoparticles
    • Abstract: Publication date: Available online 9 November 2019Source: Composites Science and TechnologyAuthor(s): Jiachen Lv, Huazhao Wang, Yu Liu, Jiafu Chen, Hongbing Chen, Jinjiang Xu, Jie Sun, Haixia Zhao, Chunhua Zhu Polyurethane (PU) is a widely used polymer material, but continuous use in radiation environments make it age rapidly. To improve the service life of PU under irradiation, polydopamine nanoparticles (PDAPs) were used as free radical scavengers to prepare PU/PDAPs nanocomposites by the solution casting method. PU/PDAPs nanocomposites with different PDAPs contents were irradiated by 60Co γ-ray. The cross section of pure PU has obvious cracks after radiation at 200 kGy, whereas almost no cracks were observed after addition of only 1% PDAPs. When added to PU in low amounts (1 wt%), polydopamine caused a dramatic increase (by approximately 50 °C) in its corresponding temperature of maximum decomposition rate. Moreover, DTG curves of PU/PDAPs nanocomposites before and after irradiation was almost the same. These results indicated that polydopamine induced thermal stabilization and radiation resistance on PU. The mechanical properties of PU/PDAPs nanocomposites also have a significant improvement even at 200 kGy radiation. The breaking strength of PU increased from 1.48 MPa (pure PU) to 5.48 MPa (5% PDAPs). The elongation at break of pure PU decreased by about 33.9% after being exposed to 200 kGy irradiation, where the PU added with PDAPs increased by approximately 6.5% (1% PDAPs), 3.7% (2.5% PDAPs) and 19.3% (5% PDAPs). The mechanism of radiation resistance of PU/PDAPs nanocomposites is described. Therefore, PDAPs can be used as an effective anti-irradiation filler to improve the life and stability of polyurethane in radiation environment.Graphical abstractPolyurethane/Polydopamine nanoparticles nanocomposites (PU/PDAPs) were fabricated easily by the solution casting method, where radiation resistance was improved effectively by excellent free radical scavenging ability of PDAPs. Additionally, the mechanical properties of PU matrix increased significantly with the increase of PDAPs content after γ ray radiation at 200 kGy (see Figure).Image 1
       
  • 3D printing of optimized composites with variable fiber volume fraction
           and stiffness using continuous fiber
    • Abstract: Publication date: Available online 9 November 2019Source: Composites Science and TechnologyAuthor(s): Kentaro Sugiyama, Ryosuke Matsuzaki, Andrei V. Malakhov, Alexander N. Polilov, Masahito Ueda, Akira Todoroki, Yoshiyasu Hirano In this study, we optimized the curved fiber trajectories to realize variable fiber volume fraction and stiffness composites (VVfSC) using a continuous fiber composite 3D printer. During optimization, the fiber orientation was maintained along the principal stress direction based on preliminary stress field calculations, and the fiber trajectories were subsequently obtained. The fiber volume fraction was calculated from the obtained fiber trajectories; then, stress field calculations and redetermination of the fiber trajectories were performed. Optimization was achieved by repeating this sequence until convergence was obtained. Based on the optimization result, the specimens were molded using a continuous carbon fiber 3D printer and evaluated with bolt joint tensile tests. It was demonstrated that the stiffness and strength per unit weight of the optimized VVfSC were 9.4 and 1.6 times greater than those of conventional linear laminates, respectively.
       
  • Rapid production of few layer graphene for energy storage via dry
           exfoliation of expansible graphite
    • Abstract: Publication date: Available online 5 November 2019Source: Composites Science and TechnologyAuthor(s): Fukun Ma, Liqiang Liu, Xiaolin Wang, Min Jing, Wenjie Tan, Xiaopeng Hao Contrasted with the excellent properties of graphene, searching for an effective industrial production method is still necessary for progressing from the laboratory to commercial applications. This study presents a rapid and mass production method to get large-scale few layer graphene using the expansivity of expansible graphite. Under a suitable thermal treatment temperature (550 °C), the interlayer spacing of expansible graphite can increase sharply, then assisted with simple mechanical crushing, large-scale few layer graphene are obtained. By this dry exfoliation method, we exfoliated expansible graphite into graphene with high quality and structural integrity. The method can be achieved with yield of 93% and the Atomic force microscopy (AFM) results show the nanosheets have a thickness about 2.3 nm. Using the availability of this method, we show the excellent application values of graphene in phase change material (PCM) field for energy storage. This work shows huge potential applications of graphene in many practical fields.
       
  • A constitutive model of the solid propellants considering the interface
           strength and dewetting
    • Abstract: Publication date: Available online 31 October 2019Source: Composites Science and TechnologyAuthor(s): Ming Lei, Jianjun Wang, Jiming Cheng, Jinyou Xiao, Lihua Wen, Haibao Lu, Xiao Hou The solid propellant as a typical viscoelastic composite, consists of oxidizer particles, fuel particles, and polymeric binders. After experiencing the service conditions under complex stress states and temperature cycles, solid propellants would be damaged by the interface dissociation between polymeric binders and oxidizer particles, termed dewetting. The dewetting behaviors would cause combustion instability of solid propellants, and might lead to failure of the rocket motor. To evaluate the health of solid propellants, we introduced a parameter of the normalized crack length to describe the interface dissociation, and developed a physics-based constitutive model. To predict the thermal-mechanical response of solid propellants under complex loading conditions, this model considers the interface strength, the volume relaxation of voids, and the viscoelasticity of polymeric binders. We programmed this model into the finite element software, validated the model by comparing with the experiments, and analyzed the responses at various loading conditions. Towards applications, we modeled the dumbbell-shaped samples in tensile tests and the cylindrical grain under impact loading, and analyzed the damage field. Overall, the developed model can be used to predict the thermal-mechanical responses of solid propellants in the structure level, and to evaluate the state of a solid rocket motor under service.
       
  • A continuum approach for consolidation modeling in composites processing
    • Abstract: Publication date: Available online 31 October 2019Source: Composites Science and TechnologyAuthor(s): Pavel Šimáček, Suresh G. Advani During composite processing, consolidation refers to the application of pressure and/or temperature cycle to the fiber preforms and the uncured liquid resin to increase the fiber volume fraction. The goal is to eliminate voids before the resin solidifies. Consolidation process involves two stages. In the first stage voids are filled and reinforcement compressed due to the application of pressure. Elevated temperatures facilitate this by reducing the viscosity of the resin. In the second stage, the resin cures and the structure solidifies.This paper describes the modeling approach for the first stage of the consolidation process. Governing equations are presented for reinforcement deformation, resin redistribution and porosity evaluation and a semi-implicit numerical scheme well suited to handle complex material models is formulated to track the evolution of part properties during the consolidation process. The applicability of the model is demonstrated with the help of two diverse examples: (1) Consolidation of prepreg facesheets during co-cure of a sandwich panel and (2) Corner consolidation during autoclave processing of a prepreg-based panel. The effects of geometry (such as radius of curvature) and materials (such as initial porosity) are discussed.
       
  • A novel mesoscopic progressive damage model for 3D angle-interlock woven
           composites
    • Abstract: Publication date: Available online 31 October 2019Source: Composites Science and TechnologyAuthor(s): Tao Zheng, Licheng Guo, Jinzhao Huang, Gang Liu In this paper, a novel mesoscopic progressive damage model is proposed to investigate the effective properties and damage mechanisms of 3D angle-interlock woven composites. The damage activation is based on the three-dimensional version of Puck criterion. Given that there may be multiple cracks in the transverse direction of the fiber yarns, a set of fracture angle-dependent damage variables are introduced to eliminate the stress abnormal phenomenon. In addition, an innovative exponential damage evolvement scheme, based on the equivalent displacement and stress, characteristic element length and fracture toughness, is proposed to govern the damage variables. Furthermore, a representative mesoscopic volume cell model, accounting for the fluctuation, distortion and actual cross-section size of fiber yarns, is constructed to represent the realistic interlaced architecture of the woven composites. The anisotropic damage model is applied to investigate the failure behavior of the 3D woven composites subjected to uniaxial tensile loading along the warp and weft directions. Some typical quasi-static tension experiments are performed to validate the accuracy of the simulations. The numerical predictions including failure strength and damage accumulation process are coincident with the corresponding experimental results.
       
  • Matrix and interface cracking in cross-ply composite structural battery
           under combined electrochemical and mechanical loading
    • Abstract: Publication date: Available online 31 October 2019Source: Composites Science and TechnologyAuthor(s): Johanna Xu, Janis Varna In this paper propagation of matrix cracks and debonds at the coating/matrix interface in the 90°-layer of a cross-ply structural composite battery are studied numerically. The structural composite battery consists of micro-battery units, made of a solid electrolyte coated carbon fiber embedded in an electrochemically active polymer matrix. During charging the fiber swells and the matrix shrinks leading to high stresses on the fiber/matrix scale and to anisotropic free expansion of the composite ply. Two load cases are considered, pure electrochemical load (intercalation) and combined electrochemical and thermomechanical load. Energy release rates (ERR) of radial matrix cracks along two potential propagation paths are calculated using 2-D finite element models of the transverse plane in a cross-ply laminate with a square packing of fibers in the 90°-ply and using homogenized 0°-ply. Results show that the matrix crack growth towards the nearest fiber is unstable, and that the debond crack growth is in mixed mode. For a cross-ply structural battery composite the sequence of macro-scale crack forming events differs from a conventional cross-ply composite, as well as for a UD composite battery laminate. The most likely course of failure events in a cross-ply laminate are: 1) vertical radial matrix crack initiation and unstable growth; 2) debond is initiated at certain length of the matrix crack.
       
  • Thermo-mechanical and morphological characterization of needle punched
           non-woven banana fiber reinforced polymer composites
    • Abstract: Publication date: Available online 31 October 2019Source: Composites Science and TechnologyAuthor(s): Jack J. Kenned, K. Sankaranarayanasamy, J.S. Binoj, C. Suresh Kumar The purpose of this study is to employ a novel technique for the fabrication of natural fiber reinforced polymer composites that could stand toe to toe with glass fiber composites in terms of thermo-mechanical properties without any chemical treatment. The reinforcement fibers were extracted from the pseudostem of the nendran banana plant. Later a non-woven fabric composite consisting of banana fibers reinforced with unsaturated polyester (UPE) matrix was fabricated using the needle punching technique. Composite specimens were subjected to tensile, flexural, hardness, quasi-static indentation (QSI) and dynamic mechanical analysis (DMA) test for evaluating mechanical properties. However, the optimal properties was achieved at 40 wt% fiber content with an increase in tensile and flexural strength of 36% and 33% for needle-punched banana fiber composites (NPBFC) compared with random banana fiber composites (RBFC) respectively. It was also evidenced from the load bearing capacity and hardness of NPBFC having 2420 N and 87 HRRW, proves its superiority over RBFC and comparable with RGFC. Further, the viscoelastic properties of UPE and NPBFC were analysed. Subsequently, the characteristic bonds of cellulose were represented through infra-red spectroscopy and the crystallinity index was exposed through X-ray diffraction analysis. In addition, thermal analysis was done and the stability of the optimized NPBFC witnessed was up to 260 °C. Also, morphology-properties correlation was established. Finally, the experimental results were validated using theoretical models. This study concludes that the synthesized novel NPBFC endorses its potentiality as a probable reinforcement in industrial safety helmet, automotive door panel and light weight structural applications.
       
  • Polyethylene/graphene oxide composites toward multifunctional active
           packaging films
    • Abstract: Publication date: Available online 23 October 2019Source: Composites Science and TechnologyAuthor(s): Rodrigo Silva-Leyton, Raúl Quijada, Roberto Bastías, Natali Zamora, Felipe Olate-Moya, Humberto Palza The addition of nanoparticles into a polymer can produce multifunctional films having not only gas barrier and antimicrobial characteristics for active packaging, but also improved mechanical and thermal behaviours. Among the different nanoparticles, graphene oxide (GO) has the potential to develope active polymers due to its layer structure and biocide property. In this study, linear low density polyethylene (LLDPE) was melt mixed with GO nanoparticles having different oxidation and exfoliation degrees. Our results shown that the elastic modulus of LLDPE composites increased with the amount of GO, and by using highly oxidated GO this reinforcement effect was observed without reducing the elongation at break. The thermal stability of the composites under either inert and oxygen atmosphere also increased as compared with the pure matrix. Regarding the barrier properties, the oxygen permeability of the composites depended on the amount and kind of filler, and while GO with low oxidation increased dramatically the permeability of the polymer, highly oxidated GO decreased this value. These results were explained through the Felske model. Water vapor permeation otherwise was not affected by the presence of the nanofillers. The LLDPE/GO nanocomposites further presented antimicrobial behaviour against Salmonella Typhi and Listeria monocytogenes strains. These results confirmed that GO can be designed as an active filler in polymer nanocomposites for packaging applications.
       
  • Improving the open-hole tension characteristics with variable-axial
           composite laminates: Optimization, progressive damage modeling and
           experimental observations
    • Abstract: Publication date: Available online 23 October 2019Source: Composites Science and TechnologyAuthor(s): José Humberto S. Almeida, Lars Bittrich, Axel Spickenheuer This study consists of a numerical and experimental investigation on the unnotched and open-hole tensile characteristics of fiber-steered variable-axial (also known as variable angle-tow and variable-stiffness) composite laminates. The fiber path was obtained from an optimization framework taking manufacturing characteristics of the Tailored Fiber Placement (TFP) technology into account, in which both fiber angle and thickness are locally optimized; besides, unnotched coupons, open-hole specimens with unidirectional fibers, fibers along principal stress directions and with optimized fiber paths were manufactured and tested under longitudinal tensile loading. The tests were assisted by digital image correlation (DIC) to accurately capture the strain and failure behavior. A progressive damage model was then developed to simulate the experimental observations. The notched strength-to-weight (specific strength) of the open-hole coupon with an optimized fiber pattern has a notched strength even higher than the unnotched sample. Optical measurements via DIC and numerical predictions evidenced no strain concentrations around the hole near the final failure for coupons with optimized fiber path, where the reinforcing mechanism alleviated the strain concentrations by redistributing the stress uniformly around the coupon.
       
  • Determining the interphase thickness and properties in carbon fiber
           reinforced fast and conventional curing epoxy matrix composites using peak
           force atomic force microscopy
    • Abstract: Publication date: Available online 22 October 2019Source: Composites Science and TechnologyAuthor(s): Yixin Qi, Dazhi Jiang, Su Ju, Jianwei Zhang, Xin Cui Quantitative analyses of the thickness and properties of the interphase in carbon fiber reinforced resin matrix composites, which play an important role in loading transfer, are essential and intuitive to accurately design the properties of the composites. In this study, to know the distinctions of the interphase between the carbon fiber reinforced fast and conventional curing epoxy matrix composites quantitatively and completely, in addition to modulus map, adhesion map by Peak Force Quantitative Nano-Mechanics technology was newly introduced and applied to determine the interphase thickness and properties. The interphase in the fast curing epoxy matrix composites in modulus image was found to be soft with an average thickness of 20.03 ± 2.04 nm, while it was 40.48 ± 4.17 nm in the conventional curing epoxy matrix composites, and the modulus of the interphase formed a depression between the fiber and the matrix. Consistent with the interphase thickness determined by the modulus, the average interphase thickness in the fast and conventional curing epoxy matrix composites were 19.45 ± 0.68 nm and 41.01 ± 3.98 nm, respectively, based on the adhesion contrast in the interphase, and the adhesion of the interphase reached a peak between the fiber and the matrix. Compared with the conventional curing epoxy matrix composites, the modulus and the adhesion of the interphase changed more sharply in the fast curing epoxy matrix composites. Obviously, numerous distinctions of the interfacial properties existed between the fast and conventional curing epoxy matrix composites.
       
  • Biobased thermoplastic elastomer with seamless 3D-Printability and
           superior mechanical properties empowered by in-situ polymerization in the
           presence of nanocellulose
    • Abstract: Publication date: Available online 20 October 2019Source: Composites Science and TechnologyAuthor(s): Jun Mo Koo, Jaeryeon Kang, Sung-Ho Shin, Jonggeon Jegal, Hyun Gil Cha, Seunghwan Choy, Minna Hakkarainen, Jeyoung Park, Dongyeop X. Oh, Sung Yeon Hwang A biobased and biocompatible thermoplastic elastomer (TPE) with superior 3D printability was demonstrated with great potential for customized manufacturing technologies and fabrication of biointegrated devices. The inherent structural and stereochemical disadvantages of biobased monomers, such as 2,5-furandicarboxylic acid, in comparison with today used petroleum based monomers like terephthalic acid generally lead to lower mechanical performance for the biobased replacement polymers. This is additionally enhanced by poor interfacial adhesion and fusion commonly encountered during customized manufacturing technologies like 3D printing. Herein, we demonstrate that in-situ polymerization in the presence of trace amounts of cellulose nanocrystals (CNCs) can homogeneously distribute the nanofiller leading to dramatically strengthened thermally 3D-printable bio-furan-based TPE. This TPE exhibited a tensile strength of 67 MPa which is 1.5–7-fold higher than the values reported for silicone and thermoplastic urethane, which are widely used in biomedical applications. In addition, the TPE had an impressive extensibility of 860% and negligible in vivo cytotoxicity; such properties have not been reported to date for bio-based or petrochemical TPEs. While a petrochemical 3D printed TPE counterpart retained only half of the tensile strength compared to the hot-pressed analogue, the 3D-printed biobased TPE in-situ modified with nanocellulose maintained 70–80% of its strength under the same experimental conditions. This is explained by inter-diffusion between interfaces facilitated by the nanocellulose and the furan rings. Using the ergonomic shape of a wrist as a 3D-printable design, we successfully manufactured a wearable thermal therapeutic device from the nanocellulose modified biobased TPE, giving promise for wide variety of future applications.
       
  • Polylactide/hemp hurd biocomposites as sustainable 3D printing feedstock
    • Abstract: Publication date: Available online 19 October 2019Source: Composites Science and TechnologyAuthor(s): Xianglian Xiao, Venkata S. Chevali, Pingan Song, Dongning He, Hao Wang Industrial hemp hurd (HH) is emerging as a bio-based filler in thermoplastic biocomposites. In this paper, HH/polylactide (PLA) biocomposites were developed as fused deposition modelling (FDM) feedstock through parametric analysis of the effects of HH loading with respect to melt flow, rheology, physical, thermo-mechanical, and mechanical properties of the biocomposites. Poly (butylene adipate-co-terephthalate) (PBAT) and ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EGMA) were used as toughening and compatibilisation agents respectively in melt-compounding and extrusion to produce FDM filament. The FDM-printed standard samples were compared against corresponding injection-moulded biocomposites. The FDM filament exhibited a diameter tolerance within ±0.02 mm, and roundness variability below 0.03 mm, and the FDM-printed parts with HH loading under 30 phr showed higher impact toughness than the commercial PLA filament control. In addition, the FDM-printed samples exhibited greater dimensional accuracy with increasing HH loading.
       
  • Surface grafting of acrylonitrile butadiene rubber onto cellulose
           nanocrystals for nanocomposite applications
    • Abstract: Publication date: Available online 19 October 2019Source: Composites Science and TechnologyAuthor(s): Emmanuel O. Ogunsona, Prachiben Panchal, Tizazu H. Mekonnen Grafting of carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) to cellulose nanocrystals (CNCs) surfaces was investigated to tailor the properties of CNCs for polymer composite applications. Toluene and dimethyl sulfoxide (DMSO) and their combinations at varying volume ratios were examined as the reaction media with a goal of achieving efficient coupling of the CTBN while maintaining the high crystallinity of CNCs. Fourier transform infrared spectroscopy and nuclear magnetic resonance (+H-NMR) confirmed the grafting of CTBN to the CNCs. Transmission electron microscopic (TEM) analysis revealed that the modified CNCs (mCNCs) was coated with CTBN. Likewise, the dispersion of mCNCs in toluene was observed to be better than in water as observed from TEM. mCNCs with 11.74% coupling efficiency was added to polylactic acid (PLA) via a solvent casting process at 1 and 5 wt%. For the composites containing 1 and 5 wt% of mCNCs, an increase in the tensile strengths of 25% were observed in both cases. Whereas, those containing CNCs exhibited changes of 7 and -12% for concentrations of 1 and 5 wt%, respectively. Interestingly, the modulus remained mostly the same when comparing the mCNCs and CNCs despite the presence of rubber chains on the mCNC. However, increases of ca. 40 and 58% were observed for composites containing 1 and 5 wt% of either CNCs or mCNCs. Results from this study show that CNCs properties can be tailored to improve their dispersion and enhance mechanical properties of polymers.
       
  • Impact response of Kevlar/rubber composite
    • Abstract: Publication date: Available online 17 October 2019Source: Composites Science and TechnologyAuthor(s): Amin Khodadadi, Gholamhossein Liaghat, Hamed Ahmadi, Ahmad Reza Bahramian, Omid Razmkhah This study aims to investigate the impact performance of composite panels consisting of plain-woven Kevlar fabric and rubber matrix. A finite element (FE) model in conjunction with experimental tests was developed to simulate the response of neat fabric and composite under impact loading. Each warp and weft yarn of fabric was individually modeled and combined with rubber matrix network to form the composite. To understand the effect of natural rubber on impact resistance of Kevlar/rubber composites, two types of rubber with different formulation were considered and their mechanical properties were obtained by split Hopkinson pressure bar tests and assigned to the model. Numerical results showed good agreement with the experimental data for both neat fabric and composite. It was shown that rubber matrix improves the ballistic performance of Kevlar fabric by keeping composite flexibility. High hardness rubber matrix composite has higher energy absorption capacity compared to the low hardness rubber matrix composite, due to presence of stronger intermolecular chains. Additionally, deformation and damage mechanism of fabric and composite were investigated under impact loading. The results were presented, discussed and commented upon.
       
  • Conductive graphite nanoplatelets (GNPs)/polyethersulfone (PES) composites
           with inter-connective porous structure for chemical vapor sensing
    • Abstract: Publication date: Available online 17 October 2019Source: Composites Science and TechnologyAuthor(s): Nan Zheng, Ling Wang, Hao Wang, Jiefeng Gao, Xiaoli Dong, Yiu-Wing Mai Conductive polymer composites (CPCs) are good candidates as chemical vapor sensors. However, it is still challenging to develop CPC-based vapor sensors with low percolation thresholds and excellent sensing property (for example, high response intensity, low detection limit and good recyclability). Herein, electrically conductive and porous graphite nanoplatelets (GNPs)/polyethersulfone (PES) composites were prepared using vapor induced phase separation (VIPS) and freeze drying. VIPS was not only responsible for forming the inter-connective porous structure but also promoting the distribution of GNPs on the surfaces of PES skeletons, yielding a low percolation threshold of 0.52 wt%. When the conductive composites were used to detect chemical vapors, the response rate and vapor sensing intensity were controlled by the vapor pressure and the solubility parameters of solvent and polymer. It was found that the response intensities of the composites for saturated vapors of dichloromethane, acetone, tetrahydrofuran and ethanol were ∼8.4 × 103, 5.6 × 102, 10.3 and 3.5, respectively. The detection limit for acetone vapor was as low as 30 ppm. Excellent recyclability for the conductive composites as a chemical vapor sensor was also achieved.
       
  • Quantification of gas permeability of epoxy resin composites with graphene
           nanoplatelets
    • Abstract: Publication date: Available online 17 October 2019Source: Composites Science and TechnologyAuthor(s): Q.J. Zhang, Y.C. Wang, C.G. Bailey, Oana M. Istrate, Zheling Li, Ian Kinloch, Peter M. Budd This paper presents the development and validation of a numerical simulation method using the Lattice Boltzmann Method (LBM) to predict the permeability of epoxy resin (ER) composites with graphene nanoplatelets (GNPs).Gas permeability tests were carried out for a series of GNP/ER nanocomposites with different loadings and diameters of GNPs. The experimental results confirm that inclusion of GNPs in ER significantly decreased the effective gas permeability, with the highest reduction of 66% when the GNP loading was 3 wt%. The effects of using different diameters of GNPs show that using GNPs of 25 μm in diameter achieved less reduction in gas permeability than using GNPs of smaller diameters of 5 and 15 μm at the same loading of 1 wt%. This unexpected result has now been explained by the developed numerical model.The microstructures of GNPs filled ER composites were numerically reconstructed for the relative gas permeability prediction model using LBM. The 3D X-ray CT scan images clearly show agglomeration of GNPs, in particular when the diameter of GNPs is large (25 μm), due to strong van der Waals forces. An agglomeration sub-model was thus incorporated when numerically constructing the microstructure of GNPs filled ER composites. Agglomeration of GNPs results in the formation of a small number of super-thick GNPs, leaving large spaces as ER-rich area without any GNP. This led the GNPs filled ER with 25 μm of GNP diameter to obtain a lower reduction in gas permeability than smaller GNPs filled ER.The results of numerical sensitivity studies on surface area, rotation, curling and folding of GNP flakes suggest that it is acceptable to use flat disk shaped flakes to represent amorphous GNPs with small degrees of deformation (less than 20° and 1.5 for folding angle and curling rate respectively). The results also show that the projection area perpendicular to the overall gas flow direction dominates the overall gas barrier effect of GNPs. The feasibility of using 2D models is demonstrated and it is acceptable to assume that the GNPs in the prepared samples are uniformly sized with a diameter equal to the nominal diameter.This numerical simulation model significantly improves the accuracy for prediction of reduction in gas permeability, over that of existing analytical models, when compared against the authors’ experimental results and experimental data from literature.
       
  • Bio-inspired platelet reinforced elastomeric-ceramic composites for impact
           and high strain rate applications
    • Abstract: Publication date: Available online 17 October 2019Source: Composites Science and TechnologyAuthor(s): Robert G. Crookes, Houzheng Z. Wu, Simon J. Martin, Christopher Kay, Gary W. Critchlow In this paper we introduce a new elastomeric-ceramic platelet composite inspired by the biological structure of nacre. Composites were manufactured through bulk solvent casting methods with high platelet loadings up to 50% by volume. These platelet-containing composites were specifically engineered and optimised for impact and high strain rate applications where the elastomer undergoes a high degree of non-linear strain rate sensitivity. As such, the mechanical properties of these composites were characterised using dynamic testing methods, namely: dynamic mechanical analysis, and the split Hopkinson pressure bar. It was determined that the composite properties are greatly influenced by the matrix-platelet interface strength, consequently, a coupling agent was used to promote interfacial bonding. The resulting optimised composites showed greatly increased high strain rate compressive strength whilst maintaining high toughness, resulting in a six-fold increase in strain energy over the original elastomer. These elastomeric composites are intended for ballistic impact protection, mainly as an alternative to polyurea strike face coatings on steel.
       
  • Highly porous 3D sponge-like shape memory polymer for tissue engineering
           application with remote actuation potential
    • Abstract: Publication date: Available online 16 October 2019Source: Composites Science and TechnologyAuthor(s): Mohadeseh Zare, Nader Parvin, Molamma P. Prabhakaran, Jamshid Aghazadeh Mohandesi, Seeram Ramakrishna Shape memory polymers (SMPs) based on poly(ε-caprolactone) have been recently investigated in biomedical application field owing to their intrinsic biocompatibility, biodegradability and capacity to undergo shape deformation on exposure to external stimuli. Porous SMPUs prepared by electrospinning technique are usually 2D structures not appropriate for cell proliferation. In this study, an attempt has been made to manufacture a 3D SMP scaffold using self-assembly electrospinning and simultaneous photo-crosslinking. A detailed investigation disclosed that suitable crosslinking between SMP chains, conductivity of the solution, and concentration of components play major role in fabricating 3D scaffold. Gold nanoparticles (GNPs) of 10-nm diameter were impregnated in 3D porous structure to cause remote actuation by infrared irradiation or magnetic field application for further studies. Results of scanning electron microscopy and transmission electron microscopy showed a highly porous structure with uniform distribution of GNPs. Sponges had an average porosity of 93±1.8%, demonstrating super-high absorption capacity. Thermal characterization performed using DSC and TGA demonstrated that the switching temperatures of the shape memory composites were near to body temperature and the degradation temperatures of the scaffolds were high enough for thermal stability. Cyclic, thermomechanical tensile tests revealed that the 3D scaffolds had good shape-memory (SM) properties with strain recovery rates of 88–98% and strain fixity rates up to 97% (after the fourth cycle), when deformations were attenuated at the body temperature range. Cytocompatibility evaluation using NIH3T3 cells showed non-toxic behavior suggesting that the GNPs incorporated scaffolds could be employed as 3D scaffolds for bio-applications.Graphical abstractImage 1
       
  • Theoretical modeling the temperature dependent tensile strength for
           particulate-polymer composites
    • Abstract: Publication date: Available online 15 October 2019Source: Composites Science and TechnologyAuthor(s): Ying Li, Weiguo Li, Xi Lin, Mengqing Yang, Ziyuan Zhao, Xin Zhang, Pan Dong, Niandong Xu, Qi Sun, Yuanbo Dai, Xu Zhang, Liming Chen In this work, a temperature dependent tensile strength model for particulate-polymer composites was developed. The combined effects of temperature, particle volume fraction, particle radius, the evolution of interfacial bonding strength and polymer matrix strength with temperature are considered in this theoretical model. It was verified by comparison with the available tensile strength of particulate-polymer composites at different temperatures. Good agreement between the theoretical predictions and experimental results is obtained, which demonstrates the reasonability and applicability of the model. Additionally, we discussed the comparisons between the proposed model and commonly used Pukanszky's model, and performed the influencing factors analysis regarding the temperature dependent tensile strength of particulate-polymer composites in detail. This study offers a reasonable method to predict the tensile strength of particulate-polymer composites at different temperatures, which could replace phenomenological models that do not have predictive capability. Meanwhile, some useful insights concerning the material evaluation, strengthening, and optimization are obtained.
       
  • Fabrication and mechanical behaviors of an all-composite sandwich
           structure with a hexagon honeycomb core based on the tailor-folding
           approach
    • Abstract: Publication date: Available online 15 October 2019Source: Composites Science and TechnologyAuthor(s): Xingyu Wei, Dafu Li, Jian Xiong The tailor-folding method is proposed to make an all-composite sandwich panel with a carbon fiber reinforced polymer (CFRP) hexagon honeycomb core. Using this method, a CFRP honeycomb core with continuous fibers is fabricated automatically from a continuous plain woven prepreg to reinforce the constraints between adjacent cell walls. The analytical expressions were derived for predicting the stiffness and strength of the CFRP hexagon honeycomb sandwich panels for out-of-plane compression and shear loadings. The corresponding failure mechanism maps were also constructed for estimating the dominant failure mode of the honeycomb core, including elastic buckling and fracture under out-of-plane compressive and shear loadings. Selected geometries of the sandwich panels were tested to illustrate these failure modes, with a reasonable agreement between the analytical predictions and experiments. It was observed that the CFRP hexagon honeycomb exhibit good specific energy absorption ability. The tailor-folding method has the potential to provide new opportunities for lightweight multifunctional honeycombs.
       
  • Low-voltage and -surface energy SWCNT/poly(dimethylsiloxane) (PDMS)
           nanocomposite film: Surface wettability for passive anti-icing and
           surface-skin heating for active deicing
    • Abstract: Publication date: Available online 15 October 2019Source: Composites Science and TechnologyAuthor(s): Fangxin Wang, Tong Earn Tay, Yongyang Sun, Wenyan Liang, Bin Yang Icing is a multiphase/multiscale/multiparameter physical process, and is of frequent occurrence when suitable conditions with temperature, pressure and humidity are met. In the present work, we prepared a series of PDMS-matrix nanocomposite films with different SWCNT contents, which were endowed with hydrophobicity based on the low-surface-energy PDMS matrix and the conductivity on the SWCNT filler. Furthermore, by etching the pillar-textured structure on its surface, the nanocomposite with 5.0 wt% SWCNT was given the superhydrophobicity. These nanocomposites can be easily switched from a hydrophobic anti-icing mode to an electro-thermal deicing mode by supplying a low voltage. Using non-contact infrared thermometry, we presented an analysis of the freezing phase transition process of a single water droplet on cooling surfaces with different wettability, and investigated their ice nucleation rate and macroscopic growth velocity on these surfaces. The ice-retarding capability of superhydrophobic nanocomposite surface subjected to lots of condensed droplets was also confirmed, and understanding in light of weak contact interaction with droplets. Also under consideration is the icephobicity after freezing in terms of ice shear strength. In addition, we performed a statistical analysis about the Joule heat distribution on nanocomposite surface, the results of which demonstrated that the nanocomposite could supply a suitable heating function for active deicing, demonstrating with an energy-input deicing experiment subsequently.
       
  • Synchronously oriented Fe microfiber & flake carbonyl iron/epoxy
           composites with improved microwave absorption and lightweight feature
    • Abstract: Publication date: Available online 15 October 2019Source: Composites Science and TechnologyAuthor(s): Hanyi Nan, Yuchang Qing, Hui Gao, Hongyao Jia, Fa Luo, Wancheng Zhou In this study, Fe microfibers (FMF) with a low percolation threshold and flake carbonyl iron (FCI) particles with high complex permeability were filled in an epoxy matrix, and shear force was applied to obtain synchronously oriented microstructures. The effect of the contents of FMF and/or FCI particles on the electromagnetic and microwave-absorbing properties of these composites was investigated in the frequency range of 2–18 GHz. Compared with single component-filled composites, the mixture of FMF and FCI imparted both suitable complex permittivity and enhanced complex permeability to the composite materials. Interestingly, the electromagnetic parameters of the composites could be tailored via simply regulating the ratio of FMF to FCI; thin and light microwave absorbers operating in the broadband range were obtained under the state of low content because of the synergy between the two components and the synchronous orientation of the fillers. An effective absorption of frequencies ranging from 3.5 to 18 GHz with reflection loss 
       
  • Modifications induced in photocuring of Bis- GMA/TEGDMA by the addition of
           graphene nanoplatelets for 3d printable electrically conductive
           nanocomposites
    • Abstract: Publication date: Available online 15 October 2019Source: Composites Science and TechnologyAuthor(s): R. Moriche, J. Artigas, L. Reigosa, M. Sánchez, S.G. Prolongo, A. Ureña The incorporation of nanoreinforcement in photocurable polymeric matrices can strongly affect the degree of curing and properties of the final nanocomposites as well as the process parameters for 3D printing. Particularly, the addition of GNPs in contents from 1 up to 10 wt% limits the degree of curing to 60% in Bis-GMA/TEGDMA. The increase up to 10 wt% causes a diminution of ∼20% in the mentioned property. Additionally, the maximum thickness that can be cured by UV light abruptly decreases with the GNPs content, being ∼400 μm when using 1 wt% and below 20 μm for nanocomposites filled with 10 wt%. Above the percolation threshold, the electrical conductivity of the photocured monolayers is dependent on the curing time, making possible the use of this materials as self-sensor of the degree of curing in additive manufacturing technologies.
       
  • Graphene oxide nanoflakes as an efficient dispersing agent for nanoclay
           
    • Abstract: Publication date: Available online 14 October 2019Source: Composites Science and TechnologyAuthor(s): Mina Abdolmaleki, Morteza Ganjaee Sari, Mehran Rostami, Bahram Ramezanzadeh A lab-synthesized graphene oxide (GO) is utilized as a dispersing agent for nanoclay (NC) in epoxy-phenolic. Various weight ratios of GO/NC as composite particles are prepared. They are used at 1 wt% concentration. Analytical techniques, i.e. X-ray diffraction and thermo-gravimetric analysis are used. The results show the composite particles have obtained greater d-spacing. They certify that GO has been able to cover up the clay lamellae like a surfactant. Mechanical performance is evaluated by both dynamic and static mechanical measurements as well as fracture morphology assessment. The outcomes show the composite particles have been able to simultaneously increase the mechanical strength and fracture energy. Some composite particle-containing samples show an increase of 23.5% in storage modulus, 36.3% in Young modulus and 51% in fracture energy. The fracture patterns likewise show much more scattered paths, an evidence for the enhanced state of dispersion of the composite particles.Graphical abstractImage 1
       
  • Short carbon fibre-reinforced epoxy composite foams with isotropic
           cellular structure and anisotropic mechanical response from liquid foam
           templates
    • Abstract: Publication date: Available online 14 October 2019Source: Composites Science and TechnologyAuthor(s): Wenzhe Song, Georgios Konstantellos, Diyang Li, Koon-Yang Lee In this work, we show that mechanically anisotropic short carbon fibre (sCF)-reinforced epoxy foams with an isotropic cellular structure can be fabricated from liquid foam templates. Short carbon fibres were mechanically frothed in an uncured liquid epoxy resin to produce an air-in-resin liquid foam template, followed by subsequent polymerisation to produce sCF-reinforced epoxy foam with an isotropic cellular structure. Fracture toughness test showed that the incorporation of chopped carbon fibres into epoxy foams led to a significant increase in critical stress intensity factor. It was also observed that neat epoxy foams failed catastrophically whilst sCF-reinforced epoxy foams failed in a progressive manner. Compression test further showed that the in-plane compressive moduli of mechanically frothed sCF-reinforced epoxy foams were significantly higher than their out-of-plane compressive moduli, signifying an anisotropic mechanical response. This anisotropic mechanical response stemmed from the radial flow generated by the high intensity mechanical frothing process, facilitating the preferential orientation of the added chopped carbon fibres in-plane whilst the entrained air bubbles during the mechanical frothing process were in equilibrium with the surrounding uncured liquid epoxy resin, resulting in an epoxy foam with an isotropic (spherical) cellular structure.
       
  • The coupling effect of interfacial traps and molecular motion on the
           electrical breakdown in polyethylene nanocomposites
    • Abstract: Publication date: Available online 14 October 2019Source: Composites Science and TechnologyAuthor(s): Daomin Min, Haozhe Cui, Weiwang Wang, Qingzhou Wu, Zhaoliang Xing, Shengtao Li Low-density polyethylene (LDPE) based nanocomposites are capable of suppressing the accumulation of space charges and enhancing the resistivity and electrical breakdown strength, which are beneficial for the performance and reliability of high voltage direct current power cables. Incorporating nanofillers into polymers can form interfacial regions inside and affect both the trap distribution and molecular motion characteristics, resulting in changes in the dielectric properties of polymer nanocomposites. To unravel the influencing mechanism of interfacial traps and molecular motion on the dc electrical breakdown strength, we investigate the dc electrical breakdown properties of LDPE/Al2O3 nanocomposites as a function of nanofiller loading, pressure, ramping rate of voltage, and sample thickness by experiments and simulations of the charge transport and molecular displacement modulated electrical breakdown. Experimental and simulation results are consistent and show that dc electrical breakdown strength increases firstly and then decreases with the increase of nanofiller loading, increases monotonically with increasing pressure and ramping rate of voltage, and decreases with the increase in sample thickness, obeying an inverse power law. It is indicated that the dc electrical breakdown of LDPE/Al2O3 nanocomposites is triggered by the local current and energy multiplication caused by charge carriers jumping over deep traps when they gain sufficient energy in the enlarged free volume via molecular displacement. It is concluded that both the increase in deep trap energy and the restraint of the motion dynamics of molecular chains with occupied deep traps can enhance the dc electrical breakdown strength of LDPE/Al2O3 nanocomposites.Graphical abstractImage 1
       
  • High performance epoxy-based composites for cryogenic use: A approach
           based on synergetic strengthening effects of epoxy grafted polyurethane
           and MWCNTs-NH2
    • Abstract: Publication date: 10 November 2019Source: Composites Science and Technology, Volume 184Author(s): Liying Jia, Pengfei Qi, Ke Shi, Xin Liu, Wenli Ma, Song Lin, Fei Zhang, Xiaolong Jia, Qing Cai, Xiaoping Yang Synergetic strengthening effects of epoxy grafted polyurethane (EP-PU) and aminated MWCNTs (MWCNTs-NH2) on mechanical performance of EP-based composites at 77 K were systematically investigated using the tested results at room temperature (RT) as comparisons. EP-PU was successfully synthesized by controlling the reaction between –OH in EP and –NCO in PU prepolymer, which showed the advantages of relatively low viscosity and outstanding chemical miscibility with EP matrix. The most obvious enhancements were achieved with contents of 30 wt% EP-PU and 0.2 wt% MWCNTs-NH2 in tensile, flexural, impact and KIC fracture toughness properties of EP composites as well as flexural properties and interlaminar shear strength (ILSS) of carbon fiber (CF)/EP composites at both RT and 77 K, which confirmed the synergetic strengthening effects of EP-PU and MWCNTs-NH2. Specifically, KIC fracture toughness of EP composites and ILSS of CF/EP composites at 77 K were enhanced by 26.0 and 31.4%, respectively, compared with the corresponding neat composites. The EP-PU component showed β or γ relaxation behavior at cryogenic condition and existed in form of scattered micro-spheres in cured EP matrix due to the phase separation. The riveting and bridging of MWCNTs-NH2 around EP-PU micro-spheres were considered to provide extraordinary synergy on the effective stress diversion and crack propagation inhibition at cryogenic condition through establishing the chemically bonded multi-scale interface.
       
  • Simultaneously enhanced thermal conductivity and fracture toughness in
           polystyrene/carbon nanofiber composites by adding elastomer
    • Abstract: Publication date: 10 November 2019Source: Composites Science and Technology, Volume 184Author(s): De-xiang Sun, Qi-qi Bai, Xin-zheng Jin, Xiao-dong Qi, Jing-hui Yang, Yong Wang The common strategy to enhance the thermal conductivity of the polymer composites through increasing filler content usually results in the deterioration of the fracture toughness of the composite articles, which greatly restricts the real engineering application of the composites. In this work, carbon nanofibers (CNFs) and elastomer (styrene-ethylene/butylene-styrene, SEBS) were simultaneously incorporated into polystyrene (PS) through melt-compounding method. The dispersion state of CNFs and the processing flowability of the composites were comparatively investigated. The results show that SEBS tailors the dispersion of CNFs and promotes the formation of CNF assemblages and simultaneously, the processing flowability of the composites is improved to a certain extent. The thermal conductivity of the composites gradually increases with increasing CNF content, and it can be further enhanced by adding SEBS. The PS/20CNF and PS/20CNF/30SEBS composite samples show thermal conductivities of 1.074 and 1.358 W/m·K, respectively, which are 496.6% and 654.5% higher than that of the pure PS sample. Furthermore, incorporating SEBS greatly improves the fracture toughness of the composite samples. For example, the PS/20CNF/30SEBS composite sample shows impact strength of 45.2 kJ/m2, which is 407.9% higher than that of the PS/20CNF composite sample (8.9 kJ/m2). The simultaneously enhanced thermal conductivity and fracture toughness endow the ternary PS/CNF/SEBS composites with great potential applications in the fields relating to heat transfer and mechanical impact.
       
  • Enhanced electrochemical performance of solid PEO/LiClO4 electrolytes with
           a 3D porous Li6.28La3Zr2Al0.24O12 network
    • Abstract: Publication date: 10 November 2019Source: Composites Science and Technology, Volume 184Author(s): Xuelian Fu, Yuchao Li, Chengzhu Liao, Weiping Gong, Mingyang Yang, Robert Kwok Yiu Li, Sie Chin Tjong, Zhouguang Lu Low ionic conductivity and large interfacial impedance between the electrode and electrolyte are the main bottleneck issues of the current solid electrolytes. In this study, a novel 3D hierarchical solid electrolyte was developed to tackle the large interfacial impedance problem. A flexible polyethylene oxide/lithium chlorate (PEO/LiClO4) was in-situ formed inside the 3D porous Li6.28La3Zr2Al0.24O12 (LLZAO) network by simply using a cleanroom wiper as the template. The obtained 3D LLZAO-PEO/LiClO4 composite solid electrolyte exhibited a high ionic conductivity of 2.25 × 10−5 S cm−1 at 30 °C, being 30.7 times higher than that of pristine PEO/LiClO4 electrolyte. The improved ionic conductivity was attributed to the 3D porous LLZAO structure with continuous fast ion transport pathways. In addition, the 3D LLZAO network can effectively inhibited the growth of lithium dendrite, leading to excellent stability and desirable safety during lithium stripping/plating cycling. Furthermore, the all-solid-state LiFePO4/Li battery system based on the obtained 3D LLZAO-PEO/LiClO4 electrolyte showed a high initial discharge specific capacity of 143.8 mAh·g−1 and a high capacity retention of 86% after 200 cycles at 60 °C. This 3D composite solid electrolyte design is very effective in reducing the interfacial impedance and provides a solution for the further development of high-performance solid electrolyte for all-solid-state rechargeable batteries.
       
  • Low-temperature plasma assisted growth of vertical graphene for enhancing
           carbon fibre/epoxy interfacial strength
    • Abstract: Publication date: 10 November 2019Source: Composites Science and Technology, Volume 184Author(s): Zhao Sha, Zhaojun Han, Shuying Wu, Fan Zhang, Mohammad S. Islam, Sonya A. Brown, Chun-Hui Wang The interfacial interaction between fibres and polymer matrix is critical to the mechanical and functional properties of fibre-reinforced composites. In this work vertical graphene (VG) is directly grown on carbon fibres using plasma-enhanced chemical vapour deposition (PECVD) operating at a relatively low-temperature around 400 °C. The VG height is controlled via plasma density that can be controlled by adjusting the distance between the substrate and plasma centre. The effects of VG with different heights on fibre surface roughness, wettability, tensile strength, and interfacial shear strength between carbon fibre and epoxy are investigated. Our results show that grafting VG at 400 °C does not degrade the mechanical strength of the carbon fibres; instead, it improves the interfacial shear strength between the carbon fibre and the epoxy, with the maximum increase in IFSS of ~118.7% at a VG height of ~4.2 μm. This increase can be attributed to the greatly improved surface roughness and the reinforcement effect of vertical graphene surrounding the fibres. The research demonstrates the potential of grafting VG on carbon fibres in improving the mechanical properties of carbon fibre reinforced composites and developing multifunctional hierarchical carbon fibre reinforced composites.
       
  • Graphene and related materials in hierarchical fiber composites:
           Production techniques and key industrial benefits
    • Abstract: Publication date: Available online 11 October 2019Source: Composites Science and TechnologyAuthor(s): Filippo Valorosi, Enea De Meo, Tamara Blanco-Varela, Brunetto Martorana, Antonino Veca, Nicola Pugno, Ian A. Kinloch, George Anagnostopoulos, Costas Galiotis, Francesco Bertocchi, Julio Gomez, Emanuele Treossi, Robert J. Young, Vincenzo Palermo Fiber-reinforced composites (FRC) are nowadays one of the most widely used high-tech materials. In particular, sporting goods, cars and the wings and fuselages of airplanes are made of carbon fiber reinforced composites (CFRC). CFRC are mature commercial products, but are still challenging materials. Their mechanical and electrical properties are very good along the fiber axis, but can be very poor perpendicular to it; interfacial interaction have to be tailored for specific applications to avoid crack propagation– and delamination; fiber production includes high-temperature treatments of adverse environmental impact, leading to high costs. Recent research work shows that the performance of CFRC can be improved by addition of graphene or related 2-dimensional materials (GRM). Graphene is a promising additive for CFRC because: 1) Its all-carbon aromatic structure is similar to the one of CF. 2) Its 2-dimensional shape, high aspect ratio, high flexibility and mechanical strength allow it to be used as a coating on the surface of fiber, or as a mechanical/electrical connection between different fiber layers. 3) Its tunable surface chemistry allows its interaction to be enhanced with either the fiber or the polymer matrix used in the composite and 4) in contrast to carbon fibers or nanotubes, it is easily produced on a large scale at room temperature, without metal catalysts. Here, we summarize the key strategic advantages that could be obtained in this way, and some of the recent results that have been obtained in this field within the Graphene Flagship project and worldwide.
       
  • Maximum deformation of shape memory alloy based adaptive fiber-reinforced
           plastics
    • Abstract: Publication date: Available online 11 October 2019Source: Composites Science and TechnologyAuthor(s): Moniruddoza Ashir, Andreas Nocke, Chokri Cherif In order to simplify and improve the existing kinematic functional range, the elimination of conventional joints and external drives as well as a reduction in the number of gear elements is required. This aim can be achieved by means of adaptive fiber-reinforced plastics (FRPs) due to their lightweight and intrinsic actuator properties. Hence, this research project presents adaptive FRPs including shape memory alloys (SMAs) that were structurally integrated into reinforcing fabrics using the open reed weaving technology. The functionalized preform for the formation of adaptive FRPs was varied by the number of interlacements with weft yarns, SMA length, and thickness ratio. For each variation, a hinged structure was developed in order to realize greater deformation. The adaptive FRPs were characterized thermo-mechanically. Results revealed that the maximum deformation of adaptive FRPs is proportional to SMA length and thickness ratio but inversely proportional to the number of interlacements.
       
  • Predicting the effective thermal conductivity of composites from cross
           sections images using deep learning methods
    • Abstract: Publication date: Available online 11 October 2019Source: Composites Science and TechnologyAuthor(s): Qingyuan Rong, Han Wei, Xingyi Huang, Hua Bao Effective thermal conductivity is an important property of composites for different thermal management applications. Although physics-based methods, such as effective medium theory and solving partial differential equations, are widely applied to extract effective thermal conductivity, recently there is increasing interest to establish the structure-property linkage through machine learning methods. The prediction accuracy of conventional machine learning methods highly depends on the features (descriptors) selected to represent the microstructures. In comparison, 3D convolutional neural networks (CNNs) can directly extract geometric features of composites, which have been demonstrated to establish structure-property linkages with high accuracy. However, to obtain the 3D microstructure in the composite is challenging in reality. In this work, we use 2D cross-section images and 2D CNNs to predict effective thermal conductivity of 3D composites, since 2D pictures can be much easier to obtain in real applications. The results show that by using multiple cross-section images along or perpendicular to the preferred directionality of the fillers, 2D CNNs can provide quite accurate prediction. Such a result is demonstrated with isotropic particle filled composites and anisotropic stochastic complex composites. In addition, we also discuss how to select representative cross-section images. It is found that the average over multiple images and the use of large-size images can reduce the uncertainty and increase the prediction accuracy. Besides, since cross-section images along the heat flow direction can distinguish between serial structures and parallel structures, they are more representative than cross-section images perpendicular to the heat flow direction.
       
  • Assessment of osteogenesis for 3D-printed polycaprolactone/hydroxyapatite
           composite scaffold with enhanced exposure of hydroxyapatite using rat
           calvarial defect model
    • Abstract: Publication date: Available online 10 October 2019Source: Composites Science and TechnologyAuthor(s): Yong Sang Cho, Meiling Quan, Se-Hwan Lee, Myoung Wha Hong, Young Yul Kim, Young-Sam Cho In the polycaprolactone/hydroxyapatite scaffold fabricated by the melting-extrusion-type 3D-printing system, hydroxyapatite (bioceramic) particles are usually covered by a thin-film polycaprolactone (thermoplastic polymer) layer because of the rheological characteristics of the melting-extrusion process. The original bioactive characteristics of the bioceramic particles can be disrupted by this thin-film thermoplastic polymer. Therefore, in this study, an alkaline erosion process was employed to eliminate the thin-film polycaprolactone layer to expose the hydroxyapatite particles. To investigate the influence of the enhanced exposure of hydroxyapatite on cell proliferation and bone regeneration, the polycaprolactone scaffold, polycaprolactone scaffold with alkaline erosion, and polycaprolactone/hydroxyapatite scaffold were compared with the polycaprolactone/hydroxyapatite scaffold with alkaline erosion. Furthermore, to identify the characterization of the 3D-printed composite scaffold for hydroxyapatite's exposure, the morphology, pore size, porosity, mechanical compressive modulus, in-vitro cell proliferation, and in-vivo bone regeneration were assessed. Consequently, the proposed alkaline erosion for the exposure of hydroxyapatite did not change the structural characteristics of the 3D-printed scaffolds, such as the pore size, porosity, and mechanical property. Additionally, we verified that the exposure of hydroxyapatite particles on the scaffold's surface promoted the bone-regeneration ability of the scaffold because of enhanced osteoconduction by hydroxyapatite's exposure.
       
  • Largely enhanced thermal conductive, dielectric, mechanical and
           anti-dripping performance in polycarbonate/boron nitride composites with
           graphene nanoplatelet and carbon nanotube
    • Abstract: Publication date: Available online 10 October 2019Source: Composites Science and TechnologyAuthor(s): Xiuxiu Jin, Jianfeng Wang, Lunzhi Dai, Wanjie Wang, Hong Wu Highly thermal conductive polymer composites synchronously with excellent dielectric and mechanical properties are highly desired in electronic devices. In this work, largely enhanced thermal conductivity (TC), dielectric constant and mechanical property were synchronously realized in polycarbonate (PC) matrix via incorporating boron nitride (BN) together with few graphene nanoplatelets (GnPs) and carbon nanotubes (CNTs). Significantly reduced interfacial thermal resistance between BN and matrix in PC/BN@GnP@CNT composites was the main reason contributed to the largely enhanced TC. By synchronously adding 20 wt% BN (BN-20), 1 wt% GnPs and 1 wt% CNTs, the TC of PC/BN-20@GnP@CNT composites reached up to 1.42 W/mK, enhanced by 647% and 103% compared with that of neat PC and PC/BN-20 composites, respectively. The dielectric constant of PC/BN-20@GnP@CNT reached up to 177 at 100 Hz (enhanced by ∼50-fold compared with PC/BN-20) while the dielectric loss was kept at a low level. Compared with PC/BN-20, the yield strength, elongation at break, fracture toughness and notched impact strength of PC/BN-20@GnP@CNT were enhanced by 42%, 103%, 146% and 8%, respectively. Meanwhile, PC/BN/GnP@CNT composites showed significantly reduced ignitability and remarkable anti-dripping performance. This work promotes an effective, feasible strategy for fabricating dielectric thermal conductive polymer composites with excellent mechanical and anti-dripping performance.
       
  • Mercerization to enhance flexibility and electromechanical stability of
           reduced graphene oxide cotton yarns
    • Abstract: Publication date: Available online 10 October 2019Source: Composites Science and TechnologyAuthor(s): Yong Ju Yun, Hyun Joo Lee, Tae Hyeong Son, Hyeontae Son, Yongseok Jun Graphene-based textiles combining reduced graphene oxide (RGO) nanosheets and cotton textiles such as cotton yarns (CYs) and cotton fabrics show promise as multifunctional electronic textiles (e-textiles) that can be fabricated at reasonable cost by a simple solution process. However, realizing e-textiles with high flexibility and excellent mechanical stability is still challenging. Here, we report a facile strategy for the fabrication of highly flexible and electromechanically stable graphene yarns composed of RGO nanosheets and CYs. More specifically, the fully conformal wrapping of RGO sheets onto the surface of CYs is achieved by combination of conventional mercerization and simple dipping. We optimized the surface chemistry, morphology, and elasticity of the CYs as substrates by conventional mercerization. Using the obtained mercerized CYs, which had a more hydrated surface, round shape, smooth morphology, and good elasticity, we successfully fabricated high-quality graphene yarns. We evaluated the electrical and electromechanical behavior of the RGO-coated mercerized cotton yarns for e-textile and wearable applications. They exhibited a good electrical conductivity of ∼1.0 S/cm, which is approximately 1000 times that of RGO-coated CYs without mercerization, and exceptional flexibility and electromechanical stability under 50,000 bending cycles with a maximum bending radius of 0.5 mm. We successfully demonstrated the potential application of our novel graphene yarns as wearable electronics with a fire/flame sensor. We believe that our process offers an easy approach to improve the flexibility and electromechanical reliability of two-dimensional nanomaterial-based cotton textiles such as fiber, yarn, and fabric than those that might be expected in advanced e-textiles and wearable devices.
       
  • Natural bauxite nanosheets: A multifunctional and sustainable 2D
           nano-reinforcement for high performance polymer nanocomposites
    • Abstract: Publication date: Available online 9 October 2019Source: Composites Science and TechnologyAuthor(s): Omid Zabihi, Mojtaba Ahmadi, Mahmoud Reza Ghandehari Ferdowsi, Quanxiang Li, Seyed Mousa Fakhrhoseini, Roya Mahmoudi, Amanda V. Ellis, Minoo Naebe Synthesis of two dimensional (2D) nanomaterials from natural resources for the fabrication of high performance multifunctional polymer nanocomposites has gained great interest. Herein, we report on a facile method for synthesizing 2D bauxite nanosheets (BNS) directly from its ore using a combination of ball-milling and hydrothermal processes. Successful preparation of the BNS was confirmed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) specific surface area, and particle size distribution. The changes in phases monitored by X-ray diffraction (XRD), before and after ball-milling and hydrothermal treatment, indicated the presence of γ-Al2O3 in the BNS structure. As a promising application, the BNS was introduced into a thermosetting epoxy resin. Thermal analysis and rheological analyses were performed to understand the influence of BNS on the curing and processing of the epoxy matrix. Higher mechanical performance of the epoxy resin reinforced with BNS was achieved and characterized using tensile, flexural, and dynamic thermo-mechanical (DMT) analyses. Thermal stability of the epoxy nanocomposites containing BNS were also evaluated using thermogravimetry analyses (TGA). The overall results indicate that BNS can effectively serve as a cost-effective multifunctional reinforcing agent in fabrication of high performance epoxy nanocomposites.
       
  • Personalized 4D printing of bioinspired tracheal scaffold concept based on
           magnetic stimulated shape memory composites
    • Abstract: Publication date: Available online 8 October 2019Source: Composites Science and TechnologyAuthor(s): Wei Zhao, Fenghua Zhang, Jinsong Leng, Yanju Liu Shape memory polymers (SMPs) can be triggered by an external stimulus to realize the shape changing from temporary shape to its original shape. Due to its biodegradability, easy forming properties and shape memory effect, SMPs have been widely considered in bio-medical applications. This paper details an application of SMP in personalized 4D printing of a bio-designed tracheal scaffold. Compared with the traditional tracheal scaffolds, the SMP tracheal scaffolds can conform to the issue to keep the best fixed state. Moreover, the design of tracheal scaffold based on the microstructure of the glass sponge exhibits higher strength and stability. The distinctive design endows it with the ability to adapt the complex environmental conditions in the soft-tissue of patients. Combined with 4D printing, the bioinspired tracheal scaffold can realize customization in consideration of different size of trachea. The SMP based bio-designed tracheal scaffolds showed excellent performances and were proved to be a potential replacement for the traditional tracheal scaffold.
       
  • Highly thermally conductive and mechanically robust composite of linear
           ultrahigh molecular weight polyethylene and boron nitride via constructing
           nacre-like structure
    • Abstract: Publication date: Available online 8 October 2019Source: Composites Science and TechnologyAuthor(s): Ai Shi, Yue Li, Wei Liu, Jia-Zhuang Xu, Ding-Xiang Yan, Jun Lei, Zhong-Ming Li With the rapid development of modern electronic, developing highly thermally conductive and mechanically strong composites for achieving efficient and reliable thermal management has become an urgent task. In this work, boron nitride/linear-ultrahigh molecular weight polyethylene (LUHMWPE) composites with strong mechanical performance and high thermal conductivity (23.03 W/(mK) were fabricated by solid-state extrusion (SSE) method. The thermal conductivity achieved in this work is the highest for bulk polymer so far. The effects of extrusion draw ratio (EDR) on the morphology, structure, and thermal properties were also investigated. With increase in EDR, the original isotropic structure gradually transforms into nacre-like structure due to the extensive elongational flow field during SSE, accompanied by the augment of thermal conduction performance and mechanical properties. We attribute the high thermal conductivity and mechanical properties to the construction of nacre-like structure, where the h-BN platelets and LUHMWPE molecular chains are highly oriented. Our bioinspired composites have potential applications in thermal management field for modern electronics.
       
  • Carbon nanofiber reinforced Co-continuous HDPE/PMMA composites: Exploring
           the role of viscosity ratio on filler distribution and electrical/thermal
           properties
    • Abstract: Publication date: Available online 7 October 2019Source: Composites Science and TechnologyAuthor(s): Marjan Alsadat Kashfipour, Molin Guo, Liwen Mu, Nitin Mehra, Zhihan Cheng, Jordan Olivio, Sunsheng Zhu, João M. Maia, Jiahua Zhu Double percolation threshold method was used in this work to fabricate conductive polymer blend composites comprising of high density polyethylene (HDPE), poly (methyl methacrylate) (PMMA), and carbon nanofibers (CNFs). Distribution of fillers and their consequent effect on electrical conductivity (EC) and thermal conductivity (TC) is a function of many parameters including viscosity ratio (VR) of polymeric components, which varies with processing temperatures. Here, the effect of VR on the ultimate TC and EC of this polymer blend composite was investigated by blending the components at two processing temperatures of 150 and 230 °C with VR of 3.5 and 0.9, respectively. The obtained results demonstrated more homogeneous distribution of CNFs in the blend with VR of 0.9 while it was mostly aggregated in the blend with VR of 3.5 leading to different TC and EC properties at the same loading of CNF. This means that the composite with higher EC showed lower TC and vice-versa. These phenomena can be explained due to passage of electrons through the filler-matrix interface with tunneling effect, whereas phonons will be scattered at the interfaces. Therefore, although more homogenous distribution of fillers results in improved EC, it is accompanied with formation of more interfacial area and phonon scattering, and less enhancement of TC. This study provides a better understanding of the TC and EC mechanisms, and also the importance of VR in optimization of these properties, which can be applied for fabrication of the desired composites based on their targeted applications.
       
  • Frequency-selective and tunable electromagnetic shielding effectiveness
           via the sandwich structure of silicone rubber/graphene composite
    • Abstract: Publication date: Available online 7 October 2019Source: Composites Science and TechnologyAuthor(s): Gui Wang, Xia Liao, Jianming Yang, Wanyu Tang, Yuan Zhang, Qiuyue Jiang, Guangxian Li Flexible electromagnetic interference (EMI) shielding materials are urgently required considering the rapid development of flexible electronics, such as foldable displays, fast-growing micro-robots, wearable devices, and sealing elements. In this study, a novel flexible sandwich-structured silicone rubber (SR)/graphene composite with a unique feature of frequency-selective EMI shielding effectiveness (SE) and insulation in shielding direction was achieved through the selective localization of graphene at the surface layers of SR. The average and maximum EMI SE values were 30.42 dB and 34.72 dB, respectively, with a graphene content of 3.00 wt%, indicating a 59.60% and 72.39% increase higher than those of their homogenous-structured composite counterparts. In addition, a frequency-selective EMI SE was observed in the sandwich-structured composite, which was ascribed to the Fabry–Pérot cavity resonance. The position of the shielding peak could be tuned by adjusting the thickness of the interlayer and graphene content in the surface layers. Moreover, it has been confirmed that the insulation of the interlayer is necessary for the appearance of the shielding peak. The flexible EMI shielding materials designed in this study will benefit the booming production of flexible electronic devices and offer a promising strategy for fabricating new-generation EMI shielding materials with frequency-selective and tunable EMI SE.
       
  • Interfacial microstructure and mechanical properties of carbon fiber
           composite modified with carbon dots
    • Abstract: Publication date: Available online 5 October 2019Source: Composites Science and TechnologyAuthor(s): Caixia Chu, Heyi Ge, Nianliang Gu, Kaili Zhang, Chaosheng Jin The weak interfacial adhesion between carbon fiber (CF) and resin matrix is an urgent problem that researchers have been attempting to ameliorate. Sizing can effectively improve the interfacial adhesion between CF and resin matrix, which is extensively used in CF industrial preparation process. In this study, a novel simple two-step sizing method was adopted to improve the interfacial properties of the CF/epoxy (CF/EP) composite. The CF was initially covered by carbon dots (CD). Subsequently, the sizing agent (SD) was more evenly sized on the CF surface by the bridge of CD. The sized CF was characterised by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The interface of the CF composite was characterised by SEM and atomic force microscopy (AFM). The results show that CF-CD-SD/EP exhibited good interfacial adhesion due to the synergistic effect of CD and SD. The interlaminar shear strength (ILSS) value of the resulting composite increased by 16.21% and 38.49% when compared with those of CF-SD/EP and desized CF/EP, respectively. This method has potential applications in the CF industry.
       
  • Multi-scale interphase construction of self-assembly
           naphthalenediimide/multi-wall carbon nanotube and enhanced interfacial
           properties of high-modulus carbon fiber composites
    • Abstract: Publication date: Available online 5 October 2019Source: Composites Science and TechnologyAuthor(s): Jiawei Lin, Peng Xu, Lili Wang, Yuhang Sun, Xin Ge, Gang Li, Xiaoping Yang Amino terminated and π-conjugate naphthalenediimide (NDI) was designed and novel interphase with self-assembled NDI/multi-wall carbon nanotube (MWNT) was constructed on high-modulus carbon fiber (HMCF) surface, and the interfacial properties and reinforcing mechanisms of HMCF composites with various interphase were investigated. The nanoscale stiffening interphase with intertwined MWNT and flat ensiform nanostructure from NDI self-assembly were observed on MWNT@HMCF and NDI@HMCF surface, while multi-scale stiffening interphase with oblique ensiform nanostructure was constructed on NDI/MWNT@HMCF surface which was based on NDI self-assembly under confinement constraint of MWNT substrate. Compared to Pristine HMCF and MWNT@HMCF composites, the TFBT strength and IFSS of NDI@HMCF and NDI/MWNT@HMCF composites were improved by effective buffered load from stiffened interphase and smooth transition of modulus between carbon fiber and epoxy matrix. The schematic models of interphase reinforcing mechanisms were proposed as bulk failure in NDI@HMCF composite and cohesive failure in NDI/MWNT@HMCF composite, which were attributed to the shift of stress concentration and crack propagation from HMCF surface toward modulus platforms amongst nanoscale and multi-scale stiffening interphase.
       
  • A facile fabrication of polypropylene composites with excellent
           low-temperature toughness through tuning interfacial area between matrix
           and rubber dispersion by silica nanoparticles located at the interface
    • Abstract: Publication date: Available online 4 October 2019Source: Composites Science and TechnologyAuthor(s): Erwen Jia, Shunjie Zhao, Yonggang Shangguan, Qiang Zheng In order to fabricate super low-temperature tough polymer composites which can withstand extreme environments, hydrophobic silica nanoparticles were incorporated into polypropylene/ethylene propylene rubber (PP/EPR) blends with the hope to tailor the brittle ductile transition temperature (Tbd). Compared with PP/EPR blends, PP/EPR/SiO2 composites presented much lower Tbd, and Tbd decreased with the increase of EPR content and SiO2 content. It was found that PP/EPR/SiO2 composites could present excellent low-temperature toughness with little rigidity loss. Phase morphology showed that the silica nanoparticles were located at the interface of PP and EPR. It was found that silica nanoparticles at the interface could not only suppress the phase coarsening in PP/EPR/SiO2 composites greatly, but also tailor the shape of rubber particles. A detailed investigation on rubber particle size, interparticle distance and interfacial area indicated that the tremendous drop of Tbd should be ascribed to the increased interfacial area between the matrix and rubber phase due to the decreased size and more irregular shape of rubber particles. As a result, a quantitative correlation between Tbd and interfacial area in PP/EPR/SiO2 composites was established. This study provided a facile approach to fabricate polymer composites with super low-temperature toughness or other functions through tuning the size and shape of rubber domains by adding nanoparticles.Graphical abstractPolypropylene composites with excellent low-temperature toughness and slight rigidity loss were prepared through tuning the size and shape of rubber dispersion by nanoparticles located at the interface between PP and EPR phase. Subsequently the quantitative correlation between brittle ductile transition temperature and interfacial area was proposed for PP/EPR/SiO2 composites to describe toughening at low-temperature.Image 1
       
  • Comparing non-destructive 3D X-ray computed tomography with destructive
           optical microscopy for microstructural characterization of fiber
           reinforced composites
    • Abstract: Publication date: Available online 2 October 2019Source: Composites Science and TechnologyAuthor(s): Imad Hanhan, Ronald Agyei, Xianghui Xiao, Michael D. Sangid Due to their lightweight, relatively high stiffness properties, and formability into complex shapes, discontinuous fiber composites are advantageous for producing small and medium size components. Improved characterization techniques and post-processing methodologies are required for more reliable quantification of the microstructure and defect distributions in these materials, in order to employ model-based approaches to assess their structural integrity. This work compares a non-destructive X-ray approach with a destructive optical microscopy approach for characterizing the microstructural attributes, specifically the fiber volume fraction, porosity volume fraction, fiber orientation distribution, and fiber length distribution of discontinuous glass fibers in a polypropylene matrix. Additionally, a method for destructively determining the ambiguous components of the orientation tensor (related to the sign ambiguity of the out-of-plane angle in a destructive cross-sectional cut of a fiber) over a large surface area is included. It was found that fiber volume fraction and average fiber aspect ratio matched well, while fiber orientation and porosity detection had small but notable differences. The differences in the detection capabilities of each technique are quantified and discussed shedding light on the specific advantages and disadvantages of each approach, and enabling engineers to quantify uncertainty in their microstructural characterization measurements especially as they relate to model based structural integrity activities.
       
  • Graphene-based Polymer Composite Films with Enhanced Mechanical Properties
           and Ultra-high In-plane Thermal Conductivity
    • Abstract: Publication date: Available online 30 August 2019Source: Composites Science and TechnologyAuthor(s): A.A. Tarhini, A.R. Tehrani-Bagha Graphene has very high electrical and thermal conductivities and thus is a promising candidate for use as a filler to enhance the conductivity of polymer composites. The main challenge is properly dispersing and aligning graphene nanoflakes (GNFs) within a polymer matrix. We report here a simple and scalable solution mixing and molding process to make such a composite film. These films were analyzed using SEM, ATR-FTIR, XRD, DSC, and TGA. An optical tensiometer and a laser flash analyzer were used to measure the water contact angle and in-plane thermal diffusivity of the films, respectively. The poly(vinylidene fluoride-co-hexafluoropropylene) composite films had an in-plane thermal conductivity (κ) that reached a new record of ∼25 W m-1 K-1 at a GNF concentration of 20 wt%. The presence of GNFs had a noticeable effect on the surface morphology, crystal structure, and hydrophobicity of the polymer matrix. The tensile strength and Young’s modulus of the composite films increased by the addition of GNFs up to 20 wt%. The composite films showed very high electrical conductivity due to the presence of highly conductive graphene layers. This manufacturing process ensured the in-plane orientation of graphene layers, which allowed the transport of phonons and electrons through the composite films.
       
  • Shear-pressure multimodal sensor based on flexible cylindrical pillar
           array and flat structured carbon nanocomposites with simple fabrication
           process
    • Abstract: Publication date: Available online 30 September 2019Source: Composites Science and TechnologyAuthor(s): Changyoon Jeong, Hangil Ko, Hoon Eui Jeong, Young-Bin Park Measuring shear displacement and pressure simultaneously is essential for various applications, such as tactile sensors for robotic finger tips, shoe soles for gait monitoring, etc. We present a simple means of transducing shear displacement and pressure change to flexible composite sensor. The presented sensor consists of an array of cylindrical pillars standing on a flat substrate, which is composed of carbon nanotubes (CNTs) and polydimethylsiloxane. The sensing mechanism is based on changing CNT network in pillar and flat structure under shear and pressure. When a shear displacement change occurs in the pillar array, which transfers shear and pressure to flat structure in the sample, the CNT network in the sample is changed due to bending of the pillars. Under pressure, the load is transferred from the pillar array to flat structure inducing changes in relative resistance. Load transfer through this hierarchical structure enabled measurement of shear displacement and pressure up to 5 mm and 1200 kPa, respectively. Therefore, it shows great potential applications in monitoring or even recognizing various human physiological activities.
       
  • Grafting hyperbranched polyester on the energetic crystals: Enhanced
           mechanical properties in highly-loaded polymer based composites
    • Abstract: Publication date: Available online 29 September 2019Source: Composites Science and TechnologyAuthor(s): Chengcheng Zeng, Congmei Lin, Jianhu Zhang, Jiahui Liu, Guansong He, Yubin Li, Shijun Liu, Feiyan Gong, Zhijian Yang The interfacial strength usually plays a key role for exhibiting great effects on mechanical performances. In this work, typical energetic crystal 1,3,5-triamino-2,4,6-trintrobenzene (TATB) was firmly coated by the strong adhesion of polydopamine (PDA), then two HBPs with fatty and aromatic structure were grafted onto the surface of TATB, by using the hydroxyl groups of the PDA layer as secondary reaction platform. Four highly-loaded polymer based energetic composites (solid loading was 95%) were prepared with fluoropolymer binders as substrate. The results showed that the surface of grafted samples with 0.5 wt% HBP was more easily wetted by non-polar liquid. Improved storage modulus and creep resistance properties were exhibited in polymer bonded explosives (PBXs). The static mechanical properties of tensile and compressive strength were increased significantly by 26.5% and 19.8%, respectively, due to the strong interfacial reinforcement of HBPs.
       
  • High-performance bio-inspired composite T-joints
    • Abstract: Publication date: Available online 28 September 2019Source: Composites Science and TechnologyAuthor(s): Roya Akrami, Sakineh Fotouhi, Mohamad Fotouhi, Mahdi Bodaghi, Joseph Clamp, Amir Bolouri This paper introduces a novel bio-inspired design strategy based on the optimised topology of bird bone's joint to improve the strength-to-weight ratio and damage tolerance of composite T-joints. Better structuring the constituents' materials near the sharp bends results in re-distribution of stress over a larger area and reduces the stress concentration. This is done by an integrally formed support structure that is spaced apart from the main body of the T-joint in the vicinity of the bend using a Polyvinyl Chloride (PVC) foam. The support structure acts as a buttress across the bend and improves the performance of the T-joint. The T-joints are fabricated using wet layup process, from 2/2 twill TC35-carbon fibre fabric/SR5550 epoxy resin, and are subjected to quasi-static and fatigue bending, and quasi-static tensile pull-out tests. The quasi-static results reveal that the bio-inspired T-joint design has huge improvements compared to a conventional T-joint in the elastic stiffness (over 60%), peak load (over 40%) and absorbed mechanical energy (over 130%). There is only 3% weight increase in the bio-inspired T-joint compared to the conventional one. The fatigue results show a significant improvement for the bio-inspired design proving the efficiency of the novel bio-inspired design for both quasi-static and cyclic loadings.
       
  • Facile synthesis of cobalt-zinc ferrite microspheres decorated
           nitrogen-doped multi-walled carbon nanotubes hybrid composites with
           excellent microwave absorption in the X-band
    • Abstract: Publication date: Available online 28 September 2019Source: Composites Science and TechnologyAuthor(s): Ruiwen Shu, Yue Wu, Zhenyin Li, Jiabin Zhang, Zongli Wan, Yin Liu, Mingdong Zheng Herein, nitrogen-doped multi-walled carbon nanotubes/cobalt-zinc ferrite (NMWCNTs/Co0·5Zn0·5Fe2O4) hybrid composites were synthesized through a facile one-step solvothermal route. Results of morphology observations revealed that Co0·5Zn0·5Fe2O4 microspheres were uniformly loaded on the surface of NMWCNTs and three-dimensional (3D) conductive networks were in-situ constructed by the entanglement of NMWCNTs in the as-prepared hybrid composites. Moreover, the influence of contents of NMWCNTs on the electromagnetic parameters and microwave absorption properties of NMWCNTs/Co0·5Zn0·5Fe2O4/paraffin wax composites were elaborately investigated. It was found that the obtained hybrid composites demonstrated superior microwave absorption performance in the X-band. Remarkably, the minimum reflection loss reached −64.7 dB with a matching thickness of 3.1 mm and effective absorption bandwidth achieved 4.3 GHz (11.7–16.0 GHz) with a thickness of merely 2.1 mm. Furthermore, a dual-band (C and Ku bands) microwave absorption characteristic was observed in the obtained hybrid composites. Besides, the microwave absorption properties of as-prepared hybrid composites could be facilely tuned by changing the matching thicknesses and contents of NMWCNTs. The superior microwave absorption properties of obtained hybrid composites mainly originated from the synergistic effects of magnetic loss, conduction loss and dielectric loss, and optimized impedance matching. It was believed that our results could be helpful for the structural design and facile fabrication of 3D MWCNTs-based hybrid composites as high-efficient microwave absorbers.
       
  • Optimizing the dielectric energy storage performance in P(VDF-HFP)
           nanocomposite by modulating the diameter of PZT nanofibers prepared via
           electrospinning
    • Abstract: Publication date: Available online 28 September 2019Source: Composites Science and TechnologyAuthor(s): Yangyang Zhang, Xiaoru Liu, Jinyao Yu, Mingzhi Fan, Xumin Ji, Binzhou Sun, Penghao Hu Polymer-based dielectric nanocomposites are excellent in developing dielectric energy storage devices, and the one-dimensional shape has been considered as a superior morphology for the ceramic nanofillers in dielectric nanocomposite. In the present work, a series of PbZr0.52Ti0.48O3 nanofibers (PZT-NF) were prepared via electrospinning. Three different diameter distributions of 500–600 nm, 300–400 nm and around 100 nm were obtained by adjusting the parameters in the electrospinning process, respectively. The nanocomposite films of PZT-NF/P(VDF-HFP) contained with different diameter nanofibers were prepared. The dielectric properties of the nanocomposites were comparatively investigated and the one with the thinnest nanofibers exhibits the best performances. The increasing dielectric permittivity with nanofiber diameter decrease is in accord with effective medium theory and the enhanced breakdown strength is well demonstrated by phase-field simulation. With larger dielectric displacement and breakdown strength, the nanocomposite loaded 3 vol% thinnest nanofibers represents maximal energy density of 12.58 J/cm3 at 470 kV/mm. The strategy of modulating nanofiber diameter in electrospinning has great potential in further enhancing energy density in dielectric nanocomposites.
       
  • Regulating Cu(II)-benzimidazole coordination structure in rigid-rod aramid
           fiber and its composites enhancement effects
    • Abstract: Publication date: Available online 28 September 2019Source: Composites Science and TechnologyAuthor(s): Zheng Cheng, Qian Yin, Hang Wu, Taijun He, Longbo Luo, Xiangyang Liu Coordination crosslinking, as the kind of strongest supramolecular interaction, has been widely introduced into flexible polymer chains, including rubbers and aerogels, while that in rigid-rod polymer is much rare, due to the difficulty in rigid-rod macromolecules' configuration change. Moreover, the exact coordination structure inside those polymers is not clear. Herein, this coordination interaction was incorporated into a traditional rigid-rod polymer, aramid fiber, by Cu2+-benzimidazole coordination reaction, through the careful control of the dynamic reaction conditions, and the structural/performance relationships of fiber and its composites are detailed studied. It is seen that two different coordination structures, S-coordination style (Cu2+ coordination with single benzimidazole unit) and M-coordination style (Cu2+ coordination with multiple benzimidazole units from different macromolecular chains), could be both obtained inside fiber, using different solvents as the reaction medium. Moreover, using reaction kinetics equilibrium, we presented a mathematical method to investigate those two coordination structures in detail, including their average coordination numbers of Cu2+ and reaction equilibrium constant (K). Further, the experimental results show that the fiber with average coordination number of 2 exhibits a comprehensive improved performance in heat/solvent resistance, fluorescence emission as well as fiber's transverse properties, with the corresponding increase of 54.2% and 47.1% for its composites interfacial properties and compressive strength, compared with untreated fiber.
       
  • Effect of room-temperature annealing on structures and properties of
           SSBR/BR blends and SSBR/BR/SiO2 composites
    • Abstract: Publication date: Available online 27 September 2019Source: Composites Science and TechnologyAuthor(s): Xinping Zhang, Lei Cai, Chuanwei Wang, Aihua He Room temperature annealing process lies between high-temperature mixing process and high-temperature vulcanization process in rubber processing technology, and definitely affects the performances of rubber composites. In this work, the influences of room-temperature annealing on the structures and properties of unfilled SSBR/BR blends and silica-filled SSBR/BR composites have been evaluated in detail. For the unfilled SSBR/BR vulcanizates, the tensile strength, tear strength and fatigue resistance deteriorate due to the reduced rubber matrix strength with lower crosslinking density and less chain entanglements with annealing time extending. While for the SSBR/BR/SiO2 vulcanizates with dual networks including filler-filler networks and polymer-polymer networks, the tensile strength and fatigue resistance reduce, the tear strength, dynamical properties concerning abrasion, heat built-up and rolling resistance improve obviously with extending annealing time, which are attributed to the enhanced filler-polymer interactions, severe silica flocculation, and reduced internal hysteresis loss with annealing time prolonging. This work is expected to provide fundamental understanding of the annealing process in the rubber processing technology for development of high-performance rubber composites.
       
  • Improvement of physical and mechanical properties on bio-polymer matrix
           composites using morphed graphene
    • Abstract: Publication date: Available online 26 September 2019Source: Composites Science and TechnologyAuthor(s): O. Velazquez-Meraz, J.E. Ledezma-Sillas, C. Carreño-Gallardo, W. Yang, N.M. Chaudhari, H.A. Calderon, I. Rusakova, F.C. Robles Hernandez, J.M. Herrera-Ramirez Chitosan is a natural-occurring biopolymer found commonly in the exoskeleton of crustaceans, vegetables, fungi and plants. Due to its relatively high mechanical properties, chitosan, is attractive for structural applications. Here, we show the benefits of morphed graphene as reinforcement for chitosan composites. Morphed graphene is incorporated into the chitosan matrix via thermomechanical process to produce composites with tunable mechanical performances that are ideal for applications where impact resistant (toughness) and elasticity are required. Optimum sintering conditions were determined by means of thermogravimetry and calorimetry. The characterization results show a clear homogeneity of the microstructure between chitosan and the reinforcement material. The characterization of the composite was carried using X-ray diffraction (XRD), Raman and infrared spectroscopies, optical microscopy, scanning and transmission electron microscopy. The mechanical properties were evaluated by nanoindentation and microhardness tests. The composite sintered at 180 °C for 3 h with 5 wt% of morphed graphene demonstrated to provide the best performance with 33% higher density, 78% less porosity, 133% higher maximum penetration depth, 25% superior hardness, and 73% higher elastic energy ratio. The combination of the reinforcement, morphed graphene, and the technology presented herein are ideal to produced fully dispersed/highly homogeneous composites with up to 5 wt% C. Therefore, morphed graphene additions have unique benefits as chitosan reinforcement material can be used for structural applications such as packaging with environmental advantages over polymers such as Polyethylene Terephthalate. The manufacturing methodology has potential for industrial scalability and presumably the composite is recyclable and compostable.Graphical abstractImage 1
       
  • Osteoinduction of 3D printed particulate and short-fibre reinforced
           composites produced using PLLA and apatite-wollastonite
    • Abstract: Publication date: Available online 25 September 2019Source: Composites Science and TechnologyAuthor(s): Priscila Melo, Ana-Marina Ferreira, Kevin Waldron, Thomas Swift, Piergiorgio Gentile, Marlin Magallanes, Martyn Marshall, Kenny Dalgarno Composites have clinical application for their ability to mimic the hierarchical structure of human tissues. In tissue engineering applications the use of degradable biopolymer matrices reinforced by bioactive ceramics is seen as a viable process to increase osteoconductivity and accelerate tissue regeneration, and technologies such as additive manufacturing provide the design freedom needed to create patient-specific implants with complex shapes and controlled porous structures. In this study a medical grade poly(l-lactide) (PLLA) was used as matrix while apatite-wollastonite (AW) was used as reinforcement (5 wt% loading). Premade rods of composite were pelletized and processed to create a filament with an average diameter of 1.6 mm, using a twin-screw extruder. The resultant filament was 3D printed into three types of porous woodpile samples: PLLA, PLLA reinforced with AW particles, and PLLA with short AW fibres. None of the samples degraded in phosphate buffered solution over a period of 8 weeks, and an average effective modulus of 0.8 GPa, 1 GPa and 1.5 GPa was obtained for the polymer, particle and fibre composites, respectively. Composite samples immersed in simulated body fluid exhibited bioactivity, producing a surface apatite layer. Furthermore, cell viability and differentiation were demonstrated for human mesenchymal stromal cells for all sample types, with mineralisation detected solely for biocomposites. It is concluded that both composites have potential for use in critical size bone defects, with the AW fibre composite showing greater levels of ion release, stimulating more rapid cell proliferation and greater levels of mineralisation.
       
  • Manufacturing of unidirectional glass-fiber-reinforced composites via
           frontal polymerization: A numerical study
    • Abstract: Publication date: Available online 25 September 2019Source: Composites Science and TechnologyAuthor(s): S. Vyas, E. Goli, X. Zhang, P.H. Geubelle Frontal polymerization (FP) is explored as a faster and energy-efficient manufacturing method for dicyclopentadiene (DCPD) matrix, E-glass-fiber-reinforced composites through a series of numerical simulations based on a homogenized reaction-diffusion model. The simulations are carried out over a range of values of fiber volume fraction using (i) a transient, nonlinear, multi-physics finite element solver, and (ii) a semi-analytic steady-state solver. We observe that the front velocity and temperature decrease with an increase in the fiber volume fraction until a critical point is reached, beyond which FP is no longer observed as the front is quenched. To highlight the effect of the material properties of the reinforcing phase, the dependencies of the front velocity, width and maximum temperature on the fiber volume fraction obtained for glass/DCPD composites are compared to those associated with carbon/DCPD composites.
       
  • A novel approach for the interfacial stress analysis of composite
           adhesively bonded joints
    • Abstract: Publication date: Available online 17 September 2019Source: Composites Science and TechnologyAuthor(s): Xiao Wei, Hai Wang, Hui-Shen Shen This paper presents a novel approach for the interfacial stress analysis of composite single-lap joints (SLJ). The analytical modeling is based on the interface elasticity where both the shear and peel stresses are assumed to be variant across the adhesive layer thickness. The unknown interfacial parameters are determined by using an experiment-based inverse method. The finite element simulation is then performed to calculate the interfacial stress distributions and evaluate the effect of the structural parameters on the interfacial behavior of the composite bonded joints. It is shown that both the peel and shear stresses at the interface are influenced by the interface energy and geometry parameters of the composite bonded joint. Numerical results are presented both to demonstrate the advantages of the present model over existing ones and to illustrate the main characteristics of interfacial stress distributions.
       
  • Application of X-ray computed tomography for the virtual permeability
           prediction of fiber reinforcements for liquid composite molding processes:
           A review
    • Abstract: Publication date: Available online 17 September 2019Source: Composites Science and TechnologyAuthor(s): M.A. Ali, R. Umer, K.A. Khan, W.J. Cantwell X-ray computed tomography (XCT) combined with computer simulations have proved to be an extremely powerful and versatile tool for material characterization in recent years. The use of XCT for measuring reinforcement permeability in the liquid composite molding (LCM) processes is a topic of great interest. This is mainly because current LCM characterization approaches involve costly, time-consuming, and tedious experimental procedures. Existing numerical permeability computation procedures use geometric models of the reinforcements that do not always capture either the realistic fiber architectures or the deformations associated with the compaction process. CT-scans can extract information that can simultaneously yield the compaction response and permeability values utilizing a single sample, potentially saving substantial labor and material costs. Herein, we present a detailed review outlining how the XCT system can be used as a process characterization tool to gather useful and high quality 3D images which then can be used to generate computational models to determine both the compaction response and the virtual permeability of complex fiber reinforcements for LCM processes. This article also reviews current types of equipment, X-ray power requirements, voxel sizes, resolutions, and unit cell size effects on permeability computation. The aspects relating to microstructural characteristics, such as tow geometry changes, inter and intra tow gap variations during compaction, which have direct influence on reinforcement permeability, are also discussed. This paper also highlights key limitations associated with the permeability predictions faced at various stages and identifies where improvements can be made.
       
  • Graphene oxide-reinforced poly(2-hydroxyethyl methacrylate) hydrogels with
           extreme stiffness and high-strength
    • Abstract: Publication date: Available online 12 September 2019Source: Composites Science and TechnologyAuthor(s): Andreia T. Pereira, Patrícia C. Henriques, Paulo C. Costa, Maria Cristina L. Martins, Fernão D. Magalhães, Inês C. Gonçalves Designing hydrogels with high-strength and stiffness remains a challenge, limiting their usage in several applications that involve load-bearing. In this work, in situ incorporation of different amounts of graphene oxide (GO) into poly(2-hydroxyethyl methacrylate) (pHEMA) was used to create hydrogels with outstanding stiffness (Young's modulus of up to 6.5 MPa, 8.3x higher than neat pHEMA) and tensile resistance (ultimate tensile strength of up to 1.14 MPa, 7.4x higher than neat pHEMA) without affecting the water absorption capacity, surface wettability and cytocompatibility of pHEMA. Such magnitude of improvement in Young's modulus and ultimate tensile strength was never before described for GO incorporation in hydrogels. Moreover, these stiffness and tensile resistance values are higher than the ones of most hydrogels (few hundred kPa), achieving a stiffness comparable to polydimethylsiloxane (PDMS), cartilage and artery walls and a tensile resistance similar to rigid foams, PDMS and cork. These new materials open a wide range of application for pHEMA in different fields.
       
 
 
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