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Composites Science and Technology
Journal Prestige (SJR): 1.702
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0266-3538
Published by Elsevier Homepage  [3184 journals]
  • Improving the interlaminar toughness of the carbon fiber/epoxy composites
           via interleaved with polyethersulfone porous films
    • Abstract: Publication date: Available online 14 September 2019Source: Composites Science and TechnologyAuthor(s): Chao Cheng, Chenyu Zhang, Jinli Zhou, Minqiang Jiang, Zeyu Sun, Shuai Zhou, Yong Liu, Zhengguo Chen, Lei Xu, Hui Zhang, Muhuo YuAbstractIn this study, a phase inversion approach was employed to fabricate four different thicknesses (20 μm to 100 μm) of polyethersulfone (PES) films with visible holes (1 hole/cm2) on the surface, applied as interleaves to improve the interlaminar fracture toughness of carbon fiber/epoxy composite laminates prepared by vacuum assistant resin infusion process (VARI). The film could dissolve into the epoxy resin which as clearly evident by the optical microscopy under a controlled condition. It was noted that the thickness of the resin-rich layer and the distribution of PES microspheres in the interlaminar layer depended on the thickness of the PES film. Also, mode I and mode II fracture toughness, interlaminar shear strength (ILSS), flexural properties as well as tensile properties of the CF/EP composites had all been characterized and analyzed in detail and in order. The results demonstrated that mode I and mode II fracture energies at the optimal interleaved laminates for the toughened system were increased by 61.5% and 55.1% compared to the composites without interleaves, respectively. Besides, PES film interleaved laminates displayed an increase of 32% for the interlaminar shear strength and no significant changes in the flexural and tensile properties. It was observed that the films induced toughening via two mechanisms: i) cohesive failure in a thicker resin region and ii) crack deflection and microcrack caused by PES microspheres, illustrated in the microstructure analysis of failure surfaces and the observations of the crack propagation path.
       
  • Relationship between the structure and thermal properties of
           polypropylene/graphene nanoplatelets composites for different
           platelet-sizes
    • Abstract: Publication date: Available online 14 September 2019Source: Composites Science and TechnologyAuthor(s): Ziwei Xu, Suihua He, Jingjing Zhang, Shijun Huang, Anfu Chen, Xiaoling Fu, Peng ZhangAbstractPolypropylene (PP) nanocomposites reinforced with different types of graphene nanoplatelets (GNPs) and their hybrid systems are prepared via melt extrusion. On the basis of experimental analysis and simulation, the factors of thermal property of the PP/GNPs nanocomposites, including GNPs size, weight filling ratio and proportion of various sizes, are systematically investigated. At high GNPs content (9,12 wt %), GNPs are widely distributed in PP matrix and the thermal paths are basically formed. The thermal conductivity of composites is determined by the size and thermal properties of GNPs. At low GNPs content (6 wt %), for single system, the larger diameter with moderate distribution would be more conducive to achieve the higher thermal conductivity, indicating the formation of thermal paths dramatically affects the thermal conductivity. For hybrid system, the PP filled with medium and small diameter GNPs obtains the highest thermal conductivity at the ratio of medium diameter GNPs to small diameter GNPs is 8:2, and is 23.8% higher than the single system of PP filled with small diameter GNPs. More precisely, the small diameter GNPs plays a role in connecting the scattered medium diameter GNPs, as mass thermal paths are formed. This shows that the distribution state by combining the synergistic effect of various GNPs significantly affects the thermal conductivity of PP/GNPs nanocomposites. Moreover, a numerical simulation dealing with the synergistic effect of different GNPs, is developed on the thermal conductivity of GNPs-reinforced PP matrix. The heat flux images demonstrate the existence of synergistic effect between different type of GNPs.
       
  • A nonlinear mechanics model of soft network metamaterials with unusual
           swelling behavior and tunable phononic band gaps
    • Abstract: Publication date: Available online 13 September 2019Source: Composites Science and TechnologyAuthor(s): Hang Zhang, Xu Cheng, Dongjia Yan, Yihui Zhang, Daining FangAbstractSoft mechanical metamaterials with negative swelling responses represent a class of man-made materials with specially engineered micro-architectures, which are attractive for applications in areas such as biomedical engineering, aerospace and microelectronics. These soft mechanical metamaterials are usually constructed with laminated filaments that serve as building block structures in periodic lattices, with capabilities to convert hydraulic deformations of active materials into large bending deformations of the filamentary microstructures. The previous studies mainly relied on massive calculations of finite element analyses (FEA) as the core process of metamaterial designs to achieve targeted mechanical properties. The FEA calculations could, however, be very cumbersome and time-consuming, especially when the micro-architecture involves a large number of complex microstructures. This paper introduces a theoretical model that can predict accurately the swelling-induced deformations in such soft mechanical metamaterials consisting of sandwiched horseshoe microstructures. This model takes into account the evident shape change of sandwiched cross section observed in experiments, during the hydration process. Experimental and computational studies on mechanical metamaterials with a wide range of microstructure geometries were carried out to validate the developed model. These results unveil the significant role of out-of-plane deformations on the swellability of the mechanical metamaterials. The theoretical model sheds light on the essential microstructure-property relationship, which could serve as a reference of metamaterial designs to achieve desired swelling behavior. Furthermore, we leverage the active control of microstructure geometry during hydration to offer tunable phononic band structures, with potential applications in noise/vibration control and wave mitigation.
       
  • 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. GonçalvesAbstractDesigning 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.
       
  • Flexible, quickly responsive and highly efficient E-heating carbon
           nanotube film
    • Abstract: Publication date: Available online 12 September 2019Source: Composites Science and TechnologyAuthor(s): Mohamed Amine Aouraghe, Fujun Xu, Xiaohua Liu, Yiping QiuAbstractJoule heating materials with excellent thermal behavior, easy processability and reusability are very desirable in soft robotics, multifunctional smart structures, and wearable electronics. Carbon nanotube film (CNTF) formed by floating catalyst chemical vapour deposition (FFCVD) method possesses high electrical conductivity which makes it a potential candidate as a joule heating material. In this study, the electro-heating (E-heating) behaviors of CNTF with various dimensions and deformations were investigated by applying various voltages. The as-produced CNTF reached a steady-state temperature of 310 °C (1 cm × 0.5 cm) within 1 s under a low voltage of 2.5 V by the homogeneous temperature distribution. Furthermore, E-heating behavior of CNTF remained stable after bending and twisting deformations as well as On/Off voltage switching cycles (up to 200 times). As a potential application, the CNTF embedded 3D spacer woven composites de-iced the ice by 338 times weight ratio within 9 min, demonstrating its promising E-thermal performance.
       
  • Direct effects of UV irradiation on graphene-based nanocomposite films
           revealed by electrical resistance tomography
    • Abstract: Publication date: Available online 12 September 2019Source: Composites Science and TechnologyAuthor(s): Marialaura Clausi, Elisa Toto, Sabina Botti, Susanna Laurenzi, Valeria La Saponara, M. Gabriella SantonicolaAbstractThe integration of surface sensing elements providing an in situ monitoring of the UV-induced degradation effects in composite materials and structures is crucial for their applications in hostile environments characterized by high levels of radiation, such as space. In this work, the electrical response of a novel UV-sensitive nanocomposite film was investigated using electrical resistance tomography (ERT). The conductivity changes measured at the irradiated surfaces were compared with results from morphology analysis by scanning electron microscopy (SEM) and surface analytical techniques, such as Raman microscopy. Highly conductive and UV-sensitive nanocomposite coatings were prepared by embedding the graphene and deoxyribonucleic acid (DNA) component in a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) matrix. The coatings were deposited onto carbon-reinforced laminated structures fabricated by resin transfer molding process using an aerospace-grade epoxy resin. Two different irradiation conditions were tested by exposing the nanocomposite surfaces to UV-C irradiances of 2.6 and 4.0 mW/cm2. Results show that the ERT technique has great potential for the in situ health monitoring of carbon-based materials and structures for aerospace applications, which are subject to degradation by UV-C radiation: it allows mapping of the conductivity changes occurring at the surface of the graphene/DNA/PEDOT:PSS coatings during irradiation.
       
  • Mesoscale damage analysis of needle-punched carbon/carbon composite
           considering randomness of inherent defects
    • Abstract: Publication date: Available online 11 September 2019Source: Composites Science and TechnologyAuthor(s): Meng Han, Chuwei Zhou, Vadim V. SilberschmidtAbstractNeedle-punched carbon/carbon composites (NP C/Cs) are widely used in aerospace applications thanks to their good high-temperature mechanical properties with relatively low cost. To improve their out-plane stiffness and strength, short-cut fibres are introduced into interlayers between plies using a needle-punching technology. This could result in some defects that decrease their in-plane stiffness and strength. Circle-arc beam elements and extended spring elements are proposed in this research to model mechanical performances of punched fibre bundles, isotropic pyrocarbon matrix and short-cut carbon fibre felts in NP C/Cs, respectively. Aided by this beam-spring finite element model, the impacts from features of mesoscopic defects, e.g. irregularity of distribution of local imperfection in planar fiber bundle caused by punching process, to mechanical properties of NP C/Cs are focused in this study. The ranges of bending modulus and bending strength for a NP C/C are estimated considering the randomness of these defects.
       
  • Flexible, self-powered, magnetism/pressure dual-mode sensor based on
           magnetorheological plastomer
    • Abstract: Publication date: Available online 11 September 2019Source: Composites Science and TechnologyAuthor(s): Jiaqi Xu, Lei Pei, Jun Li, Haoming Pang, Zhiyuan Li, Binshang Li, Shouhu Xuan, Xinglong GongAbstractA flexible self-powered magnetism/pressure dual-mode sensor, which consists of magnetorheological plastomer (MRP), was developed in this work. The working mechanism of the self-powered sensor was based on the displacement reaction of Fe and CuSO4. Different from traditional flexible pressure sensors, it was not only sensitive to a slight pressure (1.3 kPa), but also responsive to a small magnetic field (12 mT). Under an external magnetic field, the micro-scale carbonyl iron (CI) particles in the MRP electrode aggregated into the chain-like and the cluster-like structures, which enhanced the electrochemical activity of ions in the electrolyte of the electrode materials and formed the conductive network. The voltage increased with the magnetic field strength and the sensitivity was 4.2% at a 252 mT magnetic field. To further explore the mechanism of sensor, the microstructure evolution of CI particles inside the electrode materials under different magnetic fields was simulated by particle-level dynamics method. Finally, a smart writing board based on a self-powered magnetism/pressure dual-mode sensor array was developed and it was sensitive to different magnetic fields without an external power supply, which demonstrated a broad potential for mobile electronic device in the non-contact state.
       
  • Effect of pyrolyzed catecholamine polymers for concurrent enhancements of
           electrical conductivity and mechanical strength of graphene-based fibers
    • Abstract: Publication date: Available online 11 September 2019Source: Composites Science and TechnologyAuthor(s): Joonhui Kim, Hoseong Hwang, Sung Chan Yoo, Hojin Seo, Seongwoo Ryu, Soon Hyung HongAbstractGraphene fibers are regarded as a novel platform material for flexible electronic applications based on their superior electrical conductivity, mechanical properties and potential for mass production. However, properties of graphene fibers are still far from commercial level and considerable effort has been made recently to improve these characteristics. In this paper, we drastically enhanced both the mechanical and electrical properties of graphene-based fibers by converting infiltrated polydopamine (PDA) into N-doped graphitic layers. Graphene-based fibers were fabricated from a liquid crystalline graphene oxide dispersion, and PDA was introduced into the fibers. After pyrolysis, the mechanical properties, i.e., the tensile strength and Young's modulus, of the composite graphene-based fibers exhibited 3.56- and 3.95-fold increases, respectively, compared with those of pristine graphene fibers. Furthermore, the electrical conductivity also dramatically increased to 7.3 × 104 S/m, which is almost 10 times that of pristine graphene fibers. These results show the achievement of advantages superior to those in previously reported studies based on polymer-grafted graphene composite fibers. This hybridized composite fabrication process provides a new way of reinforcing graphene fibers and contributes to expanding the application of graphene-based fibers in flexible electronic devices.
       
  • Versatile magnetorheological plastomer with 3D printability, switchable
           mechanics, shape memory, and self-healing capacity
    • Abstract: Publication date: Available online 9 September 2019Source: Composites Science and TechnologyAuthor(s): Song Qi, Jie Fu, Yuanpeng Xie, Yaping Li, Ruyi Gan, Miao YuAbstractThe rapid advancement in soft actuators imposes an emergent requirement for soft stimuli-sensitive materials that are deformable and stiffness variable and show designability and adaptivity. Soft actuators based on magneto-sensitive materials with outstanding magnetic-control performance are highly desirable in research. In this paper, we developed a versatile magnetorheological plastomer (MRP) based on polycaprolactone (PCL)/thermoplastic polyurethane (TPU) polymer blends. The MRP showed 3D printability, switchable mechanics, shape memory, and self-healing properties. The thermoplasticity of the matrix enables fused deposition modeling 3D printing, which affords the MRP excellent shape designability. By taking advantage of the phase transition and magnetorheological effect, the dramatic switchable mechanical properties of MRP can be triggered by thermal stimulus and magnetic field. The influences of matrix, particle content, temperature and magnetic field on the mechanical properties were discussed comprehensively, and possible physical mechanisms were proposed so that the result can be qualitatively explained. Based on hybrid crystalline and amorphous regions of PCL and TPU, the MRP exhibited superior shape memory and self-healing properties. This work may play an important role in the future development of multifunctional magneto-sensitive material and promote the application of soft actuators in the fields of soft robotics, medical care, and bionics applications.
       
  • Fatigue damage evolution in thick composite laminates: Combination of
           X-ray tomography, acoustic emission and digital image correlation
    • Abstract: Publication date: Available online 4 September 2019Source: Composites Science and TechnologyAuthor(s): Abderrahmane Djabali, Toubal Lotfi, Redouane Zitoune, Saïd RechakAbstractThe main purpose of this study is to provide a thorough experimental investigation of fatigue damage mechanisms and evolution in thick carbon/epoxy laminate subjected to bending load. The use of X-ray computed tomography (CT) in this study has allowed the visualization of all damage present in the studied laminates, which made it possible to identify, quantify and locate them precisely and therefore, to identify the physical origin of residual strength decrease and acoustic emissions (AE). Furthermore, the results of the AE analysis have provided very valuable information about the nature and evolution of damage. However, the determination of the depth and size of internal damage was not possible with this technique. The displacement field measured by digital image correlation (DIC) made it possible to determine and monitor the strain field evolution during the experiments. The combination of the results of the three non-destructive techniques used in this work has allowed better characterization of fatigue damage evolution in the studied laminates, and provide a complete and accurate description of the different mechanisms involved during their damage process.
       
  • Eco-friendly lightweight filament synthesis and mechanical
           characterization of additively manufactured closed cell foams
    • Abstract: Publication date: Available online 4 September 2019Source: Composites Science and TechnologyAuthor(s): Balu Patil, B.R. Bharath Kumar, Srikanth Bontha, Vamsi Krishna Balla, Satvasheel Powar, V. Hemanth Kumar, S.N. Suresha, Mrityunjay DoddamaniAbstractEnvironmentally pollutant fly ash cenospheres (hollow microballoons) are utilized with most widely consumed, relatively expensive high density polyethylene (HDPE) for developing lightweight eco-friendly filament for 3D printing of closed cell foams. Cenospheres (20, 40 and 60 by volume %) are blended with HDPE and subsequently extruded in filament to be used for 3D printing. Cenosphere/HDPE blends are studied for melt flow index (MFI) and rheological properties. MFI decreases with cenospheres addition. Complex viscosity, storage and loss modulus increase with filler loading. DSC results on the filament and printed samples reveal increasing crystallization temperature and decreasing crystallinity % with no appreciable change in peak melting temperature. Cooling rate variations exhibit crystallinity differences between the filament and the prints. CTE decreases with increasing cenosphere content resulting in lower thermal stresses and under diffusion of raster leading to non-warped prints. Micrography on freeze fractured filament and prints show cenospheres uniform distribution in HDPE. Intact cenospheres lower the foam density making it lightweight. Tensile tests are carried out on filaments and printed samples while flexural properties are investigated for 3D prints. Cenospheres addition resulted in improved tensile modulus and decreased filament strength. Tensile and flexural modulus of printed foams increases with filler content. Results are also compared with injection molded samples. Printed foams registered comparable tensile strength. Specific tensile modulus is noted to be increased with cenospheres loading implying weight saving potential of 3D printed foams. Property map reveals printed foams advantage over other fillers and HDPE composites synthesized through injection and compression molding.
       
  • Ceramic nanoparticles and carbon nanotubes reinforced thermoplastic
           materials for piezocapacitive sensing applications
    • Abstract: Publication date: Available online 4 September 2019Source: Composites Science and TechnologyAuthor(s): T. Marinho, P. Costa, E. Lizundia, C.M. Costa, S. Corona-Galván, S. Lanceros-MéndezAbstractThis work reports on the development of polymer composites for load sensing applications. Three thermoplastic polymers, one with elastomeric behaviour, namely poly(styrene-butadiene-styrene) and poly(styrene–ethylene/butylene-styrene), and a semi-crystalline fluorinated polymer, poly(vinylidene fluoride), were selected as hosting matrices. In order to improve the sensing capacity, both ceramic nanoparticles (barium titanate, BT) and carbon nanotubes (CNTs) have been incorporated through solvent mixing followed by spreading the solution onto a glass substrate and subsequent solvent evaporation. Scanning electron microscopy results show that nanoparticles remain uniformly distributed through the nanocomposite at concentrations as high as 50% by weight. Polymer-filler interactions and thermal stability of the nanocomposites were assessed by Fourier transform infrared spectroscopy and thermogravimetric analysis, respectively, in which these nanocomposites present physical interaction between constituents rather than chemical interaction and thermal stability increases slightly for larger filler contents. The mechanical properties are dependent on the matrix, filler type and amount in which the incorporation of both fillers in the elastomeric matrices increases the initial modulus of the nanocomposites up to 3-times. Electrically insulating BT increases dielectric properties and electrically conducting CNTs increase the dc conductivity of nanocomposites, respectively, and the combination of both fillers results in a synergetic effect. Finally, the changes induced by applied static loads on the capacitance variation (ΔC) of the nanocomposites were evaluated, showing a marked enhancement on the ΔC upon the incorporation of both fillers due to the synergetic effect provided by electrically insulating BT together with electrically conducting CNTs.
       
  • Peroxide crosslinked butyl rubber composites using TEMPO and sorbates
    • Abstract: Publication date: Available online 3 September 2019Source: Composites Science and TechnologyAuthor(s): Jinyuan Wang, Jian Wu, Yuqing Luo, Yong Zhang, Sharon Guo, Sanshui PanAbstractPeroxide curing can provide rubber products with good thermal aging resistance, low compression set and light color. But butyl rubber (IIR) and bromobutyl rubber (BIIR) will incur severe main chain degradation when using a peroxide as a curing agent. The presence of 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) and in situ formed zinc disorbate (ZDS) in dicumyl peroxide cured BIIR system can inhibit the degradation of BIIR without compromising the curing extent of BIIR vulcanizates. ZDS is grafted on BIIR, while TEMPO functions as a free radical scavenger and nitroxide mediator for the grafting reaction. The in situ formation and grafting reaction of ZDS in BIIR are characterized by FTIR, XRD and NMR spectroscopy. In the presence of TEMPO and ZDS, BIIR does not suffer degradation but exhibits a continuous increase in torque and crosslink density with time during the post-cure period. The presence of TEMPO could effectively improve the thermal stability and aging resistance of BIIR vulcanizates. The study provides an effective route to avoid the degradation and promote the crosslinking of BIIR that can easily incur β-scission when reacting with peroxides.
       
  • Effectively enhanced interlaminar shear strength of carbon fiber
           fabric/epoxy composites by oxidized short carbon fibers at an extremely
           low content
    • Abstract: Publication date: Available online 3 September 2019Source: Composites Science and TechnologyAuthor(s): Hui-Jie Nie, Xiao-Jun Shen, Bo-Lin Tang, Chen-Yang Dang, Shu Yang, Shao-Yun FuAbstractCarbon fiber reinforced epoxy composites have high specific strength and modulus but relatively low interlaminar shear strength (ILSS). Herein treated short carbon fibers (SCFs) with ethanol and concentrated nitric acid are added to epoxy matrix to improve the ILSS of carbon fabric (CF)/epoxy composite. The effects of SCF content and treatment (oxidization) time are systematically examined on the ILSS of the CF/EP composite. An effective enhancement of 13.5% in the ILSS of the CF/EP composite is achieved by oxidized-SCFs at an extremely low content of 0.07 wt% relative to the epoxy matrix. The main mechanisms for enhancing the ILSS of CF/EP composite are explored by the addition of oxidized-SCFs. This strategy is of great practical significance since SCFs are very cheap and also can be easily dispersed in epoxy resins compared with nano-fillers etc. previously used for this purpose.
       
  • Dual functionality of hierarchal hybrid networks of multiwall carbon
           nanotubes anchored magnetite particles in soft polymer nanocomposites:
           Simultaneous enhancement in charge storage and microwave absorption
    • Abstract: Publication date: Available online 1 September 2019Source: Composites Science and TechnologyAuthor(s): Shital Patangrao Pawar, Guilherme Melo, Uttandaraman SundararajWe demonstrated, for the first time, the use of submicron size insulative junctions of magnetite (Fe3O4) in conductive networks of multiwall carbon nanotubes (MWNTs) for simultaneously achieving enhanced charge storage and superior microwave absorption in X-band (8.2–12.4 GHz) frequency range. Herein, electrical conductivity in fluoroelastomer matrix was attained by dispersion of MWNTs, whereas low dielectric loss was achieved by employing Fe3O4 particles as insulative spacers between MWNT networks. High-performance charge-storing nanocomposites were developed using unique approach where relatively large insulative Fe3O4 spacers were anchored to MWNT networks leading to disrupted conductive pathways. The size of Fe3O4 particles was controlled such a way that the distance between discrete MWNTs at the insulative junction is larger than the critical distance required for hopping and tunneling of nomadic charges. This also resulted in optimum impedance matching and additional magnetic loss associated with Fe3O4, which led to the synergistic absorption of microwaves. Taken together, the anchoring of sub-micron size Fe3O4 particles with MWNTs provided dual functionality of high real permittivity (ε') along with decreased dielectric loss which are both favorable for charge storage. Furthermore, it led to improved impedance matching and we were able to achieve maximum microwave absorption.Graphical abstractImage 1
       
  • High-performance polyketone nanocomposites achieved via plasma-assisted
           mechanochemistry
    • Abstract: Publication date: Available online 31 August 2019Source: Composites Science and TechnologyAuthor(s): Jiwan You, Han-Hyeong Choi, Tae Ann Kim, Min Park, Jeong Sook Ha, Sang-Soo Lee, Jong Hyuk ParkAbstractPolyketone (PK) is an engineering plastic with excellent impact strength, chemical resistance, barrier properties, and flame retardancy. However, the development of PK nanocomposites with further improved properties obtained via compounding is challenging due to the poor compatibility between PK and nanofillers. Also, since PK is not soluble in common organic solvents, it is difficult to enhance the affinity between components by applying wet chemistry processes widely used to make other composites. Herein, we report an effective solution to improve the compatibility of PK and nanofillers via a completely dry process. The plasma-assisted mechanochemistry (PMC) process can form chemical bonds between polymers and nanofillers, thereby promoting the dispersion of the nanofillers in polymer composites. PK was compounded with graphite nanoplatelets (GNPs) using the PMC process, and the structure and properties of the composites were investigated. The composites displayed greatly improved mechanical and gas barrier properties, and thermal conductivity; compared with conventionally prepared composites having the same GNP content (10 wt%), the composites prepared via the PMC process had 9.7 times higher elongation at break (112.1%), 2.2 times higher impact strength (89.2 J/m), 2.2 times better barrier performance (0.9 g/m2·day), and 2.5 times higher thermal conductivity (1.6 and 13.9 W/mK in the through-plane and in-plane directions). This approach is an innovative route to high-performance polymer nanocomposites, even those constructed from insoluble and incompatible polymers such as PK.
       
  • Hyperplastic material model with damage for woven composites
    • Abstract: Publication date: Available online 31 August 2019Source: Composites Science and TechnologyAuthor(s): T. Mandys, T. Kroupa, V. Laš, L. LobovskýAbstractA hyperplastic material model with damage was developed in order to describe the non-linear mechanical behaviour of woven composites. The proposed model is based on thermodynamic principles and considers the additive decomposition of logarithmic strain in accordance with assumed finite strain theory. The damage is modelled using the proposed degradation functions dependent on the relevant elastic strains. This model was implemented into the commercial FEM software Abaqus using UMAT and VUMAT subroutines. Experimental cyclic tensile and compressive static tests were performed on selected woven composites. Mathematical optimization is used for identification of material parameters of the presented model. The capability of the material model was verified by means of experiments on the specimens using geometry that provides a highly complex combination of plasticity and damage states during loading. Strain distributions were experimentally analysed using digital image correlation and the results compared with results from numerical simulations.
       
  • Local fiber orientation from X-ray region-of-interest computed tomography
           of large fiber reinforced composite components
    • Abstract: Publication date: 20 October 2019Source: Composites Science and Technology, Volume 183Author(s): Thomas Baranowski, Dascha Dobrovolskij, Kilian Dremel, Astrid Hölzing, Günter Lohfink, Katja Schladitz, Simon ZablerAbstractThe local fiber orientation is a micro-structural feature crucial for the mechanical properties of parts made from fiber reinforced polymers. It can be determined from micro-computed tomography data and subsequent quantitative analysis of the resulting 3D images. However, although being by nature non-destructive, this method so far has required to cut samples of a few millimeter edge length in order to achieve the high lateral resolution needed for the analysis.Here, we report on the successful combination of region-of-interest scanning with structure texture orientation analysis rendering the above described approach truly non-destructive. Several regions of interest in a large bearing part from the automotive industry made of fiber reinforced polymer are scanned and analyzed. Differences of these regions with respect to local fiber orientation are quantified. Moreover, consistency of the analysis based on scans at varying lateral resolutions is proved. Finally, measured and numerically simulated orientation tensors are compared for one of the regions.
       
  • Toward high thermoelectric performance for polypyrrole composites by
           dynamic 3-phase interfacial electropolymerization and chemical doping of
           carbon nanotubes
    • Abstract: Publication date: 20 October 2019Source: Composites Science and Technology, Volume 183Author(s): Wusheng Fan, Yichuan Zhang, Cun-Yue Guo, Guangming ChenAbstractPolymer thermoelectric composites have received significant attention in recent years. To achieve high thermoelectric performance is one main aim, especially when being compared with their inorganic counterparts. Here, we report high-performance thermoelectric composites based on single-walled carbon nanotube (SWCNT) and polypyrrole (PPy), which are prepared by dynamic 3-phase interfacial electropolymerization and subsequent physical mixing. We found that both SWCNT content and chemical doping of SWCNT dramatically affected the composite thermoelectric performance. The maximum power factor at room temperature of the PPy composite reaches as high as 240.3 ± 5.0 μW m−1 K−2, which may be the highest value for PPy and its composites reported so far. The present study demonstrates that the dynamic 3-phase interfacial electropolymerization combining SWCNT chemical doping is effective to fabricate high-performance polymer thermoelectric composites.
       
  • Fatigue damage of cohesive interfaces in fiber-reinforced polymer
           composite laminates
    • Abstract: Publication date: 20 October 2019Source: Composites Science and Technology, Volume 183Author(s): S.S.R. Koloor, M.A. Abdullah, M.N. Tamin, M.R. AyatollahiAbstractThe weak interfaces in fiber-reinforced polymer (FRP) composite laminates often dictates the reliability of the composite structures. In this respect, a new cyclic cohesive zone model (CCZM) is introduced for accurate quantitative description of the interlaminar fatigue failure process. The model incorporates the interlaminar damage through the measured fatigue degradation of the strength, stiffness, and critical energy release rate properties. A combined experimental-finite element (FE) approach is employed to establish the residual interlaminar properties. The new CCZM is examined for the case study on the end-notched flexure (ENF) beam specimen of unidirectional carbon fiber-reinforced polymer (CFRP) composite laminate. The calculated applied resultant shear stress at the critical interface material point, adjacent to the pre-existing crack front, fluctuates at (τmax = 30 MPa, R = 0.1). The interlaminar shear-induced damage shows a sigmoidal form of the damage evolution curve. The pre-existing interface crack propagation begins at 301750 cycles, while maintaining an almost straight advancing crack front.
       
  • 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-BaghaAbstractGraphene 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.
       
  • Toughening in nanosilica-reinforced epoxy with tunable filler-matrix
           interface properties
    • Abstract: Publication date: Available online 30 August 2019Source: Composites Science and TechnologyAuthor(s): Catalin R. Picu, Krzysztof K. Krawczyk, Zehai Wang, Hojabr Pishvazadeh-Moghaddam, Manfred Sieberer, Alice Lassnig, Wolfgang Kern, Anton Hadar, Dan M. ConstantinescuAbstractIn this work we develop an epoxy nanocomposite reinforced with silica nanoparticles in which the filler-matrix interfaces are functionalized with photosensitive phenylazide moieties, which allows controlling the interface mechanical properties by exposure to UV radiation. We demonstrate that the ability of the material to deform plastically and its toughness depend significantly on the strength of interfaces. Significant toughness improvement is obtained at low filling fractions (1 wt%) when using Stöber silica of 520 nm diameter with weak interfaces. We perform testing under different loading modes in order to control the crack tip plastic zone size, and observe substantial toughness improvement when crack tip plastic dissipation is enabled, which we associate with void growth at filler particles. Increasing the filler-matrix interfacial strength by photochemical (UV) activation of phenylazides leads to the reduction of the toughening effect.
       
  • A microscale integrated approach to measure and model fibre misalignment
           in fibre-reinforced composites
    • Abstract: Publication date: Available online 30 August 2019Source: Composites Science and TechnologyAuthor(s): T.A. Sebaey, G. Catalanotti, N.P. O'DowdAbstractComputational micromechanics of fibre-reinforced polymers (FRPs) relies on the ability of the representative volume elements (RVEs) to take into account the different features that characterise the geometry of the material system under consideration. Fibre misalignment has been proven experimentally to have a significant effect on the mechanical properties at the macroscale, but is not currently taken into consideration in models at the individual fibre level, perhaps due to the difficulty in statistically characterising the fibre misalignment. In this work, an integrated approach is presented to measure and model fibre misalignments in FRPs. A computed tomography (CT) scan is used to identify the fibre geometry and statistically characterise the fibre misalignment angle distribution. Using a methodology recently developed by the authors, three-dimensional (3D) RVEs were generated by requiring their misalignment angle distribution to fit the empirical distribution. The methodology proposed provides a framework for the systematic numerical analysis of the influence of fibre misalignment on mechanical properties of FRPs.
       
  • Insight into the effect of interface on the mechanical properties of
           Mg/PLA composite plates
    • Abstract: Publication date: Available online 30 August 2019Source: Composites Science and TechnologyAuthor(s): Hong Cai, Xuan Li, Chenglin Chu, Feng Xue, Chao Guo, Qiangsheng Dong, Jing BaiAbstractMicro-arc oxidation (MAO) is used for interface modification of biodegradable poly(lactic acid) (PLA) based composite reinforced with magnesium alloy sheets (MASs/PLA). The intermolecular force and strong mechanical interlocking between the MgO and PLA play a significant role in the interface strengthening. Tensile-shear tests reveal 3 times improvement of the interface tensile-shear strength after MAO treatment of MASs, thereby leading to the enhanced macroscopic properties of the composite plate. Investigations based on the lamination theory suggest the tensile stress of PLA on the bottom of composite plate can be improved from 38 MPa to 47 MPa by interfacial constraint strengthening derived from MAO. The experimental and theoretical analysis of mechanical properties of the Mg/PLA composites is useful for further optimizing their preparation technology.
       
  • Structural evolution of stretch deformed HDPE/RGO nanocomposites: An
           in-situ synchrotron SAXS and WAXD study
    • Abstract: Publication date: Available online 30 August 2019Source: Composites Science and TechnologyAuthor(s): Yiguo Li, Tianchen Duan, Guibin Yao, Yujing Tang, Weijun Miao, Zongbao WangAbstractWe have reported that the incorporation of reduced graphene oxide (RGO) can induce epitaxial crystallization of high density polyethylene (HDPE) on RGO surfaces and then enhance mechanical properties of HDPE/RGO nanocomposites, but the underline intensifying mechanism remains unclear. Herein, to further unveil the influence of epitaxial crystallization imposing on the improvement of mechanical properties, the structural evolution of HDPE/RGO nanocomposites during the stretching process is explored as a function of RGO content by in-situ synchrotron wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) techniques. It has shown that the introducing of RGO apparently retards the structural evolution in the tensile deformation and the hysteresis is accentuated dramatically with increasing RGO content. The epitaxial growth of HDPE upon RGO surfaces forms large sized crystals and the amount of epitaxial crystals enlarges with RGO content. The coupling of the remained existence of large sized crystals and the smaller density after stretching demonstrates that the interplay between RGO and large amount of epitaxial crystals can undergo the strong stress and thus hampers and delays the structure change and crystal fragmentation during the tensile deformation of HDPE/RGO nanocomposites. The present results not only makes clear that it is the epitaxial crystallization stemming from interfacial interaction between HDPE and RGO that plays the major role to delay the structural evolution and damage and thus lead to the enhancement of mechanical properties of HDPE/RGO nanocomposites, but reveal the underline stress-induced fragmentation-recrystallization mechanism for this tensile deformation.
       
  • Understanding and control of interactions between carbon nanotubes and
           polymers for manufacturing of high-performance composite materials
    • Abstract: Publication date: Available online 29 August 2019Source: Composites Science and TechnologyAuthor(s): Cécile A.C. Chazot, A. John HartAbstractComposite materials combining carbon nanotubes (CNTs) and polymers have been widely sought to achieve high strength, high toughness, and in some cases multifunctional performance. Individual CNTs exhibit outstanding mechanical, electrical and thermal properties, and their nanometer-scale diameter and high aspect ratio enables load transfer to polymers via van der Waals, π interactions, or covalent bonding. Yet, while most early research on CNT-polymer composites focused on using CNTs as a filler to polymer matrices at low loadings, recent emphasis has been placed on processing methods that leverage organized CNT assembles, such as forests, sheets, or fibers, to achieve highly loaded CNT composites via polymer infiltration. Realization of such composites requires understanding of the how CNT-polymer interactions govern processability and mechanical properties. As such, this review summarizes the fundamental principles that govern CNT-polymer interaction, and how polymer characteristics coupled with CNT network properties influence wetting and infiltration, governing the final composite morphology. Various approaches to infiltration of CNT materials with polymers are explained, and the resulting mechanical properties are discussed in terms of their limiting mechanisms.
       
  • Ultrathin, flexible transparent Joule heater with fast response time based
           on single-walled carbon nanotubes/poly(vinyl alcohol) film
    • Abstract: Publication date: Available online 29 August 2019Source: Composites Science and TechnologyAuthor(s): Bing Zhou, Xueqing Han, Liang Li, Yuezhan Feng, Tao Fang, Guoqiang Zheng, Bo Wang, Kun Dai, Chuntai Liu, Changyu ShenAbstractUltrathin flexible transparent film heaters (TFHs) with fast response time are fabricated by embedding single-wall carbon nanotubes (CNTs) into transparent poly(vinyl alcohol) (PVA) film using a green all-water based solution process. Typically, CNTs network was firstly constructed on the surface of commercial polycarbonate film by a continuous hot roll pressing and spraying technique. The obtained CNTs network was then transferred to the surface of ultrathin PVA film using a transfer spinning technique coupled with hot pressing approach. The resulting film not only shows well optical and electrical properties of 475 Ω/aq with a transmittance of 77.3%, but also exhibits strong interfacial adhesion (standing 100 repeated scratches with 3 M sticky tape) and good flexibility (allowing more than 1000 bending cycles). Very interestingly, the fabricated PVA/CNT TFHs presents a quick Joule heating effect with a very fast heating time and rate of 8 s and 11.4 °C/s, respectively, under low impressed voltage (
       
  • Fabrication of flax fibre-reinforced cellulose propionate thermoplastic
           composites
    • Abstract: Publication date: Available online 27 August 2019Source: Composites Science and TechnologyAuthor(s): W. Woigk, C.A. Fuentes, J. Rion, D. Hegemann, A.W. van Vuure, E. Kramer, C. Dransfeld, K. MasaniaAbstractNatural materials such as wood exhibit high mechanical properties through cellulose structured at multiple length scales and embedded in a matrix of similar chemical structure. These hierarchical materials have inspired the design of lightweight composites composed of naturally occurring polymers. However, the close proximity of melt and decomposition temperature remain a challenge. In this work, cellulose propionate (CP) is modified to reduce its glass transition temperature and melt viscosity, allowing its use as a matrix in a natural fibre-reinforced composite. Through better impregnation, the modified CP matrix composites showed an increase in stiffness and strength of ∼10% and 20%, respectively, in comparison to unmodified CP matrix composites. The impact properties also increased by up to 28%, showing that modified CP is a credible matrix for realising sustainable all-cellulose natural fibre composites with high stiffness, strength and toughness.
       
  • Diamond nanothread reinforced polymer composites: Ultra-high glass
           transition temperature and low density
    • Abstract: Publication date: Available online 27 August 2019Source: Composites Science and TechnologyAuthor(s): W.M. Ji, L.W. ZhangAbstractDiamond nanothread (DNT), a novel carbon-based nanomaterial exhibiting ultra-light density and outstanding mechanical properties, has attracted intensive attentions in polymer composites. This study investigates the influences of DNT on the glass transition temperature (Tg) of poly (methyl methacrylate) (PMMA) composites and reveals the glass-rubber transition mechanism through molecular dynamics simulation. We demonstrates that DNT exhibits better improvement than other carbon-based nanomaterials in enhancing the Tg of PMMA composite, suggesting that DNT is a promising reinforcement for polymer nanocomposite with higher service temperature and better mechanical performances. Significantly, we find that interfacial interactions including van der Waals interaction and mechanical interlocking play an important part in glass transition of PMMA composite. The transition from glassy state to rubbery is induced through the interfacial debonding brought by the enlargement of free volume at the interface. According to the interfacial degrading mechanism, cross links between DNT reinforcement and PMMA chains are introduced to provide bidirectional hindrance for free motions of polymer chains, resulting in a 70 K enhancement of Tg of PMMA composites. These findings not only shed light to the prospective application of DNT in advanced nanocomposite, but also provide important guidance to improve the reinforcing efficiency of nanomaterials in engineering application, such as building and aerospace industry.
       
  • Carbon nano bowl array derived from a corncob sponge/carbon
           nanotubes/polymer composite and its electrochemical properties
    • Abstract: Publication date: Available online 27 August 2019Source: Composites Science and TechnologyAuthor(s): Zeming Fang, Lin Cao, Fenglin Lai, Debin Kong, Xusheng Du, Huaijun Lin, Zhidan Lin, Peng Zhang, Wei LiAbstractIn this paper, carbon nano bowl array with an octopus sucker-like morphology was fabricated for the first time. A ternary corncob sponge/carbon nanotube/ethylene-vinyl acetate copolymer (CS/CNT/EVA) composite was used as the carbon source and turned into a nano bowl array after a one-step heat treatment. The corncob sponge substrate was carbonized to be a honeycomb-like sponge composed of carbon sheets, and carbon nano bowls originate from EVA were generated on the sheets due to the comprehensive effects of surfactants and CNT, resulting in a carbon nano bowl array structure. This structure endowed the resulting material with a high capacitance of 213.4 F g−1 at a current density of 0.5 A g−1, good rate ability and excellent cycling stability with a loss of less than 2% over 10000 cycles. The solid-state capacitors assembled possess a good energy density of 0.98 W h kg−1 at a power density of 8000 W kg−1. These findings show that our method for fabricating a new kind of carbon nanostructures is promising and that the material obtained is a candidate for supercapacitor electrodes.
       
  • A trade-off study toward highly thermally conductive and mechanically
           robust thermoplastic composites by injection moulding
    • Abstract: Publication date: Available online 23 August 2019Source: Composites Science and TechnologyAuthor(s): Yanjuan Ren, Haichang Guo, Yuhang Liu, Ruicong Lv, Yafei Zhang, M. Maqbool, Shulin BaiAbstractIn order to achieve high thermal conductivity (TC) for graphene-reinforced thermoplastic polymer composites, many efforts have been made to reduce the interfacial thermal resistance. However, good mechanical properties may be conflicting with thermal properties due to the poor interaction bonding between matrix and fillers. In this work, graphene sheets (GSs) filled thermoplastic polypropylene (PP) composite are prepared by three different molding methods: i) melt extrusion with subsequent injection moulding, ii) single injection moulding and iii) hot-pressing. The relationship among processing methods, microstructures and properties are systematically demonstrated in detail. It is found that single injection moulding can be used to realize a random distribution of the filler with modest size to keep good mechanical properties, and an acceptable conductive network in the matrix to improve the thermal transfer ability of the composites. As a result, high TC of 2.07 Wm−1K−1 and tensile strength of 24 MPa are simultaneously achieved for 20 wt% GSs/PP composite, realizing a tradeoff between thermal and mechanical properties. Finite element simulation is also conducted to perceive the dependence of the thermal properties on the size and distribution of GSs filler. We think that this work provides an instructive route to design thermoplastic composites with overall consideration of thermal and mechanical properties and allows a considerable step to its industrial application.
       
  • Microstructural analysis of short glass fiber reinforced thermoplastics
           based on x-ray micro-computed tomography
    • Abstract: Publication date: Available online 26 July 2019Source: Composites Science and TechnologyAuthor(s): Patrick Arthur Hessman, Thomas Riedel, Fabian Welschinger, Kurt Hornberger, Thomas BöhlkeAbstractAs a result of the injection molding process, short glass fiber reinforced thermoplastics (SFRT) exhibit complex microstructures with fibers of different length and orientation as well as spatially varying fiber volume fractions. Their mechanical and functional performance can therefore only be predicted and ensured based on precise knowledge of said microstructure. To that end, x-ray micro-computed tomography (μCT) is commonly employed, with analysis software most-often yielding the fiber orientation tensors but lacking more detailed results. In order to increase the quality of the microstructural data, more accurate analysis techniques are necessary that include single fiber information for detailed correlations of microstructural parameters. In this work, a novel algorithm is suggested that relies on an iterative single fiber segmentation and merging procedure to obtain the fiber characteristics: orientation, location, radius and length. The algorithm is implemented in an efficient manner in Python, making heavy use of parallelization techniques. It is then applied to μCT scans and artificially generated 3D data of short glass fiber reinforced polyamide 6.6 with fiber mass fractions of 35%. The algorithm has been validated using reference data, commercial software and experimental fiber length data from an incinerated specimen and was shown to be both robust and accurate.
       
  • Corrigendum to ‘experimental investigation on graphene oxides coated
           carbon fibre/epoxy hybrid composites: Mechanical and electrical
           Properties’[Compos. Sci. Technol. 179 (2019) 134–144]
    • Abstract: Publication date: Available online 18 July 2019Source: Composites Science and TechnologyAuthor(s): Lokasani Bhanuprakash, Sampath Parashuram, Soney Varghese
       
  • In-situ 3D fracture propagation of short carbon fiber reinforced
           polymer composites
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Kaifeng Wang, Shenli Pei, Yang Li, Jingjing Li, Danielle Zeng, Xuming Su, Xianghui Xiao, Nannan ChenAbstractThis paper explored the 3D progressive fracture process of a short carbon fiber reinforced polymer composite under uniaxial tensile loading via high-resolution in-situ micro X-ray computed tomography (μXCT). Microstructural features extracted from the μXCT images were analyzed with the Halpin-Tsai model, laminate analogy approach, and shear-lag model to calculate the mechanical properties and interpret the different fracture morphologies and progressions observed in the “skin-core-skin” structure. The in-situ μXCT scanning revealed a clear fracture progression in the skin layer, which was defined by four stages, i.e., nucleation of small pores at fiber ends, coalescence of pores, initiation of cracks, and propagation of cracks until fracture, whereas no significant fracture feature was found in the core layer. To analyze the difference in the fracture mechanisms in the skin and core layers, the maximum fiber normal stress and average interfacial shear stress were calculated from the microstructural features. The results were also confirmed by the 3D strain distribution quantified via a volumetric digital image correlation method. It was determined that the dominant fracture mechanism in the skin layer was fiber pull-out, rather than fiber breakage, as a consequence of pore formation at the fiber ends; its extent mainly depended on the fiber length and orientation angle. Fiber/matrix debonding was the main fracture mechanism in the core layer, which resulted from the propagation of cracks initiated from the skin layer.
       
  • Microwave loss percolation effect and microwave self-healing function of
           FeNip/PP nanocomposites
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Ruru Bai, Hanzhe Zhu, Diyin Xie, Zhenghou Zhu, Qi Zhong, Jie Chen, Hui Zhao, Dengyu LiuAbstractBased on the study of microwave loss percolation effect of FeNip/PP nanocomposites, the microwave healing technology of FeNip/PP nanocomposites was proposed and its mechanism was studied. There is a unique microwave loss percolation characteristic between the microwave loss factor (tanδ) of FeNip/PP nanocomposites and the content of FeNi powders (0–20 wt%), and the percolation area is the range of 2–10 wt%. The microwave healing technology can realize the self-healing property of the PP-based composites. When the composites received the microwave signal, the magnetic nanopowders generate heat effect to heat the resin matrix, which forms a mobile phase. The mobile phase, melted PP matrix with some magnetic nanopowders, moved toward the microcracks, thereby healing or reducing microcracks inside the composite. The optimum time for microwave treatment was 15 min. After microwave healing, the microcracks of the composites were closed, and the tensile strength of FeNip/PP nanocomposites can be restored to 90% of that before damage.
       
  • Human-interactive drone system remotely controlled by printed
           strain/pressure sensors consisting of carbon-based nanocomposites
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Byeong-Cheol Kang, Tae-Jun HaWe demonstrate human-interactive drone remote control system consisting of high-performance printed strain/pressure sensors with carbon-based nanocomposites, fabricated by all-solution-process at 80 °C. The armband-type drone remote control system was designed by a main control operation module, a sensing module and a signal processing module at an overall size of 12  cm × 7  cm x 1.5 cm (width x length x height). Rapid and accurate sensing properties of the sensing module were realized by the structural integration of nanocomposites on flexible/stretchable substrates attached to the human body. Furthermore, simultaneous visualization of processed data on the user's smartphone with an Android application by detecting the movements of human-body in real-time can open up new routes for the upcoming internet of things platform based on nanocomposition in industries. Notably, it is the feasible demonstration of a system-level drone remote controller operated by signal processing in real-time from highly sensitive printed strain/pressure sensors with carbon-based nanocomposites, exhibiting important functionality of waterproof and electric-isolation for human-interactive electronics.Graphical abstractImage 1
       
  • An improved technique for dispersion of natural graphite particles in
           thermoplastic polyurethane by sub-critical gas-assisted processing
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): An Huang, Hankun Wang, Thomas Ellingham, Xiangfang Peng, Lih-Sheng TurngAbstractDispersing fillers uniformly is the main technological challenge when considering nanocomposites. In this paper, a novel and efficient sub-critical gas-assisted processing (SGAP) technique is explored—an environmentally benign process that utilizes compressed CO2 to help effectively disperse aggregated natural graphite particles (NGPs) (3 wt%) in a thermoplastic polyurethane (TPU) matrix. A twin-screw extruder (TSE) equipped with a simple CO2 injection unit consisting of a standard gas cylinder, regulator, valve, and metal hose is employed for the melt mixing. Results from the structural, thermal, rheological, mechanical, microcellular injection molding, dielectric, and thermal conductive properties of the SGAP pellets, in addition to the resultant TPU/NGP nanocomposites, confirmed significantly improved dispersion compared to those obtained via conventional melt blending in the TSE. This technique offers a simple, cost-effective approach to the large-scale production of high-performance polymer nanocomposites without the requirement for complicated processing steps such as supercritical fluid (SCF) processes or chemical treatments.
       
  • Conductive shear thickening gel/Kevlar wearable fabrics: A flexible body
           armor with mechano-electric coupling ballistic performance
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Chunyu Zhao, Yunpeng Wang, Saisai Cao, Shouhu Xuan, Wanquan Jiang, Xinglong GongAbstractThis work reported a novel conductive shear thickening gel-Kevlar fabrics (c-STG/Kevlar) body armor material which possessed both anti-impact performance and dynamic mechano-sensing behavior. Due to the excellent shear thickening effect, the c-STG/Kevlar showed a higher safeguarding property than the neat Kevlar. Under low-velocity drop tower loading, the maximum center force of c-STG/Kevlar was only 5768 N, which was nearly half of the neat Kevlar (11414 N). During the high-velocity ballistic testing, the monolayer c-STG/Kevlar sample could absorb 21.6% impact energy. The c-STG/Kevlar displayed a mechano-electric coupling character since the electrical resistance of the c-STG/Kevlar was linearly dependent on the external impacts. A possible sensing mechanism was proposed and it was found that the impact damages could be evaluated by the resistance variation. Finally, an in situ impact-sensing helmet was obtained by using c-STG/Kevlar, which indicated that the above smart fabrics had wide potential in next generation body armor materials and wearable devices.
       
  • Failure mode maps of bio-inspired sandwich beams under repeated
           low-velocity impact
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): S.H. Abo Sabah, A.B.H. Kueh, N. Muhamad BunnoriAbstractExisting sandwich structures failure maps are confined only to data from the quasi-static bending tests even for describing failure modes due to the impact event. Strengths of the constituent layers, which are not well-described by these maps, can reasonably change especially under the repeated impact load case. Hence, a new series of more realistic failure mode maps have been developed from the experimentally and numerically obtained observations on recently proposed bio-inspired dual-core sandwich beams in the presence of repeated low-velocity impacts of different energy levels. The beams consist of top and bottom carbon fiber reinforced polymer skins sandwiching the rubber and aluminum honeycomb cores. Departing from the modified Gibson model, an actual presentation of skin and core behaviors has been modeled following the trend of strengths variations for the construction of the failure mode maps when subjected to numerous impact numbers and energies. The produced maps offer the flexibility to accommodate the changes in strengths due to deterioration or densification of constituent layers after impact, and hence following more favorably the physical failure description of the sandwich beams. Accompanying these maps, a general set of mathematical expressions have also been produced for practical convenience. It is found that the failures from observations are within the proposed map boundaries with accuracies ranging from 85.7% to 100%.
       
  • Recyclable nanocomposite foams of Poly(vinyl alcohol), clay and cellulose
           nanofibrils – Mechanical properties and flame retardancy
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Lilian Medina, Federico Carosio, Lars A. BerglundAbstractFoam-like clay-nanocellulose hybrids are of great interest as load-bearing structural foams with excellent fire retardancy, due to unique effects from clay on thermal cellulose degradation. For the first time, the fire retardancy of clay-nanocellulose foams are studied in detail, in particular the effect of a third polymer phase, poly(vinyl alcohol). The composition with optimum mechanical properties and fire retardancy is identified and analyzed. Foams are prepared by freeze-drying and the compositions are varied systematically. Thermogravimetric analysis is performed on foam degradation. Mechanical properties from compression tests and fire retardancy data from cone calorimetry are reported, together with cellular structures from SEM and relative density estimates for the foams. Self-extinguishing foams are obtained with superior flame retardancy to commercial polymer foams. Addition of poly(vinyl alcohol) is beneficial for mechanical properties of clay-nanocellulose foams, but impedes the fire retardancy by reducing clay-cellulose synergies and cellulose charring during degradation.
       
  • Polyacrylonitrile/liquid crystalline graphene oxide composite fibers –
           Towards high performance carbon fiber precursors
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): N.V. Salim, X. Jin, J.M RazalAbstractWe have prepared high performance, continuous carbon fiber precursors mimicking the industrial processing by wet spinning technology using polyacrylonitrile (PAN)/liquid crystalline graphene oxide (LCGO) for the first time. This work highlights the unexplored production of novel PAN composite fibers with addition of very low percentage of LCGO without using any surface modifications or coating. Following the coagulation process, as spun PAN/LCGO fibers were passed through a series of wash baths operated at various temperatures and multiple hot stretching baths prior to drying, and taken-up using a traversing winder. Current study also investigates the chemical and microstructural changes of PAN due to the addition of very low amounts of GO without the use of binders or surface treatments. The tensile strength and tensile modulus of the fibers were significantly improved with low filler content up to 1 wt% of LCGO into PAN dope that is, a 115% improvement of tensile strength and 152% increase of tensile modulus were achieved at a filler loading of 0.5 wt% whereas 138% improvement in tensile strength at 1 wt% of LCGO. This study revealed that it is possible to produce high strength precursor fibers by wet spinning with the addition of low filler content by make use of LCGO in PAN solution; this can further provide pathways for making high performance carbon fibers.
       
  • Improving the electrical conductivity and fracture toughness of carbon
           fibre/epoxy composites by interleaving MWCNT-doped thermoplastic veils
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Dong Quan, Chiara Mischo, Xiping Li, Gennaro Scarselli, Alojz Ivanković, Neal MurphyAbstractPolyethylene terephthalate (PET) veils doped with and without multi-walled carbon nanotubes (MWCNT) were used to interlay a unidirectional carbon fibre/epoxy composite. The electrical and fracture properties of the laminates were studied. Significant improvements in the Mode-I fracture energy (GIC) and Mode-II fracture energy (GIIC) of the laminates were observed for interlaying the original PET veils. This was associated with a considerable drop in the electrical conductivity. Doping a small amount of MWCNTs on the PET interlayers strikingly improved the electrical conductivity of the laminates, especially in the through-thickness direction. However, it also resulted in moderate decreases in GIC and GIIC. Interestingly, this was caused by an improved PET fibre/epoxy adhesion due to the presence of the MWCNTs on the PET fibres, that restrained the PET fibre bridging in the fracture process. The experimental results demonstrated the potential of developing both highly electrically conductive and tough laminates by interlaying MWCNT-doped thermoplastic veils.
       
  • Preparation of electrospun chitosan/poly(ethylene oxide) composite
           nanofibers reinforced with cellulose nanocrystals: Structure, morphology,
           and mechanical behavior
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Dong Wang, Wanli Cheng, Qingxiang Wang, Junjiao Zang, Yan Zhang, Guangping HanAbstractCellulose nanocrystals-reinforced chitosan-poly(ethylene oxide) (CNC/CS-PEO) nanofibers were successfully prepared by electrospinning. The nanofibers reinforced with CNC exhibited excellent mechanical performance. The tensile strength of CNC/CS-PEO nanofibers with 6 wt% CNC loading was increased by 5.76 MPa, 33.5% higher than that of CS-PEO nanofibers. Smooth nanofibers with diameters of about 500 nm could be obtained with lower CNC loading. The diameter of CNC/CS-PEO nanofibers increased with increase in CNC loading and cross-linking between fibers was observed with 8 wt% CNC loading. The thermal stability of nanofibers was enhanced due to interactions between CS-PEO matrix and CNC nano-reinforced phase. Too strong or too weak CNC chain migrations reduced the crystallization of CS-PEO. FT-IR results showed that CS-PEO and CNC were physically mixed together. The CNC reinforced nanofibers show excellent performance, have low cost, and are degradable and hence have potential applications in biological field.
       
  • Realising bio-inspired impact damage-tolerant thin-ply CFRP Bouligand
           structures via promoting diffused sub-critical helicoidal damage
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Lorenzo Mencattelli, Silvestre T. PinhoAbstractIn this work, we manufactured bio-inspired thin-ply Carbon Fibre Reinforced Plastic (CFRP) laminates, mimicking the helicoidal architecture of the mantis shrimp's dactyl club periodic region, with the smallest inter-ply (pitch) angle in the literature (2.5∘), thus better mimicking the actual micro-structure of the dactyl club. We conducted Low Velocity Impact (LVI) tests on a wide range of pitch angles (2.5∘, 5∘, 10∘, 20∘, 45∘), thus demonstrating that decreasing the pitch angle leads to a progressively smoother double helicoidal evolution of damage, reduces delamination areas, diffuses sub-critical damage, and enhances damage tolerance. We then conducted Compression After Impact (CAI) tests, thereby demonstrating that the residual strength and failure strain are preserved as the pitch angle is reduced, even though there is a steep decrease in the proportion of 0∘-plies (plies aligned with the loading direction) as the pitch angle decreases. Via detailed modelling, we then developed and proposed an explanation for why very small pitch angles are required to achieve the beneficial damage mechanisms exhibited by biological Bouligand structures.
       
  • Heterogeneous nucleation promoting formation and enhancing microwave
           absorption properties in hierarchical sandwich-like polyaniline/graphene
           oxide induced by mechanical agitation
    • Abstract: Publication date: Available online 12 August 2019Source: Composites Science and TechnologyAuthor(s): Jia Liu, Yuping Duan, Lulu Song, Jianjun Hu, Yuansong ZengAbstractIn this paper, polyaniline/graphene oxide composites were prepared by a one-step intercalation polymerization of aniline in the presence of GO layers under different mechanical agitation duration period, and the formation mechanism and microwave absorbing mechanism were investigated for an entire hierarchical sandwich-like structured polyaniline/graphene oxide composites. The morphology and structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) nitrogen sorption-desorption measurement and vector network analysis (VNA). The results revealed that mechanical agitation duration promoted the heterogeneous nucleation of aniline on graphene oxide layers and induced the formation of PANI-GO-PANI sandwich-like microstructure. The minimum reflection loss of entire sandwich-like structure reaches −28.12 dB at 5.675 GHz and an ultra-wide effective absorbing bandwidth (RL  
       
  • Stretchable photodetector utilizing the change in capacitance formed in a
           composite film containing semiconductor particles
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Sungwoo Jun, Kwang Wook Choi, Kwang-Seok Kim, Dae Up Kim, Chan-Jae Lee, Chul Jong Han, Cheul-Ro Lee, Byeong-Kwon Ju, Jong-Woong KimAbstractConventional photodetectors (PDs) are based on measuring photocurrent, which is formed by the separation of electron-hole pairs generated in semiconductors upon light irradiation, through electrodes in direct contact with the semiconductors. Such devices are usually fabricated through complicated and precise processes such as thin film formation by vacuum deposition and fine patterning by photolithography and etching. In addition, PDs have a drawback that the contact quality between the electrode and the semiconductor is easily affected by external stress applied to the device. These issues make it difficult to implement a mechanically flexible device driven by conventional sensing mechanisms. Here we report a simple structured PD based on a semiconductor particle-polymer composite layer surrounded by two facing transparent electrodes, inspired by the fact that the dielectric properties of certain semiconductors change upon light irradiation with a photonic energy greater than or equal to their bandgap. In order to realize this, we synthesized a transparent and stretchable polymer, polyurethane-urea (PUU), which is compatible with Ag nanowires (AgNWs) and polydimethylsiloxane (PDMS) used for implementing stretchable electrodes, and dispersed ZnS:Cu particles into the PUU to form a sensory layer. The fabricated composite surrounded by two facing AgNW-based transparent electrodes was transparent and stretchable, and the capacitance formed at the composite sensitively changed upon irradiation of light with a wavelength of 420 nm and a power of 1.2 mW/cm2 even when the device was stretched or cut in half.
       
  • Morphologies and properties of epoxy/multi-walled carbon nanotube
           nanocomposite foams prepared through the free-foaming and limited-foaming
           process
    • Abstract: Publication date: Available online 8 August 2019Source: Composites Science and TechnologyAuthor(s): Lijun Wang, Yue He, Tuanhui Jiang, Xiang Zhang, Chun Zhang, Xiangfang PengAbstractMicrocellular epoxy/multi-walled carbon nanotube (EP/MWCNT) composite foams loaded with 2 wt% (mass fraction) of MWCNT were prepared through the free-foaming process (Fre-foam) and limited-foaming process (Lim-foam) using chemical foaming agent (CFA), respectively. The morphologies of EP/MWCNT composite foams with different densities were analyzed by scanning electron microscopy (SEM). It was found that the cell size of both Fre-foam and Lim-foam decreased with increasing the density, while Lim-foam exhibited a smaller cell size and a higher cell density in contrast to those of Fre-foam at similar density. In addition, the dynamic mechanical properties, thermal stability, and electrically and thermal conductive properties of the EP/MWCNT foams in the density range of 0.278 g/cm3–1.108 g/cm3 were investigated and the difference in performances between Fre-foam and Lim-foam was analyzed. Lim-foam had an obviously lower crosslink density than that of Fre-foam due to the effect of compressed gas, which was clearly reflected in the results of gel fraction, glass transition temperature (Tg), molecular weight between crosslinks (Mc), and initial thermal decomposition temperature. Compared with Fre-foam, Lim-foam had superior thermal conductive property and exhibited weak electrically conductive property, indicating the conductive pathway was affected by the foaming process.
       
  • Method to determine the required microstructure size to be represented by
           a second order fibre orientation tensor using X-ray micro computed
           tomography to evaluate compression moulded composites
    • Abstract: Publication date: Available online 8 August 2019Source: Composites Science and TechnologyAuthor(s): Trevor Sabiston, Kaan Inal, Pearl Lee-SullivanAbstractThe second order fibre orientation tensor has been used to predict the mechanical response of injection and compression moulded composites with the capability to couple mould filling with structural finite element simulations to account for the microstructure. In order to accurately model these materials the mesh size used simulations must be representative of the actual microstructure of the composite. Herein a method to determine the microstructure size required to achieve a near constant value of the orientation tensor based on its derivative is presented. The method is demonstrated with the microstructure of a sheet moulding compound composite which has been evaluated using X-ray micro computed tomography. The average values of the derivative of the orientation tensor and its standard deviation approach constant values with increasing microstructure size. For the material considered a microstructure size of 5 mm square is sufficient to achieve a near constant value of the fibre orientation tensor, which is called a microstructural unit.
       
  • A stochastically homogenized peridynamic model for intraply fracture in
           fiber-reinforced composites
    • Abstract: Publication date: Available online 8 August 2019Source: Composites Science and TechnologyAuthor(s): Javad Mehrmashhadi, Ziguang Chen, Jiangming Zhao, Florin BobaruAbstractThe quasi-static fracture behavior in the transverse cross-section of unidirectional fiber-reinforced composites (FRCs) is investigated using a new intermediately-homogenized peridynamic (IH-PD) model and a fully homogenized peridynamic (FH-PD) model. The novelty in the IH-PD model here is accounting for the topology of the fiber-phase in the transverse sample loading via a calibration to the Halpin-Tsai model. Both models, overall, capture well the measured load-displacement behavior observed experimentally for intraply fracture, without the need for an explicit representation of microstructure geometry of the FRC. The IH-PD model, however, is more accurate and produces crack path tortuosity as well as a stick-slip load-crack-opening softening curve, similar to what is observed experimentally. These benefits come from the preservation of some micro-scale heterogeneity, stochastically generated in the IH-PD model to match the composite's fiber volume fraction, while its computational cost is equivalent to that of an FH-PD model. The two models lead to dramatically different failure modes for the case of an asymmetric pre-notch: with the FH-PD model, failure always starts from the pre-notch tip, while with the IH-PD model, when the pre-notch is sufficiently far from the center, the composite is predicted to fail from the center of the sample, not from the pre-notch. Experiments that can confirm these findings are sought.
       
  • Low percolation 3D Cu and Ag shell network composites for EMI shielding
           and thermal conduction
    • Abstract: Publication date: Available online 8 August 2019Source: Composites Science and TechnologyAuthor(s): Seung Hwan Lee, Seunggun Yu, Faisal Shahzad, Junpyo Hong, Seok Jin Noh, Woo Nyon Kim, Soon Man Hong, Chong Min KooAbstractMetal-coated polymer bead based composites are promising as electromagnetic interference (EMI) shielding and thermally conductive materials because they form a percolation 3D metal shell network at very low filler content. Herein, we fabricated 3D Cu/Ag shell network composites through electroless plating of metal on polymer beads and a simple hot pressing technique. Cu and Ag shells provide a continuous network for electron and heat conduction; thus, yielding excellent EMI shielding effectiveness of 110 dB at a 0.5 mm thickness and a thermal conductivity of 16.1 W m−1K−1 at only 13 vol % of metal filler. The properties of composites depend on the size of polystyrene (PS) beads and large size metal-coated PS bead composites exhibit higher electrical conductivity, EMI shielding effectiveness, and thermal conductivity than small size bead composites. These results are ascribed to the reduction in the number of contact interfaces between metal-coated beads, which minimizes the interfacial resistance. This study is set to pave the way for designing advanced EMI shielding and thermal conductive materials by a scalable and efficient synthesis approach.
       
  • Warp direction fatigue behavior and damage mechanisms of centrally notched
           2.5D woven composites at room and elevated temperatures
    • Abstract: Publication date: Available online 7 August 2019Source: Composites Science and TechnologyAuthor(s): Jian Song, Weidong Wen, Haitao Cui, Yuejiao Wang, Yang Lu, Wujian Long, Lixiao LiAbstractFatigue behavior, notch sensitivity and environmental effect are three of the principal concerns in composite applications, especially those for aeroengines that require mechanical fastening and fatigue resistance at elevated temperatures. As a new generation of woven composites, 2.5D woven composites (2.5DWC), have drawn increasing amounts of interest due to the excellent fatigue resistance of these materials. However, the lack of temperature-dependent fatigue explorations into centrally notched 2.5DWC (N-2.5DWC) significantly limits the engineering applications of these materials. Therefore, the objective of this paper is to investigate the temperature-dependent fatigue behavior of N-2.5DWC. Warp direction tension-tension fatigue tests of N-2.5DWC were performed at 20 °C and 180 °C for the first time. The fatigue lives and the related failure mechanisms were obtained experimentally. Interestingly, the fatigue life at the same temperature exhibited a sudden increase with a decreasing stress level. A temperature-dependent fatigue life prediction model was established, and the fatigue lives and damage propagation processes at various temperatures and stress levels were predicted. The predicted damage propagation process was a “L” shaped, which was consistent with the corresponding experimental fracture morphologies. Finally, the effects of temperature and warp arranged density on the warp direction fatigue life were discussed.
       
  • A highly adhesive flexible strain sensor based on ultra-violet adhesive
           filled by graphene and carbon black for wearable monitoring
    • Abstract: Publication date: Available online 6 August 2019Source: Composites Science and TechnologyAuthor(s): Ping Liu, Jian Liu, Xun Zhu, Chen Wu, Yue Liu, Weidong Pan, Junnan Zhao, Xiaohui Guo, Caixia Liu, Ying Huang, Aiguo SongAbstractEnsuring the accuracy of signal detection under repeated deformation is a challenge for flexible sensor reported in recent years, and achieving reliable adhension between the sensor and substrate is a key factor. Here, this article reported a highly adhesive flexible strain sensor based on ultra-violet adhesive filled by modified graphene and carbon black for wearable monitoring. This strain sensor with a typical resistive behavior shows gauge factor calculated at 0∼10% strain is 2.1. It exhibits short curing time (∼1 h), fast response (∼40 ms), excellent adhesive strength (4500 kPa), and adhesiveness to various bending surfaces. Furthermore, this strain sensor can be directly prepared on elastic columns and rubber gloves, and exhibits excellent performance in three-dimensional force detection and writing gesture recognition. The ability of adhesive conformability to arbitrary and complex surfaces shows that the strain sensor has broad application prospects in wearable devices.
       
  • Experimental investigation of high velocity oblique impact and residual
           tensile strength of carbon/epoxy laminates
    • Abstract: Publication date: Available online 6 August 2019Source: Composites Science and TechnologyAuthor(s): Ashwin R. Kristnama, Xiaodong Xu, David Nowell, Michael R. Wisnom, Stephen R. HallettAbstractComposite components are required to be resilient against Foreign Object Damage (FOD) induced by localised high velocity impact events. Here an experimental investigation into high velocity oblique impacts and residual tensile strength of thin quasi-isotropic carbon/epoxy laminates is reported. Oblique (45°) impacts between 100 m/s and 350 m/s were carried out using 3 mm steel cubes on the edge and the centre of the laminates, mounted as a cantilever beam. Impact induced damage was characterised using X-ray Computed Tomography (CT) and the residual strength of impacted laminates was determined through quasi-static tensile tests. The residual strength shows a strong dependence on the impact damage size, characterised in terms of fibre fracture width and delamination area. Machined notches were then investigated and compared to impacted laminates in terms of residual strength.
       
  • Free standing flexible conductive PVA nanoweb with well aligned silver
           nanowires
    • Abstract: Publication date: Available online 3 August 2019Source: Composites Science and TechnologyAuthor(s): Kiran Yadav, Ratyakshi Nain, Manjeet Jassal, Ashwini K. AgrawalAbstractIn the present study, polyvinyl alcohol (PVA) nanofibres having uniformly distributed, well aligned, and highly inter-connected silver nanowires are electrospun. Using the approach, a very high amount of nanowires (up to 34.5 wt%) could be successfully incorporated into the nanofibres. A free standing, highly conducting nanoweb is fabricated with the conductivity of approximately 655 S/cm. These conductive nanowebs are of interest for a number of electronic devices such as sensors or energy storage systems requiring flexibility and high surface area.
       
  • A high performance all-organic thermoelectric fiber generator towards
           promising wearable electron
    • Abstract: Publication date: Available online 3 August 2019Source: Composites Science and TechnologyAuthor(s): Xiaoqi Lan, Tongzhou Wang, Congcong Liu, Peipei Liu, Jingkun Xu, Xiaofang Liu, Yukou Du, Fengxing JiangAbstractFiber-based materials have gained great concern in wearable organic electrons due to reliable flexibility and excellent electron transport property. Thermoelectric (TE) conversion has been regarded as a promising energy harvesting for protable electron devices. However, the development of n-type organic material with good environmental stability hinder the further assembling of an all-organic TE generator. Herein, we designed and proposed an all-organic TE fiber generator composed of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and carbon nanotube (CNT) fibers. The p-type conductive fabrics with a relatively high electrical conductivity (18.8 S cm−1) were prepared based on the common cotton fabric (CNF) by simple soaking in PEDOT:PSS solution. The n-type CNT (n-CNT) fibers were obtained through polyethylenemine (PEI) treated p-type CNT (p-CNT) resulting in a high electrical conductivity (871 S cm−1) and Seebeck coefficient (−58 μV K−1) with excellent environmental stability. The flexible fiber-based TE generator was assembled by connecting p-type PEDOT:PSS-coated CNF (CNF@PP) and n-CNT fibers in series allowing a large output power (375 μW). The fabrication of all-organic fiber generator can promote the further development of organic TE energy harvest in wearable electrons.
       
  • Experimental and numerical investigation of the toughening mechanisms in
           bioinspired composites prepared by freeze casting
    • Abstract: Publication date: Available online 3 August 2019Source: Composites Science and TechnologyAuthor(s): Jingyu Liu, Ruixiang Bai, Zhenkun Lei, Chun Xu, Qingsong Ye, Wayde Martens, Prasad KDV. Yarlagadda, Cheng YanAbstractStrength and toughness have been generally deemed as two incompatible properties in many materials. However, balanced toughness and strength have been observed in biomaterials, whose hard and soft phases are arranged into unique and hierarchical architectures. Therefore, it is necessary to understand the underpinning toughening mechanisms and develop reliable procedures that can mimic these unique structures at different length scales. Here, alumina-Poly(methyl methacrylate) (PMMA) composites were prepared using freeze casting combined with interface modification (silanization treatment). High failure strain (∼4.5%) is achieved in these composites. The overall toughness can be tailored through modifying the interfacial strength between alumina and PMMA. A weaker interface (∼8 MPa) leads to a greater toughness (3.1 MPa m1/2), which is even greater than the constituent phases, i.e., alumina (2.71 MPa m1/2) and PMMA (1.1 MPa m1/2). Using a cohesive zone model and extended finite element method (XFEM), the toughening mechanism has been investigated.
       
  • Particle-toughened interlayers enhance mechanical response of composite
           laminates
    • Abstract: Publication date: Available online 2 August 2019Source: Composites Science and TechnologyAuthor(s): Minh Hoang Nguyen, Paul Davidson, Anthony M. WaasAbstractToughened composite materials, where the toughening agents are micro-particles dispersed within the interlayer resin rich regions, provide enhanced delamination resistance. This delay in delamination promotes intralaminar micro-cracking and macro-cracking, thus providing superior toughness. In this paper, a thorough study of damage accumulation was conducted to identify and quantify failure mechanisms in the ±45∘ laminate axial tensile test. Progression of damage accumulation was captured with digital image correlation techniques, in-situ inspection with high-resolution cameras and interrupted tests at different loading stages. Detailed cross-section microscopy of specimens were used to observe progression of crack formation, density of cracks formed and crack branching at the toughened interface.
       
  • Controlling of resin impregnation and interfacial adhesion in carbon
           fiber/polycarbonate composites by a spray-coating of polymer on carbon
           fibers
    • Abstract: Publication date: Available online 1 August 2019Source: Composites Science and TechnologyAuthor(s): Ting-Ting Yao, Yu-Ting Liu, Hong Zhu, Xiao-Fang Zhang, Gang-Ping WuAbstractTo improve the interfacial properties between carbon fibers (CFs) and polycarbonate (PC) resin, the PC resin was pre-coated onto the CF surfaces by a spray-coating method, and a post-heating process was applied for ensuring uniformity of the coating layer. To further investigate the interfacial interactions between the CFs and the coating layers, the physically-adsorbed PC resins were removed from some coated CFs by washing with solvent. The results showed that the CF/PC interfacial adhesion properties could be related to the coating thickness (or the resin impregnation) and fiber-matrix interactions. For a PC coating layer thinner than 0.15 μm, the PC could not be fully-impregnated into the CF bundles, thus leading to inferior CF/PC interfacial properties and mechanical properties in the final composites; while for a coating layer with thickness ranging from 0.15 to 0.32 μm, it allowed formation of well-impregnated interfaces; if coupled with a further hot-pressing for strengthening the interfacial bonding interactions, both the CF/PC interfacial shear strength and mechanical properties for the corresponding composites were significantly enhanced. The interfacial interactions and reinforcing mechanisms for the CF/PC composites were schematically proposed.
       
  • A novel aluminium/CFRP hybrid composite with a bio-inspired
           crossed-lamellar microstructure for preservation of structural integrity
    • Abstract: Publication date: Available online 31 July 2019Source: Composites Science and TechnologyAuthor(s): R. Häsä, S.T. PinhoAbstractIn this paper, we demonstrate that a novel hybrid composite of aluminium and Carbon Fibre Reinforced Polymer (CFRP) with a microstructure inspired by a biological crossed-lamellar microstructure is an attractive alternative for applications where structural integrity is paramount. Composites with such microstructure are prototyped and tested using both standard and thin-ply CFRP prepreg. Three-point bend tests are carried out in an SEM environment, showing extensive diffuse damage in the CFRP and yielding in the aluminium. This is the first hybrid crossed-lamellar-inspired microstructure in the literature and the results demonstrate that this novel microstructure can be loaded up to record large curvatures (in comparison with other CFRPs and hybrid CFRPs) while retaining its structural integrity and dissipating energy under stable conditions.
       
  • A new three-dimensional progressive damage model for fiber-reinforced
           polymer laminates and its applications to large open-hole panels
    • Abstract: Publication date: Available online 28 July 2019Source: Composites Science and TechnologyAuthor(s): Lixiao Wei, Wenqing Zhu, Zhongliang Yu, Junjie Liu, Xiaoding WeiAbstractWith fiber-reinforced Polymers (FRPs) widely used in aircraft, design and analysis of the mechanical performance and stability of structures and parts made of FRPs with various open-holes become very important. Currently, accurately predicting the failure patterns and ultimate strength of open-hole FRP structures remains very challenging. In this paper, a three-dimensional progressive damage model based on Puck's criterion on unidirectional FRP laminates has been developed. More importantly, a scaling algorithm that can differentiate the shear deformation modes and automatically modify the shear toughness has been proposed and implemented in the model. With this modified shear damage evolution law, our model accurately estimates the tensile strengths and captures the failure pattern of carbon fiber reinforced polymer (CFRP) panels consist of different stacking schemes with large open-holes in the middle. Furthermore, our model results point out that in panels of [±45]5 stacking scheme the inter-laminar stresses, although relatively small in magnitude, have a significant influence on the damage initiation locations.
       
  • Preparation and energy storage performance of transparent dielectric films
           with two-dimensional platelets
    • Abstract: Publication date: Available online 27 July 2019Source: Composites Science and TechnologyAuthor(s): Fei Wen, Hanyu Lou, Jianfei Ye, Wangfeng Bai, Luwen Wang, Lili Li, Wei Wu, Zhuo Xu, Gaofeng Wang, Zhicheng Zhang, Lin ZhangAbstractPolymer-based dielectric composites exhibiting high dielectric permittivity, low loss, high energy density, high charge-discharge efficiency, and easy process are critical to the development of cost-efficient and lightweight capacitors. BaTiO3/poly (vinylidene fluoride) (BT/PVDF) composites using two-dimensional (2-D) platelets were prepared and investigated in this work. The composites were prepared by a simple combination of solution cast and quenching treatment, without multiple-layer architecture or surface chemical treatment. The dielectric properties and energy storage performance of the composite were improved significantly compared to pristine PVDF. The composite film with a very low content of BT (1 wt%) illustrates a high discharge energy density of 9.7 J/cm3 at 450 MV/m, which is 2 times of pristine PVDF and nearly 5 times than the best commercial biaxially-oriented polypropylenes. In addition, the composite films show an excellent cycle stability and fatigue endurance. Simulation further revealed the local electric field and local polarization distribution of composite. The energy performance also matches or surpasses many previous reported composites with zero-dimensional (0-D) BT particles, one-dimensional (1-D) BT nanowires, and other 2-D dielectric fillers. This study provides a solution for obtaining high energy density dielectric composites with very low filler content by a simple and easy method, which is highly desired for power systems and advanced electronics.
       
  • Compressive failure of fiber composites containing stress concentrations:
           Homogenization with fiber-matrix interfacial decohesion based on a total
           Lagrangian formulation
    • Abstract: Publication date: Available online 27 July 2019Source: Composites Science and TechnologyAuthor(s): Vedad Tojaga, Selcuk Hazar, Sören ÖstlundAbstractCompression failure by fiber kinking limits the structural applications of fiber composites. Fiber kinking is especially prevalent in laminates with holes and cutouts. The latter behavior is characterized by strain localization in the matrix material and fiber rotations. To study fiber kinking on the level of the individual constituents, a homogenization of fiber composites is presented. It is based on a total Lagrangian formulation, making it independent of fiber rotations. It accounts for the microstructure of the composite, including fiber-matrix interfacial decohesion, and enables all types of material behavior of the constituents. The response of each constituent of the composite is modeled separately and the global response is obtained by an assembly of all contributions. The model is implemented as a user-defined material model (UMAT) in ABAQUS and used for multiscale modeling of notched uniaxial plies subjected to compression. The model performs well in agreement with a finite element model of an explicit discretization of the microstructure and literature results. The simulations predict the formation of a kink band in near 0-degree plies and show that the open-hole compression strength is sensitive to the degree of fiber-matrix interfacial decohesion. The present work suggests a convenient and computationally efficient tool for simulating the elastic-plastic behavior of fiber composites on the fiber-matrix level and predicting the compressive strength of laminates.
       
  • Snap-through and stiffness adaptation of a multi-stable Kirigami composite
           module
    • Abstract: Publication date: Available online 24 July 2019Source: Composites Science and TechnologyAuthor(s): Aditya Lele, Vishrut Deshpande, Oliver Myers, Suyi LiAbstractMulti-stable composite laminates have been used to create adaptive and shape-morphing structures for many applications. However, it remains challenging to use these composites to obtain complicated shape changes and mechanical property adaptations. This study proposes a “Kirigami composite” concept to help address this challenge. By strategically placing slit cuts into the composite laminate with carefully designed fiber layout, one can release the internal constraints and significantly enrich the achievable shapes and adaptive functions. This study focuses on the elementary Kirigami composite module consisting of a single slit cut and two bistable patches. Experiments and finite element simulations show that this Kirigami module exhibits four different stable equilibria and its snap-through instability originates from a rapid “run-away” growth of surface curvature inversions due to connecting tab. This study also investigates a stiffness adaptation function. These results can be used for creating more sophisticated Kirigami composite structures with multiple patches and cuts.
       
  • Microstructural and mechanical properties of biocomposites made of native
           starch granules and wood fibers
    • Abstract: Publication date: Available online 23 July 2019Source: Composites Science and TechnologyAuthor(s): Arnaud Regazzi, Maxime Teil, Pierre J.J. Dumont, Barthélémy Harthong, Didier Imbault, Robert Peyroux, Jean-Luc PutauxAbstractNovel biocomposites were fabricated using preforms of unmodified starch powder and wood pulp fibers. Stacks of preforms were consolidated using thermo-compression (TCM) and ultrasonic compression moldings (UCM). The characterization of the microstructure of the biocomposites showed that TCM enabled a better preservation of the crystallinity of starch granules during their welding than UCM. However, UCM allowed a significant gain in processing time. For the best set of forming and material parameters, the composites exhibited an elastoplastic response with strain hardening. Their Young's modulus, flexural strength and strain at ultimate stress reached up to approx. 6 GPa, 70 MPa, and 8%, respectively. The best properties were associated to the partial preservation of the native crystallinity of starch and lowered porosity. Bleached and fibrillated fibers with a large aspect ratio also contributed to the enhancement of composite properties. These effects were explained by a better starch-fiber interface and the presence of a network of connected fibers within the composites.
       
  • Enhancement of the mechanical properties of basalt fiber-reinforced
           polyamide 6,6 composites by improving interfacial bonding strength through
           plasma-polymerization
    • Abstract: Publication date: Available online 23 July 2019Source: Composites Science and TechnologyAuthor(s): Siwon Yu, Kyung Hwan Oh, Soon Hyung HongAbstractThis study aimed to develop basalt fiber (BF)/polyamide (PA) 6,6 thermoplastic composites with high strength and light-weight, by employing BF as an environmentally friendly reinforcing material and applying plasma polymerization for improving the interfacial bonding strength between BF and PA6,6. 3-aminopropyltriethoxysilane (APTES) was used as a precursor for BF surface modification. Plasma polymerization of the APTES was applied to the BF surface for 3, 5, 7, and 9 min. The reaction mechanism during plasma polymerization was investigated and compared to that from a conventional solution dipping method. We examined the changes in chemical composition of the BF surface and the resulting interfacial bonding strength and mechanical properties of the BF/PA6,6 composites. The results showed that APTES plasma-polymerized BF formed a strong interface with PA6,6, demonstrating a 50.3% increase in interfacial shear strength and a 32.5% increase in tensile strength compared with untreated BF. Furthermore, APTES plasma-polymerized BF showed excellent results, with 25.7% higher interfacial shear strength as well as 15.1% higher tensile strength compared to the solution dipping results. This is because plasma polymerization formed a thick polymeric layer highly compatible with PA6,6 on the BF surface, and imparted excellent physical and chemical bonding to the PA6,6 matrix.
       
  • Ultrathin iron phenyl phosphonate nanosheets with appropriate thermal
           stability for improving fire safety in epoxy
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Qinghong Kong, Youliang Sun, Caijiao Zhang, Haomin Guan, Junhao Zhang, De-Yi Wang, Feng ZhangAbstractNovel ultrathin iron phenyl phosphonate (FePP) nanosheets has been devised and synthesized with appropriate thermal stability for epoxy resin (EP), which was incorporated into EP matrix for preparing uniformly dispersed EP/FePP nanocomposites with intercalated structure. The results indicate that the incorporation of FePP nanosheets greatly improve the thermal stability and residual yield at higher temperature. When the amount of FePP is only 4 wt%, EP/4 wt%FePP nanocomposites is close to V-0 rating with 15 s of t1+t2 value, and LOI value is up to 35.1. Meanwhile, FePP nanosheets availably inhibit the heat release and restrict the smoke and toxic gas production of EP/FePP nanocomposites in combustion, and the PHRR, THR, TSP and COP peak values of EP/4 wt%FePP nanocomposites reduce by 42.6%, 26.3%, 33.3% and 49.8% by comparison with those of pure EP. The outstanding flame retardancy and smoke suppression performances were ascribed to ultrathin FePP nanosheets with appropriate thermal stability, outstanding catalytic carbonization performance of iron and excellent synergistic flame-retardant capability of phosphorus compounds.
       
  • Flexible, stretchable and electrically conductive MXene/natural rubber
           nanocomposite films for efficient electromagnetic interference shielding
    • Abstract: Publication date: Available online 22 July 2019Source: Composites Science and TechnologyAuthor(s): Jia-Qi Luo, Sai Zhao, Hao-Bin Zhang, Zhiming Deng, Lulu Li, Zhong-Zhen YuAbstractThe rapid popularity of portable and wearable electronics requires high-performance flexible electromagnetic interference (EMI) shielding materials to cope with increasingly severe electromagnetic wave pollution problems. To combine outstanding EMI shielding performance and excellent mechanical flexibility, we demonstrate an efficient vacuum-assisted filtration approach for the fabrication of flexible and highly conductive Ti3C2Tx MXene/natural rubber (NR) nanocomposite films by constructing interconnected MXene networks in NR matrix. The electrostatic repulsion forces originated from the negative charges of MXene and NR latex enable the MXene sheets to selectively distribute at the interfaces of the NR particles, forming an interconnected network for efficient electron transport and load transfer at low MXene contents. The resultant nanocomposite with 6.71 vol% of MXene shows a superb electrical conductivity of 1400 S m−1 and an outstanding EMI shielding performance of 53.6 dB. Furthermore, the robust and three-dimensional MXene network provides significant reinforcement to the NR matrix, exhibiting obviously enhanced tensile strength and modulus by 700% and 15000% as compared to those of neat NR, respectively. The stable EMI shielding capability and stretchability under cyclic deformations make the high-performance MXene/NR nanocomposite films promise in next-generation flexible and foldable electronics.
       
  • Chemical grafting of nano-SiO2 onto graphene oxide via thiol-ene click
           chemistry and its effect on the interfacial and mechanical properties of
           GO/epoxy composites
    • Abstract: Publication date: Available online 22 July 2019Source: Composites Science and TechnologyAuthor(s): Mingye Wang, Lichun Ma, Longlong Shi, Peifeng Feng, Xuejie Wang, Yingying Zhu, Guangshun Wu, Guojun SongAbstractA facile and rapid come close to the manufacture of advanced epoxy nanocomposites by grafting of nano-silicon dioxide (nano-SiO2) onto the graphene oxide (GO) through thiol-ene click reaction was reported. The correlations between surface modification, morphology, dispersion/exfoliation, interfacial interaction of sheets and the corresponding mechanical properties of the composites were methodically explored. It appeared that nano-SiO2 have been grafted onto GO via covalent bonding successfully, which effectively improved the interface compatibility and dispersion in epoxy matrix. The reinforcing mechanisms has been also elaborated. It is demonstrated that the tensile strength and elastic modulus for filler with 0.1 wt% GO-SiO2/epoxy composites increased by 32.18% and 22.86% compared to neat epoxy, respectively. It is believed that the simplistic and effectual method may provide a novel and promising strengthen design strategy for next‐generation advanced nanocomposite structures.
       
  • Novel modified distribution functions of fiber length in fiber reinforced
           thermoplastics
    • Abstract: Publication date: Available online 22 July 2019Source: Composites Science and TechnologyAuthor(s): Dayong Huang, Xianqiong ZhaoAbstractAmongst the present prediction models of mechanical properties, the Weibull distribution has been introduced to describe the fiber length distribution. However, the Weibull distribution cannot capture the long tail decay, leading to underestimation of the fiber length factor (χ2). For the first time, two novel modified distribution functions are proposed based on Erlang-2 distribution and Weibull distribution, respectively. The modified Erlang distribution is derived from introducing a shape parameter to capture the sharp peak better, whereas the modified Weibull distribution is developed by introducing a polynomial function instead of the exponential function to reduce the decay rate for the long fibers. The modified distribution functions are investigated by experimental data reported in literatures and the experimental data of GFRPA66 we obtained. The relationship between the shape parameters (α and β) and k can be described by a linear growth function when α>β, and the slope of α∼k is larger than that of β∼k. The scale parameters (λ, λα and λβ) can be considered as the linear growth function of ln. The relationship between the improvement in fiber length factor (Δ) and the improvement in number-average fiber length (δ) can be described by a fitting power function with an offset. In comparison to the Weibull distribution, the modified distribution functions improve more than 4% in χ2. The modified Weibull distribution tends to capture the actual fiber length distribution for LFT, whereas the modified Erlang distribution captures that for SFT.
       
  • Microwave assisted sinter molding of polyetherimide/carbon nanotubes
           composites with segregated structure for high-performance EMI shielding
           applications
    • Abstract: Publication date: Available online 22 July 2019Source: Composites Science and TechnologyAuthor(s): Dong Feng, Qingqing Wang, Dawei Xu, Pengju LiuThe formation of segregated conductive structure in a polymer matrix can remarkably improve the electrical and EMI shielding performance. Nevertheless, the insufficient interfacial bonding force among polymer domains generated during the conventional hot compressing process will seriously deteriorate the mechanical property of the final composite. Herein, high-performance polyetherimide/carbon nanotubes (PEI/CNTs) composites with segregated structure were facilely fabricated for EMI shielding applications using CNTs as both solder and a conductive framework. The surface-localized CNTs were selectively and vigorously heated upon exposure to microwave (MW) irradiation, with an appropriate pressure stress applied subsequently, ensuring enhanced local polymer mobility and entanglement across the interfacial regions. Consequently, an excellent conductivity and EMI shielding effectiveness of 17.98 S/m and 34.6 dB, respectively, at 8.2–12.4 GHz were achieved in the PEI/CNTs composites only employing 4.0 wt% CNTs, along with the tensile strength of ∼36 MPa, due to the superb welding induced by the MW selective sintering. All the results indicated that this effort provided a novel, economical and easily industrialized concept for fabricating segregated high-performance polymer composites for EMI shielding applications.Graphical abstractImage 1
       
  • Genipin-enhanced nacre-inspired montmorillonite-chitosan film with
           superior mechanical and UV-blocking properties
    • Abstract: Publication date: Available online 19 July 2019Source: Composites Science and TechnologyAuthor(s): Benliang Liang, Yingqi Shu, Pan Wan, Hewei Zhao, Shaohua Dong, Weichang Hao, Penggang YinAbstractChitosan, as a functional material, has special characteristics: biocompatibility, biodegradability and sterilizable properties, suitable for use in many fields. However, the weak mechanical properties of this material limit its applications. Herein, inspired by the relationship between the hierarchical “brick-and-mortar” structure and excellent mechanical properties of natural nacre, monolayer montmorillonite sheet was selected as reinforcement nanoplatelet to construct nacre-mimetic layered structure with chitosan together. Genipin, a naturally occurring cross-linking agent, was introduced to further strengthen the nacre-mimetics through chemically cross-linking the amino group of chitosan matrix under alkaline condition. The effects of MMT content, GP crosslinking, and pH on the microstructure and interfacial interactions of the hybrid films were studied systematically. It is proved that the synergistic effect originating from hydrogen and covalent bonds improves the mechanical property of the bioinspired composites, generating a tensile strength of 226.3 MPa and a toughness of 5.1 MJ/m3. Meanwhile, the hybrid film has excellent UV-blocking ability (the transmittance is 10.0% at 365 nm) because the spontaneous reaction between GP and CS forms dark blue pigments. Such bioinspired hybrid films with improved mechanical properties and excellent UV-blocking ability has promising applications in aerospace, tissue regeneration, and construction.
       
  • Computationally fast morphological descriptor-based microstructure
           reconstruction algorithms for particulate composites
    • Abstract: Publication date: Available online 19 July 2019Source: Composites Science and TechnologyAuthor(s): Hangil You, Yeonghwan Kim, Gun Jin YunAbstractIn this paper, we propose a series of novel algorithms for microstructure reconstruction based on constituent morphologies. The proposed algorithm can generate statistically equivalent representative volume elements (RVE) from shape repository consisting of the actual particles from micro-computed tomography (CT) images. The reconstruction algorithm is also general in that it can adopt any morphological descriptors. CDFs errors of the morphological descriptors between the targeted and reconstructed RVEs are minimized within the proposed algorithmic framework. High reliability of the microstructure reconstructions stems from unique and efficient design of the algorithmic framework. One of the novelties of the proposed algorithm is that it does not rely on time-consuming two-point correlation function (TPCF) calculations while it can replicate distributions keeping realistic morphologies of particles. To verify the proposed reconstruction algorithm, the TPCF and homogenized effective properties were compared between targeted and reconstructed RVEs. Moreover, mechanical responses of the targeted and reconstructed RVEs are evaluated and compared by 3D finite element analyses.
       
  • On the optimal design of manufacturing-induced residual stresses in
           filament wound carbon fiber composite cylindrical shells reinforced with
           carbon nanotubes
    • Abstract: Publication date: Available online 16 July 2019Source: Composites Science and TechnologyAuthor(s): Behzad Asghari, Ahmad Reza Ghasemi, Ali TabatabaeianProcess-induced residual stresses occur in composite structures composed of dissimilar materials. As these residual stresses could result in fracture, their consideration when designing composite parts is necessary. In this research, the residual stresses behavior is characterized in terms of three manufacturing features including ‘environmental’, ‘materialistic’ and ‘dimensional’ features. In experimental part, after the fabrication of carbon nanotubes (CNTs) reinforced composite shells, the slitting technique is employed to measure the released strains. Then, the elements of the stiffness matrix are obtained accomplishing an extensive computational modeling in ANSYS commercial software. The obtained results of experimental and computational parts are correlated using a MATLAB programming code, and residual stresses are calculated by calibration factors. Additionally, a statistical analysis is carried out to analyze the influence of mentioned parameters in overall scale. The experimental results had a good agreement with the analytical ones. Finally, this study highlights the complexity and the multifaceted characteristic of residual stresses development in terms of mentioned parameters in CNT-reinforced carbon fiber composite shells.Graphical abstractImage 1
       
  • Enhanced thermal conductivity of benzoxazine nanocomposites based on
           non-covalent functionalized hexagonal boron nitride
    • Abstract: Publication date: Available online 16 July 2019Source: Composites Science and TechnologyAuthor(s): Lin Chen, Kui Li, Bo Li, Dengxun Ren, Sijing Chen, Mingzhen Xu, Xiaobo LiuAbstractHigh thermal conductivity composites with ideal electrical properties have a wide potential application of electronic packaging systems in aerospace, electrical and electronic fields. Hexagonal boron nitride (h-BN) has been widely used in heat conduction systems due to its good insulation and thermally conductivity. However, its application has been limited due to its surface inertness and low strength. In this work, dopamine (DA) was used to provide a polymer coating (PDA) in the hexagonal boron nitride (h-BN) surface to improve its uniform dispersion and interfacial compatibility in the polymer matrix (A-ph/CE). Polymer nanocomposites with different nanofiller loadings were prepared by simple curing casting procedure. Among them, the thermal conductivity of A-ph/CE/h-BN@PDA nanocomposites with 20 wt% h-BN@PDA increases to 0.71 W/m⋅K. The thermal conductivity of nanocomposites was predicted by using the classical equation Agari model. With the nanofiller amounts increasing, the thermal stability of the nanocomposites also improved. The thermal decomposition and Tg with A-ph/CE/h-BN@PDA nanocomposites with 20 wt% h-BN@PDA increase to 350.8 °C and 339.9 °C, respectively. And its dynamic storage modulus reaches 7390 Mpa. And the prepared composites had ideal dielectric properties. The dielectric constant and dielectric loss of 20 wt% A-ph/CE/h-BN@PDA nanocomposites at 1000 Hz were 5.72 and 0.0148 respectively, the volume resistivity was 4.08 × 108 Ω cm, and dielectric breakdown strength was 61.6 kV/mm. The nanofiller (h-BN@PDA) reinforced polymer nanocomposites (A-ph/CE/h-BN@PDA) prepared in this work has good thermal conductivity, ideal electrical properties, and excellent thermal stability, etc., which has great potentiality in the demanding field of electronic packaging.
       
  • Two-dimensional layered double hydroxides nanoplatelets assembled in situ
           on SiO2 nanoparticles for high-performing hydrogenated nitrile butadiene
           rubber
    • Abstract: Publication date: Available online 15 July 2019Source: Composites Science and TechnologyAuthor(s): Yanan Wang, Fanghui Wang, Sai Gao, Yonglai Lu, Jianjun Liu, Hong ZhuAbstractA series of layered double hydroxide nanoplatelets-silica (LDH-SiO2) nanocomposites were assembled in situ and utilized for improving hydrogenated nitrile butadiene rubber (HNBR). The composition, morphology, and structure of both the hybrid fillers and the HNBR composites were characterized. The effects of the LDH nanoplatelets and LDH-SiO2 nanocomposites on the properties of HNBR were studied. The results show that the assembly of two-dimensional (2D) LDH nanoplatelets on the surface of SiO2 efficiently restrains the aggregation of SiO2 nanoparticles and improves the dispersion of the filler in the rubber matrix. Significantly, the highest tensile strength (27.74 MPa) of LDH-SiO2/HNBR, which is two times, one point seven times, and fourteen times higher than those of SiO2/HNBR, LDH/HNBR, and unfilled HNBR, respectively, was achieved at the LDH:SiO2 mass ratio of 0.8 and the filler loading of 40 phr. Furthermore, LDH-SiO2/HNBR exhibits better thermal stability and thermo-oxidative aging performance than SiO2/HNBR. Our work highlights the hybrid filler reinforcement systems for enhancing the mechanical properties of elastomer composites.
       
  • Cellulose nanocrystal-polyetherimide hybrid nanofibrous interleaves for
           
    • Abstract: Publication date: Available online 15 July 2019Source: Composites Science and TechnologyAuthor(s): Jing Wang, Thomas R. Pozegic, Zhen Xu, Rinat Nigmatullin, Robert L. Harniman, Stephen J. EichhornAbstractThe effect of electrospun cellulose nanocrystals (CNCs)-polyetherimide (PEI) hybrid nanofibrous mats on Mode I and Mode II interlaminar fracture toughness of unidirectional carbon/epoxy composite laminates is demonstrated. It is shown that the CNCs reinforced PEI nanofibrillar interleaves result in a ∼28% increase in Mode I initial fracture toughness values compared to neat PEI nanofibrous interleaves. Specifically, the interrelated micro- and nano-scale toughening mechanisms including carbon fibre bridging, fibre necking, fibre rupture with CNCs aggregates, and nanofibre rupture contributed to the fracture toughness improvements under Mode-I loading. Nano-scale mechanisms of shear hackles, and crack pinning by CNCs aggregates increased the Mode II fracture toughness up to ∼3 kJ/m2 as a result of a 6 wt% CNCs reinforced PEI nanofibrillar mat interleaves. Interleaving laminated composites with electrospun CNCs-PEI hybrid nanofibrillar mats has been demonstrated as a novel and prospective strategy to strengthen and toughen interlaminar zones of carbon/epoxy composite laminates.
       
  • Constructing a weaving structure for aramid fiber by carbon nanotube-based
           network to simultaneously improve composites interfacial properties and
           compressive properties
    • Abstract: Publication date: 29 September 2019Source: Composites Science and Technology, Volume 182Author(s): Zheng Cheng, Yang Liu, Chenbo Meng, Yu Dai, Longbo Luo, Xiangyang LiuAbstractCompared with carbon fiber, aramid fiber exhibits weak performance in its transverse direction, and it is the bottleneck problem for its further application. To address the problem, a new weaving strategy is proposed by incorporating carbon nanotube (CNT)-based network inside bulk fiber to bundle the extended macromolecules together. Firstly, this unique three dimensional CNT-based network (CNT-NT) was synthesized and incorporated into bulk fiber by solution blending. Then, the influences of CNT-NT on fibers' axial and transverse performance are evaluated. The results of macromolecules' axial orientation suggest that the macromolecules could easily penetrate into this three dimensional network (CNT-NT), forming a weaving structure, and this further hinders the movement of macromolecules and decrease its orientation in axial direction. More importantly, fiber transverse performance is greatly improved by this weaving structure, mainly due to (1) the improvement of skin/core connection and (2) the restraining of nanofibrils' relative sliding. It is found that the composites interfacial failure mode changes from fiber's skin/core destruction to fiber/resin debonding, and the composite interfacial properties and fiber’ compressive strength are correspondingly increased by 131% and 82%. Unlike traditional “increasing the macromolecules interaction” strategy, it is believed this new weaving strategy integrates the advantage of easy production, cost-effective as well as simultaneously improving fiber's composite interfacial properties and compressive strength, and can be employed as valuable guidance for the design and manufacture of other high performance organic fibers.
       
  • Assessment of the ablation characteristics of carbon/phenolic composites
           using X-ray microtomography
    • Abstract: Publication date: Available online 13 July 2019Source: Composites Science and TechnologyAuthor(s): Jae Hee Cheon, Eui Sup ShinAbstractIn this study, the ablation characteristics of carbon/phenolic composites were evaluated using X-ray microtomography. The ablation tests of carbon/phenolic composites were performed using a 0.4 MW arc-heated wind tunnel, and the composite samples were scanned using micro-computed tomography (Micro-CT) to analyze the ablation characteristics according to the duration of the ablation test. Through calibration of the scanned raw images, ∼2,000 cross-sectional images were generated with micrometer level intervals. Using these obtained cross-sectional images, the porosity and density distributions in the longitudinal direction of the samples were calculated. The mass was then calculated using the analyzed porosity and density, and gave an error of 0.1–3.4% compared to the mass measured using an electronic balance. Our observations indicate that the physical properties of carbon/phenolic composite samples can be calculated using X-ray microtomography, and we expect that our results will be useful in analyzing the behavior of ablative composites.
       
  • Design of remotely, locally triggered shape-memory materials based on
           bicontinuous polylactide/epoxidized natural rubber thermoplastic
           vulcanizates via regulating the distribution of ferroferric oxide
    • Abstract: Publication date: Available online 13 July 2019Source: Composites Science and TechnologyAuthor(s): Jiarong Huang, Jianfeng Fan, Shiheng Yin, Yukun ChenIn this work, we successfully designed remotely, locally thermal/magnetic/light triggered shape memory biobased polylactide/epoxidized natural rubber thermoplastic vulcanizates (PLA/ENR TPVs) via regulating the distribution of ferriferrous oxide (Fe3O4). The TPVs exhibited novel bicontinuous structure, which played a vital role in shape memory effect (SME). The distribution of Fe3O4 in the TPVs was regulated by changing the feeding sequence of Fe3O4 during the dynamic vulcanization. Exhilaratingly, when Fe3O4 was selectively distributed in the ENR phase, the biobased TPVs exhibited the highest Rf (∼99%) and Rr (>90%) even after five cycles because of the impeccable structure and reinforcement of ENR. Meanwhile, the TPVs also exhibited super-toughness (88.06 kJ/m2) without sacrificing its tensile strength. Moreover, the incorporation of Fe3O4 provided the TPVs with remotely/locally triggered SME, in which the TPVs could quickly recover to their initial shape in an alternating magnetic field or under near-infrared light (808 nm), which showed great potential in intelligent medical devices.Graphical abstractImage 1
       
  • 3D printed continuous fibre-reinforced composites: Bio-inspired
           microstructures for improving the translaminar fracture toughness
    • Abstract: Publication date: Available online 12 July 2019Source: Composites Science and TechnologyAuthor(s): Yentl Swolfs, Silvestre T. PinhoAbstractTranslaminar fracture toughness is a vital property governing the notch sensitivity and damage tolerance of composites. Nature has shown that incorporating material transitions can increase toughness significantly. This work presents finite element models demonstrating that such transitions can indeed increase the translaminar fracture toughness. The designed microstructures were then 3D printed using continuous glass and carbon fibres. The specimens consisted primarily of glass fibres, but with local carbon fibre strips. A new compact tension specimen with a side groove was designed to ensure proper failure. When the strips were sufficiently large, toughness improvements of 20–60% were found after the crack had grown through the strips. These results reveal a powerful strategy for locally increasing the toughness in areas where it is needed the most.
       
  • Improved out-of-plane strength and weight reduction using hybrid interface
           composites
    • Abstract: Publication date: Available online 12 July 2019Source: Composites Science and TechnologyAuthor(s): Filip Stojcevski, Daniel J. Eyckens, James D. Randall, Lucas I. Marinovic, Gaspard Méric, Luke C. HendersonAbstractCarbon fiber composites with increased fiber-to-matrix bonding are often susceptible to premature failure due to the creation of overly rigid interfaces. This paper investigates the use of electrochemically functionalised carbon fibers used in novel ‘hybrid interface’ arrangements to improve out-of-plane bending. An improvement of 103.6% in single fiber interfacial shear strength (IFSS) was able to improve out-of-plane strength by 33.6% for short beam shear laminates. However, by combining both functionalised and non-functionalised fibers in complex hybrid interface arrangements such as nature inspired turtle-shell interfaces and circular patterns, mechanical performance was improve significantly. A 170.9% increase to out-of-plane strength was observed using a turtle-shell arrangement which correlated to an 8.7% reduction in composite weight as compared to control fibers.
       
  • Mechanical and physical performance of carbon aerogel reinforced carbon
           fibre hierarchical composites
    • Abstract: Publication date: Available online 10 July 2019Source: Composites Science and TechnologyAuthor(s): Sang Nguyen, David B. Anthony, Hui Qian, Chuntong Yue, Aryaman Singh, Alexander Bismarck, Milo S.P. Shaffer, Emile S. GreenhalghAbstractCarbon aerogel (CAG) is a potential hierarchical reinforcement to improve the matrix-dominated mechanical properties of continuous carbon fibre reinforced polymer (CFRP) composites in both multifunctional and purely structural applications. When using CAG to reinforce a polyethylene glycol diglycidyl ether (PEGDGE) matrix, the interlaminar shear strength, compressive modulus and strength increased approximately four-fold, whilst the out-of-plane electrical conductivity increased by 118%. These mechanical and electrical performance enhancements significantly improve the multifunctional efficiency of composite structural supercapacitors, which can offer weight savings in transport and other applications. However, CAG also has the potential to reinforce conventional continuous CF composites in purely structural contexts. Here, CAG reinforcement of structural epoxy resin composites marginally increased compressive (1.4%) and tensile (2.7%) moduli respectively, but considerably reduced compressive, tensile and interlaminar shear strengths. Fractographic analysis shows that the reduced performance can be attributed to poor interfacial adhesion; in the future, alternative processing routes may resolve these issues to achieve advances in both moduli and strengths over conventional structural CFRPs.
       
  • Thermal conductivity of highly filled polymer nanocomposites
    • Abstract: Publication date: Available online 6 July 2019Source: Composites Science and TechnologyAuthor(s): A.D. Drozdov, J. deClaville ChristiansenAbstractA model is developed for the effective thermal conductivity of composites with polymer matrices reinforced with randomly distributed micro- and nano-particles. The model takes into account formation of infinite conducting paths and finite aggregates of particles on the one hand, and thermal barriers at the interfaces between the matrix and filler, on the other. Material parameters are determined by matching observations on a number of composites with ceramic and carbon fillers. The intensity of thermal barriers is evaluated by means of the Kapitza radius. Comparison of experimental data with results of simulation demonstrate that this parameter is determined by filler only, and it is weakly affected by the matrix material.
       
  • Flexible transparent wood prepared from poplar veneer and polyvinyl
           alcohol
    • Abstract: Publication date: Available online 5 July 2019Source: Composites Science and TechnologyAuthor(s): Anantha Subba Rao, Giridhar Nagarajappa, Sreeja Nair, Anish Chathoth, Krishna K. PandeyAbstractThe fabrication of transparent wood (TPW) has generated lot of interest in the recent past due to its favorable physical, mechanical and fascinating optical properties. The present work, describes a ‘green’ method to fabricate a biodegradable and highly flexible transparent wood-polymer composite from poplar wood veneers and polyvinyl alcohol (PVA). In this method, the wood veneers are chemically treated under mild conditions to remove the light-absorbing components in wood without damaging the hierarchical wood structure. Then, the mesoporous template structure of bleached wood is infiltrated with an aqueous PVA dispersion and dried to obtain flexible TPW. The effect of plasticizing PVA with propylene glycol (PG) on the mechanical and optical properties of TPW has been studied. The flexibility of TPW increased with increase in PG content in PVA. The TPW prepared from the aqueous dispersion of PG:PVA (1:1) exhibited optical transmittance as high as 80% and haze of 90% with excellent flexibility, optical and mechanical anisotropy. The potential application of such optically anisotropic and flexible wood-polymer composite as light shaping diffuser is successfully demonstrated.
       
  • Failure criteria for fiber composite materials, the astonishing sixty year
           search, definitive usable results
    • Abstract: Publication date: Available online 5 July 2019Source: Composites Science and TechnologyAuthor(s): Richard M. ChristensenAbstractA materials failure postulate is established giving upper and lower bounds on the numbers of failure parameters involved with any associated failure criterion. The failure postulate is based upon the symmetry properties for the material, any macroscopically homogeneous material form. It is of significant and decisive help in deriving failure criteria. A wide variety of examples of its usage are given but most of them are aimed at the standard forms for fiber composite materials. Specific failure criteria are the end result for everything from unidirectional, highly anisotropic composites at one extreme to the quasi-isotropic laminate form at the other extreme. Almost all of the work is for fiber composites with any degree of anisotropy. Section 7 and part of Section 4 have highly anisotropic conditions taken as appropriate to carbon fiber/polymeric matrix composites. The results are summarized in Section 8 and they are responsive to the field's many years of searching for the failure criteria of composite materials.
       
  • Highly stretchable and sensitive liquid-type strain sensor based on a
           porous elastic rope/elastomer matrix composite structure
    • Abstract: Publication date: Available online 4 July 2019Source: Composites Science and TechnologyAuthor(s): Jiaxin Wan, Qi Wang, Siyao Zang, Xinan Huang, Tao Wang, Guoqing Liu, Chunsheng Li, Xiaomin RenAbstractIn this study, we present a new liquid-type strain sensor based on porous elastic rope/elastomer matrix (PER/EM) composite structure. The liquid-impregnated porous elastic rope (LIPER) was immersed into a flexible silicone matrix to fabricate the sensor, making the manufacture process easy. The effect of liquid viscosity on the hysteresis of the sensor has been understood through selecting water, ethylene glycol and hydrogel as the sensing liquids. The most attractive performance of the PER/EM strain sensor is its ability to detect both stretching and compression deformations as well as to realize temperature sensing. Simultaneously, high stretch strain over 100% and pressures up to 612 kPa can be subjected. A minimum tensile strain of 0.5% and a minimum applied pressure of 5 kPa can be detected, indicating the good sensitivity of the as-fabricated strain sensor to the subtle deformation. In particular, our devices exhibited the excellent long-term durability after completing>6000 stretching-releasing cycles (100% strain) and>10000 compression-expansion cycles (50 kPa). On this basis, the PER/EM strain sensor was successfully employed to detect the full-scale human motion ranging from swallowing to joint bending. We further made a smart insole and achieve the real-time monitoring of walking, running and jumping. Our results show that the as-fabricated PER/EM strain sensor has the great potential for the applications in healthcare, human motion monitoring and electronic skin.
       
  • Bamboo-like ultra-high molecular weight polyethylene fibers and their
           epoxy composites
    • Abstract: Publication date: Available online 4 July 2019Source: Composites Science and TechnologyAuthor(s): Weiwei Li, Xiaojing Liu, Ming Feng, Jie YangAbstractIt is important for most structural material to achieve both good strength and toughness. However, they are generally mutually exclusive, which is the lower-strength, and hence higher-toughness. Ultra-high molecular weight polyethylene (UHMWPE) fibers have excellent mechanical properties, unfortunately, the interfacial adhesion of UHMWPE fiber reinforced polymer composites is extremely low. Inspired by the shape of bamboo in nature, we herein designed and prepared UHMWPE fiber with new structure. UHMWPE fibers were periodically decorated with polymer lamellar crystals using a polymer solution crystallization method, resulting in bamboo-like structure. It was showed that the strength and toughness of bamboo-like UHMWPE fibers reinforced epoxy (EP) composites were improved simultaneously, which were attributed to the special interface structure between UHMWPE fibers and EP. The strengthening mechanism of the composites is mainly due to the bamboo-like crystals on the fiber surface, which plays a role of pinning and increases the crack propagation path.
       
  • Directional xylitol crystal propagation in oriented micro-channels of
           boron nitride aerogel for isotropic heat conduction
    • Abstract: Publication date: Available online 3 July 2019Source: Composites Science and TechnologyAuthor(s): Marjan A. Kashfipour, Russell S. Dent, Nitin Mehra, Xutong Yang, Junwei Gu, Jiahua ZhuAbstractSelf-assembly and orientation of thermally conductive fillers into ordered scaffold often lead to composites with anisotropic thermal properties. Though large thermal conductivity (TC) can be achieved in the direction of filler orientation, TC in transverse direction is greatly restricted. In this work, boron nitride (BN) scaffold was prepared by an ice-template method and then filled with xylitol crystals to form a new family of composites featuring isotropic TC. The crystallization of ice facilitates the formation of aligned BN walls in the aerogel and the subsequent filling of xylitol in the microchannels of the BN aerogel pushes the crystallization of xylitol in transverse direction. Combination of aligned crystal packs and BN walls in these composites results in high TC in both horizontal and vertical directions. TC of the composites increases with increasing BN content and the TC reaches as high as 4.53 W m−1 K−1 at BN loading of 18.2 wt%. These new results offer an alternative strategy to fabricate isotropic thermally conductive composites that can be used for the next generation of heat dissipating materials.
       
  • Opto-electro-mechanical percolative composites from 2D layered materials:
           Properties and applications in strain sensing
    • Abstract: Publication date: Available online 15 June 2019Source: Composites Science and TechnologyAuthor(s): Sangram Mazumder, Jorge A. Catalan, Alberto Delgado, Hisato Yamaguchi, Claudia Narvaez Villarrubia, Aditya D. Mohite, Anupama B. KaulAbstractThe fragmentation rate (FR) of two-dimensional layered materials (2DLMs) MoS2, WS2, and graphene in N-methyl-pyrrolidinone (NMP) was computed, where FR is a measure of the particle size reduction with ultrasonication time. For the 2DLMs, the highest FR generally occurred for sonication times tsonic = 30 min, with FRGraphite ∼ −1176.4 μm-hr−1, FRWS2 ∼ −32.4 μm-hr−1and FRMoS2 ∼ −3.8 μm-hr−1. This is in contrast to a non-layered material, Al nanoparticles, where FRAl ∼0 μm-hr−1 for tsonic = 30 min. Knowledge of the particle size as a function of tsonic has not been reported previously for 2DLMs, and is extremely important as these materials are integrated into additively manufactured platforms, such as ink-jet printing and three-dimensional (3D) printing. The treated materials were then infused with two types of polymers, flexible and stretchable polyisoprene, and an optically transparent acrylic, poly-methyl-methacrylate (PMMA) for opto-electro-mechanical strain-based sensing device applications. In particular, the hybrid composites of graphene with optically transparent and bendable PMMA revealed the potential of forming opto-mechanical filters, where optical filtering can be engineered through the graphene loading. The polyisoprene-graphene composites were piezoresistive with potential for wearable electronics, where mechanical strain, as induced at joint movements on a finger for example, modulates the current with joint displacement. Strain levels of up to 200% were observed and the gauge factor of these devices was measured to be ∼75 which is > 10X higher compared to conventional metal-foil based strain sensors. This work sheds fundamental insights into the role of sonication on the materials properties of 2DLMs in solution dispersions and shows their potential in hybrid composites for opto-electro-mechanical strain based sensing applications and in wearable electronics.
       
  • 3D printing of carbon nanotubes reinforced thermoplastic polyimide
           composites with controllable mechanical and electrical performance
    • Abstract: Publication date: Available online 7 June 2019Source: Composites Science and TechnologyAuthor(s): Wenli Ye, Wenzheng Wu, Xue Hu, Guoqiang Lin, Jinyu Guo, Han Qu, Ji ZhaoAbstractExisting aerospace metal parts or structural parts have the problems of finite elasticity, large mass, difficult manufacture of complex parts, expensive equipment, narrow range of shielding and electrostatic regulation. This study analyzed the tensile and bending properties of pure thermoplastic polyimide (TPI) 3D printing specimens printed by the nozzles with different diameters. The effects of different carbon nanotube (CNT) contents on the thermal and electrical properties of carbon nanotube composites were investigated. The relationship between the electrical conductivity, tensile properties, bending properties, resistivity and cyclic bending deformation of 3D printed specimens with different carbon nanotube contents was studied. Compared with the 0.4 mm nozzle, the tensile and bending strength of pure TPI specimen printed by a 0.8 mm nozzle were increased by 40% and 20%, respectively. In order to ensure the excellent mechanical and electrical properties of 3D printed composites, 3%wt carbon nanotubes-thermoplastic polyimide (CNTs-TPI) composites with appropriate tensile and bending strength were used to print the characteristic structure, and then the relationship between the deformation and conductive resistance was studied. By optimizing the 3D printing parameters and the filling contents of CNTs, it is possible to print complex parts which can be used in aerospace and industrial fields with special properties, such as electrical conductivity, mechanical properties, temperature resistance and anti-electromagnetic shielding.
       
 
 
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