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Composites Science and Technology
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0266-3538
Published by Elsevier Homepage  [3157 journals]
  • FeSiAl/metal core shell hybrid composite with high-performance
           electromagnetic interference shielding
    • Abstract: Publication date: Available online 12 January 2019Source: Composites Science and TechnologyAuthor(s): Pradeep Sambyal, Seok Jin Noh, Jun Pyo Hong, Woo Nyon Kim, Aamir Iqbal, Seung Sang Hwang, Soon Man Hong, Chong Min Koo Herein, for the first time, FeSiAl (sendust)/metal hybrid materials were synthesized with a magnetic core and a highly electrically conductive metal shell for shielding electromagnetic interference (EMI) pollution. Soft magnetic sendust flakes were electroless-plated with electrically conductive Ag or Ni metal to form Ag-plated and Ni-plated sendust core-shell hybrids. The magnetic and metal hybrid-incorporated paraffin wax composites exhibited a better absorption-dominant EMI shielding performance of 65.6 dB and 58.5 dB, respectively, than that of the sendust wax composite and the composite with a mixture of sendust and electrically conductive Ag/Cu dendrite. The superior shielding performance was attributed to the synergistic combination of the effective magnetic loss, dielectric loss, and conduction loss. These exceptional properties of the new hybrid composite showed that it could be used in absorption-dominant EMI shielding applications.
       
  • Enhanced dielectric permittivity in surface-modified graphene/PVDF
           composites prepared by an electrospinning-hot pressing method
    • Abstract: Publication date: Available online 11 January 2019Source: Composites Science and TechnologyAuthor(s): Bo Lin, Zeng-Tian Li, Ying Yang, Ying Li, Jie-Ci Lin, Xu-Min Zheng, Fu-An He, Kwok-Ho Lam In the present work, the surface-modified graphene (SMG)/poly(vinylidene fluoride) (PVDF) fibrous membranes obtained from the electrospinning were treated by the hot pressing in the laminating mode to form the SMG/PVDF composites. The SMG was prepared by subjecting the graphene oxide to silane modification, NaBH4 reduction, and PVDF grafting in sequence. The successful surface modification of graphene was confirmed by TEM, XPS, Raman spectroscopy, FTIR, WAXD, and TGA. Furthermore, the structures of SMG/PVDF composites fabricated by the electrospinning-hot pressing method were studied by SEM, FTIR, and WAXD, which exhibited the well dispersion of SMG in the PVDF matrix. Finally, the investigation showed that the dielectric permittivities of SMG/PVDF composites increased with the SMG content, which were significantly higher than that of pristine PVDF. The dielectric permittivity of SMG (16 wt%)/PVDF composite (83.8) at 1000 Hz was found to be ten-fold that of the corresponding value of pristine PVDF (8.3) with a relatively low dielectric loss factor (0.34) and a relatively high thermal conductivity (0.679 W/mK).
       
  • Fabrication and properties of poly(vinyl alcohol)/β-tricalcium phosphate
           composite scaffolds via fused deposition modeling for bone tissue
           engineering
    • Abstract: Publication date: 1 March 2019Source: Composites Science and Technology, Volume 172Author(s): Gang Chen, Ning Chen, Qi Wang Polymer/bioceramic composite scaffolds have been widely regarded as promising biomimetic substitutes for bone tissue engineering owing to their tailored mechanical properties and improved bioactivity. Fused deposition modeling (FDM), which is a simple and cost-effective 3D printing technology, enables the fabrication of scaffolds with predetermined and controllable internal architecture. In this study, poly(vinyl alcohol)/β-tricalcium phosphate (PVA/β-TCP) composite scaffolds were constructed using FDM. The thermal behavior, printability, microstructure and mechanical properties of the composite scaffolds were investigated. The results showed that β-TCP particles were homogeneously dispersed into the PVA matrix with the assistance of solid state shear milling. Hydrogen bonding interactions were formed between β-TCP and PVA, which helped to improve the interface strength of the composites. By using water and glycerin as a co-plasticizer, the as-prepared composite filaments that were suitable for the FDM process exhibited improved thermal processability. In addition, the printability window of the material was theoretically established based on the ratio of its compressive modulus to the apparent viscosity. SEM and μCT analyses indicated that as-fabricated scaffolds had well-structured shapes and totally interconnected channels. Meanwhile, the loading-bear capabilities of the composite scaffolds were significantly enhanced with an increase in the β-TCP content up to 20 wt%; e.g., the maximum stress increased from 8.3 to 10.7 kPa. Moreover, in vitro cell culture studies revealed that the resulting composite scaffolds possess good biocompatibility, which is favorable to cell adhesion and proliferation. These results strongly indicate the potential of the fabricated scaffolds in tissue engineering applications.
       
  • Transparent wood bearing a shielding effect to infrared heat and
           ultraviolet via incorporation of modified antimony-doped tin oxide
           nanoparticles
    • Abstract: Publication date: Available online 10 January 2019Source: Composites Science and TechnologyAuthor(s): Zhe Qiu, Zefang Xiao, Likun Gao, Jian Li, Haigang Wang, Yonggui Wang, Yanjun Xie Optically transparent wood (TW) is an emerging candidate for applications in energy efficient buildings. In this study, anti-ultraviolet and infrared heat shielding TW was prepared based on the delignification of the wood's substrate. This was followed by infiltration of pre-polymerized methyl methacrylate (PMMA) with modified antimony-doped tin oxide (ATO) nanoparticles. The ATO addition enhanced the interfacial bonding among the compounds, which improved the fracture strength, leading to a high fracture strength of 96.4 MPa and modulus of 4.27 GPa with addition of 0.3% ATO. Furthermore, the obtained ATO/TW exhibited high transparency, excellent near infrared (NIR) heat shielding performance, and ultraviolet (UV) shielding properties according to the ultraviolet–visible spectrophotometer measurement, the infrared heat shielding simulation test, and the UV-shielding test. The TW treated with 0.3% ATO still maintained a very low thermal conductivity of around 0.2 W m−1 K−1. After addition of 0.7% ATO, the obtained TW had a quite low UV transmittance of <20%. The Aspergillus niger maintained high viability after UV irradiation treatment when shielded with TW treated with 0.7% ATO. The findings indicate that the multifunctional and durable ATO/TW has a potential to be used as energy-saving building material.
       
  • Polyaniline-based all-polymeric adhesive layer: An effective lightning
           strike protection technology for high residual mechanical strength of
           CFRPs
    • Abstract: Publication date: Available online 9 January 2019Source: Composites Science and TechnologyAuthor(s): Vipin Kumar, Tomohiro Yokozeki, Takao Okada, Yoshiyasu Hirano, Teruya Goto, Tatsuhiro Takahashi, Ahmed Arabi Hassen, Toshio Ogasawara Carbon fiber reinforced plastics (CFRPs) are vulnerable to lightning strikes due to their low electrical conductivity and low heat resistance. A lightning strike can damage CFRP structure catastrophically. Most common lightning strike protection (LSP) technology, consists of expanded metal foils/films on top of composite structures. This technology possesses disadvantages such as increased weight, galvanic corrosion, expensive integration and repair costs. In the present study, authors introduce a novel, easy to apply and all-polymeric LSP material. A doped intrinsic conductive polymer i.e. Polyaniline (PANI) dispersed in a thermosetting cross-linking polymer divinylbenzene (DVB) has been used to prepare an adhesive layer of 0.25–0.4 mm thickness. CFRP structure coated with PANI-based LSP layer, when tested against simulated lightning impulse current of 100 kA, demonstrated effective dissipation of the current, rendering almost 100% safety to the CFRP structure. PANI showed the capability to create a 3-D conductive network due to its self-assembling property, which makes it superior compared to its counterpart carbon/metal nano-filler based LSP technologies. Almost 100% residual strength of PANI-LSP protected CFRPs is reported in this work.
       
  • Mechanical and thermal properties of poly(vinyl chloride) composites
           filled with carbon microspheres chemically modified by a biopolymer
           coupling agent
    • Abstract: Publication date: Available online 6 January 2019Source: Composites Science and TechnologyAuthor(s): Yunhua Lu, Santosh Khanal, Saad Ahmed, Shiai Xu In this study, carbon microspheres (CMSs) were prepared using L(+)-ascorbic acid by hydrothermal carbonization and then modified with a polyether titanate coupling agent (eTi4000) and a self-synthesized biopolymer coupling agent (CCS), respectively. These modified CMSs (mCMSs) were added into poly(vinyl chloride) (PVC) to prepare mCMSs/PVC composites. The results suggest that CCS has a better modification effect than eTi4000, which imparts CCS-CMSs/PVC composites with good thermal stability and mechanical properties. The impact strength of CCS-CMSs/PVC composite (8.7 kJ m−2) is remarkably increased by 64.2% compared with that of CMSs/PVC composite (5.3 kJ m−2), and its rapidest decomposition temperature (309 °C) is increased by 29 °C and 16 °C in comparison with that of PVC and CMSs/PVC composite, respectively. The interfacial interaction between PVC and mCMSs is evaluated by dielectric loss and DMA. In conclusion, CCS is an effective biopolymer coupling agent that can endow CCS-CMSs/PVC composites with good comprehensive properties.
       
  • Mechanical and dynamic performance of woven flax/E-glass hybrid composites
    • Abstract: Publication date: Available online 6 January 2019Source: Composites Science and TechnologyAuthor(s): M. Cihan, A.J. Sobey, J.I.R. Blake Flax composites demonstrate superior damping properties to conventional fibres. These materials are already being utilised in some products but the mechanical properties they exhibit are too low for many structural applications. Hybridization of flax with higher strength fibres has been shown to yield materials, which balance damping and load carrying capabilities alongside improved environmental credentials for flax/carbon hybrids. However, the most used composite material is E-glass but the current literature does not facilitate the prediction of damping properties for these hybrid composites, where it is expected that they will behave differently due to the difference in material properties. The woven flax and E-glass fibres specimens embedded with epoxy resin are manufactured via resin infusion to understand the damping and mechanical properties possible from an industrial process and the dominant factors affecting them, rather than the relationships between individual variables and these properties. These experiments allow the hybrids to be profiled for the first time and it is observed that hybridization of flax and E-glass fibres results in an increase in damping, from 1.97% to 2.63% for the best hybrid, especially when the flax plies are placed on the outer skin, however the compromise in tensile properties is significant, from 473.28 MPa to 166.53 MPa.
       
  • Enhanced dispersion, flame retardancy and mechanical properties of
           polypropylene/intumescent flame retardant composites via supercritical CO2
           foaming followed by defoaming
    • Abstract: Publication date: 8 February 2019Source: Composites Science and Technology, Volume 171Author(s): Pengke Huang, Fei Wu, Yongyan Pang, Minghui Wu, Xiaoqin Lan, Haibin Luo, Bin Shen, Wenge Zheng The broad technological exploitation of polypropylene (PP)/intumescent flame retardants (IFR) composites with outstanding flame retardancy and mechanical properties is stifled by the lack of effective methods to improve the IFR dispersion, since the opposite polarity between PP and IFR would result in poor compatibility and uneven dispersion. In this work, we have demonstrated an industrially viable and efficient approach for the fabrication of PP/IFR composites with more uniform dispersion by combining the advantages of supercritical CO2 (scCO2) plasticization and biaxial bubble stretching through the scCO2 foaming technique followed by defoaming, and the increasing of the foam expansion ratio could lead to the better IFR dispersion of the final defoamed solid PP/IFR composites due to stronger bubble stretching force. Moreover, the improved IFR dispersion could result in the greatly enhanced flame retardancy and mechanical properties in comparison with those of uneven dispersed ones. We believe that the approach here can be used to guide the future design of high-performance materials on inorganic/organic hybrid polymer composites with homogenous dispersion.Graphical abstractIn this work, we have demonstrated an industrially viable and efficient approach for the fabrication of PP/IFR composites with more uniform dispersion by combining the advantages of supercritical CO2 (scCO2) plasticization and biaxial bubble stretching through the scCO2 foaming technique, and the increasing of the foam expansion ratio could lead to the better IFR dispersion of the final defoamed solid PP/IFR composites due to stronger bubble stretching force. Moreover, the improved IFR dispersion could result in the greatly enhanced flame retardancy and mechanical properties.Image 1
       
  • Corrigendum to “Relative planar strain control and minimizing
           deformation work in elastomeric sheets via reinforcing fiber arrays”
           [Compos. Sci. Technol. 142 (2017) 50–64]
    • Abstract: Publication date: 8 February 2019Source: Composites Science and Technology, Volume 171Author(s): Michael Krieg, Kamran Mohseni
       
  • Controllable wavelength-selective optical composite based on
           nano-polymeric films with doped dyes
    • Abstract: Publication date: Available online 4 January 2019Source: Composites Science and TechnologyAuthor(s): Aiqin Gao, Danna Fu, Aiqin Hou, Kongliang Xie The novel color optical composites with controllable light absorption from the solar energy based on polyvinyl alcohol (PVA) as matrix materials were investigated. The nanoparticles with molecular level dye-doped were prepared by microemulsion polymerization. The structure and morphology of the nanoparticles and the color nano-films were characterized by Fourier transform infrared spectrum (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) analysis. Three nanoparticles with dye-doped are all homogeneous nanospheres with regular shape and size of 50–70 nm. Three PVA color films containing nanoparticles possess different absorption bands in the visible light region. A controlled sunlight absorption film filter using dye-doped nanoparticles can be arbitrarily designed and assembled by adjusting the recipe to selectively transmit specific wavelengths from sunlight. Because the dye molecules are stabilized in the nanoparticles, the absorption band of the membranes can be precisely controlled. It can be conveniently assembled or deposited on other substrates to form nano-membranes. The composite containing color nanoparticles is simple, flexible, and cost-effective. They have potential applications in many fields, such as energy, agriculture, environment and biotechnology.Graphical abstractImage 1
       
  • Synergism of binary carbon nanofibres and graphene nanoplates in improving
           sensitivity and stability of stretchable strain sensors
    • Abstract: Publication date: Available online 4 January 2019Source: Composites Science and TechnologyAuthor(s): Fan Zhang, Shuying Wu, Shuhua Peng, Zhao Sha, Chun H. Wang Stretchable strain sensors with high sensitivity and good stability are crucial for wearable healthcare devices and tactile sensors for robots. Herein we present a new technique to synergistically improve sensors' sensitivity and cyclic stability by hybridising carbon nanofibers (CNFs) with graphene nanoplates (GNPs) within a polydimethylsiloxane (PDMS) medium. The results reveal that, compared with equivalent sensors containing only CNFs or GNPs, the hybridised sensors show a significantly better performance with a greater linear range up to ∼50% of strain and much improved stability (less drift) under repeated loading, which is quantitatively reflected by the synergy ratio of linear range and drift. Increasing the concentration of hybrid carbon fillers can increase sensors sensitivity. Therefore, the hybridisation of 1D and 2D nano-carbon materials offers a new route for increasing the sensitivity and cyclic stability of flexible strain sensors.
       
  • Evaluation of composite interfacial properties based on carbon fiber
           surface chemistry and topography: Nanometer-scale wetting analysis using
           molecular dynamics simulation
    • Abstract: Publication date: Available online 31 December 2018Source: Composites Science and TechnologyAuthor(s): Peng Xu, Yunhua Yu, Zhenjiang Guo, Xianren Zhang, Gang Li, Xiaoping Yang According to surface chemistry and topography of different high-modulus carbon fiber (HMCF), interfacial properties of various HMCF composite were evaluated, and nanoscale wetting analysis of HMCF were studied using experimental methods and molecular dynamics simulation. Hierarchical amount of active functional groups and nanoscale grooves were detected on the surface of pristine HMCF (p-HMCF), anodic oxidized HMCF (a-HMCF) and sized HMCF (s-HMCF). Remarkable enhancements in interfacial properties of a-HMCF and s-HMCF composites were obtained, which was ascribed to free-void interface from improved surface energy and wettability. Poor interfacial bonding of p-HMCF composites was due to generation of many nanobubbles with pinned contact lines during the wetting of the surface microgrooves with high aspect ratio and chemical inertness. Schematic of interfacial compatibility mechanisms was proposed to illustrate the correlation between surface features of carbon surface and interfacial properties of their composites.
       
  • Dynamical properties of flax fibre reinforced PA11 over a large frequency
           range
    • Abstract: Publication date: Available online 28 December 2018Source: Composites Science and TechnologyAuthor(s): Amenini Federico, Julien Brocail, Michael Chauvin, Sandrine Thuillier This paper reports the characterisation of the dynamic behaviour of a flax fibre reinforced polyamide 11 biocomposite. The film stacking and hot pressing process is used to obtain composite plates. Quasi-static tests are conducted to get information on the Young's moduli and Poisson's ratios. The aim of the present study is to identify the storage modulus and the loss factor over a wide range of frequencies. For this purpose, an inverse method inspired from the Force Analysis Technique and based on the local equation of motion is used. The out-of-plane displacements of suspended vibrating plates are measured by a laser Doppler vibrometer. Together with the plate thickness, material density and Poisson's ratios, the measured displacements constitute the inputs of the identification method. Additional tests on Dynamic Mechanical Analysis are conducted to compare the results of the two methods. A good correlation of the results is obtained. The storage modulus can be identified by the inverse method up to a frequency of 10 kHz and is rather constant, but the loss factor is not obtained with a good accuracy.
       
  • Flexible and coatable insulating silica aerogel/polyurethane composites
           via soft segment control
    • Abstract: Publication date: Available online 26 December 2018Source: Composites Science and TechnologyAuthor(s): Jaehyun Cho, Han Gyeol Jang, Seong Yun Kim, B.J. Yang We herein propose a facile approach to fabricate foldable and coatable silica aerogel polyurethane composites (APCs). For the flexibility control, the soft segment of polyurethane (PU) is manipulated. The change in soft segment length induces a difference in overall glass transition temperature of PU. When the silica aerogel content is increased, the PU with a shorter soft segment length shows brittle fracture behavior, while the PU with a longer soft segment length shows no breakage after bending. The thermal insulation properties of APCs were enhanced by 72% reduction in thermal conductivity upon 30 wt% aerogel loading and theoretically verified by a micromechanics-based thermal conductivity model considering the effects of interface and agglomeration. In addition, for the combustion behavior measurements, heat release rate and heat release capacity are substantially reduced for the APCs compared to neat PUs. Those enhanced thermal insulation properties may have a commercial impact on thermal insulation applications.
       
  • Facile large-scale alignment and assembly of conductive micro/nano
           particles by combining both flow shear and electrostatic interaction
    • Abstract: Publication date: Available online 26 December 2018Source: Composites Science and TechnologyAuthor(s): Jun Cai, Xinghao Li, Liang Ma, Yonggang Jiang, Deyuan Zhang We introduce a facile approach to align various conductive micro/nano particles in a large area using both flow shear and electrostatic interaction. The complicated three-dimensional (3D) microcoils are chosen to investigate the assembly behavior and effectiveness of the multi-physical field induced alignment in polydimethylsiloxane (PDMS) pre-polymer; and the forcing mechanism and motion behavior of the microcoils are also analyzed: the flow shear could orient the major axis of microcoils, and then the electrostatic interaction between these oriented microcoils results in their self-assembly into chains. Besides, the processing parameters are also optimized, including the gap between the polyethylene terephthalate (PET) plates of ∼100 μm, the shearing speed of ∼40 mm/s, PET plate voltage of ∼20 kV, and microcoil weight fraction of ∼2%. And the order parameter S could reach up to ∼0.96 and more than ∼70% of the particles were assembled into a chain-like structure. Furthermore, we also demonstrate the universality of this method to other conductive micro/nano particles' assembly, including silver-coated glass spheres, carbon nanotubes (CNTs), and graphene. This approach may pave the way for the large-scale fabrication of functional composites based on well-ordered conductive micro/nano particles.
       
  • Self-organization of sepiolite fibbers in a biobased thermoset
    • Abstract: Publication date: Available online 24 December 2018Source: Composites Science and TechnologyAuthor(s): Guillaume Falco, Françoise Giulieri, Nicolas Volle, Sophie Pagnotta, Nicolas Sbirrazzuoli, Edith Peuvrel Disdier, Alice Mija A self-organization of sepiolite fibbers have been found during the synthesis of sustainable nanocomposites. These auto-structured networks are synthesized starting with an epoxidized linseed oil (ELO), a bio-based hardener of dicarboxylic class and sepiolite fibbers. For the first time, the auto-organization of sepiolite fibbers into empty or solid spheres insight a bio-based thermoset matrix have been highlighted and synthesized. The influence of the thermoset formulation and the sepiolite concentration on self-organization are emphasized. The thermomechanical properties of nanocomposites have been investigated highlighting an increasing of elastic modulus from 30 to 40% in the vitreous states and from 25 to 45% in the rubbery state. This peculiar organization and behaviour of sepiolite, similar to that of surfactants, is of great interest as fundamental, applicative and industrial level.
       
  • Improved fracture toughness of epoxy resin reinforced with polyamide
           6/graphene oxide nanocomposites prepared via in situ polymerization
    • Abstract: Publication date: Available online 23 December 2018Source: Composites Science and TechnologyAuthor(s): Xiaoran Zhao, Ye Li, Wen Chen, Shuang Li, Yan Zhao, Shanyi Du In this work, a facile in situ polymerization method was developed for the preparation of polyamide 6 (PA6) chains grafted graphene oxides (GO). Based on ethanolic solution precipitation method, the powders of PA6, PA6/GO-0.5 and PA6/GO-1.0 were fabricated and dispersed uniformly into epoxy resins at varying loadings. The surface modification of GO and mechanical properties of epoxy composites were investigated systematically. The mechanical tests indicate that, without impairing tensile properties and glass transition temperature, the fracture toughness of PA6/GO-1.0 particles reinforced epoxy composites exhibits a 52.6% increase compared with neat epoxy at 1.5 wt% loading. Based on adequate fractographic study, the excellent toughening effect of PA6/GO-1.0 can be attributed to the better particle/matrix interface, rougher interface with small convex structures and more energy consumption of particle fracturing, which are resulted from the existence of PA6 chains grafted GO nanosheets. Moreover, the addition of GO and PA6 is 0.015 and 1.5 wt% respectively for the maximum fracture toughness value in this work. The dosage is very small compared with epoxy reinforced with GO or PA6 separately, giving an economically feasible method for the toughening of epoxy resin.
       
  • Meso-scale modelling of 3D woven composite T-joints with weave variations
    • Abstract: Publication date: Available online 23 December 2018Source: Composites Science and TechnologyAuthor(s): Shibo Yan, Xuesen Zeng, Andrew Long A meso-scale modelling framework is proposed to simulate the 3D woven fibre architectures and the mechanical performance of the composite T-joints, subjected to quasi-static tensile pull-off loading. The proposed method starts with building the realistic reinforcement geometries of the 3D woven T-joints at the mesoscale, of which the modelling strategy is applicable for other types of geometries with weave variations at the T-joint junction. Damage modelling incorporates both interface and constituent material damage, in conjunction with a continuum damage mechanics approach to account for the progressive failure behaviour. With a voxel based cohesive zone model, the proposed method is able to model mode I delamination based on the voxel mesh technique, which has advantages in meshing. Predicted results are in good agreement with experimental data beyond initial failure, in terms of load-displacement responses, failure events, damage initiation and propagation. The significant effect of fibre architecture variations on mechanical behaviour is successfully predicted through this modelling method without any further correlation of input parameters in damage model. This predictive method will facilitate the design and optimisation of 3D woven T-joint preforms.
       
  • Tunable negative permittivity in nano-carbon coated magnetic microwire
           polymer metacomposites
    • Abstract: Publication date: Available online 22 December 2018Source: Composites Science and TechnologyAuthor(s): Diana Estevez, Faxiang Qin, Yang Luo, Le Quan, Yiu-Wing Mai, Larissa Panina, Hua-Xin Peng While polymer-based metacomposites with embedded ferromagnetic wires have demonstrated metamaterial wave phenomena with potential applications, fine control over the electromagnetic response remains challenging. Our contribution here involves coupling carbon nanotubes (CNT) and graphene oxide (GO) with the wire via electrodeposition and tailoring the dielectric function of the resulting metacomposite by controlling the thickness and morphology of the CNT and degree of thermal reduction in the GO. As the CNT coating thickness is increased, a conversion of dielectric dispersion from Lorentz resonance to Drude plasma oscillation occurs, which is ascribed to the degree of inter-connection between the CNT networks in the coating. Also, the gradual restoration of sp2 domains and thus expansion of the delocalized π-electron network upon GO thermal reduction are responsible for such conversion in the GO-coated wires. Apart from the regulation of negative permittivity mechanism, the nano-carbon coatings also allow control over the dielectric parameters, including negative permittivity magnitude, plasma frequency and scattering rates determined by interfacial conditions, defects and roughness of the hybrid fibers. These outcomes offer an alternative way to obtain tailorable negative permittivity in the magnetic wire metacomposites and integrate the design philosophy of multiscale composites to that of metacomposites.
       
  • Amphiphilic cellulose nanofiber-interwoven graphene aerogel monolith for
           dyes and silicon oil removal
    • Abstract: Publication date: Available online 21 December 2018Source: Composites Science and TechnologyAuthor(s): Haoyi Wu, Zheng-Ming Wang, Akio Kumagai, Takashi Endo Monolithic graphene oxide (GO) and reduced GO (rGO) aerogel is recently receiving a great deal of concern as a promising adsorbent, whose structure and surface properties, however, are anticipated to be improved and adapted to the adsorption of organic contaminants with various polarities and ionic properties. Herein, super strong and hydrophilic cellulose nanofiber (CNF) was exploited as a cross-linker to interweave in between rGO layers so as to tune and balance the structural and surface properties (hydrophilicity and hydrophobicity) of the monolith. It was found that mechanical property of the monolith changes stepwise with the addition of CNF and can be greatly improved by proportion with CNF irrespective of a little sacrifice in electrical conductivity. Filling and further formation of aggregating bundle structure of CNFs in rGO monolith gradually decreases porosity at compensation of a slight increase in monolithic volume. CNF plays a critical role in separating rGO layers, leading to formation of the exposed and uniformly dispersed rGO layers in the monoliths. It can increase the amount of oxygen containing groups at the same time to generate carbonized moieties, thus ameliorating both hydrophilicity and hydrophobicity of the monolithic aerogel. The unique structural change and improved amphiphile surface property due to the addition of CNF can greatly enhance affinity of the hybridized monolith toward the adsorption of not only hydrophilic (both anionic and cationic) dyes but also hydrophobic organic oil.
       
  • Poly(vinylidene fluoride)-based nanocomposite employing oriented Bi2S3
           nanorods with double-shell structure for high dielectric performance and
           loss suppression
    • Abstract: Publication date: 8 February 2019Source: Composites Science and Technology, Volume 171Author(s): Lingyu Zhang, Yao Wang, Dalong He, Yuan Deng For polymer-based nanocomposites, designing the nanostructures of fillers, their distribution inside matrix as well as interfaces with the polymer is of crucial importance to achieve high dielectric performances. One-dimensional semiconductor Bi2S3 nanorods coated with homogeneous SiO2 and polydopamine (PDA) double shell layers were imported into the poly(vinylidene fluoride) (PVDF) with parallel arrangement via uniaxial stretching to form Bi2S3@SiO2@PDA/PVDF nanocomposite. The dielectric performances of oriented Bi2S3@SiO2@PDA/PVDF were studied in comparison with its counterparts employing Bi2S3 fillers without shell layers or alignment. A microcapacitor model was used to accurately estimate the dielectric constant along perpendicular direction. Coating conductive Bi2S3 nanorods with insulating SiO2@PDA double layer remarkably reduces the dielectric loss of the nanocomposite, while alignment of one-dimensional Bi2S3@SiO2@PDA nanorods endows electrical properties anisotropy, which was understood from J-V curves measured along two directions and moreover, via three-dimensional finite element analysis, unambiguously revealing the effects of aligned core-shell structured fillers on local electric field and current density distribution. This study provides a promising and facile approach for designing high performance dielectrics.Graphical abstractImage 1
       
  • TEMPO-oxidized cellulose nanofibril/layered double hydroxide nanocomposite
           films with improved hydrophobicity, flame retardancy and mechanical
           properties
    • Abstract: Publication date: 8 February 2019Source: Composites Science and Technology, Volume 171Author(s): Tao Wu, Bing Cai, Jinyu Wang, Chenggang Zhang, Zhuqun Shi, Quanling Yang, Guo-Hua Hu, Chuanxi Xiong High-performance and environment-friendly biomass-based composite films have drawn much attention recently. Here, bio-nanocomposites of TEMPO-oxidized cellulose nanofibrils (TOCNs) reinforced with layered double hydroxides (LDHs) were prepared through an environmentally benign pathway by aqueous dispersion. The results showed that LDHs could be uniformly dispersed in the cellulose nanofibril matrix to form an intercalated nanolayered structure due to good compatibility and the formation of ionic and hydrogen bonds between LDHs with positive charges and TOCNs with negative charges. The TOCN-LDH composite films exhibited high light transmittance, which exceeded 80% with an LDHs content of less than 10%. Moreover, the incorporation of LDHs improved not only the mechanical properties of the cellulose nanofibrils, but also their thermal stability, flame retardancy and hydrophobicity. More specifically, the highest Young's modulus and tensile strength reached 39.3 GPa of TOCN-LDH20 and 358 MPa of TOCN-LDH5, which were 364% and 178% of the neat TOCN film, respectively. The water contact angle and limiting oxygen index of the TOCN-LDH composite film increased from 46° to 103°, and from 25 to 31, respectively, with the LDH content increase from 0 to 20 wt%.
       
  • Design of mechanically stable, electrically conductive and highly
           hydrophobic three-dimensional graphene nanoribbon composites by modulating
           the interconnected network on polymer foam skeleton
    • Abstract: Publication date: Available online 20 December 2018Source: Composites Science and TechnologyAuthor(s): Cheng-Fei Cao, Guo-Dong Zhang, Li Zhao, Li-Xiu Gong, Jie-Feng Gao, Jian-Xiong Jiang, Long-Cheng Tang, Yiu-Wing Mai The development of three-dimensional (3D) graphene nanoribbon (GNR) based porous composites with both mechanical reliability and multiple functionality has attracted great interest due to their promising applications in strain sensing, oil/water separation, etc. Herein, we report a facile strategy to fabricate robust porous 3D GNR wrapped polymer foam composites through modulating an interconnected GNR network and introducing a flexible polydimethylsiloxane (PDMS) coating. By simply adjusting the graphene oxide nanoribbon (GONR) concentration in aqueous solution followed by chemical reduction, the presence of the reduced GONR (rGONR) sheets endows commercial polyurethane (PU) foam with electrical conductivity without altering their porous microstructure. The mechanical properties of the rGONR-coated PU (PGR) foam composites depend strongly on the rGONR content and exhibit poor stability at low content due to the breakage of the rGONR network during cyclic deformation. Introduction of the flexible PDMS coating effectively stabilizes the 3D rGONR network on the foam skeleton, producing excellent mechanical reliability, e.g., reversible compressibility at a compressive strain of 80% for 100 cycles. Moreover, these mechanically stable and porous PDMS modified PGR composites display excellent lipophilic-hydrophobic behavior, which provides good oil/solvent absorption capacity and highly efficient continuous oil/water separation.
       
  • Fe3O4 decorated graphene/poly(vinylidene fluoride) nanocomposites with
           high dielectric constant and low dielectric loss
    • Abstract: Publication date: Available online 20 December 2018Source: Composites Science and TechnologyAuthor(s): Yuchao Li, Dongmei Zhang, Shuangshuang Wang, Yanhu Zhan, Jie Yin, Xuquan Tao, Xiangcai Ge, Sie Chin Tjong, Hong-Yuan Liu, Yiu Wing Mai Percolative poly(vinylidene fluoride) (PVDF) composites with high dielectric constant and low dielectric loss was successfully achieved by incorporating reduced graphene oxide (rGO) decorated with magnetic iron oxide (Fe3O4) (rGO@Fe3O4) nano-fillers. The morphology, structure, thermal, electrical and magnetic properties of the composites were investigated systematically by using SEM, XRD, FTIR, TGA, DSC, impedance analyzer and magnetometer, respectively. The presence of a tiny amount of poly(sodium 4-styrene sulfonate) (PSSNa) facilitated the homogeneous distribution of rGO@Fe3O4 nanoparticles and prevented the formation of an electrical conductive network within the PVDF matrix, resulting in an excellent dielectric performance of the rGO@Fe3O4/PVDF nano-composites. With 1.0 wt% rGO@Fe3O4 incorporated in PVDF, the nanocomposite exhibited a high dielectric constant of 1297 and a low dielectric loss of 0.26 at 100 Hz. Percolation model revealed that such improvements could be attributed to the synergistic effect of the inorganic Fe3O4 and rGO, whereby the electric charges were accumulated by forming many mini-capacitors in the bulk PVDF matrix. The structure-property behavior of the final nanocomposites was discussed.
       
  • Exploration of the design freedom of 3D printed continuous
           fibre-reinforced polymers in open-hole tensile strength tests
    • Abstract: Publication date: Available online 19 December 2018Source: Composites Science and TechnologyAuthor(s): Lincy Pyl, Kalliopi-Artemi Kalteremidou, Danny Van Hemelrijck In the current work, the design freedom of 3D printed composite parts reinforced with continuous fibres is explored. The placement of continuous fibres to reduce stress concentrations around the hole is exploited in open-hole tests. Distinct counterintuitive performance in tensile strength is observed. The expected gain in ultimate tensile strength by adding contour reinforcement around the hole could only be observed for a rectangular reinforcement. Digital Image Correlation monitoring of the strain pattern demonstrated promising performance in strain reduction and the ability to locate the damage patterns outside the regions prone to stress concentrations (i.e. the hole).
       
  • Quantitative analysis of grafted CNT dispersion and of their stiffening of
           polyurethane (PU)
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Science and TechnologyAuthor(s): M.H. Jomaa, L. Roiban, D.S. Dhungana, J. Xiao, J.Y. Cavaillé, L. Seveyrat, L. Lebrun, G. Diguet, K. Masenelli-Varlot Electroactive devices are developed for energy conversion purposes. In particular, polyurethanes (PU) are lightweight and flexible materials, which have demonstrated their ability to convert electrical energy into mechanical energy (actuation by electrostriction) and vice-versa (energy harvesting). It has been shown that energy conversion efficiency can be increased by incorporating carbon nanotubes (CNTs) into a PU matrix. The counterpart of this improvement is the stiffness increase, which in turn limits the electrostriction efficiency. On the other hand, it is well known that CNTs are hardly dispersed in a polymeric matrix, and that the interfacial adhesion strength is generally poor. One solution to improve both dispersion and adhesion consists in grafting polymeric chains onto the CNT surfaces. As most of the works dedicated to improve material electroactivity are mainly empirical, this work aims to (i) better characterize these material microstructures by electron tomography, through the measurement of the CNT tortuosity, the CNT-CNT minimum distance and the number of their contacts, and (ii) and to predict their mechanical stiffness from these microstructural data. From electron microscopy observations of the studied materials, CNTs can be assumed to be composed of successive stiff rods of measured length and orientation, linked together by flexible kinks. Their mechanical stiffening effect in PU is, simply and in an original way, evaluated using the classical analytical equations derived by Halpin and Kardos, accounting for the microstructural parameters determined by electron tomography. It appears clearly that, due to their tortuosity and despite their ultra-high longitudinal stiffness, CNTs only poorly stiffen soft matrices. Fully stretching 10 μm long nanotubes increases the composite modulus by almost 10 for a fraction of only 2 vol%.
       
  • Fast processing and continuous simulation of automotive structural
           composite components
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Science and TechnologyAuthor(s): Frank Henning, Luise Kärger, Dominik Dörr, Fabian J. Schirmaier, Julian Seuffert, Alexander Bernath Due to application-specific tailoring, continuous fiber reinforced plastics (CoFRP) provide an exceptional lightweight potential and are particularly suited for structural components. The use of CoFRP specifically for weight reduction of the automotive car body is the major focus of this feature article. Automotive mass production requires fast and qualified, thus highly automated and material efficient manufacturing technologies. Consequently, CoFRP manufacturing for automotive differs considerably from conventional CoFRP manufacturing for aerospace, particularly in terms of higher throughput with higher investment, but lower operating effort. Furthermore, automotive structures have smaller dimensions with more complex shapes, which makes it more challenging to avoid forming defects and to ensure complete injection. Since manufacturing makes the main difference between automotive and aerospace composite components, this feature article puts emphasis on the process technologies and on the corresponding material behavior and process simulation methods. For a holistic product design of automotive CoFRP components, a simultaneous virtual description and virtual optimization of both manufacturing process and structural capacity is necessary. Production effects must be considered in the part design and, thus, must be reliably predicted by process simulation as well as taken into account in subsequent simulation steps. This feature article therefore evaluates the current state of the art in the continuous virtual representation of CoFRP process chains, including the process steps forming, injection and curing. Furthermore, the integrated optimization along this CAE chain is a key factor for an economic part design and therefore another major subject of this article.
       
  • Cellulose nanofibrils as reinforcing agents for PLA-based nanocomposites:
           An in situ approach
    • Abstract: Publication date: Available online 17 December 2018Source: Composites Science and TechnologyAuthor(s): Stefano Gazzotti, Riccardo Rampazzo, Minna Hakkarainen, Daniele Bussini, Marco Aldo Ortenzi, Hermes Farina, Giordano Lesma, Alessandra Silvani One-pot in situ polymerization approach was explored for the preparation of polylactide (PLA)-cellulose nanofibril (CNF) bio-nanocomposites. CNF were first prepared through enzymatic and mechanical treatment of bleached hardwood kraft pulp. The bio-nanocomposites- were then fabricated through ring opening polymerization (ROP) of L-lactide, in the presence of various amounts of fibrils. Molecular weight, thermal properties, surface morphology, mechanical and wettability properties of the PLA-CNF nanocomposites were evaluated. DSC analysis demonstrated the effect of CNF on crystallization and crystalline morphology of PLA. Improved modulus for the nanocomposites with respect to standard PLA was demonstrated, however, the differences in tensile stress were small probably due to the counteracting effects of reinforcement from CNF and the decreasing molecular weight as a function of CNF concentration. The absence of pulled-out fibers was assessed, highlighting the strong interface and covalent attachment of PLA chains on CNF surface. Finally, the covalent bonding of PLA chains on CNF surface was demonstrated by isolating the non-soluble part, consisting of PLA-grafted CNF, and characterization of this residue.
       
  • Fatigue behaviour of open-hole carbon fibre/epoxy composites containing
           bis-maleimide based polymer blend interleaves as self-healing agent
    • Abstract: Publication date: Available online 15 December 2018Source: Composites Science and TechnologyAuthor(s): V. Kostopoulos, A. Kotrotsos, A. Sousanis, G. Sotiriadis Bis-maleimides (BMIs) exhibit healing functionalities on polymer level. In the current investigation, BMI self-healing (SH) resin based on Diels-Alder (DA) reaction mechanism (identification code: BMI pp) was integrated into high performance aerospace carbon fiber reinforced plastics (CFRPs). The effect of BMI pp as self-healing agent (SHA) into CFRPs is assessed. More precisely, open-hole reference and BMI pp modified CFRP samples having [45/-45/0/90]2S stacking sequence, with similar fiber volume fractions have been tested under quasi static tensile and tension-tension fatigue loading conditions. According to quasi static experimental results, it was shown that the incorporation of the BMI pp SHA did not deteriorate the in-plane mechanical properties of the entire composite. In addition, tension-tension fatigue tests revealed that the incorporation of the BMI pp SHA into composites architecture made composites to slightly extend their fatigue life. Finally, the activation of the healing functionality of BMI pp modified composites at certain number of fatigue cycles significantly extends their fatigue life of about 75%. For all fatigue tested material sets a three-stage pattern of stiffness degradation was observed.
       
  • Designing formulation variables of extrusion-based manufacturing of carbon
           black conductive polymer composites for piezoresistive sensing
    • Abstract: Publication date: Available online 13 December 2018Source: Composites Science and TechnologyAuthor(s): Lingyan Duan, Martin Spoerk, Tom Wieme, Pieter Cornillie, Hesheng Xia, Jie Zhang, Ludwig Cardon, Dagmar R. D'hooge Highly sensitive conductive polymer composites for piezoresisitve sensing are developed by a design of the formulation variables of extrusion-based manufacturing (filler type/amount, polymer amount) and annealing (a), considering thermoplastic polyurethane (TPU) and/or olefin block copolymer (OBC) as polymer matrix and carbon black (CB) as conductive filler. With ternary composites - based on a CB type with stronger filler-matrix interactions and an appropriate OBC/TPU blend mass ratio (40/60 with CB amount of 5–10 m%; 50/50 with CB amount of 10 m%), the challenging region of both high sensitivity and static strain (maximal gauge factors (GFmax) > 50 and εmax > 100%) can be realized: GFmax > 104 and εmax = 20–240%. OBC binary composites with a high CB2 amount (e.g. 15 m%) are however needed for ultrahigh static strains (εmax > 600%). Well-designed ternary composites (e.g. OBC40-CB/TPU60-7-a and OBC30-CB/TPU70-7-a) possess a large dynamic resistance change, negligible hysteresis and high stability and display strain sensor application potential. Highly CB2 loaded binary (≥12 m%) and ternary composites (10 m%) exhibit a more obvious strain-dependent dynamic hysteretic behavior, as they switch from a dual peak to single peak pattern toward the sensing strain limit, which is interesting for self-diagnose.
       
  • Critical parameters of carbon nanotube reinforced composites for
           structural health monitoring applications: Empirical results versus
           theoretical predictions
    • Abstract: Publication date: Available online 13 December 2018Source: Composites Science and TechnologyAuthor(s): Xoan F. Sánchez-Romate, Joaquín Artigas, Alberto Jiménez-Suárez, María Sánchez, Alfredo Güemes, Alejandro Ureña This paper reports on an investigation of the critical parameters which determine the electrical and electromechanical properties of carbon nanotube (CNT) nanocomposites. For this purpose, a novel analytical model, based on the tunnelling mechanisms of CNTs, is proposed. Three dispersion parameters are introduced in the model to reflect the CNT aggregation state. Microscopy analysis and electrical and strain monitoring tests were carried out on CNT nanocomposites manufactured by toroidal stirring and three roll milling. It is observed that electrical conductivity is greatly affected by dispersion procedure as well as strain sensitivity, measured by the gauge factor (GF). Generally, well dispersed materials have higher conductivities and GF. In this regard, the aggregate ratio has a prevalent effect. Experimental data and theoretical predictions allow the correlation of dispersion parameters given by manufacturing procedures with electrical properties to develop highly sensitive nanocomposites. This demonstrates the potential and applicability of the proposed model.
       
  • All ‘green’ composites comprising flax fibres and humins'
           resins
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Science and TechnologyAuthor(s): Anna Sangregorio, Nathanael Guigo, Jan C. van der Waal, Nicolas Sbirrazzuoli The use of all “green” composite materials is a great environmental option for several applications such as construction or automotive. A new type of all green composites has been prepared by compression moulding flax fibres with humins as the matrix. Humins are macromolecular heterogeneous furanic co-products from biorefinery operations. For the first time the potential of humins as a whole thermoset-like matrix in combination with natural fibres was studied. The raw industrial humins were cross-linked with and without catalyst. The effect of the process conditions on the final properties of the composites was studied. Good tensile properties were measured by tensile test and Dynamic Mechanical Analysis. Observations of the fracture surface were done by Scanning Electron Microscope, revealing a void-free morphology. The study finally focused on the water absorption behaviour, underlining the more hydrophobic nature of the humins' composites compared to the raw flax mat. The good adhesion between the fibre and the matrix was underlined. Humins interacts with the hydrophilic fibres thus creating a good interphase, leading to improved properties. The study demonstrated the possibility of using a biorefinery co-product as a thermoset matrix for preparing composites materials.
       
  • A novel strategy for the synthesis of self-healing capsule and its
           application
    • Abstract: Publication date: Available online 8 December 2018Source: Composites Science and TechnologyAuthor(s): Tao Sun, Xuejing Shen, Chong Peng, Hongyu Fan, Minjing Liu, Zhanjun Wu Phenol formaldehyde (PF) resin capsules containing dicyclopentadiene (DCPD) as core materials are rationally designed and fabricated. The synthesis consists of preparation of polystyrene (PS) sphere, PF coating on PS sphere, followed by removal of PS core, amination modification and importing of DCPD. Solution phase switchable transport trough PF shell layer is key for the synthesis of DCDP@PF capsules. The resultant DCDP@PF capsules have a diameter of ∼500 nm, shell thickness of ∼50 nm, and core content of ∼45 wt%. The results show that DCDP@PF capsules have outstanding thermal stability with initial evaporation temperature (defined at 5% of weight loss), increased by ∼30 °C compared with that of pure DCPD, and good resistance to acetone. Preliminary results indicated that the prepared DCPD@PF capsules can effectivelly improve the mechanical properties of epoxy matrix as well as impart it self-healing properties. When 15 wt% DCPD@PF capsules were inttrouducd into epoxy matrix, 81.4% incresement in fracture toughness, 30.8% incresment in tensiles strength and 91.8% recovery in fracture toughness can be obtained. This work provides a new insight into the investigation of the fabraction of self-healing capsules.
       
  • A multiscale elasto-plastic damage model for the nonlinear behavior of 3D
           braided composites
    • Abstract: Publication date: Available online 6 December 2018Source: Composites Science and TechnologyAuthor(s): Chunwang He, Jingran Ge, Dexing Qi, Jiaying Gao, Yanfei Chen, Jun Liang, Daining Fang A multiscale elasto-plastic damage model is developed to predict the nonlinear behavior of three-dimensional (3D) braided composites. In this model, the sequential multiscale method is applied to transfer the effective properties from microscale to mesoscale, and from mesoscale to macroscale. The constituents at the microscale consist of fiber, matrix and interface which are consistent with the mesoscale ones. The fiber is considered to be elastic and brittle, and the elastic damage model is applied to degrade the stiffness. For the epoxy matrix, a coupled elasto-plastic damage model is proposed to integrate the effects of plasticity and damage, and furthermore the paraboloidal yield criterion is adopted to characterize the different types of mechanical behavior in tension and compression. The bilinear constitutive relation based on the cohesive element is used to investigate the properties of interface. A user-defined material subroutine (UMAT) in the nonlinear finite element analysis software ABAQUS is written to implement the proposed model and determine the response for 3D braided composites under quasi-static tension. The numerical simulations are compared with the corresponding experiments and the results show that they agree well with each other.
       
  • Highly flexible strain sensors based on polydimethylsiloxane/carbon
           nanotubes (CNTs) prepared by a swelling/permeating method and enhanced
           sensitivity by CNTs surface modification
    • Abstract: Publication date: Available online 5 December 2018Source: Composites Science and TechnologyAuthor(s): Rong Zhang, Cheng Ying, Hao Gao, Qingting Liu, Xudong Fu, Shengfei Hu Flexible sensors for large strain detection have recently been attracted the attention of researchers. This investigation reports a stretchable strain sensor in which carbon nanotubes (CNTs) were diffused into polydimethylsiloxane (PDMS) using a facile swelling/permeating method. The CNTs were further modified by using a silane coupling agent (SCA) to improve dispersion and the interaction between CNTs and PDMS. The CNTs permeated the skin layer of the PDMS composite and the inner core of PDMS contained few CNTs, forming a sandwich-like structure. The low CNTs content (0.48 wt%) and sandwich-like structure resulted in excellent composite flexibility which allowed work strains to exceed 350% and Young's modulus to increase from 0.25 MPa to 0.40 MPa. Surface modification of the CNTs improved their permeation depth and dispersion, which was shown to enhance composite sensitivity. The relative resistance change reached 4850% with a gauge factor of 20 by 1.0 wt% SCA modification. Cycled electromechanical properties showed a stable resistance response and sensitivity against strain. Therefore, the PDMS/CNTs nanocomposites prepared by swelling/permeating and CNTs surface modification in this study have various application potentials in the flexible sensor field.
       
  • The critical damage state controlling the tension-tension fatigue life of
           unidirectional fibre composites
    • Abstract: Publication date: Available online 4 December 2018Source: Composites Science and TechnologyAuthor(s): Bent F. Sørensen A fracture mechanics model is proposed for the prediction of the critical damage state corresponding to tension-tension fatigue failure of unidirectional fibre composites. The critical damage state is characterized by the development of longitudinal splitting cracks, enabling isolated damage zones with broken fibres to link up. The critical damage state can be expressed in terms of the size of damage zones with broken fibres. The critical damage zone size depends on the maximum applied cyclic stress level, the geometry of the splitting pattern and on the Mode II fracture energy of the composite. The model was used for predicting the critical damage size of a glass fibre composites subjected to cyclic loading. In a study reported in the literature, the damage zone size was determined experimentally by X-ray tomography just prior to fatigue failure. A good agreement was found between the predicted and reported damage zone sizes. Moreover, the reported failure involved longitudinal splitting in accordance with the model.
       
  • Highly anisotropic functional conductors fabricated by multi-melt
           multi-injection molding (M3IM): A synergetic role of multiple melt flows
           and confined interface
    • Abstract: Publication date: Available online 30 November 2018Source: Composites Science and TechnologyAuthor(s): Yanhao Huang, Zhengying Liu, Rui Chen, Shaodi Zheng, Changping Feng, Libo Chen, Wei Yang, Mingbo Yang An anisotropic conductor with graphene nanoplatelets (GNPs) well planar aligned in PP matrix has been obtained in this work through multi-melt multi-injection molding (M3IM). In this method, a second composite melt penetrated the first melt and products with three layers (skin layer, intermediate layer and core layer) were obtained. The GNPs in the three layers was entirely planar oriented along machine direction (MD) owing to the second shear flow and confined interface between intermediate layer and core layer. The finely aligned structure drastically elevated in-plane thermal conductivity of intermediate layer to as high as 7.32 W m−1 K−1 and highlighted an average thermal conductive anisotropy of 20.86 under 25 wt. % GNPs loading, as well as provided a good electric conductivity of 0.03 S m−1 in MD while insulativity in perpendicular direction. Additionally, the M3IM composite performed well in mechanical properties with tensile strength (40.33 MPa) and Young's modulus (1.15 GPa). This M3IM manufacturing provides outstanding anisotropic properties to the injection products which possess a considerable potential application in unilateral conduction field.Graphical abstractImage 1
       
  • DLC-treated aramid-fibre composites: Tailoring nanoscale-coating for
           macroscale performance
    • Abstract: Publication date: Available online 30 November 2018Source: Composites Science and TechnologyAuthor(s): M. Kanerva, S. Korkiakoski, K. Lahtonen, J. Jokinen, E. Sarlin, S. Palola, A. Iyer, P. Laurikainen, L. Xuwen, M. Raappana, S. Tervakangas, M. Valden This work aims to quantify the effect of a diamond-like carbon coating (DLC) treatment of aramid-fibres and to reveal the conversion of a fibre level performance leap on the macroscale mechanical behavior. The DLC based coating is applied directly on the reinforcement and laminates are infused with an epoxy matrix. After characterization of the coated surfaces, the performance of the composite is analyzed via interlaminar shear testing, fatigue testing and damage tolerance testing, microbond tests, and 3D finite element simulation using a cohesive zone model of the interface. The results show that the coating treatment improves the fatigue life and the S-N curve slope for the laminates while the residual strength after impact damage and environmental conditioning (water immersion at 60 °C) remains high. The scaling factor to convert the performance on macroscale was determined to be 0.17–0.39 for the DLC based fibre treatment.
       
  • Stacking sequence selection for defect-free forming of uni-directional ply
           laminates
    • Abstract: Publication date: Available online 30 November 2018Source: Composites Science and TechnologyAuthor(s): K.J. Johnson, R. Butler, E.G. Loukaides, C. Scarth, A.T. Rhead In order to meet demands for increased production rates of laminated composite components, aerospace manufacturing is being forced towards highly automated production processes such as forming. However, such automated processes increase the likelihood of inducing defects that lead to manufacturing cost and time inefficiencies which must be avoided. This paper introduces a new compatibility index, based on comparison of minimum energy (resin dominated) modes of adjacent plies that identifies stacking sequences which minimise defect formation. The index is validated using an experimental process where seven laminates with different stacking sequences are formed onto a complex tool geometry using an industrial double diaphragm former. Experimental results confirm that sequences with a high compatibility index produce defect-free parts at elevated temperature. Specifically, sequences with 90° interface angles (high compatibility indices) promote the most formable solutions and continuous 45° interfaces that spiral (e.g. 45/0/-45/90) which have a low compatibility index, produce the most problematic forming conditions owing to a shear locking behaviour. Laminate stacking sequence is thus shown to be a significant contributor, alongside temperature and vacuum rate, to quality of formed parts. The compatibility index method can therefore be used to increase production rate and quality in laminated composite manufacturing, leading to significant cost and efficiency savings.
       
  • Morphology and crystalline characteristics of polylactic acid [PLA]/
           linear low density polyethylene [LLDPE]/ microcrystalline cellulose [MCC]
           fiber composite
    • Abstract: Publication date: Available online 27 November 2018Source: Composites Science and TechnologyAuthor(s): Siddharth Mohan Bhasney, Purabi Bhagabati, Amit Kumar, Vimal Katiyar The purpose of current work is to examine the influence of microcrystalline cellulose fibre on PLA/LLDPE polyblend and their characterization by the XRD, FESEM, TEM, DSC, POM and UTM. All three constituents were taken in different loading and then extruded in the twin screw extruder via melt extrusion technique. The tensile strength and percentage elongation of PLA/LLDPE/1% MCC was reduced to 56% and increased to 9% than pure PLA while UTS and % elongation were increased and decreased to ∼12 and ∼18% than PLA/LLDPE polyblend, respectively. The toughness of PLA/LLDPE/1% MCC was decreased to 1543 kJ/m3 from PLA 1942 kJ/m3. No change was observed in Tg of polyblend composite but the crystallization temperature was reduced by 5 °C. The spherulite growth rate of PLA/LLDPE/1 wt % MCC was 2.5 μm/min higher than neat PLA (1.1 μm/min) and PLA/LLDPE/3% MCC (1.8 μm/min). This study showed noticeable changes in various properties of the polyblend composites like mechanical, morphological, and crystallinity were influenced by the orientation of fibre, composition, polymer miscibility and interaction at the edges among the matrix, disperse phase and filler.
       
  • A phase-field model for strength and fracture analyses of fiber-reinforced
           composites
    • Abstract: Publication date: Available online 1 November 2018Source: Composites Science and TechnologyAuthor(s): J.J. Espadas-Escalante, N.P. van Dijk, P. Isaksson A phase-field model for brittle fracture is proposed and evaluated for strength and fracture analyses of composites. In addition to the elastic properties, this approach makes use of only the fracture toughness and the strength of the material. The capability of the method is shown in analyses of composites at two scales. In laminates, strengths of notched laminates are estimated, including hole size effects. In a lamina, cracks developed in both transverse tension and compression are analyzed and compared to other numerical methods in the literature. The effect of a spectral and a hydrostatic-deviatoric decomposition of the strain energy density, two variants often used in phase-field formulations, are studied. It is shown that the choice of the decomposition affects the fracture development. Results are compared to experiments and simulations in the literature showing the capabilities of the phase-field approach.Graphical abstractImage 1
       
 
 
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