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Composites Part A : Applied Science and Manufacturing
Journal Prestige (SJR): 1.539
Citation Impact (citeScore): 5
Number of Followers: 218  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1359-835X
Published by Elsevier Homepage  [3159 journals]
  • Temperature effects on the compressive properties and failure mechanisms
           of composite sandwich panel with Y-shaped cores
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Junmeng Zhou, Yu Wang, Jiayi Liu, Jialin Liu, Jie Mei, Wei Huang, Yuling Tang The effects of temperature on the mechanical properties and failure mechanisms of composite sandwich panel with Y-shaped cores under out-of-plane compression have been studied in this paper. The carbon fiber composite sandwich panel with Y-shaped cores was manufactured by a hot-press method using unidirectional carbon/epoxy prepregs. The out-of-plane compression tests of composite sandwich panels were conducted at temperatures ranging from 20 °C to 200 °C. Then the stress-strain curves, failure modes, compressive stiffness and strength of composite sandwich panel at high temperatures were analyzed and compared with those ones at room temperature. The results have shown that temperature had a significant effect on mechanical properties and failure behaviors of composite sandwich panel. And high temperature resulted in the decreasing of compressive stiffness and strength. Finally, the analytical expressions were presented to predict the compressive stiffness and strength of composite sandwich panel and compared with experimental results at different temperatures.
       
  • Bamboo fibers composites based on styrene-free soybean-oil thermosets
           using methacrylates as reactive diluents
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Ming-en Fei, Wendi Liu, Anming Jia, Yang Ban, Renhui Qiu The present work aims at preparation of green composites by using bamboo fibers (BFs) as reinforcements and styrene-free soybean-oil based thermosets as matrices. To facilitate the formulation of acrylated epoxidized soybean oil (AESO) resins with a low viscosity and high crosslinking density, two methacrylate monomers, i.e., 1,4-butanediol dimethacrylate (BDDMA) and trimethylolpropane trimethacrylate (TMPTMA) were respectively used as reactive diluents (RDs) for replacing anticipatory carcinogenic styrene. Results indicated that the crosslinking density of AESO resins was improved and their viscosities were reduced simultaneously. The rheological and curing behaviors of AESO resins incorporated with RDs were investigated. The static and dynamic mechanical performance and thermal properties of bamboo fibers composites with the novel AESO resins were tested.
       
  • Selective localization of carbon nanotube and organoclay in biodegradable
           poly(butylene succinate)/polylactide blend-based nanocomposites with
           enhanced rigidity, toughness and electrical conductivity
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Veluri Sivanjineyulu, Kartik Behera, Yen-Hsiang Chang, Fang-Chyou Chiu Carbon nanotube (CNT) and organo-montmorillonite (15A) were used individually and simultaneously as reinforcing fillers to fabricate poly(butylene succinate)/polylactide (PBS/PLA) blend-based nanocomposites. Poly(butylene succinate-co-lactate) served as compatibilizer for the PBS/PLA blend. Morphological results demonstrated that the added CNT was distributed mainly in the PBS matrix, whereas the added 15A was selectively localized within the dispersed PLA domains. Adding only 15A produced a quasi co-continuous PBS-PLA morphology. DSC results confirmed the nucleation effect of CNT on the crystallization of PBS and PLA, whereas 15A facilitated only the nucleation of PLA. The CNT exerted greater influence than 15A on the samples’ rheological properties. The Young’s modulus and impact strength of the nanocomposites increased up to 4.2 and 2.8 times, respectively, compared with those of the blend. The electrical resistivity of the blend decreased by up to 11 orders at 3 phr CNT loading. The electrical-percolation threshold was constructed at 0.5 phr CNT loading.
       
  • Cell-layer dependent adhesion differences in wood bonds
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Sabine Herzele, Hendrikus W.G. van Herwijnen, Matthias Edler, Wolfgang Gindl-Altmutter, Johannes Konnerth The performance of wood adhesives depends on its internal cohesion and the adhesion to the wood surface which is structurally and chemically heterogeneous as it may be formed by different micro-surface, i.e. the compound middle lamella, the secondary cell wall layer, or the lumen surface. This study introduces an experimental protocol to directly evaluate adhesion to each of these micro-surfaces individually. Two wood fiber types presumed to differ in their surface chemistry are used as substrate. The results demonstrate that melamine-urea-formaldehyde adhesive shows excellent adhesion irrespective of the fiber type or micro-surface. While the same is the case for adhesion between untreated wood fiber surfaces and one component polyurethane, higher relative work of indentation between the lignin-rich compound middle lamella surface of medium density fiberboard fiber and one component polyurethane was observed. This observation is corroborated by a reduced polar character of this micro-surface as shown by X-ray photoelectron spectroscopy.
       
  • High breakdown strength and outstanding piezoelectric performance in
           flexible PVDF based percolative nanocomposites through the synergistic
           effect of topological-structure and composition modulations
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Lu Yang, Qiuying Zhao, Ying Hou, Rujie Sun, Meng Cheng, Mingxia Shen, Shaohua Zeng, Hongli Ji, Jinhao Qiu Over decades, the fabrication of flexible poly(vinylidene fluoride) (PVDF) based percolative nanocomposites with high piezoelectric performance is of great concern from both academia and industry. However, the issue of sharply declined breakdown strength in percolative nanocomposites poses an obstacle to realizing the full potential of conductive nanofillers in enhancing piezoelectricity. Herein, we demonstrated that through proper topological structure and composition modulations, notably improved breakdown strength and piezoelectric performance can be achieved in PVDF based percolative nanocomposites. By constructing a sandwiched structure where a layer of high breakdown strength is intercalated between layers containing high content (near percolation threshold) of conductive nanofillers, the breakdown strength of overall nanocomposites is significantly strengthened and thus allows for sufficient poling of outer layers, fulfilling the great potential of conductive nanofillers in yielding piezoelectricity enhancement. A super high piezoelectric coefficient d33 of 48 pC/N is obtained in the optimized sandwich nanocomposites.
       
  • Effective permeability averaging scheme to address in-plane anisotropy
           effects in multi-layered preforms
    • Abstract: Publication date: October 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 113Author(s): S.P. Bancora, C. Binetruy, S.G. Advani, E. Syerko, S. Comas-Cardona In Liquid Composite Molding (LCM) processes, fabric layers are stacked in a mold which may be a few meters long and wide to build up a thickness of not more than a few millimeters. Resin is introduced to fill all the empty spaces between the fibers. As the in plane dimensions are a few orders of magnitude larger than through the thickness, flow of resin through the preform can be modeled using the two-dimensional Darcy’s law, neglecting the through-thickness velocity and assigning the preform an arithmetic averaged permeability from the layers. However, there are situations in which the through-thickness flow is significant where this assumption is no longer valid or justified. To address such cases, a modified averaging scheme was proposed by Calado and Advani (1996) to account for the transverse flow between adjacent layers of a preform and consequently derive an homogenized one-dimensional value of effective permeability. In the current work, such a model is extended to account for the effect of anisotropic off-axis layers in the stack. The result is a generalized scheme for effective permeability averaging layers of heterogeneous preforms, capturing both through-thickness and in-plane effects into a one-dimensional permeability value. This methodology was validated and a parametric study was conducted with different combinations of in-plane and through-thickness permeability values to identify the influence of preform in-plane dimensions and thickness and to define a criteria that relates the material and geometric parameters to the transverse flow.
       
  • On dynamic response of corrugated sandwich beams with metal foam-filled
           folded plate core subjected to low-velocity impact
    • Abstract: Publication date: Available online 15 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Qinghua Qin, Wei Zhang, Shiyu Liu, Jianfeng Li, Jianxun Zhang, L.H. Poh The paper focuses on fully clamped corrugated sandwich beams with metal foam-filled folded plate core to investigate its response subjected to low-velocity impact. The yield criteria for the metal foam-filled corrugated sandwich beam cross-section are obtained by considering the strength effects of metal foam and folded plate. Based on the yield criteria, dynamic and quasi-static models are developed to analytically predict the large deflections of corrugated sandwich beams, respectively, which agree well with finite element results. Furthermore, it is shown that the strain hardening of face sheets and folded plate do not significantly influence the low-velocity impact response.
       
  • CNT-reinforced Metal and Steel Nanocomposites: A Comprehensive Assessment
           of Progress and Future Directions
    • Abstract: Publication date: Available online 15 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): A.V. Radha mani, Hon Chung Lau, S. Ramakrishna Carbon nanotubes (CNT) are rolled graphene sheets and are an exceptional invention in the field of nanotechnology. They have outstanding material characteristics such as high surface-to-volume ratio, high tensile strength, high thermal conductivity, and low density. Carbon nanotubes are many times stronger and yet lighter than steel and other metals, and thus a good candidate for reinforcing them. However the integration of CNTs into a metal or steel matrix is challenging and dispersion uniformity depends on processing parameters. The composite material properties are a function of the uniformity of CNT dispersion, interfacial bonding, CNT weight percent, length and alignment with the matrix. This paper reviews various methods of processing CNT-metal and CNT-steel nanocomposites, and their reported mechanical and material properties. Ways to overcome technical challenges are proposed and potential applications of CNT-steel composites as next generation structural material for the operationally demanding offshore oil petroleum industry are specifically discussed.
       
  • Wrinkle measurement in glass-carbon hybrid laminates comparing ultrasonic
           techniques: A case Study
    • Abstract: Publication date: Available online 15 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Beatriz Larrañaga-Valsero, Robert A. Smith, Rostand B. Tayong, Antonio Fernández-López, Alfredo Güemes Wrinkles, (also known as out-of-plane waviness) are, unfortunately, a common phenomenon that has caused some wind-turbine blades to unexpectedly fail in service. Being able to detect the wrinkles while in the factory will reduce the risk of catastrophic failure and characterising the wrinkles would minimise the repaired area, thus increasing the efficiency of the repair and the design. This work compares the effectiveness of three different ultrasound techniques for detecting and characterising out-of-plane wrinkles in the typical glass-carbon hybrid laminates that are used for wind-turbine blades. The tests samples were manufactured so that the laminates and the defects are representative of those used in the wind-turbine industry. Basic mechanical tests were performed to check the drop in mechanical properties due to wrinkling. The ideal probe frequency was determined as the resonance frequency of the plies using an analytical ultrasonic-propagation model. The three different ultrasound techniques used are: full-matrix capture (FMC) with the total focusing method (TFM), a commercial phased-array instrument and an immersion test with a raster-scanned single-element focused probe. When possible, severity parameters of the wrinkle were measured on the ultrasonic images and compared with the measurements of the actual sample in order to determine which method best characterises such wrinkles and which would be more appropriate to implement in an industrial environment. Not all of the techniques allowed full characterisation of out-of-plane waviness on the specimens. The FMC/TFM method gave better results whilst phased-array technology and single-element immersion testing presented more challenges. An additional enhancement to the TFM imaging was achieved using an Adapted-TFM method with an angle-dependent velocity correction.
       
  • Enhanced mechanical and dielectric properties of an epoxy resin modified
           with hydroxyl-terminated polybutadiene
    • Abstract: Publication date: Available online 14 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yujia Kou, Wenying Zhou, Bo Li, Lina Dong, Yu-E Duan, Qianwen Hou, Xiangrong Liu, Huiwu Cai, Qingguo Chen, Zhi-Min Dang Epoxy (EP) modified with nonpolar rubbers have the potential to achieve a concurrent improvement in mechanical and dielectric properties, when the EP-rubber interface is properly manipulated. Here we investigate rubber toughened EP based on a non-polar hydroxyl terminated polybutadiene (HTPB), and a coupling agent, dimer fatty acid diisocyanate (DDI), in which the rubber is covalently bonded to the epoxy. The mechanical and dielectric properties can be improved with the addition of HTPB and are maximized at 15 phr of elastomer inclusion. The enhanced mechanical toughness is attributed to the extensive shear yielding induced by a large amount of uniformly dispersed rubber particles; the same morphology can also combine the good insulating properties of HTPB and dielectrically favorable interfaces. These facts along with the reduced dielectric constant and loss for the modified EP suggest that the HTPB-DDI-EP can be used as a promising insulating packaging material for microelectronic applications.
       
  • Polymer Film Dewetting for Fabrication of Out-of-Autoclave Prepreg with
           High Through-Thickness Permeability
    • Abstract: Publication date: Available online 9 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Sarah G. K. Schechter, Timotei Centea, Steven R. Nutt Polymer film dewetting on a substrate (independent of fiber bed architecture) was explored, developed, and demonstrated as a method to produce out-of-autoclave, vacuum bag-only (OoA/VBO) prepregs with high transverse permeability and process robustness. The dimensions of the surface openings created by dewetting were measured, and the percent surface area exposed was calculated. Prepregs were fabricated with continuous and dewetted (discontinuous) films to produce trial laminates. The laminates were cured under both standard and sub-optimal conditions, and were characterized before, during, and after cure. Laminates fabricated with dewetted resin consistently achieved near-zero porosity. In contrast, laminates with continuous film displayed high levels of porosity, particularly during sub-optimal cure. The findings demonstrate that dewetting can be used effectively to produce OoA prepregs with high through-thickness permeability, which can yield porosity-free laminates via VBO processing. Furthermore, these results elucidate aspects of resin dewetting that are critical in the creation of robust OoA prepregs.
       
  • A study on amplitude transmission in ultrasonic welding of thermoplastic
           composites
    • Abstract: Publication date: October 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 113Author(s): Genevieve Palardy, Huajie Shi, Arthur Levy, Steven Le Corre, Irene Fernandez Villegas Ultrasonic welding of thermoplastic composite materials is a promising joining technique that is now moving towards up-scaling, i.e. the assembling of large industrial parts. Despite its growing technological maturation, the assumed physical mechanisms underlying ultrasonic heating (viscoelastic heating, friction) are still insufficiently understood and modelled. In particular, the hammering phenomenon, resulting from the periodic loss of contact between the sonotrode and adherends due to the high frequency vibration caused to the former, directly impacts the heating efficiency. We propose in this work an original experimental and modelling approach towards a better understanding of the hammering effect. This approach makes combined use of: (i) an experimental static welding setup provided with a high-frequency laser sensor to analyse the vibration amplitude transmitted to the adherends and (ii) an improvement of the multiphysical finite element model already presented in previous works. Results show it is possible to obtain a good estimation of the vibration transmitted to the upper adherend from laser measurements close to the sonotrode. The hammering effect is shown to decrease during the welding process, due to the heating of the interface which directly affects further heat generation. Quantitative introduction of this hammering effect in the existing numerical model results in improved predictions in terms of dissipated power in time.
       
  • Predicting the non-linear mechanical response of triaxial braided
           composites
    • Abstract: Publication date: Available online 12 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Tobias Wehrkamp-Richter, Nelson V. De Carvalho, Silvestre T. Pinho In this paper, the non-linear mechanical response of triaxial braided composites under multiple loading conditions was investigated with a meso-scale simulation strategy. Numerical predictions made by three-dimensional finite element unit cells with a realistic internal geometry in two nesting configurations correlated well with experimental stress-strain curves and damage mechanisms. Although the investigated braid topologies exhibited considerable geometric variability, the unit cell modelling approach with a compacted geometry model built from average input parameters was capable of correctly predicting the homogenised constitutive response, localisation, and damage evolution. Further, the mechanical response was predicted under variable uni-axial off-axis load cases and the effect of the textile topology on the ultimate strength of the material was investigated. Aside from providing a valuable insight into how damage propagation is affected by the meso-structure, the predicted stress-strain curves can be used to calibrate macroscopic material models suitable for large-scale crash simulations of textile composites.
       
  • Recent Advances in Electromagnetic Interference Shielding Properties of
           Metal and Carbon Filler Reinforced Flexible Polymer Composites: A Review
    • Abstract: Publication date: Available online 11 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Sowmya Sankaran, Kalim Deshmukh, M. Basheer Ahamed, S.K. Khadheer Pasha The rapid proliferation and elevated usage of electronic devices have led to a meteoritic rise in electronic pollutions such as electronic noise, electromagnetic interference (EMI) and radiofrequency interference which leads to improper functioning of electronic devices. Metals and their alloys can serve as the best EMI shielding materials but their heavy weight, high cost and low corrosion resistance have limited their applications in EMI shielding. The emergence of flexible polymer composites have substituted the metal and metal alloy based EMI shielding materials due to their unique features such as superior electrical, dielectric, thermal, mechanical and magnetic properties that are highly useful for suppressing the electromagnetic noises. In this review article, the EMI shielding effectiveness of flexible polymer composites comprising of metals and various forms of carbon nanofillers such as carbon black, carbon nanofibers, carbon nanotubes, graphite, graphene, graphene oxide, graphene nanosheets, graphene nanoribbons and graphene nanoplatelets have been deeply reviewed.
       
  • Effect of Z-Pinning on the Impact Resistance of Composite Laminates with
           Different Layups
    • Abstract: Publication date: Available online 11 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): L. Francesconi, F Aymerich The paper presents the results of an experimental investigation into the effect of Z-pinning on the impact resistance of composite laminates with different multi-directional layups. Unpinned and pinned [02/902]s, [02/±45]s and [0/±45/90]s carbon/epoxy samples were subjected to low-velocity impacts resulting in damage severities ranging from barely visible damage to full laminate penetration. The responses to impact of the laminates were characterized in terms of damage evolution, load-carrying capacity, and resistance to perforation and penetration. It was found that even though Z-pins are not capable of delaying the onset of delamination, they significantly reduce delamination size for high-energy impacts. Z-pinning improves the resistance to perforation and penetration of [02/902]s, laminates, while it does not significantly affect that of [02/±45]s and [0/±45/90]s samples. The dependence of the efficacy of Z–pins on the laminate layup is attributed to the different distribution of the delaminations through the thickness of the investigated laminates.
       
  • In Situ Growth of Polyphosphazene Particles on Molybdenum Disulfide
           Nanosheets for Flame Retardant and Friction Application
    • Abstract: Publication date: Available online 11 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Shuilai Qiu, Yixin Hu, Yongqian Shi, Yanbei Hou, Yongchun Kan, Fukai Chu, Haibo Sheng, Richard K.K. Yuen, Weiyi Xing Herein, polyphosphazene nanoparticle (PPN) functionalized MoS2 nanosheets have been successfully fabricated through a novel two-step method, involving a simple ball milling of bulk MoS2 powders to acquire exfoliated MoS2 nanolayer, followed by high temperature polymerization to achieve MoS2@PPN nanohybrids. The incorporation of P and N atoms could efficiently reduce the stacking of MoS2 nanolayers and form large number of active sites. It is noted that introducing well-characterized MoS2@PPN nanohybrids significantly improve the flame retardancy of epoxy resin (EP), i.e., 30.7% and 23.6% reductions in peak heat release rate and total heat release, respectively. The friction coefficients testing results reveal that the EP/MoS2@PPN1.0 composite exhibits the lowest friction coefficient value and volume wear rate. The excellent properties of these EP composites result from synergetic coupled effect between PPN and MoS2 ultrathin nanosheets, as well as improved interface interaction between MoS2@PPN and EP matrix.
       
  • Two-matrix Composites: Carbon Fiber Micropultrusions Embedded in Flexible
           Epoxy Matrices
    • Abstract: Publication date: Available online 10 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Sebastien J.P. Callens, Otto K. Bergsma Two-matrix composites combine fibers with two distinct matrices. This is achieved by impregnating fiber bundles with a high-stiffness matrix and embedding the cured bundles in a flexible matrix. Two-matrix composites have been shown to offer unprecedented combinations of transverse flexibility and longitudinal tensile strength, and could offer improved fiber alignment and manufacturability. Here, we explore this concept further by embedding carbon fiber micropultrusions in flexibilized epoxy matrices and examining the longitudinal compression behavior. Our results on thin-walled rings reveal that the failure mode depends on micropultrusion diameter, with small diameters resulting in micropultrusion kinking and larger diameters in splitting and crushing. Additionally, we find that two-matrix composites can offer higher compression strength than conventional composites with the same flexible matrix, despite a lower fiber volume fraction. The inherent manufacturing advantages and high anisotropy could make two-matrix composites interesting candidates for specific applications, such as morphing wings or additively manufactured composites.
       
  • An Efficient Highly Flexible Strain Sensor: Enhanced Electrical
           Conductivity, Piezoresistivity and Flexibility of a Strongly
           Piezoresistive Composite Based on Conductive Carbon Black and an Ionic
           Liquid
    • Abstract: Publication date: Available online 7 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Jirawat Narongthong, Amit Das, Hai Le Hong, Sven Wießner, Chakrit Sirisinha Flexible strain sensors based on conductive carbon black (CB) filled styrene-butadiene rubber were developed. The use of ionic liquid (IL) allows improvement of the filler dispersion, rubber-filler interaction and flexibility of the sample that finally enhances the piezoresistive performance and the sensibility. At filler loading close to the percolation threshold, the electrical conductivity increases by two orders of magnitude when the IL/CB ratio is increased from 0 to 1.5. In contrast to the use of normal plasticisers, the loss in piezoresistivity at low strains is overcome. The sensitivity at 2.5% strain using an IL/CB ratio of 1.5 is about 600% higher compared with the sample without IL. Also, the response consistency becomes better with higher IL/CB ratios. Moreover, the use of IL allows the composites to be deformed more easily while still providing high responsivity to small strains. This enables the construction of better flexible strain sensors with long-term stability.
       
  • Development of sustainable biodegradable lignocellulosic hemp fiber/
           polycaprolactone biocomposites for light weight applications
    • Abstract: Publication date: Available online 7 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Hom Nath Dhakal, Sikiru Oluwarotimi Ismail, Zhongyi Zhang, Asa Barber, Euan Welsh, Jean-Eudes Maigret, Johnny Beaugrand Biocomposites with poly(ε-caprolactone) (PCL) as matrix and lignocellulosic hemp fiber with varying average aspect ratios (19, 26, 30 and 38) as reinforcement were prepared using twin extrusion process. The influence of fiber aspect ratio on the water absorption behavior and mechanical properties are investigated. The percentage of moisture uptake increased with the aspect ratio, following Fickian behavior. The hemp fiber/PCL biocomposites showed enhanced properties (tensile, flexural and low-velocity impact). The biocomposite with 26 aspect ratio showed the optimal properties, with flexural strength and modulus of 169% and 285% respectively, higher than those of neat PCL. However, a clear reduction on the mechanical properties was observed for water-immersed samples, with reduction in tensile and flexural moduli for the aspect ratio of 26 by 90% and 62%, respectively than those of dry samples. Summarily, the optimal sample provides an eco-friendly alternative to conventional, petroleum-based and non-renewable composites for various applications.
       
  • One-step enrichment of silica nanoparticles on milled carbon fibers and
           their effects on thermal, electrical, and mechanical properties of
           polymethyl-vinyl siloxane rubber composites
    • Abstract: Publication date: Available online 4 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Xiong-Wei Zhao, Le-Yuan Song, Xiang-Dong Zhu, Kai-Guo Liu, Chong-Guang Zang, Yu-Quan Wen, Qing-Jie Jiao It is critical to develop new approaches of preparing engineered carbon-based fillers for high-performance applications. Herein, silica nanoparticles enriched milled carbon fibers (MCFs@SiO2) as novel thermal conductive and electrical insulating filler was synthesized through a simple and rapid sol-gel reaction method within one hour before their incorporation into polymethyl-vinyl siloxane rubber (MVSR). Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectrometer (XPS) were applied to analyze the surface chemical structure of synthesized MCFs@SiO2, results of which demonstrated the existence of unhydrolyzed oxyethyl groups that are beneficial to improve the compatibility with polymer matrix. Enrichment mechanism of silica nanoparticles on milled carbon fibers was also described. The MVSR composites with a 20 vol.% MCFs@SiO2 loading showed 109.7% higher thermal conductivity compared to that of neat MVSR and an excellent electrical volume resistivity of 1.04 × 109 Ω cm owing to the silica nanoparticles layer. Besides, their tensile strength increased by 145.7%, resulting from the good compatibility between MCFs@SiO2 and MVSR which was confirmed by scanning electron microscope observations.
       
  • Performance, durability and recycling of thermoplastic biocomposites
           reinforced with coriander straw
    • Abstract: Publication date: Available online 1 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): E. Uitterhaegen, J. Parinet, L. Labonne, T. Mérian, S. Ballas, T. Véronèse, O. Merah, T. Talou, C.V. Stevens, F. Chabert, Ph. Evon In this study, coriander straw fiber was effectively incorporated as a reinforcing filler in polypropylene and biobased low-density polyethylene composite materials through twin-screw extrusion compounding and injection molding. Maleic anhydride-grafted copolymers were added as a coupling agent and effectively provided fiber/matrix compatibilization. With a significant reinforcing effect, resulting in a 50% increase in the flexural and tensile strength (from 19 to 28 MPa and from 12 to 17 MPa, respectively, for polypropylene composites) as compared to the native polymer, coriander straw allowed the production of 40% filled thermoplastic biocomposites with adequate mechanical properties comparable to those of commercial wood fibers, excellent durability in terms of UV and hygrothermal weathering and high potential for recycling. At the same time, such coriander biocomposites show a favorable cost structure, with 28% reduction of the granule cost as compared to wood fiber composites.
       
  • In-plane permeability distribution mapping of isotropic mats using flow
           front detection
    • Abstract: Publication date: Available online 30 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Baris Caglar, Damiano Salvatori, E. Murat Sozer, Véronique Michaud In-plane permeability of textile fabrics is often characterized by one-dimensional rectilinear flow experiments, displaying limitations related to potential race-tracking effects and the need to run experiments at several fiber volume fractions. We propose a practical approach to alleviate these drawbacks. Resin flow front location is detected by image processing of videos and coupled to a Control Volume Finite Element solver with an error minimization routine based on Levenberg-Marquardt method comparing numerical and experimental fill times of all control volumes. Permeability of an isotropic random mat was characterized through reference experiments: cases with intentionally introduced race-tracking and cases with varying permeability along the resin flow direction with three different sections and fiber volume fractions. The method led to an efficient permeability determination and provided valuable insights on the statistics of spatial permeability distribution while highlighting the benefits of a thresholding algorithm for interpretation of permeability experiments in the presence of race-tracking.
       
  • Progressive Damage and Failure Analysis of Single Lap Shear and Double Lap
           Shear Bolted Joints
    • Abstract: Publication date: Available online 30 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Ashith P.K. Joseph, Paul Davidson, Anthony M. Waas Intra-inter crack band model (I2CBM) is proposed for studying the progressive damage and failure of laminated composite bolted joints. The model combines Schapery theory for matrix microcrack modeling with crack band theory for lamina macroscopic failure modeling in a standard 3D finite element framework and is implemented as material laws at element integration points. Three different failure planes defined by material orthotropy are considered for the modeling of macroscopic failure using crack band theory. This procedure allows the model to be used either as an intraply element or as an interply element of finite thickness by an appropriate choice of the crack planes of interest. Localized bearing failure, observed in bolted joints, is modeled using a residual strength approach in the post-peak response of individual ply elements. Simulation results for single lap shear and double lap shear bolted joint problems are compared against experiments for model validation.
       
  • Shear-deformed fabric sensor made of P(VDF-TrFE) for damage detection of
           draped composite structures: A feasibility study
    • Abstract: Publication date: Available online 30 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Ji-Hun Bae, Min-Gu Han, Seung-Hwan Chang For the damage detection of complex-shaped composite structures fabricated by vacuum bag degassing molding with a draping process, a fabric sensor made of poly(vinylidene fluoride-trifluoroethylene), was constructed. Characterization of the fabric sensor by picture frame tests and an electromechanical test was carried out. The locking angle of the fabric sensor was around 30°, and the static sensitivity of the sensor increased with the shear angles owing to an overlapping effect. Subsequently, low-velocity impact tests were performed by using a drop-weight impact machine (2.35 J–7.06 J) to confirm the feasibility of the P(VDF-TrFE) fabric sensor for the damage characterization of the composite dome structures. As the first step of health monitoring method with a new type of sensor an estimation technique for the potential failure of the composite structures was suggested by considering the relationships between the impact energy and voltage signals from the fabric sensors.
       
  • Improvement of cellulose acetate dimensional stability by chemical
           crosslinking with cellulose nanocrystals
    • Abstract: Publication date: October 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 113Author(s): Liliane C. Battirola, Daniela M. Zanata, Maria C. Gonçalves Low resistance to organic solvent attack is still a limitation in cellulose-derived polymer applications. In this work, cellulose acetate/cellulose nanocrystal composites were prepared using a bifunctional molecule, (3-Isocyanatopropyl)triethoxysilane, as a crosslinking agent. The hydrolysis-condensation of the silane agent also resulted in the formation of a polysilsesquioxane network. The composite molecular structure, thermal behavior, and morphology were investigated by infrared spectroscopy; 29Si nuclear magnetic resonance; dynamic-mechanical analysis; and scanning and transmission electron microscopies. The morphological analyses of the composites indicated that the polysilsesquioxane domains and cellulose nanocrystals were uniformly distributed throughout the homogeneous crosslinked matrix. The effect of CNC addition and polysilsesquioxane network formation on the composite swelling and dimensional stability was remarkable, particularly for composites containing the highest CNC content.
       
  • A facile strategy for fabricating aramid fiber with simultaneously high
           compressive strength and high interfacial shear strength through
           cross-linking promoted by oxygen
    • Abstract: Publication date: Available online 29 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yu Dai, Yihao Yuan, Longbo Luo, Xiangyang Liu Low axial compressive strength derived from weak lateral interaction of aramid fiber is one of the major obstacles for its engineering application. Introducing cross-linking is an effective method to improve the property. In this study, Poly-(benzimidazole-terephthalamide) (PABI) fiber was synthesized and prepared by wet-spinning, followed by heat-treating at different conditions for formation of cross-linking. During the process, trace amount of oxygen was introduced and it was confirmed that oxygen had great influence on the cross-linking reaction. The finding was characterized in detail. It is found that cross-linking of PABI can take place upon 330°C and cross-linking site is located in phenyl on benzimidazole moieties because of its higher electron density. Trace amount of oxygen can significantly catalyze the cross-linking reaction and make cross-linking degree improve. Compressive strength increases by over 50% and interfacial shear strength is improved by nearly 28% after cross-linking on the basis of maintaining excellent mechanical properties.
       
  • Determination of the longitudinal compressive strength of a CFRP ply
           through a tensile test on a laminate
    • Abstract: Publication date: Available online 29 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): F. Laurin, P. Paulmier, F.-X. Irisarri In this study, an innovative test is proposed to identify the longitudinal compressive strength of a unidirectional ply. The key idea consists in designing a laminate that, when subjected to a tensile loading, fails by compressive failure in its central 90°-ply, due to the Poisson effect, without any prior damage. Six specimens have been tensile tested to failure. No intra-laminar matrix damage could be detected before the final failure. Fibre kinking in the 90°-ply is observed experimentally in the failed specimens. This damage mechanism, located in the gauge section of the specimens, leads to the final failure. A fast computational identification method is used to determine the longitudinal compressive stress and strain within the 90°-ply at failure, from this specific tensile test. The identified average failure properties are consistent with those obtained through conventional compression tests, but the associated scattering is much lower. Consequently, this innovative method leads to an increase in the design allowable, resulting in higher performance designs.
       
  • Variational analysis of free-edge stress and displacement fields in
           general un-symmetric and thin-ply laminates under in-plane, bending and
           thermal loading
    • Abstract: Publication date: Available online 27 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): M. Hajikazemi, W. Van Paepegem A variational approach based on the minimization of complementary energy is developed to determine accurately a complete solution for both free-edge stress and displacement distributions of a laminate with arbitrary lay-ups (possibly un-symmetric and made of thin plies) under combined in-plane, bending and thermal loading. The key idea is partitioning the total stresses/displacements in a laminate with free edges into unperturbed (without free edges) and unknown perturbation stresses/displacements caused by the presence of free edges. It enables the theory of variational stress-transfer to deal easily with both applied traction and displacement boundary conditions. A methodology is introduced to obtain displacement fields for a stress-based variational approach. The resulting stress and displacement fields exactly satisfy local equilibrium equations, strain-displacement relations together with all traction/displacement boundary and continuity conditions. By comparing the results with those obtained from the finite element method, the accuracy and computational efficiency of the developed model, is confirmed.
       
  • A new in-situ peeling test for the characterisation of composite bonded
           joints
    • Abstract: Publication date: Available online 26 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): J. Cañas, L. Távara, A. Blázquez, A. Estefani, G. Santacruz At the moment, bonded joints quality on composites used in aeronautical industry is verified based on the determination of the interlaminar fracture toughness (Gc) obtained by means of the Double Cantilever Beam (DCB) or the Climbing Drum Peel (CDP) tests. Although they are well-established tests, they have known limitations. This investigation presents the design and validation of a new device that carries out a peeling test, its main advantage being the capability to perform the test in-situ, i.e. directly on the actual aircraft production line without the necessity to extract coupons for a laboratory test. An experimental campaign has been carried out, the obtained results being comparable to those obtained with the traditional DCB and CDP procedures. Numerical studies have allowed to understand the delamination mechanisms presented at the different tests, confirming that experimental Gc evaluation obtained is adequate.
       
  • Realizing the Theoretical Stiffness of Graphene in Composites through
           Confinement between Carbon Fibers
    • Abstract: Publication date: Available online 26 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Jingwen Chu, Robert J. Young, Thomas J. A. Slater, Timothy L. Burnett, Broderick Coburn, Ludovic Chichignoud, Aurèle Vuilleumier, Zheling Li It is shown that approximately 2 wt% of graphene in the matrix of a unidirectionally-reinforced carbon fiber epoxy composite leads to a significant enhancement in mechanical properties. Particularly, it is found that the axial stiffness of the composites is increased by ∼10 GPa accompanied by an increase in axial strength of 200 MPa. X-ray computed tomography and polarized Raman spectroscopy have demonstrated that the graphene is predominately aligned parallel to the carbon fibers axes. Stress-induced Raman band shifts showed that the confined and self-aligned graphene is subjected to high levels of stress during axial deformation of the composite, with an effective Young's modulus of ∼825 GPa, approaching its theoretical value of 1050 GPa. This behavior has been modeled using the rule of mixtures and shear-lag analysis and it is demonstrated that highly-aligned graphene in a constrained environment between fibers gives significantly better mechanical reinforcement than graphene in conventional polymer-based nanocomposites.
       
  • An experimental and Simulative Study on the Defects Appeared during Tow
           Steering in Automated Fiber Placement
    • Abstract: Publication date: Available online 25 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Nima Bakhshi, Mehdi Hojjati In the present study, an extensive experimental investigation using various process parameters and steering radii is performed to gain a deeper understanding of the defect formation process during tow steering in Automated Fiber Placement (AFP). Five major defects appeared during the tow steering are identified and effective factors on the formation of each of them are described. Furthermore, a finite element modeling approach is presented for the global modeling of the prepreg deposition process. The required model parameters are experimentally characterized. The application of the proposed framework for capturing and modeling two major defects appeared during steering namely, the blisters and wrinkles is presented. Simulation results are presented and compared to their corresponding AFP trial. It is demonstrated that the modeling approach is very well capable of capturing the trends, patterns, and frequency of both wrinkles and blisters.
       
  • Annealing and saponification of electrospun cellulose-acetate nanofibers
           used as reinforcement materials for composites
    • Abstract: Publication date: Available online 24 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Shunya Inukai, Naruki Kurokawa, Atsushi Hotta To enhance the mechanical properties of regenerated cellulose nanofibers (RC-NF), the annealing and the saponification of electrospun cellulose-acetate nanofibers (CA-NF) have been investigated. It was found that, by increasing the annealing time of CA-NF at 50 ˚C from 0 to 12 h, the crystallinity of RC-NF increased from 37 to 41%, which became constant after 12 h. By applying the theory proposed by Tsai, the Young’s modulus of RC-NF was found to increase from 11.2 to 28.0 GPa by increasing the annealing time from 0 to 12 h, which also became constant after 12 h. The optimized annealing time for the maximum crystallinity and Young’s modulus became shorter by increasing the annealing temperature, indicating that the crystallinity and the Young’s modulus of RC-NF were strongly correlated. Eventually, the Young’s modulus of RC-NF/PVA increased from 2.1 to 3.0 GPa at the maximum, while that of pure PVA was 1.5 GPa.
       
  • 3D printing of composite sandwich structures using continuous carbon fiber
           and fiber tension
    • Abstract: Publication date: Available online 24 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Kentaro Sugiyama, Ryosuke Matsuzaki, Masahito Ueda, Akira Todoroki, Yoshiyasu Hirano Many modern aircraft components are made from carbon fiber reinforced polymer sandwich structures with two outer skins possessing high tensile and compressive strengths separated by a lightweight core that provides shear stiffness. However, the conventional manufacturing method involves a complicated and costly bonding process. This study used a continuous carbon fiber 3D printer to manufacture sandwich structures with honeycomb, rhombus, rectangle, and circle core shapes as a single piece. The functional properties of the sandwich structures were quantified by shape evaluations and three-point bending tests. Three-point bending tests showed maximum load and flexural modulus increased as effective density increased for all core shapes, but the rhombus core shape was the strongest. Because the mechanical properties depended on the core shape, continuous carbon fiber 3D printers can be used to flexibly design core shapes that satisfy the desired strength and stiffness.
       
  • One-pot synthesis of an emulsion-templated hydrogel-microsphere composite
           with tunable properties
    • Abstract: Publication date: Available online 24 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Wing-Fu Lai, Andrey L. Rogach, Wing-Tak Wong The development of composite hydrogels is enjoying ever-increasing research interests and applications due to the high flexibility of these materials in composition and properties. This study develops an emulsion-templated hydrogel-microsphere composite with tunable properties using a one-pot synthetic approach. The composite consists of poly(trimethylolpropane ethoxylate triacrylate) microspheres crosslinked by a hydrogel, which is formed by a starch-based bifunctional emulsion stabilizer. Composites with a higher compositional ratio of the hydrogel have been found to have lower erosion susceptibility and swelling capacity. As an illustration of the unique practical potential of its amphiphilic character and tunable swelling properties, as well as its large surface area for adsorption, the composite has been loaded with model compounds with various degrees of hydrophilicity, and has been shown to be useful for applications such as drug loading and pollutant removal. The composite is a novel material displaying application potential that warrants further development.
       
  • Searching for effective compatibilizing agents for the preparation of
           
    • Abstract: Publication date: Available online 23 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): A. Martínez-Gómez, S. Quiles-Díaz, P. Enrique-Jimenez, A. Flores, F. Ania, M.A. Gómez-Fatou, H.J. Salavagione The homogeneous dispersion of graphene into poly(ether ether ketone)(PEEK) remains a challenging task mostly due to the resistance of PEEK to most common organic solvents. The present investigation describes a careful selection of compatibilizing agents that allows effectively dispersing graphene into PEEK. Polyetherimide (PEI), polysulfone, (PSU), poly(1,4-phenylene ether-ether-sulfone) (PEES) and sulfonated PEEK (SPEEK) are considered as potential compatibilizers and the mechanical, thermal and electrical properties of PEEK/graphene nanocomposites with different filler contents are evaluated. Significant electrical conductivity values are obtained for the nanocomposite with SPEEK (σ> 0.01 S.cm-1 at 4 wt.% filler content) and the one incorporating PEI exhibited a percolation threshold below 2 wt. %. Finally, the nanocomposites including SPEEK, PEI and PEES show a clear enhancement of the mechanical properties with increasing graphene content. Hence, nanocomposites incorporating PEI and SPEEK as compatibilizers displayed optimized electrical and mechanical properties, in addition to a thermal stability up to 550°C.
       
  • Strain and damage self-sensing of basalt fiber reinforced polymer
           laminates fabricated with carbon nanofibers/epoxy composites under tension
           
    • Abstract: Publication date: October 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 113Author(s): Yanlei Wang, Yongshuai Wang, Baolin Wan, Baoguo Han, Gaochuang Cai, Ruijuan Chang This study investigated the strain and damage self-sensing capabilities of basalt fiber reinforced polymer (BFRP) laminates fabricated with carbon nanofibers (CNFs)/epoxy composites subjected to tensile loadings. The conduction mechanisms based on the tunnel conduction and percolation conduction theories as well as the damage evolution were also explored. A compensation circuit with a half-bridge configuration was proposed. The results indicated the resistivity of the CNFs/BFRP laminates and CNFs/epoxy composites exhibited similar change rule, indicating that the conductive networks of CNFs/BFRP laminates were governed by CNFs/epoxy composites. With the increase of strain under monotonic tensile loading, the electrical resistance response could be classified into three stages corresponding to different damage modes. This confirmed CNFs/BFRP laminates have excellent self-sensing abilities to monitor their internal damages. Moreover, stable and repeatable strain self-sensing capacity of the CNFs/BFRP laminates was verified under cyclic tensile loading because the electrical resistance varied synchronously with the applied strain.
       
  • Numerical forming of continuous fibre reinforced composite material: A
           review
    • Abstract: Publication date: October 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 113Author(s): Philippe Bussetta, Nuno Correia This article presents a survey of the literature about the numerical forming of continuous fibre reinforced composite material. This review shows that in spite of some models are defined with data from the meso-scale, all the numerical models of the forming process are computed at the macro-scale. This work highlights the numerical model versus the type of the model – continuous, discrete and semi-discrete approaches – as well as the understanding of the material behaviour – considered phenomena – and the forming process – draping, forming of prepreg and hot-forming.
       
  • Strong linear piezoresistive response of carbon nanostructures reinforced
           hyperelastic polymer nanocomposites
    • Abstract: Publication date: Available online 19 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Muhamad F. Arif, S. Kumar, Tejendra K. Gupta, Kartik M. Varadarajan Here, we report highly strain-tolerant and sensitive strain sensors based on carbon nanostructures (CNS)-polydimethylsiloxane (PDMS) nanocomposites. CNS consist of clusters of aligned multiwall carbon-nanotubes (MWCNT) with high degree of entanglement and wall sharing between nanotubes. The unique features of CNS result in nanocomposites with very low electrical percolation threshold of 0.05 wt.% CNS content, strong linear piezoresistivity response up to 110% strain and high sensitivity with gauge factor ranging from 8 to 47. We also present a simple analytical model for predicting resistivity evolution as a function of stretch considering incompressible hyperelastic behavior of CNS/PDMS nanocomposites. CNS/PDMS nanocomposites also show good hysteresis performance and stability up to 100 repetitive stretch/release cycles for 30% maximum strain. Tunable sensitivity and linear piezoresistivity coupled with high stretchability demonstrated here suggest potential for applications in wearable health and fitness monitoring devices.
       
  • Enhanced thermal conductivity in Cu/diamond composites by tailoring the
           thickness of interfacial TiC layer
    • Abstract: Publication date: Available online 18 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Luhua Wang, Jianwei Li, Massimo Catalano, Guangzhu Bai, Ning Li, Jingjie Dai, Xitao Wang, Hailong Zhang, Jinguo Wang, Moon J. Kim Diamond particles reinforced Cu matrix (Cu/diamond) composites were fabricated by gas pressure infiltration using Ti-coated diamond particles with Ti coating from 65 nm to 850 nm. The scanning transmission electron microscopy (STEM) characterizes that the Ti coating transforms from elemental Ti to TiC after infiltration, and the crystallographic orientation relationship between diamond and TiC is [110]diamond//[110]TiC and (111)diamond//(111)TiC. The thermal conductivity of the Cu/Ti-diamond composites firstly increases and then decreases with increasing Ti coating thickness, giving a maximal value of 811 W m-1 K-1 at 220 nm Ti-coating layer. The results clearly manifest the effect of interfacial layer thickness on the thermal conductivity of Cu/diamond composites.
       
  • The Double Drum Peel (DDP) test: a new concept to evaluate the
           delamination fracture toughness of cylindrical laminates
    • Abstract: Publication date: Available online 17 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): F. Daghia, C. Cluzel, L. Hébrard, F. Churlaud, B. Courtemanche Standard delamination tests of monolithic composites prescribe configurations where the crack is a symmetry plane for both overall geometry and stacking sequence, ensuring a controlled mode ratio. These normalized configurations do not enable testing of curved specimens, like those manufactured by filament winding. Here, we propose a new concept for the delamination testing of cylindrical laminates, the Double Drum Peel , related to the peel tests used for adhesives or thin-films debonding. A global energy analysis, including all sources of energy release and dissipation, provides the expression of the critical strain energy release rate. As in the classical peel test, the energy dissipated by mechanisms other than delamination should be accounted for to determine intrinsic interface properties. The local mode mixity is evaluated based on analytical results on the classical peel test. Tests using carbon-peek rings manufactured by laser assisted tape placement are presented to illustrate the potential of the DDP.
       
  • Research on High Electromagnetic Interference Shielding Effectiveness of a
           Foldable Buckypaper/Polyacrylonitrile Composite Film via Interface
           Reinforcing
    • Abstract: Publication date: Available online 17 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Qianshan Xia, Zhichun Zhang, Hetao Chu, Yanju Liu, Jinsong Leng Herein, a series of foldable buckypaper/polyacrylonitrile (BP/PAN) composite films were developed in a facile strategy. This strategy was based on electrospun and vacuum pressurized filtration methods. The composite film had better mechanical properties than pristine BP via interface reinforcing, but not deprived of excellent conductivity. The maximum tensile strength and elongation at break of BP/PAN films were 1.45 and 11.65 times than pristine BP, respectively. Moreover, BP/PAN film had higher electromagnetic interference (EMI) shielding effectiveness (63.7-65 dB) in the Ku band (12-18 GHz) than pristine BP (34.3-42.9 dB), due to interfaces forming between PAN fibers and CNTs. The BP/PAN composite as a promising EMI shielding material could be utilized in military and civil applications, such as flexible antenna, EMI shielding clothes and soft portable electronic products.Graphical abstractGraphical abstract for this article
       
  • Interfacial adhesion assessment in flax/epoxy and in flax/vinylester
           composites by single yarn fragmentation test: correlation with micro-CT
           analysis
    • Abstract: Publication date: Available online 11 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): M.C. Seghini, F. Touchard, F. Sarasini, L. Chocinski-Arnault, D. Mellier, J. Tirillò Despite the academic interest in using plant fibres as reinforcement in polymer composites to replace glass fibres, the industrial exploitation of resulting composites in semi- or structural applications is still limited. This is mainly due to the poor adhesion at the plant fibre/polymer matrix interface dictated by their surface chemistry and strong hydrophilic behaviour. In the present work, an assessment of the interfacial adhesion at the yarn scale has been carried out. Fragmentation tests have been performed on flax/epoxy and flax/vinylester single yarn composites. High-resolution microtomography has allowed a 3-D reconstruction of the breaking area of the flax yarn. The flax/epoxy system has shown the lowest values of critical fragment length and interfacial debonding length, and the highest values of IFSS. For both epoxy and vinylester samples, it was found that the breakage of flax has been mainly concentrated in the peripheral zone of the yarn.
       
  • A 3D tomographic investigation to elucidate the low-velocity impact
           resistance, tolerance and damage sequence of thin non-crimp fabric
           laminates: effect of ply-thickness
    • Abstract: Publication date: Available online 11 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): S.M. García-Rodríguez, J. Costa, A. Bardera, V. Singery, D. Trias While thin-plies delay the onset of matrix cracking and improve certain in-plane mechanical properties, the effect they have on the out-of-plane response remains unclear. We compared the impact resistance, tolerance and sequence of failure events of thin laminates manufactured with thin- or standard-ply non-crimp fabrics (fibre areal weight of 67 and 134 gsm per ply). Damage initiation and propagation was detailed using (a) quasi-static indentation and impact tests at incremental energy levels and (b) X-ray tomography. The analysis revealed the damage mechanisms underlying the observed load drops in the force-displacement curves. In the indented specimens, the 3D post-process ascribed matrix cracks and delaminations to their corresponding plies/interfaces. Standard-ply samples develop more extended delaminations and delay fibre failure, improving the load-carrying capacity and increasing compression after impact (CAI) strength by 27% for impact at 14 J.
       
  • Mechanical, thermal and flame retardant properties of magnesium hydroxide
           filled poly(vinyl chloride) composites: The effect of filler shape
    • Abstract: Publication date: Available online 10 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yunhua Lu, Chifei Wu, Shiai Xu Magnesium hydroxide particle (MHP) and magnesium hydroxide whisker (MHW) were surface modified with a newly-synthesized polyether titanate coupling agent (eTi4000), and then incorporated into poly(vinyl chloride) (PVC) by melt blending to prepare PVC composites. The effect of filler shape on the mechanical, thermal and flame retardant properties of the resultant PVC composites was investigated. In general, MHP/PVC composites have better mechanical, thermal and flame retardant properties than MHW/PVC composites. The flexural modulus and impact strength of eTi4000 modified MHP (eTi4000-MHP)/PVC composites are 5740 MPa and 8.3 kJ m-2 at a 10 wt.% filler loading, with an increase of 217% and 48.2% compared with that of MHP/PVC composites, respectively. Significantly, eTi4000-MHP/PVC composites show good flame retardancy, and the incorporation of 30 wt.% of eTi4000-MHP results in 66.9% and 88.1% reduction of the total heat release and smoke production compared with that of pure PVC, respectively.
       
  • High wear-resistant performance of thermosetting polyimide reinforced by
           graphitic carbon nitride (g-C3N4) under high temperature
    • Abstract: Publication date: Available online 7 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Chunjian Duan, Dongming Yuan, Zenghui Yang, Song Li, Liming Tao, Qihua Wang, Tingmei Wang The two-dimensional (2D) material of graphitic carbon nitride (g-C3N4) has shown great promise for tribo-materials due to special molecular structure. In this work, we report an effective approach to enhance anti-wear of thermosetting polyimide (TPI) by filling with g-C3N4 under high temperature. TPI composite (TPT-1) and g-C3N4 were firstly prepared. Then, friction and wear behavior of TPT-1 was studied and comparatively evaluated with neat resin from room temperature to 350°C. As a result, the wear resistance of TPI was able to significantly improve and an much lower wear rate (7.29×10-7 mm3/N·m) was achieved at 350°C. Moreover, mechanism of friction and wear was demonstrated that transfer film formed by introducing g-C3N4 with high E-modulus and hardness could effectively share the load with TPI and prevent from further abrasion of resin in contact surfaces. This work could help researchers to design a new TPI tribo-material used at high temperature.
       
  • Mechanical anisotropy of paper-based all-cellulose composites
    • Abstract: Publication date: Available online 5 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Henri Kröling, Benoît Duchemin, Jan Dormanns, Samuel Schabel, Mark P. Staiger The effects of fibre orientation and laminate stacking sequence on the mechanical anisotropy of paper-based all-cellulose composites produced via a partial dissolution route is examined. As part of this work, the fibre architecture and microstructure of the paper precursor is controlled and characterised in order to follow the anisotropy of the materials through from precursor to final composite material. The fibre orientation of the precursor was found to strongly influence the mechanical anisotropy of the final composite material. The ultimate tensile strength and Young’s modulus of the paper-based all-cellulose composite laminates was 191 MPa and 17.5 GPa in the fibre direction, respectively, compared with 104 MPa and 10.4 GPa in the transverse direction, respectively. The ACC crystal structure was assessed with powder and transmission mode Wide-angle X-ray diffraction (WAXD) to measure the changes in crystallinity and crystal orientation due to the dissolution process. The mechanical response of multi-axial all-cellulose composite laminates was also determined experimentally and compared with analytical predictions by Classical Lamination Theory, demonstrating the utility of CLT for the prediction of the elastic properties of ACC laminates.
       
  • Deconsolidation of C/PEEK blanks: on the role of prepreg, blank
           manufacturing method and conditioning
    • Abstract: Publication date: Available online 5 July 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): T.K. Slange, L.L. Warnet, W.J.B. Grouve, R. Akkerman The combination of rapid automated lay-up and stamp forming has great potential for rapid manufacturing of lightweight load carrying components of thermoplastic composites. However, deconsolidation during blank heating is currently limiting the applicability of rapid lay-up blanks. This experimental work investigates the origin of deconsolidation in blanks produced by advanced fiber placement (AFP) versus traditional press consolidation. The influence of moisture on deconsolidation is investigated through deconsolidation experiments in a convection oven, as well as thermo-mechanical and residual gas analyses. The experiments revealed that thermal expansion of dissolved moisture is the main deconsolidation mechanism for press-consolidated blanks, but not for AFP blanks, which are suggested to deconsolidate mainly due to the release of frozen-in fiber stresses present in the used prepreg.
       
  • Complementary analytical imaging techniques for the characterization of
           pretreated carbon fiber reinforced plastics
    • Abstract: Publication date: Available online 30 June 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Stefan Viehbeck, Christian Iffelsberger, Frank-Michael Matysik In this work the complementary characterization of pretreatment techniques for adhesive bonding of carbon fiber reinforced plastics (CFRP) is presented. Industrial CFRP plates were pretreated with laser, plasma and corundum blasting abrasive techniques followed by chemical activation. The combined use of atomic force microscopy and chemical force microscopy enabled the characterization of the surface morphology and the specific adhesion force between a chemically functionalized cantilever and the pretreated surfaces simulating the adhesive bond. Complementary measurements with scanning electrochemical microscopy and X-ray photoelectron spectroscopy supported the experimental findings and delivered additional information about the chemical structure of the surfaces. A comparison of experimental data of mechanical tensile shear strength measurements and the applied analytical methods revealed a valid correlation of microscopic and macroscopic techniques.Graphical abstractGraphical abstract for this article
       
  • Anisotropic properties of oriented short carbon fibre filled polypropylene
           parts fabricated by extrusion-based additive manufacturing
    • Abstract: Publication date: Available online 11 June 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Martin Spoerk, Chethan Savandaiah, Florian Arbeiter, Gerhard Traxler, Ludwig Cardon, Clemens Holzer, Janak Sapkota For composites based on polypropylene (PP) filled with short carbon fibres (CF), extrusion-based additive manufacturing provides a promising and cost-effective manufacturing technique that utilises the flow-induced orientation of the fibres for their targeted alignment through the control of the printing direction. This study investigates the impact of the fibre orientation on mechanical properties and thermal conductivity of 3D-printed PP composites filled with short-CF. Provided a homogeneous fibre-dispersion and a good fibre-matrix adhesion, the composites showed considerably improved mechanical properties compared to neat PP regardless of the fibre orientation. However, for the different printing orientations, a strong anisotropy in terms of flexural and impact properties and thermal conductivity was observed. For example, it was found that the thermal conductivity along the printing and, thus, the fibre direction was three times higher than perpendicular to that direction. The present work provides a key to the fabrication of parts with tailored, orientation-dependent properties.Graphical abstractGraphical abstract for this article
       
 
 
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