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Composites Part A : Applied Science and Manufacturing
Journal Prestige (SJR): 1.539
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1359-835X
Published by Elsevier Homepage  [3184 journals]
  • Glass Fibre Sizing: A Review
    • Abstract: Publication date: Available online 9 September 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): J.L. Thomason Glass fibre reinforcements form the backbone of a composites industry with a global annual production of more than 10 million tons of high performance, light-weight materials. Possibly the most critical component involved in the manufacture of glass fibres and their composites is the fibre sizing. Yet because of the intense level of secrecy surrounding size formulations there are very few people in the vast supply chain of composite materials suppliers, processors and end users who have more than a superficial understanding of glass fibre sizings. Given the importance of sizings to the continuing success and growth of the composites industry this paper reviews some of the most relevant articles from the widely dispersed literature available around glass fibre sizings. The review covers size formulation, sizing effects in fibre and composite processing, sizing and fibre performance, sizing and interphase adhesion, and sizing effects on composite performance. The conclusions highlight the fragmented nature of the knowledge base on sizings and the lack of reliable and reproducible reference materials on which to build real progress in this critical technology.
  • A three-level hybrid metal/in-plane-CFRP/crossed-lamellar microstructure
           concept for containment applications
    • Abstract: Publication date: Available online 9 September 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): R. Häsä, S.T. Pinho This paper proposes a novel hybrid metal/Carbon Fibre Reinforced Polymer (CFRP) microstructure which includes a bio-mimetic crossed-lamellar CFRP layer (with out-of-plane fibres) as well as traditional CFRP layers (with in-plane fibres). We show that this microstructure is capable of preserving its structural integrity due to the crossed-lamellar and metal layers while the in-plane fibres provides it stiffness and strength. We studied numerically and experimentally a metal hybrid/crossed lamellar block in isolation, both with aluminium and titanium for the metal. We then proceeded to create the full microstructure, including a quasi-isotropic block. Our results show that these structures can withstand very large curvatures in a pseudo-ductile way. This makes them attractive for engineering applications where structural integrity is paramount, such as for containment structures.
  • Enhancement in thermal conductivity of polymer composites through
           vertically parallel multilayered distribution of microdiamonds
    • Abstract: Publication date: Available online 6 September 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Mingqi Sun, Lei Yang, Kang Liu, Ge Gao, Zhenhua Su, Gang Gao, Benjian Liu, Weihua Wang, Jiecai Han, Bing Dai, Jiaqi Zhu We propose a strategy to realize a vertically parallel multilayered distribution of microdiamonds in a polymeric matrix by pre-constructing layers with abundantly stacked microdiamonds. Silicone-based composites with this microdiamond arrangement exhibit interesting material properties in the through-plane direction: significant increments in thermal conductivity (335% that of composites with a random structure at a similar low loading of 24.7 vol%), and excellent dielectric properties as thermal interface materials for applications such as radars. Novel numerical models focused on this design of microdiamond arrangement are proposed to further understand mechanism of thermal conductivity increment and are found to match thermal conductivity and tendency of composites with this type of microdiamond distribution. It is revealed that adjusting microstructures in pre-constructed microdiamond layers is regarded as an effective strategy to improve further thermal conductivity of composites.
  • Fostering crack deviation via local internal stresses in Al/NiTi
           composites and its correlation with fracture toughness
    • Abstract: Publication date: Available online 5 September 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Lv Zhao, Lipeng Ding, Jeroen Soete, Hosni Idrissi, Greet Kerckhofs, Aude Simar In the framework of metal matrix composites, a research gap exists regarding tailoring damage mechanisms. The present work aims at developing an Al/NiTi composite incorporating internal stresses in the vicinity of reinforcements. The composite is manufactured by friction stir processing which allows a homogenous NiTi distribution and a good Al/NiTi interface bonding. The internal stresses are introduced via shape memory effect of the embedded NiTi particles. The induced internal strain field is confirmed by digital image correlation and the corresponding stress field is evaluated by finite element simulation. It is found that the damage mechanism is modified in the presence of internal stresses. The consequent enhancement of fracture toughness arises by the fact that the internal stresses foster discrete damages shifted from the fracture ligament line. These damages release the stress concentration at the main crack tip and lead to a deviated crack path when coalescing to accommodate fracture propagation.
  • Analytical formulation for electrical conductivity and percolation
           threshold of epoxy multiscale nanocomposites reinforced with chopped
    • Abstract: Publication date: Available online 3 September 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): M. Haghgoo, R. Ansari, M.K. Hassanzadeh-Aghdam, M. Nankali Electrical conductivity (EC) and percolation threshold of chopped carbon fiber (CF)-carbon nanotube (CNT)-reinforced epoxy multiscale nanocomposites considering tunneling resistivity are studied based on micromechanics. The percolation theory is applied to determine transition from low to high conductivity. Influences of CNT/polymer interphase and CNT waviness are considered to evaluate percolation threshold of CNT-enriched epoxy nanocomposite prior to CF percolation threshold. Multiscale fillers provide benefit of enhanced EC with different percolation thresholds for different fillers. These characteristics of multiscale filler with high aspect ratio of filler facilitate formation of conductive network even at low multiscale filler volume fraction. Variation of EC as a function of tunneling distance, CNT and CF aspect ratios and intrinsic EC for different CNT volume fractions is investigated. The nanocomposite exhibits a percolation threshold at less than 0.2 vol. % of CNTs. The percolation threshold is predicted to be reduced when higher volume fractions of CFs are considered.
  • Highly sensitive capacitive pressure sensors based on elastomer composites
           with carbon filler hybrids
    • Abstract: Publication date: Available online 31 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Kai Ke, Michael McMaster, William Christopherson, Kenneth D. Singer, Ica Manas-Zloczower Flexible pressure sensing applications such as prosthetic limbs and wearable electronics will benefit from pressure sensors with increased capacitive sensitivity. Therefore, to fabricate pressure sensors with increased sensitivity, hybrids composites of a new type of carbon nanofiller, carbon nanostructures (CNS, i.e. branched carbon nanotubes) and graphene nanoplatelets (GNP) at various compositions were mixed with thermoplastic polyurethane (TPU) to tune the composite dielectric properties. Furthermore, in congruence with the global effort towards less wasteful electronic device production, these capacitive sensors were fabricated in a facile and environment-friendly strategy. In a composition of CNS and GNP at a mass ratio of 3:1, the composite sensor shows the highest pressure sensitivity of 2.05 MPa-1 for 0-1.2 MPa pressure, compared with 0.18 MPa-1 for neat TPU, enabling potential wearable pressure sensor applications. The improved performance arises from the combination of interconnected CNS along with the high dielectric constant and suppressed loss of GNP.
  • Enhancing CF/PEEK composites by CF decoration with polyimide and
           loosely-packed CNT arrays
    • Abstract: Publication date: Available online 30 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Elwathig. A.M. Hassan, Dengteng Ge, Shu Zhu, Lili Yang, Jianfeng Zhou, Muhuo Yu The weak interfacial bonding due to non-polarity and poor wettability of carbon fiber (CF) between CF and polyetheretherketone (PEEK) presents a challenge in carbon fibers reinforced CF/PEEK composites. In this study, a combined sizing agent of polyimide and loosely-packed network of carbon nanotubes (CNT) is deposited on the surface of CF, which greatly improve mechanical performances of composites by a synergetic effect of two components. The result demonstrates that ILSS, flexural strength and modulus of modified CF/PEEK composites were enhanced by 71 %, 63% and 70%, respectively. It is also found that loosely-packed CNT arrays on CF could better improve flexural strength and modulus for CF/PEEK composite than dense CNT networks on carbon fibers, while the opposite happens for thermosetting composites. The benefit of loosely-packed CNT arrays could be attributed to easier penetration of viscous PEEK melt into this structure compared to dense CNT networks.
  • Effect of fiber surface functionalization on shear behavior at carbon
           fiber/epoxy interface through molecular dynamics analysis
    • Abstract: Publication date: Available online 28 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Hao Wang, Kai Jin, Chen Wang, Xunzhong Guo, Zhong Chen, Jie Tao Different functional group densities of carbon fiber surface were achieved by changing surface treatment duration. Dynamic adsorption and shear behavior at the interface between epoxy resin and carbon fibers were analyzed in this study through molecular dynamics analysis and microscopic verification test. The results suggested that oxygen atoms of the functional group at the end of the epoxy matrix first accumulate on the carbon fiber surface, and then the whole molecular chain is driven towards the carbon fiber surface. It was found that more functional groups are accumulated at the surface and the interfacial shear strength increase with the extension of the acid treatment time. After 60 minutes of acid treatment, the interfacial shear energy from the simulation increased by 41.1% while the shear strength increased by 29.9%. The good consistence between the experimental and simulation results indicates that the approach proposed in this work could provide a method to study the interfacial properties of fiber reinforced polymer (FRP).
  • CNT/STF/Kevlar-based Wearable Electronic Textile with Excellent
           Anti-impact and Sensing Performance
    • Abstract: Publication date: Available online 28 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Mei Liu, Shuaishuai Zhang, Shuai Liu, Saisai Cao, Sheng Wang, Linfeng Bai, Min Sang, Shouhu Xuan, Wanquan Jiang, Xinglong Gong This work reports a novel CNT/STF/Kevlar-based (CNT, carbon nanotubes; STF, shear thickening fluid) wearable electronic textile (ET) composite with excellent protective and sensing performance. The dynamic impact resistance test shows the maximum resistance force of the single-layer ET composite reaches as high as 1232 N, which is much larger than the neat Kevlar (746 N), indicating that the ET composite can absorb more energy and sustain higher impact force. Due to the incorporation of the carbon nanotubes (CNTs), the ET composite shows excellent conductivity, thus it can be applied as a sensor to monitor signals of various human body movements. Due to the good flexibility, high sensitivity, and excellent protective performance, the ET composite exhibits high potential in the intelligent wearable electronic textile product, which possesses both excellent protective and sensing performance for human bodies in different environments.
  • Fibre Hybrid Composites Consisting of Discontinuous Waste Carbon Fibre and
           Continuous Glass Filaments Developed for Load-Bearing Structures with
           Improved Impact Strength
    • Abstract: Publication date: Available online 27 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): MMB Hasan, A Abdkader, Ch Cherif, F Spennato The aim of this research is to improve the impact strength of composites manufactured from discontinuous waste carbon fibre (CF). For this purpose, novel multi-material hybrid yarns with a core-sheath structure are developed from a mix of waste CF and polyamide 6 (PA 6) fibre (60 mm) that is combined with continuous glass filaments in the core and PA 6 fibre in the sheath. The tensile and Charpy impact properties of the unidirectional hybrid composites produced from the developed multi-material hybrid yarns are compared with those of a non-hybrid composite reinforced exclusively with waste CF. Results revealed that the impact strength of hybrid composites can be augmented by 50.5 % by adding only 6 volume percentage of glass filaments to waste CF. An increase of 18.4 % in impact strength can be achieved in hybrid composites if the total fibre volume content is identical with that of non-hybrid composites.
  • Analysis of anisotropic rotary diffusion models for fiber orientation
    • Abstract: Publication date: Available online 26 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Anthony J. Favaloro, Charles L. Tucker III Anisotropic rotary diffusion (ARD) has proved useful for modeling fiber orientation in molding of discontinuous-fiber composites. A number of ARD models have been proposed, but it has been difficult to compare models or understand the effects of each model’s parameters. We cast the framework laid out by Phelps and Tucker (JNNFM, 2009) into a new form that reveals the scalar magnitude and tensorial “direction” of rotary diffusion for each model. Existing models are compared in this framework. We illustrate the parameter values needed by each model to fit a steady-state orientation in simple shear flow and briefly discuss the behavior of the fitted models in planar elongational flow. The transient overshoot of flow-direction orientation at startup of simple shear varies considerably; however, the transient of the fourth-order component that governs shear stress is very similar among ARD models. Maps of achievable orientation states in steady simple shear are presented; these maps provide first-order estimates of the model parameters needed to fit experimental data.
  • Corrigendum to “Adaptive discrete-smeared crack (A-DiSC) model for
           multi-scale progressive damage in composites” [Compos. Part A Appl. Sci.
           Manuf. 125 (2019) 105513]
    • Abstract: Publication date: Available online 26 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): X. Lu, M. Ridha, V.B.C. Tan, T.E. Tay
  • Utilization of the textile reinforcements of fiber reinforced plastics as
           sensor for condition monitoring
    • Abstract: Publication date: November 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 126Author(s): Paul Hofmann, Alisa Walch, Sonja Arnold-Keifer, Sathis Kumar Selvarayan, Götz T. Gresser In addition to increased safety by detecting possible overload, continuous component monitoring by sensor integration makes the use of fiber reinforced plastics more cost-effective. Since the components are continuously monitored, one can switch from time-based to condition-based maintenance. However, the integration of conventional sensor components causes weak points, as foreign objects are inserted into the reinforcing structure. In this paper, we examine the use of the textile reinforcement as a sensor in itself. We describe how bending sensors can be formed by slightly modifying in the composite’s reinforcement structure. We investigated two different sensor principles. (1) The integration of textile plate capacitors into the structure; (2) The construction of textile piezo elements as part of the reinforcing structure. The bending test results reveal that textile plate capacitors show a load-dependent signal output. The samples with textile piezo elements show a significant increase in signal strength.
  • A Fiber-segmentation Algorithm for Composites Imaged Using X-ray
           Microtomography: Development and Validation
    • Abstract: Publication date: Available online 24 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Peter J. Creveling, William W. Whitacre, Michael W. Czabaj This study proposes a new algorithm for three-dimensional segmentation of fibers in multi-directional fiber-reinforced composites (FRCs) imaged using X-ray microtomography (µCT). The proposed algorithm uses synthetic fiber-templates and template matching to detect fibers in 2D. Detections are used to track individual fibers in 3D using a Kalman-filter estimator. Validation of the algorithm was performed using synthetic image stacks, which mimicked the quality and resolution of existing state-of-the-art X-ray systems. Segmentation of synthetic images revealed that the proposed algorithm estimates the total number of fibers, the 3D positions of fiber cross-sectional centroids, and fiber lengths with an error less than 7% when the image resolution is greater than 9 pixels per average fiber diameter. However, the segmentation algorithm was found to underestimate fiber cross-sectional areas due to beam-hardening artifacts. This study concludes by demonstrating the versatility of the algorithm on a multi-directional FRC imaged using X-ray µCT.
  • Confusion about infusion: An overview of infusion processes
    • Abstract: Publication date: Available online 23 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Arne Hindersmann Today the impregnation of dry fibre materials is a production method preferred for large composite parts like wind turbine rotor blades or aircraft wing covers. This trend has led many researchers and many companies to deal with new processes or process modifications. Therefore, vacuum infusion is a term with many acronyms. It cannot always be clearly assigned whether a method is a new process or a modification of existing processes. This leads to a jungle of terms and acronyms, which causes confusion. Based on different publications from the past, further developments are to be represented in the present publication to the completion. The focus here is on vacuum infusion techniques and only marginally on resin transfer moulding techniques. In addition, aspects to increase process reliability, such as second vacuum bag and leakage detection, are discussed.
  • Mechanically robust and abrasion-resistant polymer nanocomposites for
           potential applications as advanced clearance joints
    • Abstract: Publication date: Available online 23 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Mengbo Qian, Pingan Song, Zhe Qin, Shaoze Yan, Lin Zhang Despite exceptional dimensional stability, polyamide 6 (PA6) still suffers relatively low mechanical strength and stiffness as compared with metallic and ceramic materials, which thus significantly limits its engineering applications. Herein, we have demonstrated the fabrication of high-performance PA6 composites with excellent mechanical and wear resistance by introducing nanoscale silicon carbide (SiC) as the reinforcer and anti-wear agents. The results show that the addition of 5wt% nanoscale SiC (NS) increases the tensile strength of PA6 by 54% (reaching 64.8 MPa) while the elongation at break is over 6 times (around 304%) of that of the PA6 matrix, which giving rise to a 9.6 times increase in the fracture toughness. Moreover, the addition of 30 wt% of NS reduces the friction coefficient from 0.31 for the PA6 to 0.12, indicating improved anti-wear performances. Such significant improvements in both mechanical and anti-wear properties are primarily due to the high stiffness of NS and the strong interfacial interactions with the PA6 matrix. In addition, the effects of friction coefficient on dynamic characteristics of mechanism with clearance are also investigated to gain an insightful understanding on the improved anti-wear properties. This work provides a facile approach to the design of advanced polymer composites combining excellent mechanical and anti-wear performances.
  • Negative Liquid Sensing Effect and Tunable Piezoresistive Sensitivity in
           Polydimethylsiloxane/Carbon Nanotubes/Water-Absorbing-Expansion Particles
    • Abstract: Publication date: Available online 23 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yi-Fu Chen, Jie Li, Jie-Hua Cai, Yan-Jun Tan, Xiao-Hong Tang, Ji-Hong Liu, Ming Wang Herein, a negative liquid sensing effect and tunable piezoresistive sensitivity was achieved in polydimethylsiloxane/multi-walled carbon nanotubes (PDMS/MWCNT) composites with water-absorbing-expansion (WAE) particles. The conductivity of the PDMS/MWCNT composites without WAE particles decreased in water, showing a typically positive liquid sensing effect. In the PDMS/MWCNT/WAE composites, the WAE particles expanded in water to several times in their volume, which compressed the PDMS/MWCNT domains and increased conductive paths. The absorption of water also enhanced the conductivity of WAE particles. As a result, the conductivity of the composites increased in water, showing an unusually negative liquid sensing effect. Furthermore, the PDMS/MWCNT/WAE composites, which showed more sensitive to water, had stable conductivity after being taken away from water at room temperature but could be recoverable at high temperature. In addition, the piezoresistive sensitivity of the samples could be tuned by the expansion ratio of WAE particles via controlling the immersing time in water.
  • Improved Prediction of Residual Stress Induced Warpage in Thermoset
           Composites Using a Multiscale Thermo-Viscoelastic Processing Model
    • Abstract: Publication date: Available online 23 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Weijia Chen, Dianyun Zhang A multiscale thermo-viscoelastic processing model is developed to predict the residual stress development in a thermoset composite due to curing. In the proposed modeling framework, a composite laminate is modeled as discrete layers of homogeneous laminae at the macroscale, while at each integration point of the homogeneous model, the constitutive relations of the lamina are determined through micromechanics using an Extended Concentric Cylinder Assemblage (ECCA) model in conjunction with the correspondence principle of viscoelasticity. Since analytical formulations are employed at the microscale, the proposed multiscale approach can efficiently predict the composite time-, temperature-, and cure-dependent responses during processing. The proposed model is employed to predict the warpage shape of an anti-symmetric laminate due to curing-induced residual stresses. Compared with other elastic processing models, the proposed processing model achieves an improved prediction of the warpage shape due to its capability to consider both curing history and stress relaxation during composite processing.
  • In-situ measurement of tension and contact forces for weaving process
           monitoring: Application to 3D interlock
    • Abstract: Publication date: Available online 22 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Carole Bessette, Mathieu Decrette, Michel Tourlonias, Jean-François Osselin, François Charleux, Dominique Coupé, Marie-Ange Bueno This study is focused on the monitoring of 3D interlock weaving, which is a process used for structural composite reinforcements. As high-density weaving leads to significant damage on warp tows, the standard execution of the process is impacted. To increase the production rate, tow-to-tow interactions need to be clearly understood, which is the aim of in-situ measurements on a sequential weaving loom. Tension and contact force between tows were measured using specific sensors. Great differences in tension and contact force were highlighted as a function of the type of crossing during the weaving cycle. Specific tow crossings generate very high peaks of tension and contact force. A significant difference has been noticed between the impact of the raising and lowering of tows during shedding motion on the tension and force values. A spectral analysis of the tension signal has shown an interesting potential for indirect tow damage monitoring and detection.
  • Cooperative influences of nanoparticle localization and phase coarsening
           on thermal conductivity of polypropylene/polyolefin elastomer blends
    • Abstract: Publication date: Available online 22 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Xi Zhang, Toru Wada, Patchanee Chammingkwan, Ashutosh Thakur, Toshiaki Taniike Polypropylene (PP)/polyolefin elastomer (POE)/aluminum oxide (Al2O3) nanocomposites were prepared based on a reactor granule technology (RGT). The effect of nanoparticle migration and phase morphology evolution on the formation of thermal conductive networks was systematically studied. The utilization of RGT and POE with high viscosity enabled successful migration of in-situ generated Al2O3 nanoparticles at the interface of PP and POE, as combined results of uniform dispersion of Al2O3 and accompanied small phase domain size of PP [1]. The localization of the nanoparticles at the interface also contributed to suppression of the phase coarsening during annealing. The nanoparticle migration to the interface and the retarded phase coarsening synergistically contributed to the enhanced thermal conductivity.Graphical abstractGraphical abstract for this article
  • Detection and imaging of local ply angle in carbon fiber reinforced
           plastics using laser ultrasound and tilt filter processing
    • Abstract: Publication date: Available online 21 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): L. Ambrozinski, J. Mrowka, M. O'Donnell, I. Pelivanov Wrinkles in carbon-fiber reinforced plastics (CFRP) are extremely dangerous, dramatically changing the performance of a composite structure. However, wrinkles are one of the most difficult defects to detect and characterize with ultrasound since they do not produce large echoes like other flaws.Recent developments in laser-ultrasound (LU) have enabled non-contact, high-resolution imaging of CFRPs, providing sub-ply resolution and detailed visualization of CFRP structures.In this paper, we demonstrate that the superior resolution of LU systems can be used to help track ply orientation variations in composites. To improve the signal-to-noise ratio of LU generated signals, we propose a local cross-correlation based tilt-filtration procedure for coherent spatial signal averaging that accounts for the shape of subsequent layers. In addition, local ply angle is a straightforward output of the proposed processing, which can be used directly as an indicator of wrinkle severity.
  • Dynamic characterisation of interlaminar fracture toughness in carbon
           fibre epoxy composite laminates
    • Abstract: Publication date: Available online 21 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): M.A. Riezzo, M. Simmons, B. Russell, F. Sket, V. Martínez, C. González In this work, the rate dependence of mode I interlaminar fracture toughness for two different materials systems, IM7/8552 and IM7/M91, both unidirectional UD carbon-fibre epoxy composite laminates have been examined over a wide range of loading rates from 0.5 mm/min up to 2000 mm/s at room temperature. Quasi-static fracture tests were performed using a DCB (double-cantilever beam) method with a screw-driven testing machine, while the dynamic tests were carried out using a WIF (wedge-insert fracture) specimen loaded dynamically in a hydraulic system. For performing the tests at high displacement rates, a special setup was designed and manufactured which allowed the insertion of the wedge within the DCB specimens at different cross-head displacement rates. The experimental technique used a pair of strain gauges attached to the bending surface of one of the arms of the cantilever beams and far from the initial crack tip. The peak values of the recorded strain were used to determine the fracture toughness under dynamic conditions through use of the compliance calibration method. A finite element model was developed to check the consistency of the measurements and validate the data reduction method used. The results exhibited rate insensitive behaviour in the case of the IM7/8552 laminates while IM7/M91 showed the contrary behaviour with maximum peak at 500mm/s of displacement rate, with a toughness increase of ≈95% with respect to the quasi-static conditions.
  • Investigating the role of 3D network of carbon nanofillers in improving
           the mechanical properties of carbon fiber epoxy laminated composite
    • Abstract: Publication date: Available online 21 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Ankita Bisht, Kinshuk Dasgupta, Debrupa Lahiri Carbon fiber epoxy composites are being used in numerous structural applications. However, fracture toughness of these composites is always less than expected. Therefore, potential of nanofillers in improving the fracture toughness of these composites, with, three different morphologies, i.e., Gr (sheet), CNT (tube) and nanodiamond (particle), in a well-connected 3D network is evaluated in this study. Both, interlaminar and intralaminar mode I fracture toughness, revealed improvement of ∼260 % and ∼53%, respectively, with 25Gr:50CNT:25ND CF-epoxy, as compared to CF-epoxy composite. Marking a total improvement of ∼1523% over pure epoxy on intralaminar fracture toughness. The composites were also assessed for tensile and interlaminar shear strength. An improvement of ∼60% and ∼16%, respectively, is noted with the addition of nanofillers. SEM analysis for delaminated and fractured surfaces revealed the toughening mechanism to be the high surface area of nanofillers, offering strong adhesion between matrix and fiber, along with improved matrix toughness.
  • Carbon fibre sheet moulding compounds with high in-mould flow: linking
           morphology to tensile and compressive properties
    • Abstract: Publication date: Available online 20 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Luca M. Martulli, Leen Muyshondt, Martin Kerschbaum, Soraia Pimenta, Stepan V. Lomov, Yentl Swolfs In-mould flow during manufacturing of Sheet Moulding Compounds (SMCs) heavily affects the material microstructure and its mechanical properties. This influence is studied here for carbon SMCs on panels compression moulded with limited charge coverage. The high in-mould flow caused severe in-plane tow distortions, while their planarity was preserved. Flow induced fibre orientation plays a paramount role in the material failure, whereas local manufacturing defects had no discernible influence. The properties difference between specimens with preferential orientation of 0° and 90° was 150% for tensile stiffness, 260% for tensile strength, 120% for compressive stiffness and 32% for compressive strength. The compressive strength and failure strain for 45° and 90° specimens were higher than those for tension, and comparable for 0° specimens. Compressive and tensile moduli were similar for specimens with the same orientation. A clear link between SMCs manufacturing and mechanical performance is highlighted, together with its implications on structural design.
  • Enhanced mechanical and thermal properties of carbon fiber-reinforced
           thermoplastic polyketone composites
    • Abstract: Publication date: Available online 20 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Jaehyun Cho, Seoung-Ki Lee, Seung-Hyun Eem, J.G. Jang, B.J. Yang Advances in thermoplastic composites have attracted interest among researchers for the development of new high-performance and recyclable engineering plastics. Herein, a novel polyketone (PK) composite containing carbon fiber (CF), as well as its thermophysical characteristics, was investigated. PK composites with different CF contents ranging from 0 to 30 wt.% were fabricated through the two-stage extruder-injection molding process. The performances of the raw and composite materials were measured by various methods, and we found that the incorporation of CF into PK enhances the thermal stability, conductivity, and mechanical properties of the composites simultaneously. To theoretically evaluate the thermomechanical characteristics of the PK composites, a series of numerical simulation was carried out. The Kapitza resistance, which was assumed to be a model constant in this study, was determined through a genetic algorithm. The predicted properties of composites with varying CF were observed to be in good qualitative agreement with the experimental results.
  • Characterization and elastic property modeling of discontinuous carbon
           fiber reinforced thermoplastics prepared by a carding and stretching
           system using treated carbon fibers
    • Abstract: Publication date: Available online 20 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Bing Xiao, Takeyuki Zaima, Keiichiro Shindo, Takuma Kohira, Jun Morisawa, Yi Wan, Guanghu Yin, Isamu Ohsawa, Jun Takahashi Fiber alignment is a critical factor in the recovery of mechanical properties of recycled carbon fiber (rCF) composites. In this study, a carding and stretching system was introduced to improve the fiber alignment of rCF in an effort to generate card web carbon fiber reinforced thermoplastics (CWTs). Virgin carbon fibers were treated to replicate rCFs and ensure comparability between them. A series of mechanical tests was conducted on several types of CWTs, while X-ray micro-computed tomography scanning analysis was applied to evaluate fiber orientation distribution. The effect of alignment on CWT was also investigated analytically. Using such a technique, most of the rCFs were aligned within ±15°. Meanwhile, satisfactory mechanical properties were also obtained in some stretched types of CWTs. Both laminate and netting theories showed good correlation with the experimental results. Overall, the netting theory was proved to be a useful tool for approximating the elastic properties of CWTs.
  • Numerical simulation correlating the low velocity impact behaviour of
           flax/epoxy laminates
    • Abstract: Publication date: Available online 19 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Benedict Lawrence Sy, Zouheir Fawaz, Habiba Bougherara Many researchers have experimentally evaluated the mechanical characteristics of flax-based laminates to understand their behaviour under different loading conditions; however, doing so required significant investment in time, money and other resources. An alternative solution is to use advanced numerical and computational tools like FEA. In this study, low velocity impact analyses of unidirectional and crossply flax/epoxy laminates are performed experimentally and numerically. The numerical simulations are conducted using the commercially available software LS-DYNA. The goal is to develop a correlated numerical model, which is able to predict the laminates’ energy absorption capability and damage response. The obtained results show good correlation between the experimental findings and numerical model simulations for the rebounding cases. The results also reveal one major limitation of the current model in that it only yields accurate predictions for impact energies below penetration.
  • Facile Construction of Enhanced Multiple Interfacial Interactions in
           EPDM/Zinc Dimethacrylate (ZDMA) Rubber Composites: Highly Reinforcing
           Effect and Improvement Mechanism of Sealing Resilience
    • Abstract: Publication date: Available online 16 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Chengjie Li, Zun Yuan, Lin Ye Based on Zn2+-carboxyl coordination strategy, EPDM-g-Glu/ZDMA composite was prepared by grafting of maleic anhydride (MAH)/glutamic acid (Glu) onto EPDM chains via reactive melting process and in situ formation of zinc dimethacrylate (ZDMA) through convenient two-roll milling/hot-pressing process. Zn2+-carboxyl coordination was proved to be formed, and ZDMA uniformly dispersed in matrix and rapidly polymerized to form single rod-shaped PZDMA containing Zn2+-based ionic multiplet during vulcanization, which was tightly embedded in matrix with strong interfacial interaction. Compared with EPDM/ZDMA composite, higher polymerization degree of ZDMA and thicker immobilized EPDM layer were achieved with reducing size of PZDMA clusters for EPDM-g-Glu/ZDMA composite. In addition, multiple interactions with higher covalent (Ve1) and ionic crosslinking density formed. Moreover, higher retention of Ve1 after ageing was obtained, while thermo-oxidative ageing process was retarded with prolonged oxidation induction time. Thus simultaneously remarkable enhancement of energy dissipation, mechanical and durable sealing resilience performance were achieved for EPDM rubber.
  • Compression after multiple low velocity impacts of NCF, 2D and 3D woven
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Mohamed Nasr Saleh, Hassan M. El-Dessouky, Milad Saeedifar, Sofia Teixeira De Freitas, Richard J. Scaife, Dimitrios Zarouchas This paper investigates the effect of the fabric architecture and the z-binding yarns on the compression after multiple impacts behavior of composites. Four fiber architectures are investigated: non-crimp fabric (NCF), 2D plain weave (2D-PW), 3D orthogonal plain (ORT-PW) and twill (ORT-TW) weave. The specimens were subjected to single and multiple low-velocity impacts at different locations with the same energy level (15 J). Non-destructive techniques including ultrasonic C-scanning, X-ray CT and Digital Image Correlation (DIC) are employed to quantitatively analyze and capture the Barely Visible Impact Damage (BVID) induced in the specimens. Although the absorbed energy was approximately the same, damage was the least in 3D woven architectures. In the case of compression after impact, 3D woven composites demonstrated a progressive damage behavior with the highest residual strength (~92%) while 2D plain weave and NCF specimens showed suddenly catastrophic damage and the residual strength of ~65% and ~55% respectively.
  • Improved interfacial property of carbon fiber composites with carbon
           nanotube and graphene oxide as multi-scale synergetic reinforcements
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Tong Zhang, Qiancun Cheng, Zhiming Xu, Bo Jiang, Caifeng Wang, Yudong Huang In the present research, carbon nanotubes (CNTs) and graphene oxide (GO) were used to enhance the composites interfacial properties synergistically by the strategy combining electrodeposition and chemical grafting. It was found that the interface between CF and matrix can be tuned by the binary addition of CNTs and GO. The interfacial shear strength (IFSS) of GO/CNTs synergistic reinforced composites based on this physical and chemical combination method via the “bridge” of Ag nanoparticles (NPs) exhibits 42.99% and 4.61% enhancement compared to that of achieved by electrophoretic deposition (physical method) and chemical grafting (chemical method), respectively. In addition, the IFSS has 69.68% and 19.54% improvement due to the synergistic effect of GO/CNTs compared to the untreated CF and GO single-reinforced CF composites. Therefore, it is a promising technique for developing multifunctional CF with the excellent interfacial performance.Graphical abstractGraphical abstract for this article
  • Flow of quasi-spherical nanoparticles in liquid composite molding
           processes. Part II: Modeling and simulation
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Dilmurat Abliz, David C. Berg, Gerhard Ziegmann This paper focuses on the modeling and simulation of the flow and filtration behavior of quasi-spherical nanoparticles (NPs) during liquid composite molding (LCM), as a succession to the experimental studies in Part I. The influence of the bimodal dispersion size characteristic of NPs and the dual-scale characteristic of the preform porous structure on the viscosity of the suspension, the permeability of the preform, and the impregnation behavior is investigated. The modeling and simulation helps not only to predict the impregnation behavior of the NP-modified matrix systems, but also to inversely study the critical particle size that may lead to cake filtration.
  • Characterisation of crystallinity at the interface of ultrasonically
           welded carbon fibre PPS joints
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): N. Koutras, J. Amirdine, N. Boyard, I. Fernandez Villegas, R. Benedictus The influence of ultrasonic welding on the crystallinity degree at the welding interface of carbon fibre reinforced polyphenylene sulphide (CF/PPS) joints was investigated. Two sets of welding force and vibration amplitude were used, (1000 N, 86.2 μm) and (300 N, 52.8 μm), representing short and long welding times, respectively. The evolution of temperature with time at the centre of the joint overlap was recorded using thermocouples while the crystallinity degree of PPS was measured using differential scanning calorimetry (DSC). The cooling rate dependency of crystallinity was determined through fast scanning calorimetry (FSC) measurements. It was found that high force and high amplitude resulted in faster cooling rates and predominantly amorphous PPS, while low force and low amplitude resulted in slower cooling rates and yielded PPS of moderate crystallinity. It is suggested that the capability of PPS to crystallize despite the very fast cooling rates could be attributed to strain-induced crystallization during the welding process.
  • Fractographic study to characterise the interaction between intralaminar
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Carla Canturri, Emile S. Greenhalgh, Leif E. Asp, Silvestre T. Pinho This paper describes the fractographic observations from the study of embedded defects subject to compression. The fractographic observations aim to characterise the interaction between intralaminar and interlaminar fractures and to understand their role in the delamination growth and the delamination migration. The influence of the stacking sequence orientation on the damage modes is studied in eight different configurations. A detailed fractographic study led to the identification of the different failure modes and failure sequence. It was also possible to establish the stacking sequences more prone to delamination migration and the failure modes more critical for damage tolerance.
  • Experimental, analytical and numerical investigation to prevent the tow
           buckling defect during fabric forming
    • Abstract: Publication date: Available online 6 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): M.M. Salem, E. De Luycker, M. Fazzini, P. Ouagne We investigate the causes, kinematic and possible ways to prevent the tow-buckling defect during the complex shape-forming of a dry woven reinforcement. Macro-scale compression leads to wrinkles; we focus on a meso-scale phenomenon generated by a non-uniform axial compression of the tow due to in-plane bending. An experimental study is presented, followed by an efficient method to predict the onset of the tow-buckling defect. This investigation is based on the combination of an experimentally validated analytical approach, with a macro-scale simulation of the forming process for a single fabric layer. A particular focus is given to the resulting tow curvatures that allows us to predict the zones of high tow buckling probability. The relatively simple numerical approach based on Lagrange assumptions does not take into account tow slippage. However, for most cases, where buckles appear before slippage, this approach alleviates the compulsory need for an expensive meso-scale representation.
  • Vacuum-Bagged Composite Laminate Forming Processes: Predicting Thickness
           Deviation in Complex Shapes
    • Abstract: Publication date: Available online 6 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Arthur Levy, Pascal Hubert This paper focuses on the manufacturing of composite laminates using vacuum-bag processes. When forming complex shapes, such as corners, the laminate thickness may deviate from the nominal thickness obtained for flat plates. This is due to two phenomena that occur in corners: (i) because of the geometry, the available consolidation pressure differs from the expected pressure; and (ii) friction may prevent adequate conformation of the laminate to the mould. The thickness deviation is associated with defects (porosity, dry or resin-rich areas or fibre wrinkling). We propose an analytical model to describe these two phenomena, which relies only on two geometric ratio: radius to flange length and thickness to radius, and two material properties: bulk factor and inter ply friction coefficient. The model estimation was compared to an extensive experimental database including a variety of configurations: male or female tools and various flange lengths, weavings and corner radii.
  • Evaluation of mechanical properties of noncircular carbon fiber reinforced
           plastics by using XFEM-based computational micromechanics
    • Abstract: Publication date: Available online 5 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): R. Higuchi, T. Yokozeki, T. Nagashima, T. Aoki The aim of this study is to investigate the mechanical properties of noncircular carbon fiber reinforced plastics (CFRPs). For an efficient study of various CFRP microstructures, this study combines an extended finite element method (XFEM), a homogenization method, and a Monte Carlo method and establishes XFEM-based computational micromechanics. This scheme made it possible to simulate CFRPs having various microstructure without remeshing and resetting boundary conditions. In the verification against general circular CFRPs, it was revealed that the developed scheme has a sufficient accuracy for the prediction of the homogenized elastic constants including their stochastic nature. Finally, the effects of the cross-sectional fiber shape on the macroscopic CFRP properties were examined. Among the five fiber shapes (circular, elliptical, two-lobed, triangular, and square), the square CFRP exhibited the best transverse mechanical properties. Therefore, it was concluded that the noncircular carbon fibers have a potential to enhance the macroscopic mechanical performance of CFRPs.
  • Influence of resin curing cycle on the characterization of the tensile
           properties of flax fibers by impregnated fiber bundle test
    • Abstract: Publication date: Available online 3 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Anurag Pisupati, Abderrahmane Ayadi, Mylène Deléglise-Lagardère, Chung Hae Park This study sheds light on the effect of resin cure cycle on the tensile properties of unidirectional flax fibers, which are assessed by the impregnated fiber bundle test (IFBT). The experimental protocol combines hand-layup and isothermal compression molding processes to fabricate unidirectional flax composites according to four different curing cycles. Isothermal and modulated DSC results indicate that the cross-linking reaction and glass transition temperature of the epoxy are affected by the resin curing cycle. SEM analyses before and after the tensile tests show that the improvement of the tensile properties of composites can be correlated to an increase of the fiber-matrix interfacial bonding. The results of the back-calculated tensile properties of flax fibers indicate that the application of the IFBT to untreated flax fibers depends on the mechanical interlocking between the matrix and the cell wall of the fibers.
  • Corrigendum to ‘Enhancement of thermal conductivity of carbon
           fiber-reinforced polymer composite with copper and boron nitride
           particles’. [Compos. Part A: Appl. Sci. Manuf. 121 (2019) 449–456]
    • Abstract: Publication date: Available online 26 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Xiru Zheng, Seongmin Kim, Chan Woo Park
  • Construction of Gradient Structure in Polyetherimide/Carbon Nanotube
           Nanocomposite Foam and Its Thermal/Mechanical Property
    • Abstract: Publication date: Available online 10 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Xuejie Sun, Xiaowen Zhao, Lin Ye MWNTs-COOH@Fe3O4 hybrid with ferromagnetism was prepared and polyetherimide (PEI)/MWNTs-COOH@Fe3O4 nanocomposite foams with continuously gradient structure were fabricated via water vapor-induced phase separation (WVIPS) method under a magnetic field. Along the magnetic field direction, a continuously gradient distribution of MWNTs-COOH@Fe3O4 formed in PEI matrix, while the average cell size gradually decreased, the cell wall thickness and apparent density increased, forming gradient cell structure for the foam. Both mechanical property and thermal stability of the foam were improved by introducing MWNTs-COOH@Fe3O4. For the composite foam, the tensile strength, elongation at break and storage modulus decreased along magnetic field direction, due to enrichment and aggregation of MWNTs-COOH@Fe3O4 in strong magnetic field. Meanwhile, tanδ decreased and thermal degradation temperature increased, revealing formation of gradient distribution of thermal and mechanical property in the foam, which showed potential application prospective in aerospace and defense area.
  • Fabrication of PLA/CNC/CNT conductive composites for high electromagnetic
           interference shielding based on Pickering emulsions method
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Bowen Yu, Zhiyu Zhao, Sirui Fu, Lu Meng, Yuhang Liu, Feng Chen, Ke Wang, Qiang Fu In this study, we proposed a new strategy to fabricate polylactide (PLA) based conductive polymer composites with excellent electrical conductivity, superior electromagnetic interference shielding efficiency (EMI SE) and good mechanical properties using a Pickering emulsions method. Cellulose nanocrystals (CNCs) were used as a stabilizer for oil-in-water Pickering emulsions and a dispersant for carbon nanotubes (CNTs) at the same time. CNC/CNT suspensions and dichloromethane (DCM) solution of PLA were used as aqueous phase and oil phase respectively. With the evaporation of DCM, PLA microparticles coated by entangled CNCs and CNTs could be formed. After compression molding, the PLA/CNC/CNT composites showed an outstanding EMI SE of 41.8 dB with only 4.3 wt% CNT loading. Simultaneously, the mechanical performance of the sample maintained a high level (tensile strength: 45.52 MPa, Young’s Modulus: 3152 MPa). Our findings provide a simple, cost-effective and environmentally friendly manufacturing route for functional polymer nanocomposites with excellent comprehensive properties.
  • Coupon scale Z-pinned IM7/8552 delamination tests under dynamic loading
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Hao Cui, Yusuf Mahadik, Stephen R. Hallett, Ivana K. Partridge, Giuliano Allegri, Sathiskumar A. Ponnusami, Nik Petrinic Dynamic impact onto laminated composite structures can lead to large-scale delamination. This can be mitigated by the introduction of through-thickness reinforcement, such as z-pins. Here, mode I & II and mixed-mode delamination tests have been designed and conducted at high loading rate, for both unpinned and Z-pinned coupons to study the effect of rate of loading. It was found that the Z-pins were not effective in delaying the dynamic crack initiation or resisting the dynamic propagation of delaminations shorter than 5 mm. However, the further growth of cracks was substantially delayed by Z-pinning, especially for the pure mode I and mode I dominated failure modes. On the other hand, the effectiveness of Z-pins in shear tests was relatively modest. The mode I dominated delamination resistance of Z-pinned laminates was found to be sensitive to the loading rate.
  • Nanoindentation and flammability characterisation of five rice husk
           biomasses for biocomposites applications
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Oisik Das, Mikael S Hedenqvist, Chaitra Prakash, Richard J.T. Lin Five different rice husks (RHs) having different geographical origins were characterised for their mechanical and fire reaction properties using nanoindentation and cone calorimetry, respectively. Analyses relating to ash and extractives contents, density and morphologies were also performed. The RHs had statistically similar extractives content, nanoindentation properties and peak heat release rates (PHRRs). The polypropylene-based composites made from these RHs also had insignificant differences in their tensile moduli, elongation and PHRR values. The RH inclusion conserved the tensile/flexural strengths while enhancing the moduli of the composites, as compared to the neat polypropylene. The material characteristics being ubiquitous amongst the different RH types enable the creation of biocomposites with foreseeable performance properties. Moreover, the individual nanoindentation and fire reaction properties of the RHs allowed the presaging of the bulk biocomposites’ properties using theoretical models. Good agreements between predicted and experimental moduli/PHRRs were achieved using rule of mixtures and Halpi-Pegano models.
  • A Double Mixing Process to Greatly Enhance Thermal Conductivity of
           Graphene Filled Polyamide 6 Composites
    • Abstract: Publication date: Available online 9 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yanjuan Ren, Yafei Zhang, Haichang Guo, Ruicong Lv, Shu-Lin Bai Tremendous investigations have been recently conducted to increase the thermal conductivity (TC) of nanofiller filled thermoplastic composites. However, the agglomeration of nanofillers limits their loading and is a bottleneck to further increase the TC of composites. In this work, a preparation technique combining the benefits of both solution mixing and melt blending is proposed, with which high loading and good dispersion of graphene sheets (GSs) filled polyamide 6 (PA6) matrix composites are achieved. Noteworthily, the through-plane TC of the composites reaches 3.55 W m-1K-1 with 20 wt% GSs, corresponding to a TC enhancement of 1167 % compared to pure PA6. The excellent performance can be attributed to high loading and uniform dispersion of GSs, which facilitate the formation of thermally conductive network for efficient heat transfer. An effective medium theory model by taking the filler-to-matrix and filler-to-filler interfacial effects into consideration is also proposed to perceive the behind mechanism. The theoretical calculation agrees well with our experimental results. Moreover, we find the Young’s modulus of the composite increases significantly and the tensile strength nearly remains unchanged even at a GSs filler loading of 20 wt%. The results provide an effective and facile route for developing low-cost and highly conductive thermoplastic composites.
  • Oxidative induction and performance of oil palm fiber reinforced
           polypropylene composites – Effects of coupling agent and UV stabilizer
    • Abstract: Publication date: Available online 8 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): John O. Akindoyo, Mohammad D.H. Beg, S. Ghazali, Hans P. Heim, Maik Feldmann, M. Mariatti Reinforced polypropylene/empty fruit bunch (EFB) fiber composites were prepared through extrusion and injection moulding. Maleic anhydride grafted polypropylene (MAPP) and CESA-light PPADOL 12020 (PDOL) were used as compatibilizer and UV stabilizer respectively. The samples were subjected to accelerated UV irradiation and the simultaneous effects of compatibilization and PDOL were investigated. Results showed that PDOL slightly improved the adhesion between PP and EFB, but did not offer mechanical strength improvement. However, oxidative induction time analysis and discoloration analysis revealed that the incorporation of PDOL plays significant role in preventing the composites from discoloration as well as UV degradation. In addition, dynamic mechanical analysis indicated that compared with ternary composites, the quaternary composite containing PDOL and MAPP exhibits lower loss modulus, accrued to good interrelationship between PP, EFB, PDOL and MAPP. Generally, it is evident herein that PDOL may be used in applications requiring higher colour stability.
  • Magnetic programming of 4D printed shape memory composite structures
    • Abstract: Publication date: Available online 3 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Fenghua Zhang, Linlin Wang, Zhichao Zheng, Yanju Liu, Jinsong Leng 4D printed shape memory polymers and their composites are currently a highly topical research area. The potential applications for 4D printed smart materials are wide-reaching, with particular promise for personalized medicine. In this work, we 4D printed various structures made of biocompatible and biodegradable polylactic acid (PLA) and PLA/Fe3O4 composite filaments. The shape memory behaviors of the 4D printed structures triggered by magnetic field were investigated. The printed structures can return to their original shapes with a high speed in just a few seconds. Moreover, the structures like bone tissues printed by PLA/Fe3O4 composites filaments with 15% Fe3O4 were actuated by magnetic field at 27.5 kHz. During the shape recovery process, surface temperature of the printed structures is uniform and around 40 ℃. This physiologically relevant operating temperature range is a highly attractive feature for potential healthcare and biomedical applications.
  • Ohmic heating curing of carbon fiber/carbon nanofiber synergistically
           strengthening cement-based composites as repair/reinforcement materials
           used in ultra-low temperature environment
    • Abstract: Publication date: Available online 2 August 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yushi Liu, Mingzhi Wang, Weichen Tian, Beimeng Qi, Zhongyao Lei, Wei Wang The repair/reinforcement of construction structures have been a challenge due to hydration termination of cement-based materials in an ultra-low temperature environment. This work presents a Carbon Fiber (CF)/Carbon Nanofiber (CNF) synergistically strengthening cement-based composite (CM-CF/CNF) as a repair/reinforcement material, in which ohmic heating curing of CM-CF/CNF is utilized to enhance structural strength at ultra-low temperature. Conductive paths in cement-based composite are formed with added CFs, which also improves mechanical properties, and the stabilization of the conductive network constructed by CFs is enhanced by incorporation of CNFs. A numerical model is established to evaluate CFs bridging behavior, and the role of CNFs in the stabilization of conductive network is numerically discussed based on permeation theory. A continuous maintenance of temperature is achieved with CM-CF/CNF cured by ohmic heating at -20℃, and the cured sample shows superior 2-day compressive and flexural strengths of 49.2 MPa and 11.5 MPa, respectively.
  • An Automatic Methodology to CT-scans of 2D Woven Textile Fabrics to
           Structured Finite Element and Voxel Meshes
    • Abstract: Publication date: Available online 30 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): W. Wijaya, M.A. Ali, R. Umer, K.A. Khan, P.A. Kelly, S. Bickerton This paper presents a novel methodology to isolate the individual tow information contained within relatively low resolution µCT scans of real textile specimens. The proposed method can process high fibre fraction (Vf>0.60) datasets in a fast and automated manner with minimal user interaction. The methodology has been validated qualitatively and quantitatively. The geometric description of the isolated tows can be used to create structured finite element meshes and voxel meshes, that contain the local tow information such as fibre volume fraction and fibre direction using an in-house meshing algorithm. The structured finite element meshes can be used as initial geometry for textile compaction simulations. The voxel meshes can be used directly for a flow simulation to predict the textile permeability. Finally, a methodology to observe the geometrical evolution of the same tows from different µCT datasets is also presented.
  • Flow of quasi-spherical nanoparticles in liquid composite molding
           processes. Part I: Influence of particle size and fiber distance
    • Abstract: Publication date: Available online 30 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Dilmurat Abliz, Benedikt Finke, David C. Berg, Carsten Schilde, Gerhard Ziegmann This paper studies the flow and filtration of two quasi-spherical NPs (silica and boehmite) during liquid composite molding (LCM) processes. The nanosuspensions are prepared differently by “top-down” and “bottom-up” approaches, and the particle size is analyzed before and after injection process. In parallel, the fiber distance distribution is systematically characterized using improved image processing techniques and algorithms. It is found that nanosuspensions that are prepared by “top-down” approach may show a bimodal particle distribution, and that the filtration of quasi-spherical NPs is closely related to the bimodal distribution characteristics of the particle size and the dual-scale characteristic of the preform. Furthermore, a threshold fiber volume fraction (Vf) of 55% is identified, at which the investigated preform shows a critical phase transition from dual-scale to single micro-scale porous structure. It is shown that above the threshold Vf even a small fraction of coarse particles can strongly hinder the impregnation process.
  • Modeling of load responses for natural fiber reinforced composites under
           water absorption
    • Abstract: Publication date: Available online 30 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Fang Tian, Zheng Zhong Based on the continuum mechanics, a constitutive model has been developed to describe the swelling-elastic deformation behavior of natural fiber reinforced composites when considering the mechanical deterioration caused by water absorption and external loadings. Two internal variables are employed to measure the effects of damages caused respectively by water absorption and by external loadings. The Helmholtz free energy function and the evolution equations of these two internal variables are investigated in detail and given explicitly for short natural fiber reinforced composites. This proposed theoretical model is then applied to analyze the mechanical performance of swollen sisal fiber reinforced composites under uniaxial tension. Theoretical estimations on the evolutions of elastic modulus as well as tensile strength are all found in good agreement with corresponding experimental results.
  • Biofabrication of a novel bacteria/bacterial cellulose composite for
           improved adsorption capacity
    • Abstract: Publication date: Available online 29 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yizao Wan, Jie Wang, Miguel Gama, Ruisong Guo, Quanchao Zhang, Peibiao Zhang, Fanglian Yao, Honglin Luo Conventional fabrication of bacterial cellulose (BC) involves treatment with hot NaOH aqueous solutions to remove bacteria (BA). Herein, we report a simpler and cheaper method for the preparation of BA/BC composite without alkalization, which keeps the BA in the nanofibrous BC network. Scanning electron microscopy (SEM) observation showed naturally distributed BA in BC matrix with a tightly entangled structure. Such BA-embedded BA/BC composite exhibited improved mechanical strength and modulus over BC. When used as adsorbent, the BA/BC composite exhibited significantly higher adsorption capacities to Pb(II), Cu(II), Ni(II), and Cr(VI) compared to bare BC. The much higher adsorption capacities of BA/BC are due to the presence of functional groups in the BA, such as amide, which are known to be involved in coordination interaction. This breakthrough strategy not only made the fabrication process simpler and more cost-effective, but also produced a new BC-based adsorbent with improved adsorption capacity to heavy metals.
  • Experimental study on the influence of cyclic compaction on the fiber-bed
           permeability, quasi-static and dynamic compaction responses
    • Abstract: Publication date: Available online 28 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): M.A Kabachi, M. Danzi, S. Arreguin, P. Ermanni Fiber-reinforcements’ permeability and compressibility are crucial parameters in Liquid Composite Molding Processes, as they represent the main textile properties that influence the behavior of the injected resin. Before designing LCM molds and optimizing manufacturing processes, permeability and compaction characterizations are performed; however, the results obtained often show considerable deviations. One reason for this behavior is the variable compaction histories of fiber-beds, which can be altered during storage or handling. This work presents a novel method to normalize compaction histories through cyclic compaction, thus increasing the reproducibility of compaction and through-thickness permeability responses. It also shows how fiber-bed’s viscoelasticity can be reduced with minor influence on permeability. It is greatly beneficial in developing processing routes for vacuum assisted processes, and for future compaction or permeability benchmarks, in defining optimal characterization methods. It provides also solid basis for the comparison and validation of compaction and through-thickness permeability models with reduced measurement errors.
  • Three-dimensional porosity characterization in carbon/glass fiber epoxy
           hybrid composites
    • Abstract: Publication date: Available online 25 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Francisco Maciel Monticeli, Heitor Luiz Ornaghi, Herman Jacobus Cornelis Voorwald, Maria Odila Hilário Cioffi The main objective of this study is to analyze the effect of the stacking sequence of glass/carbon-reinforced hybrid composites on the impregnation quality and on the formation of voids. This was achieved by creating a three-dimensional (3D) microstructure of the laminates from planar microscopy images. It was demonstrated that the impregnation quality could be improved, and the porosity could be minimized by the appropriate selection of the stacking sequence. The present methodology enables the analysis of the effect of various configurations of hybrid reinforcement on the impregnation behavior, and consequently, the formation of voids. The 3D images enable detailed characterization of porosity through the laminate thickness, including void fraction, the location and morphology of voids. Hybrid composites with glass fibers positioned in the middle proved to have more favorable impregnation, and thus, the uniformity of process-induced voids throughout the composite laminates could be reduced and controlled.
  • An Inkjet-printed, Flexible, Ultra-broadband Nanocomposite Film Sensor for
           in-situ Acquisition of High-frequency Dynamic Strains
    • Abstract: Publication date: Available online 24 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Pengyu Zhou, Yaozhong Liao, Yehai Li, Dongyue Pan, Wuxiong Cao, Xiongbin Yang, Fangxin Zou, Li-min Zhou, Zhong Zhang, Zhongqing Su We present an ultralight, flexible, nanocomposite film sensor manufactured using a drop-on-demand inkjet printing approach which leverages the integrated inks directly on flexible polyimide substrates. The ink – a hybrid of nanocomposites embracing carbon black nanoparticles and polyvinyl pyrrolidone, is rigorously designed and morphologically optimized to be stable, printable and wettable. The printed film sensor has proven capability of in situ, precisely responding to dynamic strains in a broad range from quasi-static strain, through medium-frequency vibration, to ultrasounds up to 500 kHz. This is first ever an inkjet-printed piezoresistive sensor responds to dynamic strains in such a broad band and an ultrasound of such high frequencies. Sensitivity of the sensors can be fine-tuned by adjusting the degree of conductivity via controlling the printed passes, endowing the sensors with capacity of resonating to strains of a particular frequency, authenticating inkjet-printed nanocomposite sensors can be tailor-made to accommodate specific signal acquisition demands.
  • Effect of the Thickness on the Fracturing Behavior of Discontinuous Fiber
           Composite Structures
    • Abstract: Publication date: Available online 23 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Seunghyun Ko, James Davey, Sam Douglass, Jinkyu Yang, Mark E. Tuttle, Marco Salviato In this study, we investigate experimentally and numerically the mode I intra-laminar fracture and size effect of Discontinuous Fiber Composites (DFCs) as a function of the structure thickness.Fracture tests on geometrically-scaled Single Edge Notch Tension (SENT) specimens show a notable size effect on the nominal strength of DFCs. By integrating equivalent fracture mechanics and stochastic finite element modeling we estimate, for the first time, the fracture energy and the effective size of the Fracture Process Zone (FPZ) as a function of the thickness of the DFC structure.From the integrated analysis, it is found that the fracture energy depends significantly on the structure thickness. It is shown to increase gradually with increasing thickness, t, and to saturate for t⩾3 mm to a value of 57.77 N/mm, which is 4.81 times larger than a typical aluminum alloy. For thicknesses lower than 1.1 mm, corresponding to an average number of platelets through the thickness of roughly 8, it was found that the fracturing process can often be triggered by weak spots in the structure rather than the stress-free notch.
  • In situ statistical measurement of local morphology in carbon-epoxy
           composites using synchrotron X-ray computed tomography
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Sebastian Rosini, Mark N. Mavrogordato, Olga Egorova, Emily S. Matthews, Samuel E. Jackson, S. Mark Spearing, Ian Sinclair Models are still deficient in accurately reproducing the mechanisms that trigger tensile failure in unidirectional composites, highlighting a lack of direct experimental evidence. In this study, emphasis is given to the identification of connections between local fibre misorientation, packing and Weibull strength distribution in causing tensile failure. Synchrotron Radiation Computed Tomography (SRCT) and automated image processing techniques are adopted to segment individual fibres from loaded carbon fibre coupons. Subtle indications in the misorientation of local damaged sites are assessed in novel statistical detail for systematic differentiation from non-damaged sites. It is observed that the morphology of the surrounding environment of damaged sites statistically differs from that of non-damaged sites, even though locally damaged sites (containing single or coupled breaks) do not exhibit a peculiar fibre packing arrangement. For adjacent coupled breaks, the statistical nature of fibre separation distances is also reported.
  • High fibre-volume silkworm cocoon composites with strong structure bonded
           by polyurethane elastomer for high toughness
    • Abstract: Publication date: Available online 22 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Fei Li, Yi Tan, Lei Chen, Lingxiao Jing, Dayang Wu, Tao Wang Silkworm cocoons are lightweight and tough natural composites with special structure. To enhance the mechanical performance, strong bonding force and high fibre volume fraction are very important for the natural composites. Here, the polyurethane elastomer resin (PU) was used as matrix for Bombyx mori cocoon composites by dip-molding and hot pressing treatments. Silkworm cocoon-PU composites with high fibre volume fraction (Vf ∼0.6) were achieved, of which the mechanical performance is greatly enhanced. Compared to the native cocoon, the bonding force increases by 500%, the tensile strength and modulus increases by 150%, and the breaking energy increases by 300%. The higher fibre volume fraction also contributes to better specific mechanical properties and dynamic elasticity of the composites. Generally, silkworm cocoons and polyurethane elastomer are complementary for producing lightweight composites with high toughness, which has potential for multi-scale energy absorbing applications.
  • Advanced cutting tools and technologies for drilling carbon fibre
           reinforced polymer (CFRP) composites: a review
    • Abstract: Publication date: Available online 20 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Norbert Geier, J. Paulo Davim, Tibor Szalay Carbon fibre reinforced polymer (CFRP) composites have excellent specific mechanical properties, these materials are therefore widely used in high-tech industries like the automobile and aerospace sectors. The mechanical machining of CFRP composites is often necessary to meet dimensional or assembly-related requirements; however, the machining of these materials is difficult. In an attempt to explore this issue, the main objective of the present paper is to review those advanced cutting tools and technologies that are used for drilling carbon fibre reinforced polymer composites. In this context, this paper gives a detailed review and discussion of the following: (i) the machinability of CFRP including chip removal mechanisms, cutting force, tool wear, surface roughness, delamination and the characteristics of uncut fibres; (ii) cutting tool requirements for CFRP machining; and (iii) recent industrial solutions: advanced edge geometries of cutting tools, coatings and technologies. In conclusion, it can be stated that advanced geometry cutting tools are often necessary in order to effectively and appropriately machine required quality features when working with CFRP composites.
  • Staggered ply discontinuities for tailoring the tensile behavior of hybrid
           carbon fiber/self-reinforced polypropylene composites: a study of pattern
    • Abstract: Publication date: Available online 20 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Jun Tang, Arya Aslani, Yentl Swolfs, Gianmaria Bullegas, Silvestre T. Pinho, Stepan V. Lomov, Larissa Gorbatikh This work explores the potential of discontinuities combined with hybridization in controlling the failure mechanisms of composite materials. Laser cuts, termed as discontinuities, with a predefined staggered pattern were introduced into the carbon layer of hybrid carbon fiber (CF)/self-reinforced polypropylene (SRPP) composites. Three geometrical parameters were used to define the staggered pattern: cut fraction, cut length and step length. The effects of these three parameters on the failure mechanisms of the hybrid CF/SRPP composites under tensile loading were investigated. The three geometrical parameters can be successfully used to: (1) trigger more diffused damage; (2) delay onset of carbon layer fracture; and (3) promote a transition between fiber bundle pull-out and fiber bundle fracture. Comparing to hybrids with continuous fibers, hybrids with the staggered ply discontinuities exhibited a rich diversity of failure mechanisms. The enrichment of failure mechanisms is beneficial for expanding the design space for tailoring the mechanical response of interlayer hybrid composites.
  • Comprehensive study of effects of filler length on mechanical, electrical,
           and thermal properties of multi-walled carbon nanotube/polyamide 6
    • Abstract: Publication date: Available online 19 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Han Gyeol Jang, Beomjoo Yang, Myung-Seob Khil, Seong Yun Kim, Jaewoo Kim In spite of active studies on multi-walled carbon nanotube (MWCNT)-incorporated polymer, MWCNTs of different thickness and lengths have been employed. Here, the effects of MWCNT morphology, specifically its length, on the mechanical, thermal, and electrical properties of MWCNT/polymer composites were examined in comparison with theoretical modeling. Field-emission scanning electron microscopy and micro–computed tomography observations revealed that short MWCNTs were dispersed more uniformly than long MWCNTs in a polyamide 6 (PA6) polymer. Correlation of this result with the tensile performance revealed that at low MWCNT concentrations the long-MWCNT/PA6 composite showed superior tensile properties since the effect of length was dominant. However, at high MWCNT concentrations, the short-MWCNT/PA6 showed superior tensile properties to the long-MWCNT/PA6 due to the better dispersion of the former. The thermal conductivity gradually improved with increasing MWCNT concentration, showing larger improvement for the long-MWCNT/PA6, while the electrical conductivity reached percolation threshold at 1 wt% for both MWCNTs.
  • One-step electrodeposition of Cu/CNT/CF multiscale reinforcement with
           substantially improved thermal/electrical conductivity and interfacial
           properties of epoxy composites
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Fei Yan, Liu Liu, Ming Li, Mengjie Zhang, Lei Shang, Linghan Xiao, Yuhui Ao A novel copper/carbon nanotube/carbon fiber (Cu/CNT/CF) multiscale reinforcement was successfully achieved using a one-step electrophoretic deposition technique in which CNT was introduced via two techniques. Two stabilized electrolytes containing CNT of distinct charge character were prepared to investigate the effect of CNT to the thermal/electrical conductivity and interlaminar shear strength (ILSS) of the composites. The positively charged CNT composites showed increases of 359.2%, 2761% and 34.5% for thermal conductivity and electrical conductivity in the through-thickness direction and the ILSS, respectively, in comparison with de-sized CF composites. Contrast with the two-step method, the preparation time of the one-step method has been shortened to one-fifth, and the connections between the Cu and CNT were compacted to improve the conductivity of the composites. Moreover, Cu/CNT/CF prepared according to the one-step method was highly compatible with vacuum-assisted resin infusion technology and provided a route for preparing multifunctional composites that could be easily scaled up.
  • High actuated performance MWCNT/Ecoflex dielectric elastomer actuators
           based on layer-by-layer structure
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Zewang Xu, Shaodi Zheng, Xiaotian Wu, Zhengying Liu, Ruiying Bao, Wei Yang, Mingbo Yang A layer-by-layer structure was constructed by alternately arranging conductive layers and insulating layers in a silicone dielectric elastomer (Ecoflex) to largely improve the actuated strain at a low electric field. In the electric field environment, the insulating layer blocks the transmission channel of electrons in the adjacent conductive layer, so the interfaces of adjacent conductive layers and insulating layers can accumulate and store a large number of charges, thereby greatly increasing the dielectric constant of the material. Meanwhile, the individual conductive layers are separated by an insulating layer to avoid causing large conductance losses. A high actuated strain (20.33%) at a relatively low electric field (12.5 kV mm−1) and good cyclic stability are obtained on the actuator without any pre-strain. These results demonstrate that our research provides a simple and effective method to significantly improve the actuated strain at a low electric field of DE and promote its practical application.
  • A review of the current progress and application of 3D printed concrete
    • Abstract: Publication date: Available online 17 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Jingchuan Zhang, Jialiang Wang, Sufen Dong, Xun Yu, Baoguo Han Additive manufacturing, also known as three-dimension printing (3DP), has the advantages of high building efficient, low labor cost and less construction wastes compared to traditional construction technology. 3D printed concrete is a special type of concrete, which can be deposited through a 3D printer layer by layer without any formwork support and vibration process. Its important performance indexes, including workability, setting and hardening time, and mechanical properties, can be optimized by materials selection and printing parameters. To date, many building structures have been successfully printed using 3DP technology, some of which have even achieved its real applications. The 3D printed concrete has a great potential on practical applications, such as the affordable housing construction in low-income countries, military bunkers when the soldiers fighting in the wild, and complex constructions where the formwork is difficult to manufacture. In order to comprehensively introduce 3D printed concrete, this paper reviews the progress of 3D printed concrete in terms of workability, mechanical properties and building plan design. In addition, the current applications and further developments of 3D printed concrete are also discussed.
  • A green highly-effective surface flame-retardant strategy for rigid
           polyurethane foam: transforming UV-cured coating into intumescent
           self-extinguishing layer
    • Abstract: Publication date: Available online 17 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yubin Huang, Saihua Jiang, Runcan Liang, Zhiwei Liao, Gexin You Nowadays, halogen-free high flame retardance of rigid polyurethane (RPU) foam without deteriorating its intrinsic performances is still a great challenge. Here, a green surface flame-retardant (SFR) strategy of RPU foam was proposed. In detail, a new halogen-free UV-curable self-extinguished coating was developed and then combined onto the surface of RPU, obtaining a surface flame-retardant RPU foam system (SFR-RPU). The SFR-RPU foams exhibit highly-efficient flame retardancy at a coating thickness of 25 µm, showing a fast self-extinguishing behavior. A compact porous char layer served as a good barrier can be rapidly formed on the surface of SFR-RPU. The detailed flame-retardant mechanism was proposed. Furthermore, when compared to neat RPU, the compressive strength of SFR-RPU foams is enhanced and the heat-insulation property is maintained perfectly. This facile, low-cost and environmental-friendly post-treatment of RPU foam could expand its fire safe commercial applications.
  • Detailed characterization of voids in multidirectional carbon fiber/epoxy
           composite laminates using X-ray micro-computed tomography
    • Abstract: Publication date: Available online 16 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Mahoor Mehdikhani, Ilya Straumit, Larissa Gorbatikh, Stepan V. Lomov We employed X-ray micro-computed tomography to generate an extensive dataset of void characteristics in carbon/epoxy laminates with different stacking sequences. The voids were deliberately induced by modifying the material’s cure cycle. The obtained three-dimensional images demonstrating voids were segmented and quantified using an in-house software package, VoxTex. The void characteristics, i.e. shape, size parameters, orientation, and spatial distribution, were obtained for analysis. It was found that voids are typically elongated features, aligned with the neighboring fibers. The majority of voids had slightly flattened cross-sections. The voids preferred to localize in the inner plies of the laminate, rather than in the outer ones. Near the laminate mid-thickness, they became more elongated. The stacking sequence was found to affect the size and shape of voids, with the void content being higher for a thicker laminate. The planar location of voids is not random and tends to create a pattern, corresponding to the ply orientations in the laminate. The data gathered during this study has been reported in detail and can be used, for example, as input for studies modeling similar composites with voids. The entire micro-CT data is presented as a Data in Brief article in [1].
  • Investigation of kink induced defect in aluminium sheets for Glare
    • Abstract: Publication date: Available online 16 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): D. Nardi, M. Abouhamzeh, R. Leonard, J. Sinke The quality control of Glare panels manufacturing is an important and complex process including the evaluation of the quality of the basic constituents, namely the aluminium sheets, and the glass fibre reinforced pre-preg. In particular, the handling of aluminium sheets is one of the most critical steps for the manufacturing of Glare laminates. The unintentionally induced deformations, referred to as kinks, can significantly affect the geometry and the mechanical properties of the final laminate. This paper considers the effects of kinks in Glare laminates by developing a comprehensive investigation based on controlled kink manufacturing in aluminium sheets, non-destructive and destructive evaluation of laminates with kinks, and the impact on the compressive ultimate strength. The results contribute to the understanding of the kink induced defects and to define thresholds for improving future automated laminate manufacturing.
  • An objective comparison of common vacuum assisted resin infusion processes
    • Abstract: Publication date: Available online 15 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): S. Van Oosterom, T. Allen, M. Battley, S. Bickerton This study executed an objective comparison between Resin Infusion methods currently used, providing a level comparison in identical circumstances. Six different resin infusion methods including VARTM, SCRIMP, CAPRI, DBVI, VAP, and PI were investigated to discern if the modifications made relevant to the standard VARTM process have a distinguishable effect, and how significant the effect was. Process parameters were found to vary significantly between methodologies, with large differences in infusion time, laminate pressure and relaxation, and resin usage. Fibre volume fractions were found to vary significantly both between methodologies and along the infusion length of some panels. Differences of up to 13% and 10% were found in short beam strength and compression strength between the infusion methods. There was found to be no significant difference in void content between methodologies once the best process parameters had been established, with the exception of PI which resulted in a significant increase.
  • Analyzing the UF resin distribution in particleboards by confocal laser
           scanning microscopy
    • Abstract: Publication date: Available online 13 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Daniela Altgen, Warren Grigsby, Michael Altgen, Lauri Rautkari, Carsten Mai This study uses confocal laser scanning microscopy to analyze UF resin distribution within particleboards. Particleboards with three different resin contents were produced using a labeled UF resin. Furthermore, a plasma pre-treatment was applied to study the effect of an enhanced wettability of the particles on the resin distribution. With increasing resin content, the average resin spot size was increased and the distribution of resin areas shifted towards larger resin areas. Enhancing the wood wettability through plasma treatment had the opposite effect. Increased numbers of small resin areas was generated due to a better resin spreading and blending. The study further shows that confocal laser scanning microscopy allows qualitative investigations of resin within particleboards to determine differing resin locations and behaviors within and on particles.
  • Light-Induced Rare Earth Organic Complex/Shape-Memory Polymer Composites
           with High Strength and Luminescence Based on Hydrogen Bonding
    • Abstract: Publication date: Available online 12 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Hangning Wang, Liang Fang, Zhen Zhang, Jayantha Epaarachchi, Lingyu Li, Xin Hu, Chunhua Lu, Zhongzi Xu Shape-memory polymer composites (SMPCs) with multi-capabilities have attracted growing attention in both academia and industry. However, the known fillers suffer from the deficient functionalization, which would limit the compatible capabilities and applications. Herein, we report the manufacturing of SMPCs based on the hydrogen bonding between nitrate groups from Sm(TTA)Phen(NO3)3 (STPN) and carboxyl groups from crosslinked poly(methyl methacrylate-co-itaconic acid) (P(MMA-co-IA)). SMPCs were prepared by immersing P(MMA-co-IA) in STPN solution with the concentrations of 0.001 – 0.03 mol L-1. The dispersion of STPN in P(MMA-co-IA) was highly improved in comparison with the rare earth organic complex of Sm(TTA)3Phen without hydrogen bonding. By employing STPN, the flexural modulus and strength were increased by 2.5 and 3.9 times, respectively. The properties of good transparency, fluorescence and near-infrared light induced shape-recovery were also achieved. This work provides an approach to prepare novel SMPCs with different properties including high strength, fluorescence, and light-induced shape-recovery.
  • Effect of BaTiO3 nanowire distribution on the dielectric and energy
           storage performance of double-layer PVDF-based composites
    • Abstract: Publication date: Available online 11 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yu Feng, Jia-Long Li, Wei-Li Li, Meng-Lu Li, Qing-Guo Chi, Tian-Dong Zhang, Wei-Dong Fei A series of novel double-layer PVDF-based composites filled with different concentration of BaTiO3 nanowire were fabricated employing hot-pressing process. The effects of various BT-NWs concentrations in isolated layers on the dielectric properties, energy storage density of the composites were investigated. The experimental dielectric constants of double-layer composites are lower than expected. The breakdown strength (Eb) of double-layer composites was obtained in the experiment, and predicted via capacitance series formula (CSF) and finite element analysis (FEA). Results show that the data predicted by FEA are closer to the experimental values. Compared with dielectric constant, the enhancement of Eb induced by double-layer structure is more significant for the energy storage performance of composites. A design route including Eb measurement of single-layer composites, Eb prediction of double-layer composites via FEA, selection of single-layer material and composites fabrication is proposed to prepare the multi-layer composites with excellent dielectric properties and energy storage.
  • Fabrication of core-shell structured Ni@BaTiO3 scaffolds for polymer
           composites with ultrahigh dielectric constant and low loss
    • Abstract: Publication date: October 2019Source: Composites Part A: Applied Science and Manufacturing, Volume 125Author(s): Xiaotong Zhu, Jie Yang, Davoud Dastan, Hamid Garmestani, Runhua Fan, Zhicheng Shi Dielectric composites have drawn increasing attention owing to their wide applications in electrical systems. Herein, a novel design of dielectric composites consisting of core-shell structured porous Ni@BaTiO3 scaffolds infiltrated with epoxy was developed. It is demonstrated that the dielectric constants of the composites could be as high as 6397@10 kHz, which is approximately 1777 times higher than pure epoxy matrix (εr ≈ 3.6@10 kHz). Meanwhile, the dielectric loss (tanδ ≈ 0.04@10 kHz) remains comparable to that of pure epoxy (tanδ ≈ 0.01@10 kHz). It is believed that the strong charge accumulation and interfacial polarizations on the huge interfaces, especially the Ni/BaTiO3 and Ni/epoxy interfaces, give arise to the substantially enhanced εr. Besides, the sintered insulating BaTiO3 coating can block the transportation of charge carriers, resulting in the low loss. The ultrahigh dielectric constants and low loss make these composites promising candidates for microstrip antennas, field-effect transistors and dielectric capacitors.
  • Mechanical Properties and Failure Modes of Hybrid Fiber Reinforced Polymer
           Composites with a Novel Liquid Thermoplastic Resin, Elium®
    • Abstract: Publication date: Available online 10 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): M.E. Kazemi, Logesh Shanmugam, Dong Lu, Xiaogang Wang, Bowei Wang, Jinglei Yang In virtue of recyclability purposes, higher impact and damage tolerance properties, efficient and ease of fabrication, a new liquid Methyl Methacrylate (MMA) thermoplastic resin, Elium® 188, has been recently developed. This new resin can replace (epoxy) thermoset-based resins for the fabrication of laminates at room temperature with equivalent mechanical properties. Plain weave ultra-high molecule weight polyethylene fiber (UHMWPE), carbon fiber, and their hybrid systems are fabricated by Vacuum Assisted Resin Infusion (VARI) method at ambient temperature. ASTM standard tests of tensile, compression, and shear (both intralaminar and interlaminar) are conducted to determine the mechanical properties with the aim of comparing the results with those of thermosets. Fractographic analyses are performed to have a better understanding of the behavior of these new thermoplastic-based laminates. The test results show the mechanical properties of thermoplastic-based laminates are comparable to those thermoset-based but with the aforementioned advantages, leading to wider applications in the industry.
  • High-performance electromagnetic wave absorption by designing the
           multilayer graphene/thermoplastic polyurethane porous composites with
           gradient foam ratio structure
    • Abstract: Publication date: Available online 8 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Chaozhi Wang, Jiang Li, Shaoyun Guo An excellent electromagnetic wave absorbing material (EWAM) should possess both wider effective absorption bandwidth (EB) and lower minimum reflection loss (RLmin), which depends on good impedance matching between the EWAMs and air and strong attenuation of electromagnetic wave (EW) inside the absorber. In this work, single-layer graphene/thermoplastic polyurethane (TPU) porous composites with different foam ratio and gradient foam ratio multilayer graphene/TPU porous composites with different number of layers were prepared. Not only were the EW-absorbing properties and mechanism of these composites investigated, but the mechanical properties were also examined. Compared to the single-layer samples with the same average foam ratios at the same thickness, the multilayer samples showed wider EB, 5.6, 4.6, 4.4GHz for 3L, 4L and 5L, respectively. By designing the multilayer structure of gradient foam ratio, it provides a novel path for the preparation of EWAMs with strong absorption capacity, wider EB, light weight and excellent mechanical properties.
  • Adaptive Discrete-Smeared Crack (A-DiSC) Model for Multi-Scale Progressive
           Damage in Composites
    • Abstract: Publication date: Available online 8 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): X. Lu, M. Ridha, V.B.C. Tan, T.E. Tay Apart from major cracks and delamination, extensive and diffused short matrix micro-cracks are generally observed in composite laminates. In principle, discrete crack models (DCM) offer greatest fidelity to the mechanics of crack growth, including interactions between different failure modes, but it is impractical to model numerous cracks explicitly beyond coupon-sized laminates. Smeared crack models (SCM), on the other hand, treat diffused damage by effective material degradation. However, homogenization of cracks does not model strong discontinuities and delamination-matrix crack interactions. An adaptive discrete-smeared crack model is proposed here to preserve fidelity to the fracturing process while maintaining efficiency and simplicity in modelling distributed damage. DCM is used to model individual matrix cracks at the initial stages of propagation. Subsequently, adaptive transition from DCM to coupled DCM/SCM is performed. Critical cracks are explicitly retained, while non-critical ones are modelled by dispersed damage. The method is demonstrated with off-axis and open-hole tension tests.
  • Efficient numerical simulation method for three dimensional resin flow in
           laminated preform during liquid composite molding processes
    • Abstract: Publication date: Available online 6 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Naziha Chebil, Mylène Deléglise-Lagardère, Chung Hae Park We propose an efficient simulation method of three-dimensional (3D) resin flow in laminated preform composed of multiple layers with different permeabilities at each layer. Because of the small thickness of each layer, a huge number of nodes are needed for 3D flow simulation if solid elements are adopted and full 3D simulation takes extremely long even by parallel computing. Instead of 3D solid elements, we propose multi-layered shell elements for 3D flow simulation with a short computing time. We describe the numerical formulation of multi-layered shell element method to consider the through-thickness flow as well as the planar flow. The accuracy and efficiency are evaluated by new dimensionless parameters defined in terms of preform permeability ratio and of the ratio of shell element size to the distance between the adjacent layers. Some simulation results are presented to demonstrate the advantages of the multi-layered shell element method for 3D flow simulation.
  • A coupled thermomechanical approach for finite element forming simulation
           of continuously fiber-reinforced semi-crystalline thermoplastics
    • Abstract: Publication date: Available online 5 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): D. Dörr, T. Joppich, D. Kugele, F. Henning, L. Kärger A coupled thermomechanical approach for macroscopic Finite Element (FE) thermoforming simulation of continuously fiber-reinforced semi-crystalline thermoplastic, which is implemented in the commercial FE solver Abaqus in combination with several user-subroutines, is presented. Thermal modeling takes into account radiation, convection and heat conduction as well as the prediction of recrystallization during forming. Mechanical behavior is modeled layer-by-layer and takes into account rate-dependent forming behavior by means of hyperviscoelastic constitutive equations following a nonlinear generalized Maxwell approach. The phase transition is considered in material modeling by coupling the mechanical properties to the temperature and the degree of crystallinity. In application of the presented thermomechanical approach to a generic geometry, an improved agreement of forming simulation to experimental results is observed against a purely isothermal approach. Thereby, some defects are only predicted by the thermomechanical approach, which makes a coupled thermomechanical approach considering temperature and crystallization kinetics favorable for the virtual process design.
  • Noncovalent engineering of carbon nanotube surface by imidazolium ionic
           liquids: A promising strategy for enhancing thermal conductivity of epoxy
    • Abstract: Publication date: Available online 5 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Chao Chen, Xiaojing Li, Yingfeng Wen, Jingwei Liu, Xiongwei Li, Hongxia Zeng, Zhigang Xue, Xingping Zhou, Xiaolin Xie Carbon nanotubes reinforced polymer composites with high thermal conductivity show attractive prospects as multifunctional thermal management materials for high-power electronics applications. The contradictory relationship between homogenous filler dispersion with enhanced interfacial interaction and the intrinsic properties of embedded filler, usually leads to the uncertainty and low thermal conductivity improvement efficiency of resulting polymer composites. Herein, noncovalently functionalized multi-walled carbon nanotubes with imidazolium amine-terminated ionic liquids (AIL-MWCNTs) were facilely prepared through cation-π stacking interactions and acted as low-defect fillers for improving the thermal conductivity of epoxy. The mild chemical modification process has considerable advantages for reserving the inherent intact structures of MWCNTs. Hence, the thermal conductivity enhancement of EP/AIL-MWCNTs composite (∼211%) is much higher than that of epoxy composite filled with acidified MWCNTs (∼102%) at 8 wt% loading. The noncovalent functionalization approach is a promising strategy for scalable fabrication of MWCNTs-based polymer composite with simultaneously enhanced thermal conductivity and mechanical properties.Graphical abstractNoncovalently functionalized multi-walled carbon nanotubes with imidazolium amine-terminated ionic liquids (AIL-MWCNTs) are facilely prepared through cation-π stacking interactions and acted as low-defect fillers for improving the thermal conductivity of epoxy.Graphical abstract for this article
  • Development of 3D-printed basalt fiber reinforced thermoplastic honeycombs
           with enhanced compressive mechanical properties
    • Abstract: Publication date: Available online 4 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Lin Sang, Shuangfeng Han, Xingshuang Peng, Xigao Jian, Jinyan Wang In present work, fiber reinforced thermoplastic composite filaments consisting of polylactic acid, polycaprolactone and basalt fibers for 3D printing are developed and proposed. Mechanical test, dynamic mechanical analysis and rheology test are conducted to capture the mechanical, thermal and viscoelastic properties of 3D-printed PLA-PCL/KBF specimens. Then, circular honeycombs are fabricated using four ratios of filaments via fused deposition modeling technology, and the in-plane compressive mechanical properties are explored. The results show that circular honeycombs manufactured using PLA-PCL30/KBF filament possess superior energy absorption capacity, which is ascribed to the ductility of matrix and good interfacial matrix/fiber adhesion. Furthermore, two other honeycomb structures (hexagonal and re-entrant cell geometries) are fabricated and their compressive mechanical properties are assessed. It is revealed that the hexagonal honeycombs exhibit comparative energy absorption capacity with re-entrant ones. Therefore, the PLA-PCL/KBF composite materials are promising FDM feedstock for manufacturing honeycomb structures as energy absorbers.Graphical abstractGraphical abstract for this article
  • A method for preparing epoxy-cellulose nanofiber composites with an
           oriented structure
    • Abstract: Publication date: Available online 3 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Tuukka Nissilä, Maiju Hietala, Kristiina Oksman A method was developed for processing cellulose nanocomposites using conventional vacuum infusion. Porous cellulose nanofiber networks were prepared via ice-templating and used as preforms for impregnation with a bio-epoxy resin. Microscopy studies showed a unidirectionally oriented micrometer-scale pore structure that facilitated the infusion process by providing flow channels for the resin. The permeability of the preforms was comparable to that of natural fiber mats, and the infusion time significantly decreased after optimizing the processing temperature. The flexural modulus of the bio-epoxy increased from 2.5 to 4.4 GPa, the strength increased from 89 to 107 MPa, and the storage modulus increased from 2.8 to 4.2 GPa with 13 vol% cellulose nanofibers. The mechanical properties also showed anisotropy, as the flexural and storage moduli were approximately 25% higher in the longitudinal direction, indicating that the nanofiber network inside the epoxy matrix had an oriented nature.
  • Monodisperse Highly Ordered Chitosan/Cellulose Nanocomposite Foams
    • Abstract: Publication date: Available online 3 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Sébastien Andrieux, Lilian Medina, Michael Herbst, Lars Berglund, Cosima Stubenrauch In solid foams, most physical properties are determined by the pore size and shape distributions and the organisation of the pores. For this reason, it is important to control the structure of porous materials. We recently tackled this issue with the help of microfluidic-aided foam templating, which allowed us to generate monodisperse and highly ordered chitosan foams. However, the properties of foams also depend on the properties of the pore wall constituents. In case of chitosan-based foams, the foams have poor absolute mechanical properties, simply due to the fact that the solubility of chitosan in water is very low, so that the relative density of the freeze-dried foams becomes very small. Drawing inspiration from the field of nanocomposites, we incorporated cellulose nanofibres into the foamed chitosan solutions, with a view to strengthening the pore walls in the foam and thus the mechanical properties of the final foam. We report here how the cellulose nanofibres affect the structure of both the liquid foam template and the solid foam. The resulting nanocomposite foams have improved mechanical properties, which, however, are not proportional to the amount of cellulose nanofibres in the composites. One reason for this observation is the disturbance of the porous structure of the solid foams by the cellulose nanofibres.
  • Study on the performance of different nano-species used for surface
           modification of carbon fiber for interface strengthening
    • Abstract: Publication date: Available online 2 July 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Ajitanshu Vedrtnam, Sahendra P. Sharma The interfacial strength, vibrations attenuation and delamination resistance of carbon fiber reinforced polymer composites (CFRPCs) can be significantly improved by introducing different nano-species (nanotube/nanorods/nanowalls/nanowires) on the carbon fiber (CF) surface. A review on the performance of carbon nanotubes (CNTs), zinc oxide (ZnO) nanowalls, nanowires, and other nano-species, modified CFRPCs is presented. The approaches to optimize the size and maximize the density of nanotubes and nanorods on the CF surface based on the available literature data are discussed. It could be concluded based on the discussion that the dense-thin-long-fibers produce better mechanical performance and in addition to improving interfacial strength, nanotubes/rods share the load with fibers and improve the toughness of CFRPC. The finite element (FE) model is constituted for observing the stresses at CNT, CF, and interface of CF/CNT during tensile loading. A FE model analyzing variation in mechanical properties of CF due to possible defects is reviewed. The analysis of data revealed under-utilization of the strength of CNTs in CFRPC. Later, a discussion on the fractography of CFRPCs with nano-species/other treatments along with some original FE results required for discussion is presented. This review should provide a faster and better understanding of the research area addressed.
  • Highly Enhanced Thermal Conductivity of Epoxy Composites by Constructing
           Dense Thermal Conductive Network with Combination of Alumina and Carbon
    • Abstract: Publication date: Available online 28 June 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Rong Yan, Fan Su, Ling Zhang, Chunzhong Li Achieving highly out-plane TC composites by building thermal conductive network at possible low content of conductive fillers is crucial and urgent to realize miniaturization, integration, and high-power density of electronic devices. In this study, highly thermal conductive composites based on pre-selected size of micro-Al2O3 (20 μm and 70 μm), acidified MWCNTs and silica nanoparticles (SiO2 NPs) are fabricated via a facile mixing process. Enhanced thermal conductive network was constructed by small functionalized Al2O3 (f-Al2O3) particles gap filling between large f-Al2O3 particles and the MWCNTs connection with adjacent f-Al2O3 particles. SiO2 NPs are used to avoid the sedimentation of f-Al2O3 particles and improve the dispersion of MWCNTs. The obtained composites show very high out-plane TC (1.73 W·m-1·K-1) at only 60 wt% Al2O3 (20 μm/70 μm: mass fraction, 1/3), 3 wt% MWCNTs and 8 wt% SiO2. It is attributed to the synergistic effect of different size of f-Al2O3 and the MWCNTs to form the dense thermal conduction path. The high out-plane TC and low electric conductivity provide this material great potential as candidate for heat dissipation parts in electronic devices.Graphical abstractBriefs: The construction of heat transfer path and thermal conductivity of different composites.Graphical abstract for this article
  • Cure Strain Monitoring in Composite Laminates with Distributed Optical
    • Abstract: Publication date: Available online 27 June 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Jung-Ting Tsai, Joshua S. Dustin, Jan-Anders Mansson Measuring the strain history in pre-impregnated thermoset composites during the curing process provides valuable data for manufacturing specification development, quality control, diagnostics of dimensional stability, and validation of cure models. Distributed Optical Sensors (DOS) provide information along the entire optical path length of the sensor embedded in the laminate and present a promising high-resolution sensing option for in-situ strain measurement. This study’s contribution to the field is the coupling of the optical sensor monitoring of composite cure strain with models of the cure kinetics, viscosity, and glass transition temperature of the thermoset matrix. A unidirectional (UD) laminate and a structural laminate (SL) were manufacture embedded with an optical sensor. The internal residual strain developed during each stage of the thermal cure cycle is examined for both laminate types, including after cooling, and the models of the resin’s physical property development were used to facilitate interpretation of the strain measurement data from the DOS.
  • Advances in understanding the response of fibre-based polymer composites
           to shock waves and explosive blasts
    • Abstract: Publication date: Available online 27 June 2019Source: Composites Part A: Applied Science and ManufacturingAuthor(s): A.P. Mouritz Fibre-based polymer composites are used in applications were there is the risk of an explosive blast. This paper presents a comprehensive review of published research into the blast performance of fibre-based composite materials, which includes fibre-reinforced polymer (FRP) laminates, fibre metal laminates, and sandwich composites with FRP facesheets. The dynamic loading experienced by composite materials under surface contact, near-field and far-field blast events is described. The various test methods used to experimentally evaluate the response of composites to shock wave and blast loading are reviewed. Experimental and modelling studies into the deformation and damage of composites caused by shock waves are also reviewed. The mechanisms by which fibre-polymer laminates, fibre metal laminates and sandwich composites absorb the shock wave energy generated by an explosive blast are analysed. The paper also reviews methods used to improve the blast performance of composites.
School of Mathematical and Computer Sciences
Heriot-Watt University
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