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Composites Part A : Applied Science and Manufacturing
Journal Prestige (SJR): 1.539
Citation Impact (citeScore): 5
Number of Followers: 223  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1359-835X
Published by Elsevier Homepage  [3161 journals]
  • Experimental investigation on spring-back deformation during autoclave
           curing of parabolic antenna reflectors
    • Abstract: Publication date: Available online 22 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Dhaval B. Shah, K.M. Patel, Arvind I. Patel, Vishwajit Pariyal, Shashikant J. JoshiAbstractHigh dimensional fidelity is the primary challenge for the large size carbon fiber reinforced polymer (CFRP) antenna reflectors used in space applications. Selection of crucial process parameters governs dimensional control of a composite product. In this paper, the influence of the mould materials, curing cycle, lay-up sequence and laminate thickness on spring-back deformation during autoclave curing is investigated by fabricating a large number of parabolic reflectors using the unidirectional prepreg system. The non-contact type accurate 3D scanning technique is used to measure the dimensions of the parabolic antenna reflectors. In the present work, an experimental approach is adopted for the determination of a combination of process parameters which gives minimum spring-back deformation. The results reveal that the spring-back deformation of parabolic reflectors is significantly affected by the mould material and laminate thickness, whereas the lay-up sequence and curing cycle do not have a significant effect.
       
  • Fabrication of ternary hybrid of carbon nanotubes/graphene oxide/MoS2 and
           its enhancement on the tribological properties of epoxy composite coatings
           
    • Abstract: Publication date: Available online 22 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Beibei Chen, Xiang Li, Yuhan Jia, Lin Xu, Hongyu Liang, Xiaofang Li, Jin Yang, Changsheng Li, Fengyuan YanAbstractA novel ternary hybrid of carbon nanotubes/graphene oxide/MoS2 was prepared via hydrothermal method, and its microstructure, phase composition, and enhancement effect on the tribological properties of epoxy were investigated systematically. Results revealed EP-CNTs/GO/MoS2 possessed the lowest friction coefficient and wear rate than EP and its other composite coatings reinforced by single filler or binary hybrids. In particular, its friction coefficient and wear rate were 0.042 and 3.44×10-5mm3/Nm, respectively, which were reduced by up to 90 % and 95% compared to those of pure-EP. And this was mainly attributed to uniform dispersion of CNTs, GO, MoS2 in CNTs/GO/MoS2 hybrid, and load-carrying capacity of CNTs and GO, self-lubricating effect of MoS2, as well as formation of transfer film onto counterpart surface.
       
  • The Effect of CNT-Reinforced Polyurethane Foam Cores to Flexural
           Properties of Sandwich Composites
    • Abstract: Publication date: Available online 21 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Cigdem Caglayan, Idris Gurkan, Sila Gungor, Hulya CebeciAbstractIn foam cored sandwich composites, it is crucial to understand micromechanical characteristics of foam in relation with its properties to understand synergetic effects of adding nanomaterials such as CNTs. In this study, effects of CNT dispersion and distribution on cell morphology and foamability of rigid polyurethane (PU), which is directly related to micro-structure and mechanical performance of overall structures were investigated. Raw and functional CNTs were added to rigid polyurethane foams up to 0.2 wt.% and their compressive strength is evaluated. The results showed that dispersion media such as PMDI with low viscosity revealed a better CNT dispersion and resulted with an enhancement of 13% in compressive strength compared to neat PU foams. This enhancement in foam core properties reflected in sandwich composites with an enhancement around 30% in both core shear and face ultimate strength. Hence, core shear found to be the common failure mechanism for all sandwich composites
       
  • Mechanical and tribological properties of a novel hydrogel composite
           reinforced by three-dimensional woven textiles as a functional synthetic
           cartilage
    • Abstract: Publication date: Available online 21 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Mohammadreza Arjmandi, Maziar Ramezani, Tim Bolle, Gesine Köppe, Thomas Gries, Thomas NeitzertAbstractHydrogels have been studied extensively as a potential cartilage replacement candidate as they are biocompatible, and can mimic the lubrication mechanisms found in cartilage tissue. As for the mechanical properties, there is still room for improvement. In the current research, two different three-dimensional weave patterns were developed and produced out of biocompatible polymers to reinforce the hydrogel matrix. Inspired by the articular cartilage tissue, the woven preforms featured a through-the-thickness stiffness gradient, and could resist delamination. Experiments were conducted on the hydrogel composites. Infiltration of hydrogel into the woven fabric led to a decrease in surface roughness when compared to neat textiles, and an increase in load-to-failure capacity. The wear rate and friction coefficient of the reinforced hydrogel matrix were greatly reduced under the range of applied loads and sliding velocities. These promising results are attributed to the synergistic interaction between the fiber phase and the hydrogel matrix.
       
  • Unloading during the infusion process: direct measurement of the
           dual-scale fibrous microstructure evolution with X-ray computed tomography
           
    • Abstract: Publication date: Available online 20 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Julie Hemmer, Christian Burtin, Sébastien Comas-Cardona, Christophe Binetruy, Thibaut Savart, Arthur BabeauAbstractComposites manufacturing using the infusion process involves an unloading phenomenon due to the vacuum bag flexibility. Additionally, during impregnation, woven or non-crimp fabrics exhibit a dual-scale flow. Usual modeling of both phenomena assumes that the fibrous preform is a continuous medium with a varying permeability. Nonetheless, the permeability is affected by the meso-pores size and spatial distribution, which depend on the compaction state. This paper proposes an experimental method to quantify the evolution of a given dual-scale fibrous microstructure under several controlled flow-induced compaction states. A downsized setup has been designed to conduct in situ infusion of quasi-unidirectional fabrics inside a X-ray Computed Tomography device. The downsized setup reproduces large scale infusion phenomena. Using image processing tools, it is observed that, while the stack thickness increases between dry and saturated states, tows swell and displace. The impact of this microstructural reorganization on the in-plane permeability is also identified.
       
  • Thermal and mechanical properties of soda lignin/HDPE blends
    • Abstract: Publication date: Available online 18 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Javad Sameni, Shaffiq A. Jaffer, Mohini SainAbstractEnvironmental friendlier polymer blends are targeted by the packaging and automotive industry at comparable or lower cost through the use of renewable resources. Non-wood soda (sulfur-free) lignin was blended with high density polyethylene (HDPE) at 10, 20 and 30% w/w at the mixing temperature of 150°C which is approximately: 20°C above the melting point of HDPE, 20°C above softening temperature of lignin and 20°C below degradation temperature of lignin. Addition of soda lignin to HDPE matrix at a proper processing temperature resulted in blends with improved tensile and flexural strength as well as the moduli (Young's and flexural) compared to the properties of virgin HDPE. Thermal studies showed that the melting temperature and degradation temperature of the blends were decreased by addition of lignin. Maleic anhydride-grafted-polyethylene (MAPE) was used as compatibilizer in the blends, however the mechanical properties of the blends were not improved by addition of MAPE.
       
  • Effects of Tow-to-tow Gaps in Composite Laminates Fabricated via Automated
           Fiber Placement
    • Abstract: Publication date: Available online 17 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): William E. Guin, Justin R. Jackson, Cameron M. BosleyAbstractAutomated fiber placement (AFP) is a commonly used manufacturing technique for large-scale polymer matrix composite (PMC) components. Given their nature, AFP systems are typically used to lay up large-scale components in production environments. As such, AFP-induced defects tend to arise over the course of any given build. The often-inconspicuous nature of these defects, coupled with an incomplete understanding of their consequences, represents cause for concern for AFP users. This study examines the effects of one of the most common AFP-induced defects: tow-to-tow gaps. Results show that mechanical performance can be affected by the presence of systematic tow-to-tow gaps, while the presence of incidental gapping is largely inconsequential. In cases where declines in mechanical performance are observed, the primary culprit is shown to be fiber waviness. As such, results also show that where tow-to-tow gaps have an influence on the mechanical properties of composite laminates, performance varies with loading mode.
       
  • Mechanical, Morphological, and Water Absorption Properties of a New Hybrid
           Composite Material made from 4 Harness Satin Woven Carbon Fibres and Flax
           Fibres in an Epoxy Matrix
    • Abstract: Publication date: Available online 17 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Zainab Al-Hajaj, Radovan Zdero, Habiba BougheraraAbstractThis study characterized the mechanical, morphological, and water absorption properties of a new hybrid composite material made of a Type A configuration (i.e. [0-90C2/0F12/0-90C2]) of 4 harness satin woven carbon fibres (i.e. alternating fibre bundles in a 3 over / 1 under weave with bundles at 0° and 90°) plus commercially designated “unidirectional” flax fibres, as well as a Type B configuration (i.e. [0-90C2/±45F6S/0-90C2]) of 4 harness satin woven carbon and ±45° alternating flax fibres, both in an epoxy matrix. Mechanical test measured elastic modulus, shear modulus, ultimate normal strength, or ultimate shear strength for tension, compression, bending, and torsion, as well as Rockwell E hardness. Scanning electron microscopy provided void, fibre, and matrix fractions per volume. Water absorption tests measured water weight uptake at saturation and Fickian diffusion coefficient. This new hybrid composite may be suitable for various research and industrial applications.
       
  • Influence of temperature and impact energy on low velocity impact damage
           severity in CFRP
    • Abstract: Publication date: Available online 14 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Johann Körbelin, Manuel Derra, Bodo FiedlerAbstractThis study focuses on the effect of temperature and impact energy on the damage in CFRP under low velocity impact. Quasi-isotropic laminates with a thickness of 4.1 mm were impacted with energies between 8 and 21J at temperatures ranging between 20 and 80°C. The resulting damage was assessed using ultrasonic C-scans, radiography and confocal microscopy. The residual strength was evaluated utilizing compressive tests at 20°C. It was found that delamination size is decreasing with increasing temperature. However, severe fibre failure on the impacted side occurs at elevated temperatures. This increases the visual damage detectability on the impacted side heavily while decreasing it on the opposite side. Nevertheless, the residual compressive strength is mainly dependent on the delamination area. Different impact energies can have the same effect on the residual strength, when impacted at different temperatures. As a result, visual damage severity does not correlate with the residual compressive strength.
       
  • Accelerated Microwave Curing of Fibre-reinforced Thermoset Polymer
           
    • Abstract: Publication date: Available online 12 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Chinedum Ogonna Mgbemena, Danning Li, Meng-Fang Lin, Paul Daniel Liddel, Kali Babu Katnam, Vijay Thakur Kumar, Hamed Yazdani NezhadAbstractAccelerated curing of high performance fibre-reinforced polymer (FRP) composites via microwave heating or radiation, which can significantly reduce cure time and increase energy efficiency, has several major challenges (e.g. uneven depth of radiation penetration, reinforcing fibre shielding, uneven curing, introduction of hot spots etc). This article reviews the current scientific challenges with microwave curing of FRP composites considering the underlying physics of microwave radiation absorption in thermoset-matrix composites. The fundamental principles behind efficient accelerated curing of composites using microwave radiation heating are reviewed and presented, especially focusing on the relation between penetration depth, microwave frequency, dielectric properties and cure degree. Based on this review, major factors influencing microwave curing of thermoset-matrix composites are identified, and recommendations for efficient cure cycle design are provided.
       
  • Damage mechanisms under static and fatigue loading at locally compacted
           regions in a high pressure resin transfer molded carbon fiber non-crimp
           fabric
    • Abstract: Publication date: Available online 11 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Susanne Nonn, Christoph Kralovec, Martin SchagerlAbstractManufacturing defects are an issue of composite manufacturing processes. Local clamping is proposed to prevent fiber washout during high pressure resin transfer molding of non-crimp fabrics. At the clamping regions the material is compacted by through-the-thickness compression. The current work investigates the mechanical performance of such regions under static and fatigue loading. Two typical manufacturing defects are intrinsic to the compacted regions: fiber undulation and resin starved/dry spots. In component tests the thereby generated damage is monitored using 3D digital image correlation and the complete processes of damage initiation and propagation are analyzed. Static and low cycle fatigue failure are dominated by fiber undulation at the edges of the compacted region, triggering matrix damage and delaminations. High cycle fatigue is dominated by decreasing fiber matrix adhesion within the compacted region, leading to longitudinal splitting and progressive fiber failure. Identification of damage initiation is supported by numerical finite element simulations.
       
  • Enhanced Thermal Conductivity and Electrical Insulation Properties of
           Polymer Composites via Constructing Pglass/CNTs Confined Hybrid Fillers
    • Abstract: Publication date: Available online 8 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Li Zhang, Xingyu Li, Hua Deng, Yao Jing, Qiang FuAbstractThe preparation of thermal conductive and electrical insulating polymer composites has gained extensive interest due to their important applications. The morphological control of functional fillers is thought as an effective approach to achieve this. Herein, a novel method involves the confinement of carbon nanotubes (CNTs) in phosphate glass (Pglass) domains is presented. Due to the large interfacial tension between Pglass and polymer matrix, strong confinement of CNTs can be achieved while CNTs is incorporated into Pglass. Thus, the formation of CNTs conductive networks in polymer matrix can be prohibited in ternary polymer/Pglass/CNTs composites. Comparing with similar composites having high density polyethylene (HDPE) to realize confinement on CNTs, much higher thermal conductivity and much lower electrical conductivity are observed in polymer composites based on polypropylene (PP) containing boron nitride (BN). It is thought that the use of Pglass can provide an effective method for the preparation of thermally conductive and electrically insulating polymer composites.
       
  • Finite Element Modelling of Dyneema® Composites: From Quasi-Static Rates
           to Ballistic Impact
    • Abstract: Publication date: Available online 7 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Mark K. Hazzard, Richard S. Trask, Ulrich Heisserer, Mirre Van Der Kamp, Stephen R. HallettAbstractA finite element methodology to predict the behaviour of Dyneema® HB26 fibre composites at quasi-static rates of deformation, under low velocity drop weight impact, and high velocity ballistic impact has been developed. A homogenised sub-laminate approach separated by cohesive tied contacts was employed. The modelling approach uses readily available material models within LS-DYNA, and is validated against experimental observations in literature. Plane-strain beam models provide accurate mechanisms of deformation, largely controlled through Mode II cohesive interface properties and kink band formation. Low velocity drop weight impact models of HB26 give force-deflection within 10% of new experimental observations, with in-plane shear strain contour plots from models directly compared with experimental Digital Image Correlation (DIC). Ballistic impact models utilising rate effects and damage showed similar modes of deformation and failure to that observed in literature, and provide a good approximation for ballistic limit under 600 m/s impact speed.
       
  • Effect of through-thickness electrical conductivity of CFRPs on lightning
           strike damages
    • Abstract: Publication date: Available online 7 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Vipin Kumar, Tomohiro Yokozeki, Takao Okada, Yoshiyasu Hirano, Teruya Goto, Tatsuhiro Takahashi, Toshio OgasawaraAbstractMaking carbon fiber reinforced plastics electrically conductive is an amended solution to the current lightning strike protection technology. However, optimization of the through-thickness electrical conductivity to meet a safety requirement of aircraft against lightning strikes remains unexplored. In this work, four carbon fiber reinforced plastics panels with different through-thickness electrical conductivity were fabricated using a polyaniline-based conductive resin. Their through-thickness electrical conductivity was tailored to achieve specific values using a controlled thermal treatment. The fabricated carbon fiber reinforced plastics panels were tested against a simulated lightning current of 40 kA, and the influence of through-thickness electrical properties on the performance of lightning strike protection was studied. Thermography data and ultrasonic non-destructive testing images confirmed least damage on the sample with higher electrical conductivity. Specimen with through-thickness electrical conductivity of around 110 S/m was able to retain about 92 % of the residual flexural strength after the lightning test.
       
  • Single-layer temperature-adjusting transition method to improve the bond
           strength of 3D-printed PCL/PLA parts
    • Abstract: Publication date: Available online 7 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Weiyi Lin, Hongyao shen, Guanhua Xu, Linchu Zhang, Jianzhong Fu, Xiaolei DengAbstractAlthough multi-material fused deposition modelling (FDM) has shown good progress and potential for industrial and scientific development, differences in physical and chemical properties cause weak bond strength between dissimilar materials in multi-material FDM parts. This paper proposes a single-layer temperature-adjusting transition (SLTAT) method to improve bond strength between dissimilar materials with different melting temperatures by adjusting the bonding-layer temperature. Herein, the bonding-layer temperature effects on the tensile strength of polycaprolactone (PCL)/polylactic acid (PLA) structures were investigated. PCL/PLA parts prepared with this method had 28% higher tensile strength than unprocessed parts when the bonding-layer temperature was 130°C. Bonding mechanism was proposed to explain the failure modes of the PCL/PLA parts after tensile testing. Freeze-fractured surfaces of SLTAT-processed PCL/PLA specimens were observed to better understand the correlations between bonding-layer temperature and tensile strength. This approach is promising to apply in ordinary multi-material FDM processing without adding additional equipment or compromising dimensional accuracy.
       
  • Hierarchical structures of CNT@basalt fabric for tribological and
           electrical applications: Impact of growth temperature and time during
           synthesis
    • Abstract: Publication date: Available online 6 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Garima Mittal, Kyong Y. RheeAbstractHierarchical structures are continuously drawing the attention of researchers to replace traditional polymeric structures. Here, hierarchical structures of basalt fabric coated with CNTs (BF-CNTs) were prepared using chemical vapor deposition (CVD). To understand the effects of growth temperature and growth time during chemical vapor deposition on grafting of CNTs on basalt fabric, two cases were considered i.e., grafting at 600, 650, and 700 °C for 30 min and at 650 °C for 30, 60, and 120 min. BF-CNTs were characterized using XRD, HR-Raman, FE-SEM, and DSC. Further, BF-CNTs were sandwiched with epoxy via a hand lay-up method and their effects on the tribological and electrical properties of epoxy composites were analyzed. The results show the composites with BF-CNT prepared at higher growth temperature and for longer time possessed a lower coefficient of friction (CoF), lower wear loss, lower volume resistivity, and improved electromagnetic interference shielding effectiveness (EMI SE).
       
  • CAE method for compression molding of carbon fiber-reinforced
           thermoplastic composite using bulk materials
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Yuyang Song, Umesh Gandhi, Takeshi Sekito, Uday K. Vaidya, Srikar Vallury, Anthony Yang, Tim OsswaldAbstractThere has been great interest in using fiber-reinforced polymer composites to develop lightweight components for automotive applications. Compression molding of carbon fiber (CF) reinforced thermoplastic is one of the preferred processes, as it offers the opportunity to maintain a longer fiber length and higher volume production. We have developed a unique computer aided engineering (CAE) method by utilizing viscoelastic structural analysis to accurately predict the warpage behavior of fiber-reinforced thermoplastic material under the compression molding process from a bulk charge format. A prototype structure with complex geometry was designed and manufactured for validation purposes. The fiber orientation and warpage results from both the CAE and actual part were compared to verify the accuracy of the CAE method. Additional studies related to the charge footprint effect were also conducted for the compression molding process on the same materials. The developed method and tools are expected to help in expediting the development of lightweight carbon fiber-reinforced thermoplastic parts.
       
  • A novel thermoplastic sizing containing graphene oxide functionalized with
           structural analogs of matrix for improving interfacial adhesion of CF/PES
           composites
    • Abstract: Publication date: Available online 4 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Liu Liu, Fei Yan, Ming Li, Mengjie Zhang, Linghan Xiao, Lei Shang, Yuhui AoAbstractA novel complex sizing containing PES and functionalized GO was prepared for improving interfacial adhesion of CF/PES composites. To achieve better dispersion of GO in sizing and improve the interfacial compatibility of composites, GO were covalently functionalized by 4, 4'-diaminodiphenyl sulfone (DDS) and 4, 4'-diaminodiphenyl ether, which have similar chemical structures to PES matrix. SEM, dynamic contact angle and TGA tests showed that functionalized GO were closely attached to the CF surface, and the surface energy as well as the thermal stability of CF were greatly increased. Among all the sizings, PES/GO-DDS exhibited the best reinforcing effect, revealing a significant increase of 74.1% in IFSS and 40.1% in ILSS as compared with un-sized CF. Notably, the variation trend of mechanical properties was accordant with the interfacial strength. Moreover, the interface enhancement mechanisms were proposed, the increased interfacial adhesion was benefited from the positive effect of interface layer.
       
  • Fabricating High-Quality VARTM Laminates by Magnetic Consolidation:
           Experiments and Process Model
    • Abstract: Publication date: Available online 3 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Mehrad Amirkhosravi, Maya Pishvar, M. Cengiz AltanAbstractIn recently developed magnet assisted composite manufacturing (MACM) processes, a magnetic consolidation pressure is applied on composite laminates by a set of permanent magnets during fabrication. This magnetic pressure was shown to provide considerable benefits such as increased fiber volume fraction, improved mechanical properties, and reduced void content in wet lay-up/vacuum bag processes. In this article, the effectiveness of MACM to fabricate high-quality vacuum assisted resin transfer molding (VARTM) laminates is investigated and a new, transient process model for MACM is introduced. Towards this goal, 6-, 12-, and 18-ply, random mat E-glass/epoxy composite laminates were fabricated by placing Neodymium Iron Boron (NdFeB) permanent magnets on the vacuum bag either after or before the resin infusion. In both scenarios, the magnetic pressure was shown to considerably improve surface quality, reduce laminate thickness, and increase fiber volume fraction to above 50%. The flexural strength of the 6-, 12-, and 18-ply laminates was improved by more than 28%, 23%, and 11%, respectively. The flexural modulus was also enhanced substantially, at least by 41%, 34%, and 23%, for the same set of laminates. Applying the magnets before infusion increased the filling time due to decreased fabric permeability, and consequently reduced the process-induced voids to under 1%, while the laminates made by conventional VARTM contained up to 6% voids. The transient magnetic consolidation model developed for this process is shown to accurately predict the fiber volume fraction and final laminate thickness for all the fabricated laminates.
       
  • Interlaminar fracture toughness of hybrid woven Carbon-Dyneema composites
    • Abstract: Publication date: Available online 1 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Y. Zhao, M. Cao, W.P. Lum, V.B.C. Tan, T.E. TayAbstractThis study investigates the delamination behavior of carbon-Dyneema hybrid composites with different hybridization schemes. It is found that hybridization improves both mode I and mode II fracture toughness of carbon-Dyneema interfaces. This is attributed to the large yarn size of Dyneema fibers, which results in an increase of the resin rich thickness at the interface between plies. The fracture surface with adjacent Dyneema fibers exhibits high surface roughness leading to higher fracture toughness. Additionally, the thicker resin-rich interface promotes a cohesive-type failure within the resin rich zone, while fracture in the thinner carbon-carbon interface is dominated by adhesive-type failure. The mode II delamination of the carbon-Dyneema interface shows an increasing resistance curve, which may be attributed to friction between the rough delamination surfaces. The results demonstrate that hybridization with Dyneema could potentially be an effective toughening technique for thermoset carbon fiber composites.
       
  • Interfacial performance and fracture patterns of 3D printed continuous
           carbon fiber with sizing reinforced PA6 composites
    • Abstract: Publication date: Available online 1 September 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Tengfei Liu, Xiaoyong Tian, Manyu Zhang, Dilmurat Abliz, Dichen Li, Gerhard ZiegmannAbstractA sizing procedure was utilized in 3D printing of continuous fiber reinforced thermoplastic composites (CFRTPCs) process to improve their interfacial performance. The sized carbon fiber (SCF) reinforced PA6 (SCF/PA6) was successfully printed, exhibiting 42.2% higher interlaminar shear strength (ILSS) than that of virgin carbon fiber (VCF) reinforced PA6 (VCF/PA6). The influence of sizing and printing process on interfacial performance and fracture patterns was studied systematically. Weak interfacial performance with large fiber pull-out was observed in VCF/PA6. Strong interfacial performance with fiber cut-off arose in SCF/PA6 under excessive forming pressure. They were both detrimental to mechanical properties. Moderate interfacial performance with finite fiber pull-out in SCF/PA6 under decent forming pressure achieved maximum 82% and 246% increasement in flexural strength and modulus respectively. The interface optimization strategy for 3D printed CFRTPCs was set up, which could speed up the technological progress for practical industrial applications.
       
  • Electromagnetic wave absorption properties of helical carbon fibers and
           expanded glass beads filled cement-based composites
    • Abstract: Publication date: Available online 31 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Shuai Xie, Zhijiang Ji, Bin Li, Liancheng Zhu, Jing WangAbstractThe cement based composites for electromagnetic (EM) wave absorption were prepared by introducing helical carbon fibers (HCF) and expanded glass beads (EGB), and the influences of HCF mass fraction, EGB volume fraction, and sample thickness on the EM reflection loss were investigated in 2-18 GHz. Results indicate that the EM wave absorption performance increases at first and then decreases with the increase of HCF mass fraction. And the values of absorption peaks and effective bandwidth below -10 dB increase monotonically with the increase of EGB volume fraction. The cement based composites with 2 wt% HCF, 60 vol% EGB, and 20 mm thickness exhibits optimal EM wave absorption performance. The minimum reflection loss can be -17.8 dB and the effective bandwidth for -10 dB reaches 13 GHz. The high EM absorbing capacity and wide effective bandwidth can be attributed to the unique chiral structure of HCF and low permittivity of EGB.
       
  • Temperature effect on dynamic wetting of cellulosic substrates by molten
           polymers for composite processing
    • Abstract: Publication date: Available online 28 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Monica Francesca Pucci, Benoît Duchemin, Moussa Gomina, Joël BréardAbstractImpregnation of plant fibre reinforcements by a molten polymer involves many phenomena still poorly understood, related to the solid morphology and its surface chemistry, but also to the temperature effect on liquid properties and solid/liquid interactions. The present work focuses on the temperature effect on forced dynamic wetting, using the Wilhelmy method and two model materials: a cellulosic film and two totally wetting paraffin oils. The results show that the dynamic contact angle vs. the capillary number (Ca) plot appears as a master curve. This curve is split in two domains. The domain associated with Ca>10-3 is well described by the hydrodynamic approach. The domain with Ca
       
  • Effects of Microstructure Morphology on Stress in Mechanoluminescent
           Particles: Micro CT Image-Based 3D Finite Element Analyses
    • Abstract: Publication date: Available online 25 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yeonghwan Kim, Gun Jin YunAbstractIn this paper, a novel investigation on the effect of microstructure morphology on the stress within mechanoluminescent (ML) particles is presented. It is known that the light intensity of ML materials is proportional to deviatoric stresses in the particles. A set of digital image processing techniques is introduced to compute quantitative morphological features of irregular shaped particles with high weight fraction from micro computed tomography (CT) images. The resulting 3D finite element (FE) model for a representative volume element (RVE) holds realistic shapes of ML particles providing volume-averaged von Mises stress (VAS). A total 13 morphological variables are classified into three groups, size, shape and distribution-dependent groups and statistically correlated with VAS from 3D FE analyses. As results, statistically independent and microstructure-sensitive variables for ML composites are identified. The morphological variables can be utilized for reconstruction of statistically equivalent volume elements and applied for microstructure-sensitive design of ML composites.
       
  • Evaluating the number of fibre orientations required in homogenization
           schemes to predict the elastic response of long fibre sheet moulding
           compound composites from X-ray computed tomography measured fibre
           orientation distributions
    • Abstract: Publication date: Available online 25 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Trevor Sabiston, Pascal Pinter, Julie Lévesque, Kay André Weidenmann, Kaan InalAbstractFor predicting the mechanical response of mis aligned short fibre composite materials a two step homogenization procedure coupled with orientation averaging of the elastic material properties is often used. Orientation averaging is not valid for long fibre composites due to non-symmetric strain localization tensors. A method to homogenize the stress for mis aligned long fibre composites using the Functionally Graded Interphase (FGI) approach is presented and the results are compared to two step Mori Tanaka homogenization. The microstructure of long fibre Sheet Moulding Compound (SMC) composite is evaluated using X-ray micro computed tomography. The measured fibre orientation distributions are used to evaluate the number of representative fibre orientations required to predict the stress state of the SMC due to applied strains. It is found that 60 orientations are required to capture the stress response of the long fibre SMC composite using the FGI model and two step Mori Tanaka model.
       
  • Microstructure and mechanical performance of graphene reinforced
           cementitious composites
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Gen Li, J.B. Yuan, Y.H. Zhang, N. Zhang, K.M. LiewAbstractAn experimental investigation of the microstructure and mechanical properties of graphene-reinforced cementitious composites is presented. The early-age microstructure of the grapheme/cement composites was examined by scanning electron microscopy (SEM). The SEM images revealed that ettringite, C-S-H gel and other hydration crystals were connected by graphene sheets, which formed a 3-D structure that could bridge the cracks and fill the pores in cement matrix. With the increase of hydration ages, the 3-D structure became more complicated and connection between the graphene and cement hydrates became stronger. The X-ray powder diffraction (XRD) analysis suggested that the amount of ettringite increased with the increase of graphene content, indicating that graphene sheets could promote the formation of ettringite. In addition, the mechanical strength of graphene/cement matrix was measured. The reinforcing effect of graphene is most obvious with the addition of 0.03 wt.% graphene, with which the flexural strength increased by 40%.
       
  • Heat-resistant sandwich structure with carbon fiber-polyimide composite
           faces and a carbon foam core
    • Abstract: Publication date: Available online 24 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Toshio Ogasawara, Shingo Ayabe, Yuichi Ishida, Takuya Aoki, Yuki KubotaAbstractThis paper presents the processing and properties of a new heat-resistant sandwich structure, which consist of carbon fiber-polyimide composite face sheets and a carbon foam core. A novel phenylethynyl-terminated imide oligomer (TriA-X) was applied for both matrix resin and film adhesive. Mechanical properties of the sandwich structures were evaluated using flat-wise tension tests, and three-point bending tests. Bending strength of the sandwich panel was almost constant up to 250 °C. The bending rigidity of the sandwich panels showed good agreement with the numerical result by considering the temperature-dependent elastic modulus of CFRP and carbon foam. Thermal insulating properties of the sandwich structures were evaluated using infrared lamp heating tests in a vacuum chamber, resulting in good thermal insulating property. Heat transfer analysis of the sandwich structures was conducted using finite element method. Comparison with heating test results, the validity of the heat transfer analysis model was successfully demonstrated.
       
  • The Effects of Fiber Orientation and Adhesives on Tensile Properties of
           Carbon Fiber Reinforced Polymer Matrix Composite with Embedded
           Nickel-Titanium Shape Memory Alloys
    • Abstract: Publication date: Available online 24 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Derek Quade, Sadhan Jana, Gregory Morscher, Manigandan Kannan, Linda McCorkleAbstractTensile tests of Nickel-titanium (NiTi) shape memory alloys (SMA) embedded within carbon fiber reinforced polymer matrix composite (CFRP/PMC) laminates were evaluated with simultaneous monitoring of modal acoustic emissions (MAE). Three different layup configurations utilizing two different thin film adhesives were applied to bond the materials. Ultimate tensile strengths, strains, and moduli were obtained along with cumulative AE energy of events and specimen failure location. Scanning electron microscopy was used to examine the break areas of the specimens post-test. Microscopy was used to validate failure locations revealed from MAE analysis. A unique finding within this research showed that 90° plies in the outer ply gave the strongest acoustic signals as well as the cleanest fracture of the specimens tested. Overlapping 0° ply layers surrounding the SMA was found to be the best scenario to prevent failure of the specimen itself.
       
  • Experimental and numerical investigation of the shear behaviour of
           infiltrated woven fabrics
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Christian Poppe, Dominik Dörr, Frank Henning, Luise KärgerAbstractWet compression moulding (WCM) as a promising alternative to resin transfer moulding (RTM) provides high-volume production potential for continuously fibre reinforced composite components. Lower cycle times are possible due to the parallelisation of the process steps draping, infiltration and curing during moulding. Although experimental and theoretical investigations indicate a strong mutual dependency arising from this parallelisation, no material characterisation set-ups for textiles infiltrated with low viscous fluids are yet available, which limits a physical-based process understanding and prevents the development of proper simulation tools. Therefore, a modified bias-extension test set-up is presented, which enables infiltrated shear characterisation of engineering textiles. Experimental studies on an infiltrated woven fabric reveal both, rate- and viscosity-dependent shear behaviour. The process relevance is evaluated on part level within a numerical study by means of FE-forming simulation. Results reveal a significant impact on the global and local shear angle distribution, especially during forming.
       
  • Characterisation of Tack for Uni-Directional Prepreg Tape Employing a
           Continuous Application-and-Peel Test Method
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Andreas Endruweit, Gabriel Choong, Sayata Ghose, Brice A. Johnson, Douglas R. Younkin, Nicholas A. Warrior, Davide S.A. De FocatiisAbstractEmploying a test method with coupled application and peel phases, tack was characterised for a UD prepreg tape. Different aspects of tack were explored by varying test parameters and material condition. In addition, different surface combinations were studied. In general, the test parameters, feed rate and temperature, affect the balance between cohesion within the resin and adhesion between resin and substrate. Exploring a range of parameters is required to understand the effect of viscoelastic resin properties on tack. The application pressure determines the true contact area between prepreg and substrate and hence affects tack. Changes in molecular mobility in the resin related to specimen conditioning, i.e. ageing or moisture uptake, result in maximum tack to occur at lower or higher feed rates, respectively. Differences in tack for different material combinations can be attributed to different molecular interactions at the contact interfaces and different resin distributions on the prepreg surfaces.
       
  • Corrigendum to “Improvement of cellulose acetate dimensional stability
           by chemical crosslinking with cellulose nanocrystals” [Compos. Part A:
           Appl. Sci. Manuf. 113 (2018) 105–113]
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Liliane C. Battirola, Daniela M. Zanata, Maria C. Gonçalves
       
  • Effect of prepreg gaps and overlaps on mechanical properties of fibre
           metal laminates
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): M. Abouhamzeh, D. Nardi, R. Leonard, J. SinkeAbstractDuring the automated manufacturing of fibre reinforced laminates, defects can be produced. Gaps and overlaps between adjacent prepreg layers can be produced in composites during the tape-layup process. However, the topic is not yet studied for hybrid materials, in which metal sheets and thin prepreg layers lead to different effects due to the defects than in full composites. Here, the effect of gaps and overlaps on the mechanical properties of the Fibre metal laminates (FML) is evaluated. Specimens are manufactured with a specified width of gaps/overlaps and the mechanical performance of the panels is evaluated by some selected mechanical tests. Gaps show to have a considerable effect on the mechanical performance of FML. Compression strength of samples with overlaps was rather increased. Discussions are presented on the influence on each mechanical property according to the severity of the defect (gaps/overlap) and the failure mode(s) under consideration.
       
  • Investigation and modeling of tensile failure properties of wound ceramic
           matrix composites
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yuan Shi, Neraj Jain, Dietmar KochAbstractThe paper presents enhanced studies of investigation and modeling of failure properties for wound ceramic matrix composites with varied fiber orientations under tensile loading. Based on mechanical tests and microstructure analysis, the characteristics of a virtual equivalent unidirectional layer (UD-layer) were examined and treated as input for modified Tsai-Wu failure criterion. In order to predict the mechanical properties with more accuracy, particular features of the investigated material have to be taken into consideration: definition of two material modeling groups based on the analysis of microstructure; interaction between failure strength and strain through inelastic deformation; inclusion of inhomogeneities created due to the manufacturing process in the analytical model. Based on the good correlation between the experiments and the modeling results, it can be shown that modeling approaches, considering the above mentioned particular material features, allow a very accurate prediction of the mechanical properties under in-plane tensile loading of CMC laminates.
       
  • Water vapor and oxygen barrier properties of extrusion-blown poly(lactic
           acid)/cellulose nanocrystals nanocomposite films
    • Abstract: Publication date: Available online 20 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Sonal S. Karkhanis, Nicole M. Stark, Ronald C. Sabo, Laurent M. MatuanaAbstractThis paper examined the effect of cellulose nanocrystal (CNC) content on water vapor permeability (WVP) and oxygen permeability (OP) of extrusion-blown poly(lactic acid) (PLA) films recorded at various temperatures and relative humidities. While both WVP and OP followed the Arrhenius equation, the WVP decreased with increasing temperature whereas an opposite trend was observed for OP, resulting in negative activation energy (Ep) for WVP but positive Ep for OP, regardless of CNC content. However, the Ep for both WVP and OP increased by adding CNC into PLA matrix. WVP was not affected by the relative humidity agreeing with Fick’s law. Nanocomposite films had lower WVP (∼40%) and OP (∼75%) than neat PLA films because of the tortuosity effect created by the presence of highly crystalline CNCs in the nanocomposites, which increased PLA’s degree of crystallinity. Indeed, the values of WVP and OP negatively correlated with increased crystallinity, irrespective of testing conditions.
       
  • Fiber Orientation Measurement from Mesoscale CT Scans of Prepreg Platelet
           Molded Composites
    • Abstract: Publication date: Available online 20 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Benjamin R. Denos, Drew E. Sommer, Anthony J. Favaloro, R. Byron Pipes, William B. AveryAbstractX-ray computed tomography (CT) analysis is used to measure the heterogeneous fiber orientation fields in a 20cm3 composite bracket made from prepreg platelet-based molding compound (PPMC). The as-molded mesostructure of the complete geometry is captured using material density gradients in 50µm resolution CT scans without the need to resolve individual fibers. Fiber collimation and physical density gradients within intact platelets of this material system facilitates nondestructive assessment of average local fiber orientation at the component scale. Microscopy-based validation of the local orientation measurements indicate the accuracy that can be attained utilizing the density-based structure tensor CT analysis method. Local orientation field measurements for the complete geometry can be mapped into a “digital twin” model, for purposes such as experimental performance simulation and validation of molding process orientation state predictions. Composite designers, analysts, and material suppliers can employ this methodology to more confidently utilize PPMCs and morphologically similar composite material systems.
       
  • Interfacial characteristics of carbon nanotube-polymer composites: A
           review
    • Abstract: Publication date: Available online 19 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Junjie Chen, Longfei Yan, Wenya Song, Deguang XuAbstractRecent research on the interfacial characteristics of carbon nanotube-polymer nanocomposites is reviewed. The state of knowledge in the characteristics of the interface between the carbon nanotubes and the polymer matrix is presented. Emphasis is placed on the progress of the relationships between interfacial characteristics and nanocomposite properties. Research methodologies used in studying the characteristics of the interface are described. Challenges and opportunities associated with the characterization of the interface are discussed. Critical issues in the research on the interactions at the interface are reviewed, and the advantages and disadvantages of covalent and non-covalent functionalization of carbon nanotubes are delineated. Furthermore, how the properties of the nanocomposites depend on the characteristics of the interface is discussed. The latest developments of the techniques for interface characterization are reviewed, and the strengths and limitations of these techniques are discussed. Potential topics of oncoming focus are finally highlighted.
       
  • Simulation of tensile behavior of plant fibers using the Discrete Element
           Method (DEM)
    • Abstract: Publication date: Available online 19 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Vahid Sadrmanesh, Ying ChenAbstractTensile behaviors of plant fibers significantly affect mechanical performance of the fiber reinforced composites. A numerical model was developed to simulate the tensile behavior of a plant fiber using the Discrete Element Method (DEM). The model fiber was constructed with spherical particles bonded together. The model outputs were tensile strength (σmacro) and Young’s modulus (Emacro) of fiber. Tensile tests were conducted to measure these two properties of hemp fiber to calibrate model micro-parameters. Simulation results showed that the most influential micro-parameters were micro-strength of the bond (σmicro) and Young’s modulus of particles (Emicro). The following relationships were found: σmicro = 1.89 σmacro and Emicro= 0.99 Emacro. Using the tensile test data of hemp fiber, the calibrated values were 721.81 MPa for σmicro and 19.50 GPa for Emicro. With the results from this study, the micro-parameters can be determined for DE modeling of any plant fibers, such as flax and Jute.
       
  • Effect of carbon fiber oxidization parameters and sizing deposition levels
           on the fiber-matrix interfacial shear strength
    • Abstract: Publication date: Available online 19 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Filip Stojcevski, Timothy B. Hilditch, Thomas R. Gengenbach, Luke C. HendersonAbstractThis paper investigates fifteen fiber types against two epoxy resin systems and the effects of altering electrochemical oxidization conditions and sizing deposition ratio on interfacial shear strength (IFSS). Oxidization current was altered between 0, 2, and 3.4 Amps while sizing deposition ratio was altered between unsized, 1:10, 1:15 and 1:20 parts sizing to water. Desized fibers were also compared against pristine unsized fibers. Results show, a correlation between increasing current and IFSS, however sizing has an optimal ratio for best performance. Improvements through oxidization are attributed to the introduction of oxygenated functional groups on the fiber surface while improvements due to sizing are attributed to the promotion of a chemically active intermediate layer between the fiber and resin. Fiber roughness was seen to play no effect on IFSS. Desized fibers and unsized fibers had similar IFSS results however characterisation shows chemical composition of the fiber surfaces to be very different.
       
  • Non-destructive characterisation of all-polypropylene composites using
           small angle X-ray scattering and polarized Raman spectroscopy
    • Abstract: Publication date: Available online 18 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Katalin Bocz, Kata Enikő Decsov, Attila Farkas, Dániel Vadas, Tamás Bárány, András Wacha, Attila Bóta, György MarosiAbstractSmall angle X-ray scattering (SAXS) and polarized Raman spectroscopy were used to examine the structure of unidirectional all-polypropylene composites prepared at different consolidation temperatures. Analysis of the anisotropy of the X-ray scattering pattern provided a way to quantify the disorientation of the crystallites and a direct correlation has been found between a measure of overall orientation and the Young’s modulus of the composites. In the case of the Raman spectroscopic measurements, the molecular orientation state of the reinforcing PP fibres were evaluated by classical least squares (CLS) modelling with real reference spectra. Strong correlation was evinced between the estimated relative degree of orientation of the reinforcing fibres and the Young’s modulus of the multi-layered all-polypropylene composites. Based on these results, both SAXS and Raman spectroscopy are suitable methods to predict the mechanical performance of all-polymer composites, being especially sensitive to manufacturing and application conditions, in a non-destructive way.
       
  • Temperature effects on the compressive properties and failure mechanisms
           of composite sandwich panel with Y-shaped cores
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Junmeng Zhou, Yu Wang, Jiayi Liu, Jialin Liu, Jie Mei, Wei Huang, Yuling TangAbstractThe effects of temperature on the mechanical properties and failure mechanisms of composite sandwich panel with Y-shaped cores under out-of-plane compression have been studied in this paper. The carbon fiber composite sandwich panel with Y-shaped cores was manufactured by a hot-press method using unidirectional carbon/epoxy prepregs. The out-of-plane compression tests of composite sandwich panels were conducted at temperatures ranging from 20 °C to 200 °C. Then the stress-strain curves, failure modes, compressive stiffness and strength of composite sandwich panel at high temperatures were analyzed and compared with those ones at room temperature. The results have shown that temperature had a significant effect on mechanical properties and failure behaviors of composite sandwich panel. And high temperature resulted in the decreasing of compressive stiffness and strength. Finally, the analytical expressions were presented to predict the compressive stiffness and strength of composite sandwich panel and compared with experimental results at different temperatures.
       
  • Bamboo fibers composites based on styrene-free soybean-oil thermosets
           using methacrylates as reactive diluents
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Ming-en Fei, Wendi Liu, Anming Jia, Yang Ban, Renhui QiuAbstractThe present work aims at preparation of green composites by using bamboo fibers (BFs) as reinforcements and styrene-free soybean-oil based thermosets as matrices. To facilitate the formulation of acrylated epoxidized soybean oil (AESO) resins with a low viscosity and high crosslinking density, two methacrylate monomers, i.e., 1,4-butanediol dimethacrylate (BDDMA) and trimethylolpropane trimethacrylate (TMPTMA) were respectively used as reactive diluents (RDs) for replacing anticipatory carcinogenic styrene. Results indicated that the crosslinking density of AESO resins was improved and their viscosities were reduced simultaneously. The rheological and curing behaviors of AESO resins incorporated with RDs were investigated. The static and dynamic mechanical performance and thermal properties of bamboo fibers composites with the novel AESO resins were tested.
       
  • Selective localization of carbon nanotube and organoclay in biodegradable
           poly(butylene succinate)/polylactide blend-based nanocomposites with
           enhanced rigidity, toughness and electrical conductivity
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Veluri Sivanjineyulu, Kartik Behera, Yen-Hsiang Chang, Fang-Chyou ChiuAbstractCarbon nanotube (CNT) and organo-montmorillonite (15A) were used individually and simultaneously as reinforcing fillers to fabricate poly(butylene succinate)/polylactide (PBS/PLA) blend-based nanocomposites. Poly(butylene succinate-co-lactate) served as compatibilizer for the PBS/PLA blend. Morphological results demonstrated that the added CNT was distributed mainly in the PBS matrix, whereas the added 15A was selectively localized within the dispersed PLA domains. Adding only 15A produced a quasi co-continuous PBS-PLA morphology. DSC results confirmed the nucleation effect of CNT on the crystallization of PBS and PLA, whereas 15A facilitated only the nucleation of PLA. The CNT exerted greater influence than 15A on the samples’ rheological properties. The Young’s modulus and impact strength of the nanocomposites increased up to 4.2 and 2.8 times, respectively, compared with those of the blend. The electrical resistivity of the blend decreased by up to 11 orders at 3 phr CNT loading. The electrical-percolation threshold was constructed at 0.5 phr CNT loading.
       
  • Cell-layer dependent adhesion differences in wood bonds
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Sabine Herzele, Hendrikus W.G. van Herwijnen, Matthias Edler, Wolfgang Gindl-Altmutter, Johannes KonnerthAbstractThe performance of wood adhesives depends on its internal cohesion and the adhesion to the wood surface which is structurally and chemically heterogeneous as it may be formed by different micro-surface, i.e. the compound middle lamella, the secondary cell wall layer, or the lumen surface. This study introduces an experimental protocol to directly evaluate adhesion to each of these micro-surfaces individually. Two wood fiber types presumed to differ in their surface chemistry are used as substrate. The results demonstrate that melamine-urea-formaldehyde adhesive shows excellent adhesion irrespective of the fiber type or micro-surface. While the same is the case for adhesion between untreated wood fiber surfaces and one component polyurethane, higher relative work of indentation between the lignin-rich compound middle lamella surface of medium density fiberboard fiber and one component polyurethane was observed. This observation is corroborated by a reduced polar character of this micro-surface as shown by X-ray photoelectron spectroscopy.
       
  • High breakdown strength and outstanding piezoelectric performance in
           flexible PVDF based percolative nanocomposites through the synergistic
           effect of topological-structure and composition modulations
    • Abstract: Publication date: November 2018Source: Composites Part A: Applied Science and Manufacturing, Volume 114Author(s): Lu Yang, Qiuying Zhao, Ying Hou, Rujie Sun, Meng Cheng, Mingxia Shen, Shaohua Zeng, Hongli Ji, Jinhao QiuAbstractOver decades, the fabrication of flexible poly(vinylidene fluoride) (PVDF) based percolative nanocomposites with high piezoelectric performance is of great concern from both academia and industry. However, the issue of sharply declined breakdown strength in percolative nanocomposites poses an obstacle to realizing the full potential of conductive nanofillers in enhancing piezoelectricity. Herein, we demonstrated that through proper topological structure and composition modulations, notably improved breakdown strength and piezoelectric performance can be achieved in PVDF based percolative nanocomposites. By constructing a sandwiched structure where a layer of high breakdown strength is intercalated between layers containing high content (near percolation threshold) of conductive nanofillers, the breakdown strength of overall nanocomposites is significantly strengthened and thus allows for sufficient poling of outer layers, fulfilling the great potential of conductive nanofillers in yielding piezoelectricity enhancement. A super high piezoelectric coefficient d33 of 48 pC/N is obtained in the optimized sandwich nanocomposites.
       
  • On dynamic response of corrugated sandwich beams with metal foam-filled
           folded plate core subjected to low-velocity impact
    • Abstract: Publication date: Available online 15 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Qinghua Qin, Wei Zhang, Shiyu Liu, Jianfeng Li, Jianxun Zhang, L.H. PohAbstractThe paper focuses on fully clamped corrugated sandwich beams with metal foam-filled folded plate core to investigate its response subjected to low-velocity impact. The yield criteria for the metal foam-filled corrugated sandwich beam cross-section are obtained by considering the strength effects of metal foam and folded plate. Based on the yield criteria, dynamic and quasi-static models are developed to analytically predict the large deflections of corrugated sandwich beams, respectively, which agree well with finite element results. Furthermore, it is shown that the strain hardening of face sheets and folded plate do not significantly influence the low-velocity impact response.
       
  • CNT-reinforced Metal and Steel Nanocomposites: A Comprehensive Assessment
           of Progress and Future Directions
    • Abstract: Publication date: Available online 15 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): A.V. Radha mani, Hon Chung Lau, S. RamakrishnaAbstractCarbon nanotubes (CNT) are rolled graphene sheets and are an exceptional invention in the field of nanotechnology. They have outstanding material characteristics such as high surface-to-volume ratio, high tensile strength, high thermal conductivity, and low density. Carbon nanotubes are many times stronger and yet lighter than steel and other metals, and thus a good candidate for reinforcing them. However the integration of CNTs into a metal or steel matrix is challenging and dispersion uniformity depends on processing parameters. The composite material properties are a function of the uniformity of CNT dispersion, interfacial bonding, CNT weight percent, length and alignment with the matrix. This paper reviews various methods of processing CNT-metal and CNT-steel nanocomposites, and their reported mechanical and material properties. Ways to overcome technical challenges are proposed and potential applications of CNT-steel composites as next generation structural material for the operationally demanding offshore oil petroleum industry are specifically discussed.
       
  • Wrinkle measurement in glass-carbon hybrid laminates comparing ultrasonic
           techniques: A case Study
    • Abstract: Publication date: Available online 15 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Beatriz Larrañaga-Valsero, Robert A. Smith, Rostand B. Tayong, Antonio Fernández-López, Alfredo GüemesAbstractWrinkles, (also known as out-of-plane waviness) are, unfortunately, a common phenomenon that has caused some wind-turbine blades to unexpectedly fail in service. Being able to detect the wrinkles while in the factory will reduce the risk of catastrophic failure and characterising the wrinkles would minimise the repaired area, thus increasing the efficiency of the repair and the design. This work compares the effectiveness of three different ultrasound techniques for detecting and characterising out-of-plane wrinkles in the typical glass-carbon hybrid laminates that are used for wind-turbine blades. The tests samples were manufactured so that the laminates and the defects are representative of those used in the wind-turbine industry. Basic mechanical tests were performed to check the drop in mechanical properties due to wrinkling. The ideal probe frequency was determined as the resonance frequency of the plies using an analytical ultrasonic-propagation model. The three different ultrasound techniques used are: full-matrix capture (FMC) with the total focusing method (TFM), a commercial phased-array instrument and an immersion test with a raster-scanned single-element focused probe. When possible, severity parameters of the wrinkle were measured on the ultrasonic images and compared with the measurements of the actual sample in order to determine which method best characterises such wrinkles and which would be more appropriate to implement in an industrial environment. Not all of the techniques allowed full characterisation of out-of-plane waviness on the specimens. The FMC/TFM method gave better results whilst phased-array technology and single-element immersion testing presented more challenges. An additional enhancement to the TFM imaging was achieved using an Adapted-TFM method with an angle-dependent velocity correction.
       
  • Enhanced mechanical and dielectric properties of an epoxy resin modified
           with hydroxyl-terminated polybutadiene
    • Abstract: Publication date: Available online 14 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Yujia Kou, Wenying Zhou, Bo Li, Lina Dong, Yu-E Duan, Qianwen Hou, Xiangrong Liu, Huiwu Cai, Qingguo Chen, Zhi-Min DangAbstractEpoxy (EP) modified with nonpolar rubbers have the potential to achieve a concurrent improvement in mechanical and dielectric properties, when the EP-rubber interface is properly manipulated. Here we investigate rubber toughened EP based on a non-polar hydroxyl terminated polybutadiene (HTPB), and a coupling agent, dimer fatty acid diisocyanate (DDI), in which the rubber is covalently bonded to the epoxy. The mechanical and dielectric properties can be improved with the addition of HTPB and are maximized at 15 phr of elastomer inclusion. The enhanced mechanical toughness is attributed to the extensive shear yielding induced by a large amount of uniformly dispersed rubber particles; the same morphology can also combine the good insulating properties of HTPB and dielectrically favorable interfaces. These facts along with the reduced dielectric constant and loss for the modified EP suggest that the HTPB-DDI-EP can be used as a promising insulating packaging material for microelectronic applications.
       
  • Polymer Film Dewetting for Fabrication of Out-of-Autoclave Prepreg with
           High Through-Thickness Permeability
    • Abstract: Publication date: Available online 9 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Sarah G. K. Schechter, Timotei Centea, Steven R. NuttAbstractPolymer film dewetting on a substrate (independent of fiber bed architecture) was explored, developed, and demonstrated as a method to produce out-of-autoclave, vacuum bag-only (OoA/VBO) prepregs with high transverse permeability and process robustness. The dimensions of the surface openings created by dewetting were measured, and the percent surface area exposed was calculated. Prepregs were fabricated with continuous and dewetted (discontinuous) films to produce trial laminates. The laminates were cured under both standard and sub-optimal conditions, and were characterized before, during, and after cure. Laminates fabricated with dewetted resin consistently achieved near-zero porosity. In contrast, laminates with continuous film displayed high levels of porosity, particularly during sub-optimal cure. The findings demonstrate that dewetting can be used effectively to produce OoA prepregs with high through-thickness permeability, which can yield porosity-free laminates via VBO processing. Furthermore, these results elucidate aspects of resin dewetting that are critical in the creation of robust OoA prepregs.
       
  • Predicting the non-linear mechanical response of triaxial braided
           composites
    • Abstract: Publication date: Available online 12 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Tobias Wehrkamp-Richter, Nelson V. De Carvalho, Silvestre T. PinhoAbstractIn this paper, the non-linear mechanical response of triaxial braided composites under multiple loading conditions was investigated with a meso-scale simulation strategy. Numerical predictions made by three-dimensional finite element unit cells with a realistic internal geometry in two nesting configurations correlated well with experimental stress-strain curves and damage mechanisms. Although the investigated braid topologies exhibited considerable geometric variability, the unit cell modelling approach with a compacted geometry model built from average input parameters was capable of correctly predicting the homogenised constitutive response, localisation, and damage evolution. Further, the mechanical response was predicted under variable uni-axial off-axis load cases and the effect of the textile topology on the ultimate strength of the material was investigated. Aside from providing a valuable insight into how damage propagation is affected by the meso-structure, the predicted stress-strain curves can be used to calibrate macroscopic material models suitable for large-scale crash simulations of textile composites.
       
  • Recent Advances in Electromagnetic Interference Shielding Properties of
           Metal and Carbon Filler Reinforced Flexible Polymer Composites: A Review
    • Abstract: Publication date: Available online 11 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Sowmya Sankaran, Kalim Deshmukh, M. Basheer Ahamed, S.K. Khadheer PashaAbstractThe rapid proliferation and elevated usage of electronic devices have led to a meteoritic rise in electronic pollutions such as electronic noise, electromagnetic interference (EMI) and radiofrequency interference which leads to improper functioning of electronic devices. Metals and their alloys can serve as the best EMI shielding materials but their heavy weight, high cost and low corrosion resistance have limited their applications in EMI shielding. The emergence of flexible polymer composites have substituted the metal and metal alloy based EMI shielding materials due to their unique features such as superior electrical, dielectric, thermal, mechanical and magnetic properties that are highly useful for suppressing the electromagnetic noises. In this review article, the EMI shielding effectiveness of flexible polymer composites comprising of metals and various forms of carbon nanofillers such as carbon black, carbon nanofibers, carbon nanotubes, graphite, graphene, graphene oxide, graphene nanosheets, graphene nanoribbons and graphene nanoplatelets have been deeply reviewed.
       
  • Effect of Z-Pinning on the Impact Resistance of Composite Laminates with
           Different Layups
    • Abstract: Publication date: Available online 11 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): L. Francesconi, F AymerichAbstractThe paper presents the results of an experimental investigation into the effect of Z-pinning on the impact resistance of composite laminates with different multi-directional layups. Unpinned and pinned [02/902]s, [02/±45]s and [0/±45/90]s carbon/epoxy samples were subjected to low-velocity impacts resulting in damage severities ranging from barely visible damage to full laminate penetration. The responses to impact of the laminates were characterized in terms of damage evolution, load-carrying capacity, and resistance to perforation and penetration. It was found that even though Z-pins are not capable of delaying the onset of delamination, they significantly reduce delamination size for high-energy impacts. Z-pinning improves the resistance to perforation and penetration of [02/902]s, laminates, while it does not significantly affect that of [02/±45]s and [0/±45/90]s samples. The dependence of the efficacy of Z–pins on the laminate layup is attributed to the different distribution of the delaminations through the thickness of the investigated laminates.
       
  • In Situ Growth of Polyphosphazene Particles on Molybdenum Disulfide
           Nanosheets for Flame Retardant and Friction Application
    • Abstract: Publication date: Available online 11 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Shuilai Qiu, Yixin Hu, Yongqian Shi, Yanbei Hou, Yongchun Kan, Fukai Chu, Haibo Sheng, Richard K.K. Yuen, Weiyi XingAbstractHerein, polyphosphazene nanoparticle (PPN) functionalized MoS2 nanosheets have been successfully fabricated through a novel two-step method, involving a simple ball milling of bulk MoS2 powders to acquire exfoliated MoS2 nanolayer, followed by high temperature polymerization to achieve MoS2@PPN nanohybrids. The incorporation of P and N atoms could efficiently reduce the stacking of MoS2 nanolayers and form large number of active sites. It is noted that introducing well-characterized MoS2@PPN nanohybrids significantly improve the flame retardancy of epoxy resin (EP), i.e., 30.7% and 23.6% reductions in peak heat release rate and total heat release, respectively. The friction coefficients testing results reveal that the EP/MoS2@PPN1.0 composite exhibits the lowest friction coefficient value and volume wear rate. The excellent properties of these EP composites result from synergetic coupled effect between PPN and MoS2 ultrathin nanosheets, as well as improved interface interaction between MoS2@PPN and EP matrix.
       
  • Two-matrix Composites: Carbon Fiber Micropultrusions Embedded in Flexible
           Epoxy Matrices
    • Abstract: Publication date: Available online 10 August 2018Source: Composites Part A: Applied Science and ManufacturingAuthor(s): Sebastien J.P. Callens, Otto K. BergsmaAbstractTwo-matrix composites combine fibers with two distinct matrices. This is achieved by impregnating fiber bundles with a high-stiffness matrix and embedding the cured bundles in a flexible matrix. Two-matrix composites have been shown to offer unprecedented combinations of transverse flexibility and longitudinal tensile strength, and could offer improved fiber alignment and manufacturability. Here, we explore this concept further by embedding carbon fiber micropultrusions in flexibilized epoxy matrices and examining the longitudinal compression behavior. Our results on thin-walled rings reveal that the failure mode depends on micropultrusion diameter, with small diameters resulting in micropultrusion kinking and larger diameters in splitting and crushing. Additionally, we find that two-matrix composites can offer higher compression strength than conventional composites with the same flexible matrix, despite a lower fiber volume fraction. The inherent manufacturing advantages and high anisotropy could make two-matrix composites interesting candidates for specific applications, such as morphing wings or additively manufactured composites.
       
 
 
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