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Composites Part B : Engineering
Journal Prestige (SJR): 2.039
Citation Impact (citeScore): 5
Number of Followers: 293  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1359-8368 - ISSN (Online) 1359-8368
Published by Elsevier Homepage  [3161 journals]
  • A facile and industrially feasible one-pot approach to prepare
           graphene-decorated PVC particles and their application in multifunctional
           PVC/graphene composites with segregated structure
    • Abstract: Publication date: Available online 21 January 2020Source: Composites Part B: EngineeringAuthor(s): Libing Wang, Xinyi Wei, Gang Wang, Shuai Zhao, Jian Cui, Ailin Gao, Guangfa Zhang, Yehai YanAbstractDirect hot compression of fillers-decorated polymer particles is the simplest and most developed method for the construction of segregated composites. Herein, graphene was uniformly and firmly decorated onto the surface of polyvinyl chloride (PVC) particles synthesized by suspension polymerization via vitamin C (Vc) reduction of graphene oxides (GO). Since the risky and complex change of the synthesis process of PVC is avoided, a facile and industrially feasible one-pot approach to prepare reduced GO (RGO) decorated PVC (RGO@PVC) is established. And then, the segregated PVC/graphene nanocomposites (s-PVCG) were prepared by direct hot compression of RGO@PVC. In comparison with the neat PVC and the random PVCG (r-PVCG), s-PVCG show remarkably improvement in electrical conductivity (σ), thermal conductivity (λ), thermal stability and flame retardation. The percolation threshold of σ (φc) for s-PVCG is as low as 0.012 vol%, and the ultimate σ (σmax) of s-PVCG attains 10−2 S cm−1 after 2.0 wt% RGO loading. At 4.1 wt% RGO loading, λ, the temperature of maximum weight loss (Tmax) and limited oxygen index (LOI) of s-PVCG are improved by 75%, 21 °C and 4 relative to the neat PVC, respectively.
       
  • Facile synthesis of Ag/ZrO2 nanocomposite as a recyclable catalyst for the
           treatment of environmental pollutants
    • Abstract: Publication date: Available online 21 January 2020Source: Composites Part B: EngineeringAuthor(s): Mehdi Maham, Mahmoud Nasrollahzadeh, S. Mohammad SajadiA green and in-situ strategy is reported for the biosynthesis of Ag/ZrO2 nanocomposite using Ageratum conyzoides L. extract as both reducing and stabilizer agents. Immobilizing Ag NPs on the ZrO2 surface was verified using various instrumental analyses such as field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The catalytic activity of the as-prepared Ag/ZrO2 nanocomposite was investigated in the reduction of different pollutants such as 2,4-dinitrophenylhydrazine (2,4-DNPH), 4-nitrophenol (4-NP), nigrosin (NS) and congo red (CR) in the presence of NaBH4. Furthermore, the catalyst can be recovered and used in multiple runs without significant loss of catalytic activity. The advantages of using nano-biotechnology to synthesize heterogeneous catalysts present a noteworthy area for further research.Graphical abstractImage 1
       
  • Effects of fiber geometry and orientation distribution on the anisotropy
           of mechanical properties, creep behavior, and thermal expansion of natural
           fiber/HDPE composites
    • Abstract: Publication date: Available online 21 January 2020Source: Composites Part B: EngineeringAuthor(s): Xiaolong Hao, Haiyang Zhou, Binshan Mu, Lei Chen, Qiong Guo, Xin Yi, Lichao Sun, Qingwen Wang, Rongxian OuNatural fiber/high-density polyethylene (HDPE) composites (NFPCs) were fabricated via extrusion using three types of natural fibers from poplar wood (PW), radiata pine (RP), and rice husk (RH), respectively. The specimens were cut from the extruded samples at various off-axis angles (from 0° to 90°). The effect of fiber geometry and orientation distribution on the mechanical properties, creep behavior, and thermal expansion of the NFPCs was investigated. The natural fibers in the composites showed a preferential orientation along the extrusion direction, as evidenced by the optics micrographs. The flexural properties and impact strength of the NFPCs were the highest at zero angle and decreased considerably with increasing orientation angle, which was further validated by the finite element analysis. At zero angle, the PW/HDPE composites had the highest flexural and impact strength and the smallest creep strain and thermal expansion, but a small difference in mechanical properties was observed at 90° among the NFPCs. The significant anisotropy of properties at various angles of the PW/HDPE composites was due to the high aspect ratio (L/D) of poplar wood fiber. These results indicate that high fiber L/D and orientation distribution had a beneficial effect on the properties of NFPCs.Graphical abstractImage 1
       
  • Exchange coupling and improved properties of the multilayer
           CoFe2O4/La0.7Sr0.3MnO3 thin films
    • Abstract: Publication date: Available online 21 January 2020Source: Composites Part B: EngineeringAuthor(s): Xianwu Tang, Shunjin Zhu, Renhuai Wei, Ling Hu, Jie Yang, Wenhai Song, Jianming Dai, Xuebin Zhu, Yuping SunAbstractHard/soft interface plays a role in the properties of the composite metal-based magnets, while it is less talked in the composite permanent oxide magnets on the magnetic interaction and properties due to easy interdiffusion. Here, multilayer thin films composed with hard CoFe2O4 phase and soft La0.7Sr0.3MnO3 layers were choose and synthesized without interdiffusion by a chemical solution method. Furthermore, the effects of the annealing temperature and the number of soft layer on the magnetic interaction and properties are investigated. All composite films behavior as one rigidly coupled composite magnet at room temperature, and the magnetic properties increase with increasing annealing temperature. The coercivity and maximum magnetic energy product can respectively reach 8.27 kOe and 2.4 MG Oe at the temperature of 300 K. Exchange coupling was effectively enhanced and even dominate the magnetic interaction with less soft layers for the in-plane direction. Conversely, dipolar interaction predominates, but becomes weak in the composite films with more soft layers and attenuates with increasing annealing temperature for the out-of-plane direction. All of the results suggest that a suitable grain size of the hard phase and an improved interface may be more important for a rigidly coupled composite oxide magnet with good performance.
       
  • Damage behaviors of unidirectional CFRP in orthogonal cutting: A
           comparison between single- and multiple-pass strategies
    • Abstract: Publication date: Available online 21 January 2020Source: Composites Part B: EngineeringAuthor(s): Hao Nan Li, Jun Peng Wang, Chao Qun Wu, Yong Jie Zhao, Jie Xu, Xiaoling Liu, Wei Qiang ZhuAbstractCarbon Fibre Reinforced Plastics/Polymer (CFRP) composites has experienced a rapid revolution, requiring the accurately controllable machining technology. Although efforts have been paid on CFRP machining, most of them focused on the single-pass orthogonal cutting where the perfect unprocessed surfaces were employed as the initial state. The reality is however the multiple-pass cutting with the progressive cut depths has been widely used in the industries, where the influence of the defects generated in the previous passes on the following cuts can not be ignored. To fill this gap, this paper investigated the damage behaviors of unidirectional CFRP in orthogonal cutting with the special emphasis on the difference between the single- and the multiple-pass strategies. The good agreement were found between the experimental and simulation results, where the maximal relative errors were separately 10.1%, 9.2%, and 8% for fibre pull-out depth, fibre-matrix debonding depth and cutting forces. Further discussion based on the model can draw the conclusion that, the employment of the multiple-pass cutting strategy can improve the fibre breakage length by 40%, the fibre pull-out depth by 63%, and the fibre-matrix interface debonding by 25%. This work is anticipated to not only open a new avenue to provoke more in-depth thoughts of CFPR behaviors in cutting but also to provide the practical guidance for industrial CFRP high-quality machining.
       
  • Hierarchically porous surface of PEEK/nMCS composite created by
           femtosecond laser and incorporation of resveratrol exhibiting
           antibacterial performances and osteogenic activity in vitro
    • Abstract: Publication date: Available online 20 January 2020Source: Composites Part B: EngineeringAuthor(s): Guiquan Cai, Hui Wang, Yun Kyung Jung, Zhiyan Xu, Jiahong Zhang, Jiye He, Dongliang Wang, Jung-Woog Shin, Rames Kaewmanee, Saha Nabanita, Jie WeiAbstractTo further improve the surface properties of polyetheretherketone (PEEK)/nanoporous magnesium calcium silicate (nMCS) composite (PMC), hierarchically porous surface of PMC (PMCF) were created by femtosecond laser, and resveratrol (RV) was incorporated into the porous surface of PMCF (RV@PMCF). Compared to PMC with flat surface, PMCF contained not only two types of micropores with different sizes (around 20 μm and 0.5 μm) but also nanopores (around 4 nm), which exhibited remarkably increase in surface roughness and protein adsorption. In addition, PMCF displayed a slow-release of RV while PMC showed a burst-release of RV into cell cultured medium. Moreover, compared with PMC and PMCF, RV@PMCF with antibacterial performances inhibited the growth of E. coli and S. aureus thanks to the release of RV. In addition, compared with PMC, PMCF and RV@PMCF significantly promoted adhesion and proliferation of rat bone mesenchymal stem cells (BMSC). Furthermore, compared with PMCF, RV@PMCF obviously enhanced the proliferation and osteogenic differentiation as well as bone related genes expressions of BMSC. The results demonstrated that PMCF with hierarchically porous surface and incorporating of RV displayed antibacterial performances and osteogenic activity in vitro, Therefore, as a drug-loaded implant, RV@PMCF with good cytocompatibility would have a big potential for applications in orthopaedic fields.
       
  • Cracking behavior of geopolymer concrete beams reinforced with steel and
           fiber reinforced polymer bars under flexural load
    • Abstract: Publication date: Available online 20 January 2020Source: Composites Part B: EngineeringAuthor(s): Khuram Rashid, Xiaoda Li, Yan Xie, Jun Deng, Faji ZhangAbstractThe cracking pattern and spacing in reinforced concrete (RC) structures considerably influence structural performance. Cracking may be severe with the utilization of fiber reinforced polymer (FRP) bars as compared to steel due to its low modulus of elasticity. In this study, the crack initiation, propagation and spacing, failure mode and ultimate load of RC beams reinforced with steel, basalt FRP (BFRP) and carbon FRP (CFRP) were investigated. A four-point bending test was conducted on fifteen RC beams. The beams with FRP bars exhibited worse cracking resistance and faster propagation throughout the loading process than those including steel bars. The cracking pattern was associated with failure modes from flexural to flexural-shear failure, which ultimately influenced the failure load. Furthermore, the crack spacing was analytically evaluated by three models used in conventional RC structures. The results showed that incorporating the rebar-concrete bond strength in Zhang's model resulted in more precise analytical values. Then, the bond strengths of all the FRP-concrete beams were evaluated by four codes. A strong correlation between the analytical and experimental crack spacing values was observed when considering code Canadian Standard Association (CSA) S806-12, and a significant margin of safety was obtained when considering the Japanese Society of Civil Engineering (JSCE) code.
       
  • Silica nanoparticles surface charge modulation of the electroactive phase
           content and physical-chemical properties of poly(vinylidene fluoride)
           nanocomposites
    • Abstract: Publication date: Available online 20 January 2020Source: Composites Part B: EngineeringAuthor(s): Sylvie Ribeiro, Rafaela Meira, Daniela M. Correia, Carmen R. Tubio, Clarisse Ribeiro, Carlos Baleizão, Senentxu Lanceros-MéndezComposites based on a piezoelectric polymer (PVDF) doped with different silica nanoparticles (SiNPs) content (8, 16 and 32 wt%) and functionalization (WF-without, NF-negative and PF-positive) have been investigated. Composite films were prepared by solvent casting and melt crystallization to investigate the effect of the presence of the SiNPs on the physico-chemical characteristics and, in particular, in the nucleation of the electroactive β-phase of the polymer. It is shown that the introduction of the SiNPs allows to increase water surface angle up to 34% with respect to α-PVDF, as well to increase the elastic modulus. Filler content and type have an important effect on the nucleation of the electroactive beta phase content and the dielectric properties of the composites, the larger values of both being obtained for positively surface charged nanoparticles. It is concluded that, taken into consideration the overall properties of the composites, the SiNPs-PF/PVDF nanocomposites with 8 wt% filler content offer a promising approach for applications due to the improvement of the electroactive phase of PVDF.Graphical abstractImage 1
       
  • Rapid synthesis of solid amine composites based on short mesochannel
           SBA-15 for CO2 capture
    • Abstract: Publication date: Available online 20 January 2020Source: Composites Part B: EngineeringAuthor(s): Beibei Ma, Rijia Lin, Hui He, Qinghua Wu, Shuixia ChenHydrothermal is common process for synthesizing well-ordered mesoporous silica, however, it costs time and energy simultaneously. To improve the efficiency of synthesis process, it is necessary to propose a facile synthesis strategy with less time and energy requirement. In this study, an innovative non-hydrothermal method using NH3·H2O as catalyst after ripening step is developed to prepare SBA-15 with short mesochannels (SSBA-15) for the first time. The synthesis period of SSBA-15 framework was extremely shortened within 40 min under the optimized conditions (30 min of ripening step and 25% of NH3·H2O concentration), while obtained material exhibits well-ordered hexagonal pore structure and fine particle morphology of SSBA-15 (pore length of 250 ± 50 nm and mesopore size of 9.8 nm). This method can also be employed to synthesize conventional SBA-15 successfully. Moreover, the application of SSBA-15 as support of solid amine adsorbents on CO2 adsorption and well-fitting of experimental CO2 adsorption data with Avrami and intraparticle diffusion models reveal that the adsorbents combine the advantages of micro-mesoporous structure, short mesochannel and amine reagents (high affinity of CO2), resulting in enhanced molecular diffusion, fast adsorption kinetics and high CO2 adsorption capacity. Notably, the solid amine adsorbents exhibited excellent regeneration ability during ten adsorption-desorption cycles. This work opens up new opportunities in efficient preparation of materials that require hydrothermal process.Graphical abstractImage 1
       
  • Bioinspired functionally graded gyroid sandwich panel subjected to
           impulsive loadings
    • Abstract: Publication date: Available online 20 January 2020Source: Composites Part B: EngineeringAuthor(s): Chenxi Peng, Phuong TranAbstractGradual and localised changes in mechanical properties can be achieved by functionally graded cellular structures with the aim to improve structural performance. Gyroid belongs to a class of cellular structures that naturally inspired continuous non-self-intersecting surfaces with controllable mechanical properties. In this work, dynamic compression on functionally graded gyroid and sandwich composite panels constructed from functionally graded gyroid core and metallic facets are numerically investigated and compared to evaluate the dynamic behaviours when subjected to extreme loadings. The Finite Element Analysis (FEA) is employed to characterises the deformation of proposed structures considering the rate-dependent properties, elastoplastic response and nonlinear contact. The Johnson-Cook model is utilised to capture the rate-dependent dynamic responses of the gyroid panels. The numerical model is then validated with experimental results under quasi-static compression. Owing to the symmetry, only a quarter of the gyroid panel is modelled using shell elements, which significantly reduces the computational cost. A series of studies are conducted to demonstrate the influences of different functionally graded cores on the blast resistances of gyroid composite panels. Reaction forces and critical stresses extracted from underneath protected structure are assessed. Gyroid sandwich structures clearly demonstrate unique dynamic crushing responses, impact energy mitigation & dissipation mechanisms, which leads to enhancement of the blast resistance.
       
  • Light-weight, high-gain three-dimensional textile structural composites
           antenna
    • Abstract: Publication date: Available online 20 January 2020Source: Composites Part B: EngineeringAuthor(s): Fujun Xu, Kun Zhang, Yipping QiuAbstractDue to the multiple dimensional and embeddable characterizations, the three-dimensional woven structure is of great potential as a platform for multifunctional composites. As an example of this concept, we proposed a light-weight and high-gain three-dimensional woven spacer microstrip antenna (3DWS-MA) for the first time by integrating microstrip antenna into 3D woven spacer composites. The single-element 3DWS-MA showed superb electromagnetic performance with the gain value of 7.1 dB, which is more than four orders of magnitude higher than traditional microstrip antenna (2.5 dB). Furthermore, the 3DWS-MA maintained proper resonant frequency and impedance matching after the impact of 18 J, exhibiting excellent structural integrity.
       
  • Heterojunction of vertically aligned MoS2 layers to Hydrogenated Black
           TiO2 and Rutile Based Inorganic Hollow Microspheres for the highly
           enhanced visible light arsenic photooxidation
    • Abstract: Publication date: Available online 20 January 2020Source: Composites Part B: EngineeringAuthor(s): Ali Balati, Akanksha Matta, Kelly Nash, Heather J. ShipleyIn this research, Black TiO2 (BTiO2), which consisted of Rutile Based Inorganic Hollow Microspheres (RBIHM) and hydrogenated anatase TiO2 nanoparticles, decorated with MoS2 nanosheets (HBTiO2/RBIHM-MoS2 photocatalyst) was synthesized using Pulsed Laser Ablation in Liquid (PLAL) followed by microwave irradiation. Formation of vertically aligned MoS2 nanosheets, RBIHM and HBTiO2 nanoparticles were confirmed by different characterization techniques. The spectroscopic analysis revealed phase transitions in HBTiO2/RBIHM nano and microstructures along with the formation of different crystal disorders such as amorphous layers, oxygen vacancies, trivalent titanium ions and formation of molybdenum oxide (MoO3-x) in MoS2. In addition, MoS2 films in HBTiO2/RBIHM-MoS2 nanocomposite showed both Mo5+ and Mo6+ oxidation state, which was inferred that these films have a p-type conductive behavior. Furthermore, the interconnected layers of MoS2 nanosheets led to the formation of a porous like 3D nanostructure in HBTiO2/RBIHM-MoS2, which could significantly improve its photocatalytic performance. Arsenite photooxidation efficiencies of 70.3% and 96.6% and arsenate adsorption capacities of 1600 and 5200 μg g−1 were obtained for HBTiO2/RBIHM and HBTiO2/RBIHM-MoS2, respectively. The synergetic effects originated from making RBIHM-HBTiO2, RBIHM-MoS2 and MoS2–HBTiO2 heterojunctions along with the surface and morphology modification in MoS2 NSs and HBTiO2/RBIHM can explain the nanocomposite superior photocatalytic performance. The present work can trigger a broad interest in the cost-effective nanoarchitecture of visible light driven heterostructured photocatalysts.Graphical abstractImage 1
       
  • Adjusting function of MoS2 on the high-speed emergency braking properties
           of copper-based brake pad and the analysis of relevant tribo-film of eddy
           structure
    • Abstract: Publication date: Available online 20 January 2020Source: Composites Part B: EngineeringAuthor(s): Peng Zhang, Lin Zhang, Dongbin Wei, Peifang Wu, Jingwu Cao, Cairang Shijia, Xuanhui QuAbstractIn this paper, by studying the high-speed emergency braking performance of copper-base brake pads with different MoS2 contents and the corresponding structure of tribo-film, the adjusting function of MoS2 was revealed, which is mainly achieved by the reaction of MoS2 with Cu and Fe. The hard reaction products enhance the strength of the matrix and thus increase the resistance of plastic deformation. However, excessive addition of MoS2 in the matrix leads to the reduced particle size of Fe and the increased matrix discontinuities. Those reduce the deformation resistance of friction surface and the ability to hinder the movement of substances on friction surface, thereby resulting in formation of eddy structure on friction surface of the samples containing high content of MoS2 during high-energy braking. For the sample containing the optimum content of 2 wt % MoS2, the friction coefficient is relatively high and the wear loss is only 17.13% and 5.05% of the samples without MoS2 and with 10 wt % MoS2, respectively. The abnormal high wear loss and the reduction of friction coefficient is mainly determined by the dynamic process of formation and delamination of the eddy structure.
       
  • Strain amplitude controlled fatigue of Flax-epoxy laminates
    • Abstract: Publication date: Available online 17 January 2020Source: Composites Part B: EngineeringAuthor(s): Zia Mahboob, Habiba BougheraraAbstractFatigue longevity and evolving material properties of Flax-epoxy laminates is examined under constant strain amplitude cycling. Several recent fatigue studies on Flax-composites, all of which were conducted under stress-control, found that certain laminates demonstrate a modulus increase over fatigue life, even while accumulating internal damage and permanent deformation. This study investigates whether such fatigue-stiffening phenomena are also observed under strain-control. Specimens of four layups ([0]16, [0/90]4S, [±45]4S, and [0/45/90/−45]2S) are tested under 5 Hz and strain ratio Rϵ=ϵminϵmax=0.1. Strain-life (ϵ–N) plots are generated, which are found to follow a consistent trend that can be modelled by a linearised relationship with identifiable parameters. No evidence of stiffening is observed. All specimens demonstrate stiffness degradation, thereby contradicting previous studies. The extent of degradation is proportional to loading applied. A directly proportional relationship is observed between strain-rate and measured modulus. It is proposed that the reported modulus increase in existing literature does not reflect any physical improvement of material stiffness, but is a consequence of stress-amplitude controlled loading conditions. As such, strain-controlled cycling may be more appropriate for fatigue studies on natural fibre composites.
       
  • Reduced graphene oxide-wrapped micro-rod like Ni/Co organic-inorganic
           hybrid nanocomposite as an electrode material for high-performance
           supercapacitor
    • Abstract: Publication date: Available online 16 January 2020Source: Composites Part B: EngineeringAuthor(s): S. Kumaraguru, J. Yesuraj, S. MohanA Ni/Co metal-organic frameworks (MOFs) and its reduced graphene oxide (rGO) composite has been fabricated through room-temperature route using simple 3D linker as trimesic acid. The crystalline nature, morphology, functional groups and thermal stability of the prepared materials are characterized via XRD, SEM, Raman and TGA studies. The synthesized Ni/Co-MOF/rGO reveals spherical particles decorated rod-like morphology with a length of ∼3–10 μm. The incorporation of rGO into the Ni/Co-MOF enhances conductivity and electrochemical performance. The electrochemical properties of Ni/Co-MOF and its rGO composite are evaluated in 1 M KOH. The produced Ni/Co-MOF/rGO composite (1162 F g−1) exhibits higher specific capacitance than bare Ni/Co-MOF (978 F g−1). The Ni/Co-MOF/rGO composite exposes excellent stability even after 5000 cycles and maintains 109% of its initial capacitance. This result suggests that the fabricated Ni/Co-MOF/rGO composite may be employed as an electrode material for supercapacitor applications.Graphical abstractImage 1
       
  • Damage tolerance of CFRP airframe bolted joints in bearing, following bolt
           pull-through failure
    • Abstract: Publication date: Available online 15 January 2020Source: Composites Part B: EngineeringAuthor(s): Ioannis K. Giannopoulos, Kaelan Grafton, Shijun Guo, Howard SmithAbstractThe experimental study presented herein, investigated the residual strength of bolted joints on Carbon Fiber Reinforced Polymer (CFRP) airframe structures within the context of structural damage tolerance and airworthiness regulations. The damage scenario assumed, subjected a series of bolted joint CFRP laminate specimens to quasi-static bearing loading following bolt pull-through failure events of different magnitude. Representative CFRP laminate specimens manufactured from AS7/8552 carbon fiber/epoxy matrix system were artificially damaged under bolt pull-through loading, following the herein proposed modifications to the current pull-through ASTM testing procedure. The specimens were subsequently tested in static bearing loading for examining the specimen residual bearing strength. The residual joint bearing strength was related to the displacement travelled passed the initial failure stage in pull-through mode and was measured up to a maximum of a 13% decrease for the tested samples and the maximum damage imposed. The study explored of safe utilization of bolted joints at higher operating loading levels within the context of the current airworthiness regulations. The inherent damage arrest features of the joints were highlighted. The study concluded with comments and suggestions on the expansion of the current utilization spectrum of damaged bolted joints from pull-through loading in airframe design, bound by the current airworthiness certification requirements.
       
  • The influence of fiber volume fraction and fiber length on the evolution
           of pore content and the paintability of sheet molding compounds
    • Abstract: Publication date: Available online 14 January 2020Source: Composites Part B: EngineeringAuthor(s): Marton Kardos, Enrico Körner, Dayakar Penumadu, Niels ModlerAbstractThe porosity defects from components molded using sheet molding compounds is a well-recognized issue. It is the major source of paint defects in exterior applications, hindering the widespread use of these materials despite their inherent advantages over metals and thermoplastics. This study discusses the influence of fiber volume fraction and fiber length on the pore content and on the painted surface quality of class-A compounds. Compounds with varying glass fiber fraction and fiber length were compounded, compression molded and painted to analyze the influence of the aforementioned factors on the permeability of the fibrous network, the evolution of initial to final pore content and on the painted surface quality with regards to waviness and substrate-relevant paint defects. A new indicator, the pore transport efficiency factor is introduced to help quantify the related characterization feature. The results indicate that lower fiber fractions lead to decreased pore contents and thus, improved paintability.
       
  • Evaluation of grit-blasting as a pre-treatment for carbon-fibre
           thermoplastic composite to aluminium bonded joints tested at static and
           dynamic loading rates
    • Abstract: Publication date: Available online 13 January 2020Source: Composites Part B: EngineeringAuthor(s): Karthik Ramaswamy, Ronan M. O'Higgins, Ajay Kumar Kadiyala, Michael A. McCarthy, Conor T. McCarthyAbstractLight-weighting of transportation structures necessitates multi-material design employing composites and aluminium, with thermoplastic composites being of increasing interest to the industry. Adhesive bonding is a viable solution for joining dissimilar materials, but joint performance can be considerably affected by surface preparation. In this paper, alumina grit-blasting is investigated as a surface preparation technique for thermoplastic-matrix composites to be bonded to aluminium alloys. Grit-blasting is performed on composite adherends for varying durations, and the resulting chemical and morphological modifications are analysed using goniometry, profilometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Adhesively-bonded single-lap joints are tested at quasi-static and dynamic (0.5 m/s) loading rates, and fractography analysis is performed at macro and micro scales. It is found that high lap shear strength and work-to-failure can be achieved through optimisation of the grit-blasting parameters. The optimised process produces a composite surface with plasticised matrix, minimal fibre exposure, and favourable surface chemistry for adhesive bonding. Grit-blasting can thus be a simple, yet effective surface preparation technique for composites to be bonded to aluminium.
       
  • Incorporation of functionalized reduced graphene oxide/magnesium
           nanohybrid to enhance the osteoinductivity capability of 3D printed
           calcium phosphate-based scaffolds
    • Abstract: Publication date: Available online 11 January 2020Source: Composites Part B: EngineeringAuthor(s): Hossein Golzar, Dorsa Mohammadrezaei, Amir Yadegari, Morteza Rasoulianboroujeni, Mohadeseh Hashemi, Meisam Omidi, Fatemeh Yazdian, Mohammad Shalbaf, Lobat TayebiAbstractImproving bone regeneration is one of the most pressing problems facing bone tissue engineering (BTE) which can be tackled by incorporating different biomaterials into the fabrication of the scaffolds. The present study aims to apply the 3D-printing and freeze-drying methods to design an ideal scaffold for improving the osteogenic capacity of Dental pulp stem cells (DPSCs). To achieve this purpose, hybrid constructs consisted of 3D-printed Beta-tricalcium phosphate (β-TCP)-based scaffolds filled with freeze-dried gelatin/reduced graphene oxide-Magnesium-Arginine (GRMA) matrix were fabricated through a novel green method. The effect of different concentrations of Reduced graphene oxide-Magnesium-Arginine (RMA) (0, 0.25% and 0.75%wt) on the morphology, mechanical properties, and biological activity of the 3D scaffolds were completely evaluated. Our findings show that the incorporation of RMA hybrid into the scaffold can remarkably enhance its mechanical features and improve cell proliferation and differentiation simultaneously. Of all scaffolds, β-TCP/0.25GRMA showed not only the highest ALP activity and cell proliferation after 14 days but it up-regulated bone-related genes and proteins (COL-I, RUNX2, OCN). Hence, the fabricated 3D printed β-TCP/0.25GRMA porous scaffolds can be considered as a high-potential candidate for BTE.
       
  • A study on adhesive characteristics of double cantilever beam specimens
           with inhomogeneous materials due to tensile and out-of-plane shear
           fractures
    • Abstract: Publication date: Available online 10 January 2020Source: Composites Part B: EngineeringAuthor(s): J.W. Kim, J.U. Cho, C.D. ChoAbstractIn this study, the adhesive characteristics of double cantilever beam specimens with the inhomogeneous adhesion materials due to tensile and out-of-plane shear fractures have been investigated. The experiments were conducted by applying a forced displacement rate of 3 mm/min at the upper position and fixing the lower position, while each experimental condition was maintained to be identical. In the tensile fracture of mode Ⅰ, the maximum reaction force was observed to be highest in the order of CFRP-Al, Al–Al_Foam, and CFRP-Al_Foam. The maximum energy release rate was highest in the order of Al–Al_Foam, CFRP-Al, and CFRP-Al_Foam. When the overall crack resistance curves were examined, all of the highest energy release rates could be seen to be produced at an early stage of cracking. In mode Ⅲ, the maximum reaction force was highest in the order of CFRP-Al, Al–Al_Foam, and CFRP-Al_Foam. The maximum energy release rate was observed to be highest in the order of CFRP-Al, CFRP-Al_Foam, and Al–Al_Foam. Considering that the higher reaction forces and energy release rates were produced in the specimen containing, it could be inferred that the use of a material with high rigidity increased the maximum strength of the adhesive.
       
  • Shear behavior of woven and non-crimp fabric based thermoplastic
           composites at near-processing conditions
    • Abstract: Publication date: Available online 10 January 2020Source: Composites Part B: EngineeringAuthor(s): Tobias Mattner, Michael Wrensch, Dietmar DrummerAbstractIn intra-laminar shear testing of continuous fiber reinforced thermoplastic composites at near-processing conditions, several factors influence the measured forces in picture frame tests. These influences mostly result from tight clamping of the specimen in the frame and, depending on the heating strategy, possible unmelted areas near the clamping regions, yielding in a shift of the point of rotation of the fibers. An approach to compensate these effects has recently been suggested, but generally valid compensation settings could not yet be deducted. In addition, research on the shear properties of continuous fiber reinforced thermoplastics has been limited to quasi-static deformation speeds and thermodynamically stable temperature levels. This study examines the effect of high deformation speeds and temperature levels in the transitional region between melting point and recrystallization on the intra-laminar shear behavior of different types of continuous fiber reinforced thermoplastics to deduct a material behavior, which better resembles actual processing behavior by using a custom-built picture frame setup. The edge effects are analyzed to deduct generally recommendable compensation settings using a statistical approach. In addition, variations of the pathways of individual fibers in pre-forms are measured, revealing elongation reserves of 0.4–0.5%, which can be confirmed in picture frame tests. The results furthermore show the importance of performing material tests at near-processing conditions to deduct reliable material data for usage in forming simulation. Further research is necessary to understand the complex deformation behavior in the transitional region below melting point and before recrystallization is complete.
       
  • Compression properties of polymeric syntactic foam composites under cyclic
           loading
    • Abstract: Publication date: Available online 10 January 2020Source: Composites Part B: EngineeringAuthor(s): Z. Yousaf, M.J.A. Smith, P. Potluri, W.J. ParnellAbstractIn the present work, polymer-based syntactic foams were studied under cyclic compression in order to investigate their compressibility, recoverability, energy dissipation and damage tolerance. These syntactic foams were manufactured by adding hollow polymer microspheres of various sizes and wall thicknesses into a polyurethane matrix. The associated loading and unloading curves during cyclic testing were recorded, revealing the viscoelastic nature of the materials. SEM images of the samples were obtained in order to study potential damage mechanisms during compression. It was observed that these syntactic foams exhibit high elastic recovery and energy dissipation over a wide range of compressional strains and the addition of polymer microspheres mitigates the damage under compressional loading.
       
  • The evaluation of failure mode behavior of CFRP/Adhesive/SPCC hybrid thin
           laminates under axial and flexural loading for structural applications
    • Abstract: Publication date: Available online 10 January 2020Source: Composites Part B: EngineeringAuthor(s): Muhammad Akhsin Muflikhun, Ryo Higuchi, Tomohiro Yokozeki, Takahira AokiAbstractThe failure mode behavior and the mechanical performance in terms of stress-strain of Carbon Fiber Reinforced Plastic - Steel Plate Cold Commercial (CFRP-SPCC) hybrid thin laminates are investigated in this study through axial tensile and flexural tests. Four different adhesives were used. Materials were characterized using Differential Scanning Calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Surface behavior was monitored in real time and after completion (final failure) with an optical microscope during the tensile test. The results from DSC and FTIR show that the materials undergo complete curing. The results from the tensile test indicate that by adding SPCC in hybrid laminates, the premature failure of CFRP laminates can be delayed up to 58.5%. The result shows the strain at failure increases from 1.85% of CFRP laminates to 2.1% of hybrid laminates, which equals an increased rate of more than 13%. The flexural tests demonstrate that hybrid laminates have a higher strain value compared to CFRP laminates. With the addition of SPCC layers, the failure mode is shifted from premature fiber breakage to adhesive breakage followed by final failure with fiber breakage originating from the CFRP laminates.
       
  • Electrical and thermal conductivity of polyvinylidene fluoride (PVDF) –
           Conducting Carbon Black (CCB) composites: Validation of various
           theoretical models
    • Abstract: Publication date: Available online 10 January 2020Source: Composites Part B: EngineeringAuthor(s): Ranvijai Ram, Vandna Soni, Dipak KhastgirAbstractDifferent composition dependent PVDF/CCB composites were prepared by solution mixing followed by casting technique. The morphology, crystallinity, electrical and thermal conductivity, sound velocity and storage modulus vary with composition. The effect of frequency, temperature and composition on electrical conductivity were investigated and electrical conductivity of these composites strongly depends on percolation threshold. The variation of thermal conductivity and storage modulus against temperature and concentration has also been investigated. The surface morphology has been viewed through Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Spectroscopy (AFM). The particle agglomerate structure of CCB was checked byHigh Resonance Transmission Electron Microscopy (HRTEM). Applicability of different theoretical models to predict electrical conductivity and thermal conductivity were also tested for these composites. To predict composition dependent thermal conductivity theoretical models like Series, Parallel, Geometrical mean, Maxwell, Nielsen Lewis, Hamilton-Crosser, and the Agari model have been used to check their validity for the present system.
       
  • Flexible and robust silver coated non-woven fabric reinforced waterborne
           polyurethane films for ultra-efficient electromagnetic shielding
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Wei Ren, Huixin Zhu, Yaqi Yang, Yanhui Chen, Hongji Duan, Guizhe Zhao, Yaqing LiuThe rapid popularity of portable and wearable smart electronics has put forward more stringent requirements for flexible electromagnetic interference (EMI) shielding films with excellent mechanical strength and EMI shielding effectiveness (SE). However, there are still many obstacles to simultaneously satisfy the above critical requirements and new strategy for designing high-performance EMI shielding films is needed. Herein, a flexible and highly-efficient EMI shielding waterborne polyurethane (WPU) composite film with excellent mechanical strength and shielding stability is prepared by the facile compounding with silver coated non-woven fabrics (Ag/NWF). The Ag/NWF/WPU composite film (10.5 wt% Ag) with a thickness of only 400 μm possesses an outstanding EMI SE of 72.5 dB in the frequency range of 2–18 GHz, and the tensile strength can reach 12 MPa. The incorporation of FeCo alloy deposited on reduced graphene oxide (FeCo@rGO) nanoparticles further improves the EMI SE to 77.1 dB. Moreover, because of the robust mechanical properties of the composite film, a highly reliable shielding ability is also achieved with over 95% EMI SE retention after 1000 folding cycle tests. This flexible and robust WPU film with highly-efficient shielding performance is promising for the application in next-generated flexible electronic devices.Graphical abstractImage 1
       
  • Influence of anodization of aluminum 2024 T3 for application in
           aluminum/Cf/ epoxy laminate
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Alberto L. Santos, Roberto Z. Nakazato, Sebastian Schmeer, Edson C. BotelhoAbstractThis work deals with the processing and characterization of aluminum/carbon fiber/epoxy composites obtained from anodized and non-anodized aluminum plates. In this work, the electrochemical treatment employed was the phosphoric anodization, after chemical stripping. After this treatment, the fiber metal laminate (FML) coupons were laminated, the aluminum plates were interleaved with CF/epoxy prepreg layers. The next step was the use of hot compression molding technique in order to prepare the FML with and without anodized aluminum surface treatment, for comparison purposes. Several characterization techniques were used, such as: impact and perforation resistance analysis, laminar, translaminar (Iosipescu) and compression shear strength, in addition to optical macroscopy. After the analysis of the results, it was verified that the electrochemical treatment slightly reduces the impact and the perforation resistance of FML studied, because a more adhered interface promotes larger internal tensions and consequently reduces the capacity to absorb energy until failure. However, the adhesion properties were shown to be superior in the composites produced with the anodized plates. Additionally, the treatment proved to be an important means of obtaining FMLs, since most of the plates produced with non-anodized aluminum delaminated after a few weeks in stock, while the FML obtained from anodized aluminum did not delaminate after months of their production.
       
  • Development of a low cost and green microwave assisted approach towards
           the circular carbon fibre composites
    • Abstract: Publication date: Available online 8 January 2020Source: Composites Part B: EngineeringAuthor(s): Omid Zabihi, Mojtaba Ahmadi, Chao Liu, Roya Mahmoodi, Quanxiang Li, Minoo NaebeIn this study, we have developed a rapid, cost-effective, environmentally green, and yet efficient approach for the complete reclamation of the carbon fibre composites through a microwave assisted chemical method. It was found that in a catalyst-free and one-step process using microwave irradiation, a mixture of hydrogen peroxide (H2O2) and tartaric acid (TA) can initiate decomposition of the epoxy matrix up to 95% yield, leaving behind CFs with ∼92% tensile strength and ∼94% strain-to-failure retentions compared to the original CFs. Less than 2 min microwave irradiation was used which makes this approach considerably promising for the fast reclamation of the carbon fibre composites. The repetition of reclamation for the second and third times, which have been performed on the composite laminates re-manufactured using the reclaimed CFs, indicated that further reductions in the CFs mechanical performance are typically less than 5% after first reclamation process. Our proposed reclamation process changed surface properties of the reclaimed CFs compared to original CFs, which led to a significant increase in interfacial performance of the recycled CFs-epoxy composites. Moreover, the re-manufactured composite laminates using the reclaimed CFs showed highly comparable flexural strength and modulus, compared to its original composite laminates.Graphical abstractImage 1
       
  • A strain-displacement mixed formulation based on the modified couple
           stress theory for the flexural behaviour of laminated beams
    • Abstract: Publication date: Available online 7 January 2020Source: Composites Part B: EngineeringAuthor(s): Luan C. Trinh, Rainer M.J. Groh, Giovanni Zucco, Paul M. WeaverAbstractA novel strain-displacement variational formulation for the flexural behaviour of laminated composite beams is presented, which accurately predicts three-dimensional stresses, yet is computationally more efficient than 3D finite element models. A global third-order and layer-wise zigzag profile is assumed for the axial deformation field to account for the effect of both stress-channelling and stress localisation. The axial and couple stresses are evaluated from the displacement field, while the transverse shear and transverse normal stresses are computed by the interlaminar-continuous equilibrium conditions within the framework of the modified couple stress theory. Then, axial and transverse force equilibrium conditions are imposed via two Lagrange multipliers, which correspond to the axial and transverse displacements. Using this mixed variational approach, both displacements and strains are treated as unknown quantities, resulting in more functional freedom to minimise the total strain energy. The differential quadrature method is used to solve the resulting governing and boundary equations for simply-supported, clamped and cantilever laminated beams. The deflections and stresses from this variational formulation for simply supported beams agree well with those from a Hellinger-Reissner stress-displacement mixed model found in the literature and the 3D elasticity solution given by Pagano. These strain-displacement models also accurately predict the localised stresses near clamped and free boundaries, which is confirmed by the high-fidelity Abaqus models.
       
  • Effects of nanotube agglomeration on wave dynamics of carbon
           nanotube-reinforced piezocomposite cylindrical shells
    • Abstract: Publication date: Available online 7 January 2020Source: Composites Part B: EngineeringAuthor(s): Hossein Bisheh, Timon Rabczuk, Nan WuAbstractDynamics of wave propagation in carbon nanotube (CNT)-reinforced piezocomposite cylindrical shells affected by nanotube agglomeration is investigated in this study for the first time by developing an analytical approach incorporating existing theories and models. The Mori-Tanaka micromechanics model in combination of the first-order shear deformation shell theory and wave propagation solution are employed to determine wave propagation characteristics of piezocomposite cylindrical shells reinforced with agglomerated CNTs. The effects of both partial and complete nanotube agglomeration on the effective elastic properties and wave dynamics are examined within various axial and circumferential wave numbers for different wave modes by solving an eigenvalue problem. It is found that nanotube agglomeration leads to the reduction of wave phase velocity as a result of decrease in the effective elastic properties. The developed methodology in this study can be used for analysis of the data of structural health monitoring by the non-destructive testing (NDT) in estimating the degree of nanotube agglomeration in nanocomposites.
       
  • Environmentally friendly novel covalently immobilized enzyme
           bionanocomposite: From synthesis to the destruction of pollutant
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Niyaz Mohammad Mahmoodi, Mohammad Hosein Saffar-Dastgerdi, Bagher HayatiHerein, nanozeolite - carbon nanotube composites with the covalently immobilized enzyme (Laccase) as novel bionanocomposites were synthesized and used for pollutant (Direct Red 23) bio-degradation. Different amounts of carbon nanotube (30, 50, and 70 mg) were used to synthesize carbon nanotube -zeolite nanocomposites. The synthesized nanomaterials were silanized and cross-linked by glutaraldehyde. Finally, the enzyme was immobilized on them to prepare Laccase immobilized nanomaterials. The biocatalysts were characterized using Scanning electron microscopy (SEM), X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), Brunauer-Emmett-Teller (BET), and Transmission Electron Microscopy (TEM). The effect of operational parameters on bio-degradation was investigated and optimized. The synthesized biocatalyst nanocomposite retained more than 95% of its initial activity over the first 5 cycles and its efficiency is still intact. After 10 cycles relative activity decreased gradually to 69%. Results revealed much higher stability for Laccase after the immobilization and 84% of the maximum activity of nanocomposite was preserved at 80 °C. The activity of free Laccase lost over 60% of its activity after 8 days of incubation while the nanocomposite retained about 80% of its maximal activity. They had high storage stability over 8 incubation days and good performance at thermal stability experiments (45–80 °C for 1 h).Graphical abstractImage 1
       
  • Microcrystalline cellulose, polylactic acid and polypropylene
           biocomposites and its morphological, mechanical, thermal and rheological
           properties
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Siddharth Mohan Bhasney, Amit Kumar, Vimal KatiyarModification of mechanical, morphological, thermal and rheological properties of the polymers via melt blending method has been an area of great interest. The present work describes the fabrication of microcrystalline cellulose (MCC) fibre with polylactic acid (PLA) and polypropylene (PP) blend by twin screw extruder to optimize melt processability of the PLA matrix. Compared to PLA, the tensile strength and percentage elongation of PLA80/19.9PP/0.1MCC biocomposites were reduced by ~32% and ~4%, respectively. No significant improvement was achieved in the Tg and Tc of the MCC based biocomposites. The PLA spherulite growth rate in PLA80/19.5PP/0.5MCC biocomposite was enhanced to 2.91 μm/min compared to pure PLA matrix (2.53 μm/min). The storage modulus of PLA was increased from low to high frequency while complex viscosity of PLA and its biocomposites showed shear thinning behaviour at a frequency range of 0.1–100 rad/s. Both PLA and PP, showed hydrophobic characteristics. Incorporation of MCC fibres resulted in the decrease in water contact angles of the biocomposites to ~62°. Thus, it can be concluded that blending of MCC fibres results in considerable changes in the properties of the PLA and PP polymers.Graphical abstractImage 1
       
  • Experimental and numerical study on creep and shrinkage effects of ultra
           high-performance concrete beam
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Li Zhu, Jia-Ji Wang, Xuan Li, Guan-Yuan Zhao, Xue-Jin HuoAbstractCompared with normal concrete, ultra high-performance concrete (UHPC) is of increasing interest for bridge engineering because of its superior tensile strength, compressive strength, and significantly enhanced durability. The creep and shrinkage effect have a significant influence on the long-term behavior of UHPC. However, the existing research on the time-dependent behavior of UHPC is still limited. In this research, based on numerical integration method, the ABAQUS user subroutine for simulating creep and shrinkage of both normal concrete (NC) and UHPC were developed by the recursive algorithm of adjacent stress increment in the time history. The accuracy of developed user subroutine was validated by creep and shrinkage test of reinforced NC beams. Subsequently, the long-term creep and shrinkage test of UHPC specimens was conducted with stress to strength ratio of 20%, 30%, and 40%, respectively. Based on the test results and the CEB-FIP Model code 1990, the simplified design formulas for predicting creep and shrinkage of UHPC were proposed respectively based on the developed UHPC material. In the proposed design formulas, the final shrinkage strain was 145 με, and the final creep coefficient was 0.46 for the developed UHPC specimens based on the test environment condition. The comparison between the test result and proposed formulas indicated good applicability and accuracy of the proposed formulas. Based on the developed ABAQUS user subroutine and the proposed design formula for creep and shrinkage, the finite element (FE) models of RC beam and UHPC beam were developed. The influence of creep and shrinkage on the long-term mechanical behavior of simply supported prestressed beams were investigated.
       
  • Halogen and halogen-free flame retarded biologically-based polyamide with
           markedly suppressed smoke and toxic gases releases
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Tongmin Cai, Junling Wang, Chuanhui Zhang, Min Cao, Sujun Jiang, Xin Wang, Bibo Wang, Weizhao Hu, Yuan HuPolyamide materials are regarded as one promising plastic, deriving from its exceptional physical and chemical properties. Unfortunately, the intrinsic high fire hazard (considerable heat, smoke and toxic gases generation) of polyamide strongly hinders its versatile applications. Utilizing suitable strategy to reduce its fire hazard has been more crucial. Here, the biologically-based polyamide materials are synthesized. In this work, the replacement of terephthalic acid with isophthalic acid contributes to the reduction on the melting point of polymer, which is beneficial to the processing in industry. It is found that PA10T/10I shows lower mechanical property and worse flammability than PA10T. By using halogen and halogen-free flame retardants, the dramatically reduced values of peak heat release rate can be observed. It is found that less halogen-free flame retardant are loaded to achieve V-0 rating, substantiating its higher flame retarded efficiency. Also the markedly improved limited oxygen index values are observed. TGIR results confirms the suppressed releases of toxic CO and HCN gases. Besides, the inhibited smoke generation can be found. Overall, both halogen and halogen-free strategy are effective in reducing the fire hazard of polyamide and halogen-free method show higher efficiency.Graphical abstractImage 1
       
  • Aerogami: Composite origami structures as active aerodynamic Ccontrol
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Mircea Cozmei, Tristan Hasseler, Everett Kinyon, Ryan Wallace, Antonio Alessandro Deleo, Marco SalviatoAbstractThis study explores the use of origami composite structures as active aerodynamic control surfaces. Towards this goal, two origami concepts were designed leveraging a combination of analytical and finite element modeling, and computational fluid dynamics simulations. Wind tunnel tests were performed at different dynamic pressures in conjunction with two different active control laws to test the capability of obtaining desired drag values. The experiments revealed excellent structural rigidity and folding characteristics under aerodynamic loading. These results are in very good agreement with one-way Fluid Structure Interaction (FSI) simulations, which show the potential of using high-fidelity modeling for the design and optimization of these structures.Future work will focus on developing advanced origami designs that allow for more deterministic folding as well as improved weight, stiffness, and fatigue characteristics in the use of materials.
       
  • Experimental investigation of adhesive fillet size on barely visible
           impact damage in metallic honeycomb sandwich panels
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Patrick Kendall, Mengqian Sun, Diane Wowk, Christopher Mechefske, Il Yong KimAbstractAluminum hexagonal honeycomb panels are commonly used in the aerospace industry to reduce weight due to their high stiffness to mass ratio. The panels are commonly involved in incidents where they are dented in the out-of-plane direction which causes plastic deformation in the face-sheet and buckling collapse of the thin repeating cell-walls in the core. This paper investigates the responses to barely-visible-impact-damage (BVID) in aluminum honeycomb sandwich panels in the out-of-plane direction with attention to the structural adhesive. The structural adhesive forms a fillet shape between the face-sheet and the aluminum core during the curing process and in some cases can encompass over 50% of the honeycomb core thickness. The adhesive fillets become stiff after curing and are able to brace the thin metallic cell-walls and prevent buckling in sections of the core enclosed in adhesive. It was shown that larger fillets cause the damage to occur deeper in the core. Force-displacement data collected from quasi-static experiments showed that as the amount of adhesive used in honeycomb panels was increased, the peak force required to produce a specified maximum dent depth increased as well. Absorbed energy positively correlated with an increasing quantity of adhesive; showing improvements of up to 50% when comparing panels with the largest amount of adhesive and no adhesive. This paper provides relationships between the quantity of adhesive used to fabricate metallic honeycomb sandwich panels and the damage resistance and energy absorption under BVID conditions.
       
  • The experimental and numerical study on the mechanical behaviours of
           adhesively bonded joints
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Elanur Çelebi̇ Kavdir, Murat Demir AydinAbstractExperimental and numerical analyzes of single lap joints formed by combining AA2024-T3 aluminum alloys with two-component liquid structural adhesive DP410 were carried out in the present study. Tension and four-point bending experiments of single lap joints were performed in the experimental analysis section of this study in addition to 2-D Digital Image Correlation (DIC) analyses performed via the processing of the images obtained during these experiments. Whereas, three dimensional nonlinear finite element analyses of tensile and four point bending of single lap joints were performed for the numerical analysis section of the study by taking into consideration the load and boundary conditions applied during experimental analyses. Normal and shear strain distributions obtained via DIC and finite element method were compared by taking into consideration the middle line of the adhesive layer in the case of tensile and four-point bending loads of single lap joints. As a result of this comparison, it was found that there was a sufficient level of compatibility (not very close agreement) in strain distributions between finite element analyzes and DIC technique. As a result, it can be said that three-dimensional DIC analysis will yield more harmony and more accurate results when it is taken into account that three-dimensional finite element analysis and 2D DIC analysis were performed in the study.
       
  • Compressive behavior of stretched and composite microlattice metamaterial
           for energy absorption applications
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Mahmoud M. Osman, Mostafa Shazly, Ehab A. El-Danaf, Parastoo Jamshidi, Moataz M. AttallahAbstractA new proposed truss lattice metamaterial is introduced and compared with the conventional octet truss lattice (OTL) material with regards to specific energy absorption (SEA) and energy absorption efficiency (EAE). The proposed lattice architecture resembles the Face-Centered Cubic (FCC) metamaterial with a mesostructural unit cell with an aspect ratio of 1:1:2, referred to as the stretched cell lattice (SCL). SCL and OTL samples were fabricated from stainless steel 316L by selective laser melting (SLM). Quasi-static compression experiments on the SLM fabricated metamaterials revealed an unstable twisting deformation mode for the SCL, whereas a stable crushing behavior was observed for the OTL. SCL samples provided higher SEA and EAE than OTL by 26% and 17%, respectively. Additionally, it was shown analytically, numerically and experimentally that the yield strength of the proposed SCL is ~80% higher than that of the OTL metamaterials of the same base material and relative density. A hybrid composite lattice structure based on acrylic matrix and the additively manufactured microlattice metamaterials was produced to enhance the struts buckling resistance. The hybrid composite showed a 47% higher specific strength while the SEA and EAE dropped by 31.5% and 30.7%, respectively, when compared to the bare stainless steel microlattice. Dynamic compression experiments using Split Hopkinson Pressure Bar (SHPB) at strain rates in the order of 103/s demonstrated a similar deformation plateau as the static compression experiments with a dynamic increase factor (DIF) of ~1.3 for the bare stainless steel metamaterials and ~2 for the acrylic-stainless steel hybrid composite material.
       
  • Highly efficient thermal oxidation and cross-linking reaction of catechol
           functionalized polyacrylonitrile copolymer composites for halogen-free
           flame retardant
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Ki-Ho Nam, Jeong-Un Jin, Jae Hyeok Lee, Jongho Kim, Yong Sik Chung, Hyeonuk Yeo, Nam-Ho You, Bon-Cheol KuThere have been major efforts to make polyacrylonitrile (PAN) flame retardant using halogens, heavy metals, transition metals, and phosphorus-organic compounds. These retardants may reduce the risk of fire, but they also involve high cost, toxicity, and related ecological issues. In an effort to mitigate some of these negative factors, we herein report the development of a green flame-retardant PAN based on bio-inspired dopamine methacrylamide (DMA) co-monomer. This polymer was synthesized through free radical polymerization of AN and acetonide-protected dopamine methacrylamide (ADMA), followed by deprotection of ADMA. Systematic investigation of the structural evolution of P(AN-co-DMA) confirmed that DMA provides a kinetic advantage for initiating the cyclization of PAN at significantly lower temperatures (209 °C) as well as for controlling effectively the amount of heat generated. Moreover, the effective radical scavenging capability of DMA, and the formation of a carbonaceous layer on the polymer surface, greatly improved the flame-retardant performance of PAN, without the use of conventional additives. This resulted in low heat-release capacity (HRC) and high limiting oxygen index (LOI) values of 58 Jg–1 K−1 and 37% (superior to those values of Nomex®), respectively. The thermal oxidative stabilization (TOS) process and flame retarding properties of PAN/GO composites were further investigated. TOS process and flame retarding mechanism were found to be influenced by ionic interaction and hydrogen bonding between polymer and nanomaterial. This work opens up a facile and sustainable methodology for the design of environmentally friendly and high-performance flame retardants and composites.Graphical abstractImage 1
       
  • Multifunctional performance of carbon nanotubes and graphene nanoplatelets
           reinforced PEEK composites enabled via FFF additive manufacturing
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): M.F. Arif, H. Alhashmi, K.M. Varadarajan, Joseph H. Koo, A.J. Hart, S. KumarThe study is focused on multifunctional performance of carbon nanotubes (CNT) and Graphene nanoplatelets (GNP) reinforced PEEK composites enabled via fused filament fabrication (FFF) additive manufacturing (AM) utilizing in-house nanoengineered filaments. Thermo-physical, mechanical and wear characteristics of electro-conductive PEEK nanocomposites are reported. The coefficient of thermal expansion (CTE) is found to decrease by 26% and 18% with the incorporation of 5 wt% GNP and 3 wt% CNT into PEEK polymer, respectively. The decrease in CTE provides better dimensional stability to resulting nanocomposite structures. Due to uniform dispersion of CNT and GNP in the PEEK matrix, the crystallization temperature and degree of crystallinity are both increased. The 3D printed PEEK nanocomposites reveal interfacial voids between the beads and intra-bead pores and thus exhibit lower density compared to that of the 3D printed neat PEEK. Young's and storage moduli are found to increase by 20% and 66% for 3 wt% CNT loading and by 23% and 72% for 5 wt% GNP loading respectively. However, the PEEK nanocomposites exhibit similar tensile strength to that of neat PEEK. The coefficient of friction obtained from fretting wear tests is found to decrease by 67% and 56% for 1 wt% CNT and 3 wt% GNP loaded PEEK nanocomposites, respectively and the decrease is attributed to reduced hardness and increased porosity. Multifunctional performance of carbon nanostructures reinforced AM-enabled PEEK composites demonstrated here makes them suitable for a range of applications such as orthopedics, oil and gas, automotive, electronics and space.Graphical abstractImage 1
       
  • Flexible La1.5Sr0.5NiO4/Poly(vinylidene fluoride) composites with an ultra
           high dielectric constant: A comparative study
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Keerati Meeporn, Prasit ThongbaiAbstractPoly(vinylidene fluoride) (PVDF)–based polymer composites filled with high–permittivity La1.5Sr0.5NiO4 (LSNO) particles have been fabricated to produce a composite material with excellent dielectric performance and good mechanical flexibility. Micro–sized (μLSNO) and nano–sized LSNO (nLSNO) particles are used separately as fillers. The dielectric properties of the composites are determined by their particle sizes, resultant interfacial area, and the interparticle distances between the LSNO particles. The percolation threshold of the nLSNO/PVDF composite is lower than that of the μLSNO/PVDF composite. A greatly enhanced dielectric response with a high ε′ ≈ 565.9 at 1 kHz and room temperature and an effectively suppressed low loss tangent (tanδ ≈ 0.28) are obtained in the nLSNO/PVDF composite with a filler volume fraction of 30 vol %. The greatly enhanced ε′ value of nLSNO/PVDF can be explained by a combination of the interfacial polarization at the semiconducting nLSNO–insulating PVDF interfaces, an intrinsically giant ε′ response in nLSNO particles, and shorter interparticle distances between nLSNO particles in the PVDF matrix, while the retained low tanδ value is primarily attributed to the formation of a micro–capacitor microstructure.
       
  • New processing technique for biodegradable kenaf composites: A simple
           alternative to commercial automotive parts
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Nabilah Afiqah Mohd Radzuan, Dulina Tholibon, Abu Bakar Sulong, Norhamidi Muhamad, Che Hassan Che HaronAbstractFor the first time, an innovative combed technique was used for the successful preparation of untreated kenaf fibre. Subsequent to investigations, the combed strategy, provided a smooth kenaf surface with a tensile strength of 692 MPa. Although, while the water absorption was recorded as an excellent 8%, the 92° contact angle, indicated exceptional interfacial bonding, between the fibre-matrix. These results were confirmed through morphological images, which revealed the occurrence of minimal fibre breakage. Thus, the outstanding mechanical properties that come with an untreated kenaf composite, suggest a useful alternative material for automotive parts generation such as dashboard and door panel.
       
  • Poly(isosorbide carbonate): A ‘green’ char forming agent in
           polybutylene succinate intumescent formulation
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Chi Hu, Serge Bourbigot, Thierry Delaunay, Marion Collinet, Sophie Marcille, Gaëlle FontaineAbstractA new flame retardant (FR) intumescent system for polybutylene succinate (PBS) was developed using poly(isosorbide carbonate) (PIC), a bio-based polymer, as a ‘green’ char forming agent. The use of this charring agent in PBS/ammonium polyphosphate (APP) permits to obtain better efficiency than PBS/APP alone for mass loss cone calorimetry (MLC) test: pHRR was decreased by 24% vs 19%, THR was decreased by 48% vs 25% and the yield of residue was increased to 44% vs 23% respectively. According to the temperature measured by thermocouples embedded in the sample, the char formed for PBS/PIC/APP showed a better heat barrier effect than that of PBS/APP: under the char, the temperature and the heating rate of PBS/PIC/APP is significantly lower than those of PBS/APP. Obvious differences of the chemical composition and the morphology of the chars highlight that the good results obtained for PBS/PIC/APP were governed by a glass type char formed during the MLC test.
       
  • Experimental investigation and damage simulation of large-scaled filament
           wound composite pipes
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Zhenyu Huang, Xudong Qian, Zhoucheng Su, Dinh Chi Pham, Narayanaswamy SridharAbstractThis paper investigates the progressive collapse of filament wound Toray T700/Epotech X4201 composite pipes with various layups via a combined experimental and numerical study. The experimental program examines the flexural behavior of full-diameter T700/X4201 pipes under four-point bending and the tensile behavior of filament wound coupon specimens cut from the pipes. The tests show that the composite layup significantly influences the deformation, flexural resistance, and failure mechanisms of the composite pipes. The CFRP pipe with the optimal complex layup [(90/±15/90/±453)5/±453] design has higher ultimate resistance in bending than other designs with layups of [±45]28 and [90]56. Coupon tests show similar effects of composite layup on the tensile behavior of coupon specimens. The numerical effort evolves a three-dimensional progressive damage model to predict the failure in the CFRP coupons and pipes. The damage model incorporates a nonlinear in-plane shear behavior of the T700/X4201 composite material prior to damage initiation and uses a continuum damage mechanics approach to model the matrix and fiber damage progression in the composite pipes. The combined experimental-numerical work provides a more complete understanding of the bending behavior of large-scaled composite pipes, showing distinct failure modes for filament wound pipes with different layups. The load-displacement curves, ultimate bending resistance and failure modes of the composite pipes with different layups are accurately captured using the proposed damage model, demonstrating the capability for the failure analysis of large-scaled composite pipes such as composite risers in offshore applications.
       
  • Novel phosphorus-containing imidazolium as hardener for epoxy resin aiming
           at controllable latent curing behavior and flame retardancy
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Ying-Jun Xu, Xiao-Hui Shi, Jia-Hui Lu, Min Qi, De-Ming Guo, Li Chen, Yu-Zhong WangOne-pack flame-retardant epoxy resins (EP) with long pot life before using, high curing activity during operating and satisfactory fire safety after curing are extremely needed in electrical & electronics and composite industries. Here, imidazolium diphenylphosphinate (IDPP) was designed and synthesized by a facile way, thereafter used as a hardener for diglycidyl ether of bisphenol A type EP (DGEBA). IDPP/DGEBA possessed long-term stability in liquid state at ambient temperature while cured rapidly under heating, presenting controllable latent curing behavior relying on temperature. Specific phosphorus-containing groups were finally attached to epoxy chains mainly by ionic bonds, thus slightly affected the network structures of the resins. Consequently, the cured EP simultaneously achieved high glass transition temperature (Tg), good thermal stability, excellent flame retardancy and expected dielectric performance. Especially, with only 15 wt% IDPP incorporated, the cured DGEBA exhibited a high Tg (172.7 °C), low dielectric constant (4.00) and loss (0.004) at 10 MHz respectively, and easily achieved UL-94 V-0 rating with a high limiting oxygen index (37.0%). The data obtained from cone calorimetry indicated the flammability of the resins was significantly suppressed when cured with IDPP. It was verified by thermogravimetric analysis/infrared spectrometry that IDPP showed dominating vapor-phase flame-retardant effect in DGEBA systems. Additionally, IDPP was also qualified as a latent hardener for tetraglycidyl diaminodiphenylmethane (TGDDM) with excellent thermal stability and flame retardancy.Graphical abstractA novel phosphorus-containing imidazolium was designed and synthesized as the latent hardener for both DGEBA and TGDDM with excellent thermal stability, flame retardancy and dielectric properties.Image 1
       
  • Effect of porosity on the nonlinear and time-dependent behavior of Ceramic
           Matrix Composites
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Unni Santhosh, Jalees Ahmad, Greg Ojard, Imelda Smyth, Yasser Gowayed, George JeffersonAbstractThe effect of porosity on the non-linear stress-strain response and time-dependent strain response under constant stress has been investigated. The material used in the study is a woven composite of CG-Nicalon™ fiber and SiNC matrix. The composite has been modeled using a model for spheroidal inclusions in a medium in combination with a micromechanics-based progressive damage and constituent inelasticity model for CMCs. Numerical estimates of deformation and failure are shown to compare favorably with experimental measurements. It has also been shown that porosity affects through-thickness properties more as compared to the in-plane properties and that creep rupture strength is significantly degraded by increased porosity in the material.
       
  • Constitutive modeling for time- and temperature-dependent behavior of
           composites
    • Abstract: Publication date: 1 March 2020Source: Composites Part B: Engineering, Volume 184Author(s): Orzuri Rique, Xin Liu, Wenbin Yu, R. Byron PipesAbstractStructural integrity, durability, and thermal stability represent critical areas for adequately modeling the behavior of composite materials. Polymeric matrices are prone to have time-dependent behavior very sensitive to changes in temperature that influence the effective properties of the composite. This study extends mechanics of structure genome (MSG) to construct a linear thermoviscoelastic model that allows to homogenize three-dimensional heterogeneous materials made of constituents with time- and temperature-dependent behavior. The formulation models the transient strain energy based on integral formulation for thermorheologically simple materials and treats thermal expansion creep as inherent material behavior. An analytical three-dimensional thermoviscoelastic homogenization solution has been derived for laminates modeled as an equivalent, homogeneous, anisotropic solid. Three-dimensional representative volume element (RVE) analyses and direct numerical simulations using a commercial finite element software have been conducted to verify the accuracy of the MSG homogenization. Unlike MSG, the RVE method exhibits limitations to properly capture the long-term behavior of effective coefficients of thermal expansion (CTEs) when time-dependent constituent CTEs are considered. The analyses of the homogenized properties also reveal that the shift factor of the polymeric matrix drives the temperature dependencies of the effective CTEs and engineering constants of the heterogeneous composite material regardless of the structural scale.
       
  • The fatigue repairing evaluation of hybrid woven composite patch with
           2D&3D styles bonded Al-alloy plates under UV and thermal curing
    • Abstract: Publication date: Available online 3 January 2020Source: Composites Part B: EngineeringAuthor(s): Jiaojiao Xi, Renkun Xia, Yannan He, Zhiqiang YuAbstractThe fatigue performance of repaired Al-alloy plates bonded by 2D&3D woven composite patch under UV and thermal curing was evaluated. The fatigue life N, crack growth rate da/dN, stress intensity factor range ΔΚ, the ‘m’ from Pairs equation and the fracture morphology were characterized to investigate the influence of patch styles and curing methods on the repairing effect. The results showed that fatigue performance was enhanced relative to unrepaired system. The stress was transferred from the crack tip to composite patch by adhesive for reducing the ΔK, and then da/dN was further restrained, contributing to the improvement of fatigue lifetime. The 3D patch had better repair effect than that of 2D patch, and UV curing was superior to thermal curing. It was more sensitive to the curing methods. The sample repaired by 3D patch under UV radiation (U-3D/25) presented the optimal performance, and fatigue lifetime reached 48651 cycles, increased by 806.14% relative to unrepaired system, which was proved by the decrease of ‘m’. The repair samples showed different fracture morphologies, which was attributed to changes of crack propagation path and stress distribution of different repair system. The fracture surface of U-3D/25 revealed ductile fracture features, presenting the optimal repair effect.
       
  • Highly thermal conductive and electrical insulating polymer composites
           with boron nitride
    • Abstract: Publication date: Available online 3 January 2020Source: Composites Part B: EngineeringAuthor(s): Meng Li, Mengjie Wang, Xiao Hou, Zhaolin Zhan, Hao Wang, Hui Fu, Cheng-Te Lin, Li Fu, Nan Jiang, Jinhong YuThe heat accumulation has become a serious problem due to electronic devices towards high power and intelligence. Highly thermal conductive and electrical insulating polymeric composites are potential to solving the overheating problem of electronic devices. Herein, boron nitride nanosheets (BNNSs) were successfully exfoliated by shear forces generated high pressure. Then, BNNSs and sphere BN (S-BN) were added into the polydimethylsiloxane (PDMS) matrix to prepare composites. The thermal conductivity of the BNNSs/PDMS composites achieved 1.16 W m-1 K-1 at 35 wt% fillers, which is almost 5 times that of pure PDMS and higher than that of S-BN/PDMS composites. The efficient thermal paths were constructed by BNNSs in PDMS matrix leading to enhancing the thermal transport in polymer matrix. Meanwhile, the volume resistances and breakdown strength of BNNSs/PDMS composites reach 7.5 × 1013 Ω cm and 39.8 V/μm, which are attributed to the superior electrical insulating properties of BNNSs. The result shows that the excellent thermal conductivity and electrical insulation properties of BNNSs/PDMS make it a promising application in the field of thermal management.Graphical abstractImage 1
       
  • Discontinuous micro-fibers as intrinsic reinforcement for ductile
           Engineered Cementitious Composites (ECC)
    • Abstract: Publication date: Available online 2 January 2020Source: Composites Part B: EngineeringAuthor(s): Duo Zhang, Jing Yu, Haoliang Wu, Beata Jaworska, Brian R. Ellis, Victor C. LiAbstractEngineered Cementitious Composites (ECC) has demonstrated superior mechanical and durability performance than conventional concrete. In the micromechanical reinforcing system of ECC, fiber plays a pivotal role in establishing the ultrahigh tensile ductility and autogenous crack width control. This article reviews the state-of-the-art of discontinuous micro-fibers as intrinsic reinforcement of ECC regarding technical performance as well as environmental and economic impacts. Mechanical properties of ECC made with different micro-fibers, man-made or natural, and their embodied energy, emissions and material cost, are comprehensively surveyed. Further, studies on fiber hybridization are discussed regarding the combination of different fiber types to form synergetic reinforcements that mitigate total material cost, and potentially enhance the composite performance. Recommendations on fiber selections are highlighted and directions for future research are suggested.
       
  • High-velocity impact onto a high-frictional fabric treated with adhesive
           spray coating and shear thickening fluid impregnation
    • Abstract: Publication date: Available online 2 January 2020Source: Composites Part B: EngineeringAuthor(s): Yun Ho Kim, Sarath Kumar Sathish Kumar, Yurim Park, Hyunseok Kwon, Chun-Gon KimAbstractThe ballistic performance of a bullet-proof fabric can be increased by an increment in the friction between fibres. For enhancement of this performance, numerous studies on the shear thickening fluid (STF)-impregnated fabric have been conducted. The STF as a fluid, however, has inherent shortcomings. Our research aim is to understand and compare experimentally two different bullet-proof fabrics treated with a simple spray coating and STF impregnation. In this study, 71 single yarn pull-out and 90 high-velocity impact experiments were carried out. It was remarkable that the newly proposed Heracron fabric coated with a commercial coating spray increased by more than 90% the energy absorption before penetration, with only less than 15% of add-on weight. It was found that the polymeric anchors created on the fibre produce an exceptionally high level of friction between fibres, according to a microscopic morphological analysis and the single-yarn pull-out experiment. This study revealed the physical explanation of this coating method, showed its feasibility, and considered its effectiveness with excellent results.
       
  • Fluorescence labelling and self-healing microcapsules for detection and
           repair of surface microcracks in cement matrix
    • Abstract: Publication date: Available online 2 January 2020Source: Composites Part B: EngineeringAuthor(s): Xingang Wang, Zhongfa Chen, Wei Xu, Xingjing WangFluorescence labelling and self-healing microcapsules (FLSM) with fluorescein sodium labelled epoxy resin as core materials and urea-formaldehyde resin as shell materials were synthesized by in situ polymerization via ultrasonic dispersion. Micromorphology, chemical structure, thermal stability and reactivity of FLSM were studied by ESEM, FTIR, TGA and DSC. Laser scanning confocal microscopy (LSCM) was served to characterize the surface microcracks repair process of cement paste mixed FLSM. The results showed that FLSM with full spherical particles and a certain roughness on the surface were well dispersed in the range of 150–300 μm of particle size. The addition of fluorescein sodium has no significant effect on the micromorphology, chemical structure, thermal stability and reactivity of FLSM. After being cut by the blade, the fluorescence width of FLSM increased from 9 μm to 22 μm within 0–12 h. The core materials of FLSM was basically lost, which indicated that the core materials had good fluidity. When the microcracks occur on the surface of cement paste, FLSM can not only detect the specific location of the microcracks and repair them, but also infer the width of the microcracks. It provides a new method for detecting and repairing microcracks on the surface of cement matrix.Graphical abstractImage 1
       
  • Dynamic interfacial debonding in sandwich panels
    • Abstract: Publication date: Available online 26 December 2019Source: Composites Part B: EngineeringAuthor(s): Itay Odessa, Yeoshua Frostig, Oded RabinovitchAbstractA nonlinear dynamic analytical approach is formulated aiming to investigate the dynamic interfacial debonding mechanism in sandwich panels. The approach is derived using the variational principle of virtual work and it incorporates the Extended High-Order Sandwich Panel Theory with a cohesive interface modeling for the interfaces between the face sheets and the core. The model adopts the first-order shear deformation theory kinematic assumptions for the face sheets along with a geometrically nonlinear behavior. The high-order small deformations kinematic assumptions that account for out-of-plane compressibility are considered for the core layer. The two interfaces link the three components of the panel together and the nonlinear traction-displacement laws introduce the interfacial nonlinearity into the model. The model considers dynamic effects in order to assess the influence of the inertial terms on the interfacial debonding mechanism and to examine the coupling between the two. The results of the dynamic analysis are compared with results of a static analysis for two cases: a sandwich panel with a pre-existing delamination subjected to an end-shortening loading and an intact sandwich panel subjected to three-point-bending. In the second case, the interfacial debonding triggers a dynamic response that substantially affects the structural behavior. The dynamic results, the assessment of the time scales of the process, and the comparison with the static results shed light on the significance of the dynamic nature of the interfacial debonding failure mechanism.
       
  • Thermoformability characterisation of Flax reinforced polypropylene
           composite materials
    • Abstract: Publication date: Available online 17 December 2019Source: Composites Part B: EngineeringAuthor(s): Yousef Dobah, Ioannis Zampetakis, Carwyn Ward, Fabrizio ScarpaAbstractFlax reinforced polypropylene (Flax/PP) composites are currently used as sustainable and recyclable materials in secondary load-bearing applications. This study focuses on the effects of the thermoforming parameters (temperature, dwelling time, pressure and fabricated area parameters) and moisture absorption on the mechanical and aesthetic performance of Flax/PP laminates. The manufacturing and environmental variables have been investigated following a sequential order to identify a cumulative improvement on the performance of the Flax/PP composites. Temperature and dwelling time were the parameters with greatest influence on the aesthetics and mechanical performance of the Flax/PP. The thermoforming pressure and the size of the manufacturing area were the parameters that contributed the less. Although the moisture absorption degraded the Flax/PP mechanical performance, the moisture desorption had however a negligible impact. We therefore conclude that Flax/PP thermoformed parts could be suitably produced and stored in normal room conditions.
       
  • On the fracture toughness of metal-composite adhesive joints with
           bending-extension coupling and residual thermal stresses effect
    • Abstract: Publication date: Available online 11 December 2019Source: Composites Part B: EngineeringAuthor(s): Panayiotis Tsokanas, Theodoros Loutas, Georgios Kotsinis, Vassilis Kostopoulos, Wouter M. van der Brink, Federico Martin de la EscaleraAbstractThe present work presents results from an analysis of the mode I and II interfacial fracture behavior of a new adhesive joint between thin titanium and CFRP adherents, that is destined for application in the future aircraft's leading edge. The joint is stiffened with two aluminum beams to prevent large deformations during testing. An engineering approach for the design of fracture toughness tests for the present joint is followed. The vacuum-assisted resin transfer molding technique is employed for the manufacturing of specimens subsequently tested using the double cantilever beam (DCB) and the end-notched flexure (ENF) configurations. Towards the fracture toughness determination from the experimental data, a new analytical model that considers the bending-extension coupling induced by the presence of the aluminum beams and the manufacturing-induced residual thermal stresses is applied. The analytical fracture toughness predictions are validated by two-dimensional finite element analyses. Crack propagation analyses based on the virtual crack closure technique and the cohesive zone modeling are performed to capture the experimental behavior and extract useful fracture toughness properties of the joint. A comparison of various literature's data reduction schemes reveals the level of error if factors such as the bending-extension coupling and/or the residual thermal stresses are ignored.
       
  • Effect of temperature on the bond behaviour of GFRP bars in concrete
    • Abstract: Publication date: Available online 16 November 2019Source: Composites Part B: EngineeringAuthor(s): Sandor Solyom, Matteo Di Benedetti, Maurizio Guadagnini, György L. BalázsAbstractGlass Fibre Reinforced Polymer (GFRP) bars have been employed as internal reinforcement for concrete members when corrosion of the commonly used steel bars is expected to be an issue. While a good bond is anticipated between GFRP bars and concrete at ambient temperature, the bond performance at high temperature is expected to be reduced due to the physical and mechanical changes that the matrix undergoes at temperatures approaching the glass transition temperature (Tg). Up to date this phenomenon has only been marginally investigated and most of the available bond tests are performed at ambient temperatures after cooling of the heated specimens.This paper presents the results of an experimental investigation on the bond behaviour of GFRP bars in concrete and exposed to temperature levels ranging from ~20 °C to 300 °C. The test specimens, consisting of an indented GFRP bar embedded in a cylindrical concrete block, were heated in an electric furnace. The pull-out tests were carried out within the furnace only after the temperature level, measured with thermocouples at the interface of GFRP and concrete, stabilized to the desired value.The paper discusses the effect of temperature on bond behaviour in terms of bond strength, bond stress-slip relationships and failure modes. A contactless technique measuring the free-end slip during pull-out tests at high temperatures was developed and its effectiveness demonstrated. Finally, the experimental results were used to calibrate the parameters of the two most widely used analytical models: mBPE and CMR.
       
  • Catalyst free self-healable vitrimer/graphene oxide nanocomposites
    • Abstract: Publication date: Available online 30 November 2019Source: Composites Part B: EngineeringAuthor(s): Balaji Krishnakumar, R.V.Siva Prasanna Sanka, Wolfgang H. Binder, Chanwook Park, Jiwon Jung, Vijay Parthasarthy, Sravendra Rana, Gun Jin YunCatalyst free graphene oxide (GO) promoted self-healing vitrimer nanocomposites are designed, where the synthesized vitrimer nanocomposites displays self-healing properties via disulfide exchange based covalent adaptive network behavior. This study found that GO based nanofiller enhance the self-healing properties, including the shape memory and flexural strength of the materials. The GO induced lower glass transition was helpful to achieve low temperature self-healing: when compared to epoxy vitrimers (73% and 60% self-healing) the vitrimeric nanocomposites demonstrates a 88% and 80% self-healing for the first and second cycle, respectively.Graphical abstractGraphene promoted catalyst free vitrimer nanocomposites are designed, where the nanocomposites demonstrate the self-healing properties via disulfide exchange based covalent adaptive network behavior.Image 1
       
  • An improved plastically dilatant unified viscoplastic constitutive
           formulation for multiscale analysis of polymer matrix composites under
           high strain rate loading
    • Abstract: Publication date: Available online 30 November 2019Source: Composites Part B: EngineeringAuthor(s): Christopher Sorini, Aditi Chattopadhyay, Robert K. GoldbergAbstractPolymer matrix composites are commonly used to fabricate energy-absorbing structures expected to experience impact loading. As such, a detailed understanding of the dynamic response of the constituent materials is necessary. Since the rate, temperature, and pressure dependence of carbon fiber reinforced polymer matrix composites are primarily manifestations of the rate, temperature, and pressure dependence of the polymer matrix, it is crucial that the constitutive behavior of the matrix be accurately characterized. In this work, an existing unified viscoplastic constitutive formulation is extended to ensure thermodynamic consistency and more accurately account for the tension-compression asymmetry observed in the response of polymeric materials. A new plastic potential function is proposed, and elementary loading conditions are utilized to determine relations between model constants to ensure nonnegative plastic dissipation, a necessary thermodynamic requirement. Expressions for plastic Poisson's ratios are derived and are bounded by enforcing nonnegative plastic dissipation. The model is calibrated against available experimental data from tests conducted over a range of strain rates, temperatures, and loading cases for a representative thermoset epoxy; good correlation between simulations and experimental data is obtained. Temperature rises due to the conversion of plastic work to heat are computed via the adiabatic heat energy equation. The viscoplastic polymer model is then used as the constitutive model in the generalized method of cells micromechanics theory to investigate the effects of matrix adiabatic heating on unidirectional composite response. The thermodynamic consistency of the model ensures plastic dissipation can only cause an increase in temperature. Significant thermal softening due to the conversion of plastic work to heat is observed for matrix dominated deformation modes.
       
  • Carbonized cellulose nanofibers as dielectric heat sources for microwave
           annealing 3D printed PLA composite
    • Abstract: Publication date: Available online 30 November 2019Source: Composites Part B: EngineeringAuthor(s): Ju Dong, Xingyan Huang, Pranjali Muley, Tongyao Wu, Mohamad Barekati-Goudarzi, Zhengjie Tang, Meichun Li, Sunyoung Lee, Dorin Boldor, Qinglin WuFilament fused fabrication (FFF) is an extrusion-based 3D printing technology for manufacturing thermoplastic components. One major obstacle facing 3D printed thermoplastic material is the reduced crystallinity resulting from a fast quench when material exiting the 3D printer hot nozzle solidifies quickly at the low-temperature platform, leading to reduced mechanical performance. Here, we report an accelerated annealing strategy with the assistance of microwave heating, aiming to enhance crystallinity and mechanical performance of FFF 3D printed polylactic acid (PLA) composite. We selected naturally abundant cellulose fibers as precursors for producing carbonized cellulose nanofibers (CCNFs), and compounded CCNFs with PLA to produce bi-component filament for 3D printing of final composite. After being irradiated with microwave, the embedded CCNFs in composite selectively absorbed microwave energy and generated heat. Subsequently, the localized heat transferred to the adjacent PLA regions, triggering amorphous PLA chains to repack and convert to new crystallites. In this work, annealing conditions, including heating method (i.e., oven annealing vs. microwave annealing), time (0–120 min), and temperature (80 vs. 120 °C), were systematically studied to understand the relevant effects on the resulting parameters including PLA crystallinity and composite strength. Microwave annealing method was also compared with conventional oven annealing method and results shows that microwave annealing significantly reduced the required annealing time to reach the maximum crystallinity and tensile strength. Notably, microwave annealing performed below cold crystallization temperature was exceptionally suitable to develop an optimized crystallinity and tensile strength for 3D printed PLA composite.Graphical abstractImage 1
       
  • An evaluation of life cycle assessment and its application to the
           closed-loop recycling of carbon fibre reinforced polymers
    • Abstract: Publication date: Available online 29 November 2019Source: Composites Part B: EngineeringAuthor(s): Rhys J. Tapper, Marco L. Longana, Andrew Norton, Kevin D. Potter, Ian HamertonAbstractLife cycle assessment (LCA) is a valuable tool for establishing the environmental burdens of a composite material over its lifetime. It is therefore of importance to the composites industry as a material selection tool when determining the applicability of recycled composites in the component design phase. This review paper evaluates the LCA framework and its ability to accurately determine the benefits of closed-loop composite recycling, with the aim of aiding future material selection for recycled CFRP. LCA is a powerful tool for CFRP assessment when used in combination with an economic and technical component as covered by the integrated Life Cycle Engineering approach. The broad range of values available in LCA databases may prove an issue for cross comparison between studies and provide disparate results leading to impractical conclusions. The use phase offers the greatest potential for CFRP emissions savings in the transport sector; the advent of closed-loop recycling for CFRP may provide the multiple use phases required to breakeven on the significant energy burden of production or possibly provide net environmental savings gains over traditional materials.
       
  • Thin-plies in adhesively bonded carbon fiber reinforced polymers
    • Abstract: Publication date: Available online 28 November 2019Source: Composites Part B: EngineeringAuthor(s): J. Kupski, S. Teixeira de Freitas, D. Zarouchas, R. BenedictusAbstractThe aim of this study is to evaluate the enhanced off-axis properties of thin plies to improve the performance of adhesively bonded carbon fiber reinforced polymers. Single lap bonded joints with three different ply thicknesses of 200 μm, 100 μm and 50 μm were tested under quasi-static tensile loading. Acoustic Emission and Digital Image Correlation were used to monitor the damage and strain evolution of the overlap area during testing. 3D post-mortem failure analysis of the fracture surfaces were performed using a 3D profiling microscope. Experimental results show an increase of 16% in the lap shear strength and an increase of 21% in the strain energy when using the 50 μm instead of 200 μm ply thicknesses. However, Acoustic Emission measurements show that the damage initiation is postponed up to a 47% higher load when using 50 μm instead of 200 μm ply thicknesses. Moreover, the total amount of acoustic energy released from initiation up to final failure was significantly less with thin plies. A non-linear finite element analysis up to damage initiation indicates that with decreasing ply thickness, the damage onset inside the composite is postponed to higher loads and moves away from the adhesive interface towards the mid-thickness of the adherend. It is found that, decreasing the single ply thickness of laminated composite adherends in a single overlap bonded joint increases the maximum load and delays damage initiation of the joint, however the damage progression till final failure is more sudden.
       
 
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