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Composites Part B : Engineering
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ISSN (Print) 1359-8368
Published by Elsevier Homepage  [3184 journals]
  • Novel carbon-fibre powder-epoxy composites: Interface phenomena and
           interlaminar fracture behaviour
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Dimitrios Mamalis, James J. Murray, Jake McClements, Dimitrios Tsikritsis, Vasileios Koutsos, Edward D. McCarthy, Conchúr M. Ó Brádaigh Carbon fibres with three different sizing agents were used to manufacture unidirectional composites based on a powder epoxy resin. Powder epoxy processing was investigated as a route for fast, cost-effective manufacturing of out-of-autoclave composites compared to more time-consuming vacuum infusion technologies. In this work, a heat-activated epoxy powder was used as a resin system in low-cost vacuum-bag-only prepregs for thick composite parts that are required in the renewable energy industry (e.g. wind turbine blade roots). The importance of interfacial bonding between fibres and the matrix is shown and the impact on the ultimate mechanical performance of the manufactured composites demonstrated. The surface characteristics of the sizing on the carbon fibres were investigated using atomic force microscopy (AFM) and Raman spectroscopy. Results showed that the amount of sizing on the fibres' surfaces was inextricably linked with surface roughness and coverage. This in turn influenced the mechanical and chemical interlocking phenomena occurring at the fibre/matrix interface. The composites’ mechanical performance was evaluated using tensile, flexural and interlaminar fracture toughness tests. Fractographic analysis using optical and scanning electron microscopy (SEM) was likewise employed to analyse the fracture surfaces of the tested/failed composites. Interlaminar fracture toughness testing (DCB Mode-I) revealed that the interfacial adhesion differences could alter the fracture resistance of the composites, hence emphasizing the importance of the interfacial bonding strength between the polymer matrix and the carbon fibres.Graphical abstractImage 1
       
  • Cobalt Diselenide@Reduced graphene oxide based nanohybrid for
           supercapacitor applications
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Yuanqiang Song, Ao Ran, Ziru Peng, Wutong Huang, Binglan Huang, Xian Jian, Chunhong Mu Cobalt selenide@reduced graphene oxide (CoSe2@rGO) nanohybrid was successfully synthesized by a facile one-pot hydrothermal method and the electrochemical performance of the nanohybrid was evaluated for supercapacitor applications. The CoSe2@rGO nanohybrid show superior electrochemical performance in terms of the specific capacitance (449 F g−1 at 2 mV s−1, 219 F g−1 at 0.5 A g−1) and enhanced cyclic stability (91.3% capacitance retention for 5000 cycles) relative to pure CoSe2 (196 F g−1 at 2 mV s−1, 99 F g−1 at 0.5 A g−1). Such a highly improved specific capacitance found in the CoSe2@rGO nanohybrid electrode is mainly attributed to the nanosized CoSe2 grains with perfect redox property, more electro-active sites induced by synergetic effect at the interface of CoSe2 and rGO, and high specific area of rGO nanosheets. Besides, with the combination of rGO, the electrical conductivity of the CoSe2@rGO nanohybrid is highly enhanced, the ion/electron diffusion path is also reduced leading to faster charge transport during charging/discharging process with an improved cyclic stability.
       
  • First-order shear deformation analysis of rectilinear orthotropic
           composite circular plates undergoing transversal loads
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Valerio G. Belardi, Pierluigi Fanelli, Francesco Vivio This work outlines the elastic bending analysis of transversely loaded shear-deformable rectilinear orthotropic composite annular plates. The load condition discussed in the paper, along with the displacement constraints, are derived by the composite bolted joints theoretical reference model – this analytical solution is a necessary effort for the obtainment of a custom finite element capable of simulating this kind of joints with high accuracy and limited computational effort. Firstly, the constitutive equations of the family of plate under investigation are obtained in the framework of the First-order Shear Deformation Plate Theory. The described methodology is founded on the application of the virtual displacements principle and its solution is performed according to Ritz method after the writing of displacement field approximation functions fulfilling the boundary conditions. The three unknown displacement components are obtained for different case studies concerning rectilinear orthotropic composite annular plates featuring various slenderness ratios, shape factors and stacking sequences. The outcomes comparison with FE numerical solutions evidences a high degree of fidelity. The presented results demonstrate that this enhanced version of the Ritz analytical solution method, which accounts for the composite plate shear deformability, can be more effectively employed to describe the displacement field of composite plates connected by a bolted joint in the area surrounding the bolt.
       
  • Fracture of laminated bamboo and the influence of preservative treatments
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Thomas P.S. Reynolds, Bhavna Sharma, Erik Serrano, Per-Johan Gustafsson, Michael H. Ramage Treated bamboo can be made into large, durable structural elements which have the potential to become a transformative large-scale building material, but the fracture behaviour which determines their ultimate strength in various loading scenarios has not been studied. Laminated bamboo is a promising structural engineered bamboo material, and is generally made from bamboo treated to improve its durability. Studies into the structural behaviour of laminated bamboo indicate that different preservative treatments affect the structural properties of the composite differently, with conflicting evidence from tests in different load orientations. This study uses fracture mechanical testing and microscopy to develop an understanding of the fracture mechanics of engineered bamboo, and explains why the properties of the composite under tension, compression and bending may be affected differently by the treatment processes. Two types of treated Moso bamboo are studied alongside the same material with minimal processing. The treated material had gone through one of two commercial processes: bathing in a hydrogen peroxide bleach solution, or treatment by pressurised steam (described as caramelised). The results show that the critical strain energy release rate in the caramelised material is much lower than that in the bleached, and the fracture behaviour of the bleached material is closer to that of the raw bamboo. Fracture experiments included Mode I and Mode II fracture with cracks progressing parallel to the grain, and Mode I fracture with a crack progressing perpendicular to the grain. The results shed new light on the strength of structural-size elements.
       
  • Structural health monitoring for woven fabric CFRP laminates
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): A. Alsaadi, J. Meredith, T. Swait, J.L. Curiel-Sosa, Yu Jia, S. Hayes Structural health monitoring is directly linked to structural performance, hence it is one of the main parameters in the safety of operation. This paper presents the development of an innovative structural health monitoring system for woven fabric carbon fibre reinforced polymer (CFRP) laminates fabricated using both vacuum assisted resin transfer moulding and pre-preg technique. The sensing system combines the ability to monitor strain due to applied loads, as well as to detect, and assess damage due to low velocity impact events. Bending loads were applied on a beam-type specimen and changes in electrical resistance, due to piezoresistivity of carbon fibres, were monitored. The change in electrical resistance was a function of applied load and reversible up to 0.13% strain. Two thicknesses of composite panel, 2.09 (vacuum assisted resin transfer moulding) and 1.63 mm (pre-preg) were made, and were subjected to a range of low velocity impact energies. The resultant damage areas, as measured using ultrasonic C-scanning, were plotted against changes in electrical resistance to provide a correlation plot of damage area against impact energy. An inverse analysis, using this correlation plot, was performed to predict the damage area from a known impact event. 85% accuracy in the predicted damage area was achieved in comparison with subsequent C-scan data on the unknown damage.
       
  • Multiscale analysis of notched fiber reinforced laminates
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Deepak K. Patel, Anthony M. Waas An efficient two-scale computational method to predict the progressive damage and failure response of three different polymer matrix multidirectioanl laminates used in the Tech Scout-1 challenge, conducted by Air Force Research Laboratory (AFRL) for uniaxial tensile and compressive responses is presented. The sub-scale model is an analytical model, the 2CYL (2-concentric cylinder) model, developed by Zhang and Waas [1] earlier. The material system is IM-7/977–3. The notched laminates are modeled explicitly using 3D solid elements for individual lamina and the interlaminar finite thickness layer is modeled using discrete cohesive zone elements (DCZM) [2]. The constituent level input parameters are obtained from standard unnotched [0], [90] and [+45/−45]4s coupon level experimental data, provided by AFRL. The matrix microdamage and the lamina pre-peak nonlinearity are modeled using a secant stiffness approach, while the post-peak softening failure response is modeled using a mesh-objective smeared crack approach (SCA) [3, 4], implemented at the macroscale. The proposed two-scale strategy is implemented for each fiber and matrix dominated intralaminar failure modes and interfaced with the SCA to predict the macroscopic response and the detailed local ply level progressive failure mechanisms. The predicted results are compared with experimental results [5] that show very good agreement.
       
  • The pull-out behavior of chemically treated lignocellulosic fibers
           /polymeric matrix interface (LF/PM): A review
    • Abstract: Publication date: Available online 22 June 2019Source: Composites Part B: EngineeringAuthor(s): Abdessamad Oushabi The increase of global concerns about environment and sustainability issues related to the preservation of nonrenewable natural resources has attracted a remarkable interest of the scientific community hoping to develop new eco-friendly materials and products based on natural resources. Indeed, many achievements in bio-technology in the field of materials science and composites have been reported in the literature in the last two decades. One of most studied natural resources is lignocellulosic fibers (LFs). Indeed, LFs present interesting advantages: they are biodegradable, abundant and have many high technical qualities; their important mechanical properties and their low density make them candidates to be used to replace the synthetic fibers. However, they are known to be less compatible with polymeric matrices (PMs) because of their hydrophilic nature and the presence of non-cellulosic materials on their surface preventing the formation of strong covalent bonds in LF/PM interface. The aim of this paper is to present a general review on the effect of the most studied chemical treatments on lignocellulosic fibers (LFs). The structural aspects and properties of lignocellulosic fibers (LFs), the effect of chemical treatment on the LF/PM interface using the pull-out testing method and the mechanical properties of final LF-PM biocomposites are discussed in this review article.
       
  • Dynamic crack growth based on moving mesh method
    • Abstract: Publication date: Available online 22 June 2019Source: Composites Part B: EngineeringAuthor(s): Francesco Fabbrocino, Marco Francesco Funari, Fabrizio Greco, Paolo Lonetti, Raimondo Luciano, Rosa Penna A new methodology to predict dynamic crack propagation under generalized loading conditions is proposed. The numerical modeling combines structural mechanics and moving mesh method with the purpose to predict geometry variation produced by the evolution of existing material discontinuities. In particular, moving mesh method is implemented to enforce crack tip displacements by using an explicit crack criterion based on referential and moving configurations. In this framework, the use of mesh regularization method based on proper rezoning equations is able to reduce the use of remeshing attempts, typically required by standard crack propagation procedures. Dynamic crack growth is predicted by a rate dependent criterion, expressed in terms of crack angle and driven forces based on energy release rate definition. The model is quite suitable to predict the evolution of material discontinuities, typically observed in composite structures. Numerical implementation, developed in the framework of a finite element formulation and details on the solving procedure, are presented. The proposed modeling is validated by several comparisons with experimental and numerical data, which show accuracy and robustness of the numerical approach. Moreover, sensitivity analyses in terms of mesh dependence and time required for the solving procedure are also developed.
       
  • Through-thickness inhomogeneity in microstructure and tensile properties
           and tribological performance of friction stir processed AA1050-Al2O3
           nanocomposite
    • Abstract: Publication date: Available online 21 June 2019Source: Composites Part B: EngineeringAuthor(s): R. Darzi Bourkhani, A.R. Eivani, H.R. Nateghi Friction stir processing (FSP) is used to fabricate Al-Al2O3 nanocomposite by addition of Al2O3 nanoparticles into a groove in AA1050 aluminum alloy and being processed using FSP. Evolution of grain structure, distribution of the Al2O3 nanoparticles, tensile properties and tribology are investigated in four samples extracted from each 2 mm of the fabricated composite, respectively from top surface. It was found that the finest grain structure formed in the second region from the top surface due to the most efficient stirring in this region. In addition, the presence of nanoparticles with an efficient distribution in this region may inhibit grain growth and lead to an eventually fine grain structure. After one pass of FSP, nanoparticles were found to be efficiently distributed in the top surface and less uniformly distributed in other regions leading to formation of particle depleted regions (PDRs) and coarse agglomerated particles. Fracture in the tensile test samples changed from ductile to brittle in the sample with agglomerated particles. Application of the second cycle of FSP leaded to further grain refinement, more uniform distribution of nanoparticles and less agglomerated coarse particles and consequently leaded to more uniformity in tensile properties and tribology behavior of the samples. This was the most effective on grain refinement for the regions which were not efficiently refined or with more extended PDRs in the first cycle. Coefficient of friction (CoF) of aluminum was significantly reduced with addition of Al2O3 particles which was attributed to increase in strength and reduction in sliding contact area.
       
  • Investigating the effects of hybrid reinforcement particles on the
           microstructural, mechanical and tribological properties of friction stir
           processed copper surface composites
    • Abstract: Publication date: Available online 21 June 2019Source: Composites Part B: EngineeringAuthor(s): Titus Thankachan, K. Soorya Prakash, V. Kavimani Friction Stir Processing (FSP) technique was employed in this research to fabricate copper surface composites through incorporating a hybrid mixture of reinforcement particles. Hybrid combination of advanced nitride based ceramic particles (25% AlN + 75% BN) was dispersed onto the surface of copper matrix at varying volume fractions through FSP technique. Results demonstrated an increase in mechanical properties with respect to increase in the amount of particle dispersion. Mechanism of fracture of developed set of surface composites was studied with the aid of the fractography. A tremendous increase in wear resistance was observed with respect to increase in the hybrid particle dispersion owing the hardness and the self-lubricating characteristics of dispersed ceramic particles.
       
  • Structural performance of a hybrid FRP composite – Lightweight
           concrete bridge girder
    • Abstract: Publication date: Available online 20 June 2019Source: Composites Part B: EngineeringAuthor(s): Tomasz Siwowski, Mateusz Rajchel A novel hybrid fibre-reinforced polymer (FRP) composite – lightweight concrete (LWC) girder was developed and implemented in a bridge superstructure as a result of the comprehensive R&D project. The new bridge system is intended to have durable, structurally sound, lightweight, and cost effective hybrid FRP/LWC girders that will take full advantage of inherent and complementary properties of composites and lightweight concrete. The proposed hybrid girder consists of a FRP shell with trapezoidal cross-section and a lightweight concrete slab, reinforced with glass fibre-reinforced polymer (GFRP) rebars and acting compositely with the shell. Before implementation, a test specimen fabricated as a full-scale model of prototype bridge girder was subjected to a series of quasi-static and fatigue loading tests. This paper presents the selected results of research on evaluation of stiffness, strength, ultimate capacity, and global factors of safety against failure. The test results were compared to the performance criteria formulated in the relevant bridge standards. The output of research confirmed that the proposed hybrid bridge girder has an excellent performance from the structural engineering point of view, and fulfils the appropriate standard conditions to be implemented in an actual bridge. Moreover, due to quite high safety factors it seems to be possible to optimize the hybrid girder design by reducing the amount of FRP material required.
       
  • Synchronous growth of bamboo-shaped CNTs and PyC for fabricating
           super-elastic nanocomposites
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Gang Kou, Ling-jun Guo, He-jun Li, Ning-kun Liu, Wei Li, He Shen, Li-jing Bai In the field of carbon fibers reinforced pyrocarbon matrix (C/C) composites fabrication, normally the carbon fiber preform is densified with the pyrocarbon matrix (PyC) after it is produced and weaved. Such two-step method is due to the different structures and different fabrication conditions that matrixes and reinforcements require. Here, we achieve the synchronous growth of matrix (PyC) and reinforcement (bamboo-shaped carbon nanotubes, CNTs) in one step using a controlled thermal gradient chemical vapor deposition (TGCVD). This proposed one-step method can greatly simplify the fabrication process of traditional C/C composites. And the fabricated bamboo-shaped carbon nanotubes reinforced pyrocarbon matrix (CNTs/PyC) nanocomposites achieve improved mechanical performance and show isotropy and super-elastic property. The CNTs/PyC nanocomposites can be the substitution of traditional C/C composites and isotropic PyC materials. And such method can provide a new technical strategy for synthesizing multi-carbon structures and other nanocomposites.Graphical abstractImage 1
       
  • Holographic polymer nanocomposites with ordered structures and improved
           electro-optical performance by doping POSS
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Mingli Ni, Guannan Chen, Yong Wang, Haiyan Peng, Yonggui Liao, Xiaolin Xie Holographic polymer nanocomposites containing the liquid crystal (LC) have garnered a great deal of attention primarily because of their unique electric-switchable optical properties. Herein, three types of polyhedral oligomeric silsesquioxane (POSS) are doped into the holographic polymer nanocomposites to tune their ordered structure and electro-optical performance. These POSS dopants are methacryl POSS with eight reactive double bonds, methacrylisobutyl POSS with one reactive double bond, and aminopropylisobutyl POSS with nonreactive groups. Interestingly, methacryl POSS is primarily chemically bonded to the polymer network within the constructive regions, which deteriorates the diffraction efficiency and electro-optical performance due to the depressed ordered structures. In contrast, methacrylisobutyl POSS displays a negligible effect on the diffraction efficiency and electro-optical performance while significantly improving the thermostability of holographic polymer nanocomposites, although it is also chemically linked to the polymer network within the constructive regions. Distinctively, aminopropylisobutyl POSS mainly locates in the destructive regions and clearly improves the electro-optical performance and thermostability of holographic polymer nanocomposites.
       
  • From ferroconcrete to Cf/UHTC-SiC: A totally novel densification method
           and mechanism at 1300 °C without pressure
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Ping Hu, Yuan Cheng, Dongyang Zhang, Liancai Xun, Meng Liu, Chi Zhang, Xinghong Zhang, Shanyi Du Traditional densification of UHTC matrix composites normally requires towering sintering temperature over 1800 °C and high pressure, or dozens of PIP circles around 1600 °C. Illuminated by realization of ferroconcrete, Cf/UHTC-SiC is prepared via a novel densification method and mechanism at 1300 °C without pressure, using liquid polycarbosilane to 50 nm SiC as sufficient supplementation to filling holes and ensuring a strong bonding between dispersive ZrC particles inside carbon fabric after slurry injection. The obtained Cf/ZrC-SiC not only achieves high density at 4.19 g/cm3, but also has robust strength and graceful toughness at 286 ± 25 MPa and 11.12 ± 1.25 MPa m1/2, meanwhile gains a level of ascension in work of fracture to 3046 J/m2.
       
  • Cobalt-containing nanoparticles embedded in flexible carbon aerogel for
           spilled oil cleanup and oxygen reduction reaction
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Lei Wang, Jian Cheng, Quansheng Kang, Rui Wang, Jifeng Ruan, Lixia Li, Lixin Wu, Zhenming Li, Ning Ai To address the global environmental and energy issues, creating multi-functional, effective and lightweight carbon materials as catalysts and adsorbents is of significant importance. Here, ultralow, hydrophobic, superparamagnetic and compressible Co-doped carbon aerogel (CCA) was fabricated by pyrolyzing precursor, namely cobaltiferous resorcinol-formaldehyde/graphene (RFG-Co) composite aerogel obtained through a low-temperature and scale-up hydrothermal process. Due to its outstanding structural features, such aerogel can serve as a good adsorbent for various organic pollutants, with a maximum adsorption capacity of 132 times its own weights as well as excellent recyclability for long lifetime. Besides, the presence of Co-containing nanoparticles on the sheets of the aerogel also endows CCA remarkable electrocatalytic performance toward oxygen reduction reaction (ORR) (onset potential: −0.15 V, half-wave potential: −0.243 V). This work offers a cost-effective strategy to produce multifunctional three-dimensional macroscopic carbon-based material with promising application in both environment and energy fields.Graphical abstractHigh-performance Co-doped carbon aerogel (CCA), which can apply in environment and energy fields, was fabricated by a facile route.Image 1
       
  • Novel dynamic compressive and ballistic properties in 7075-T6 Al-matrix
           hybrid composite reinforced with SiC and B4C particulates
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Min Chul Jo, Jin Hyeok Choi, Jisung Yoo, Donghyun Lee, Sangmin Shin, Ilguk Jo, Sang-Kwan Lee, Sunghak Lee In this study, a hybrid Al-matrix composite reinforced with both SiC and B4C ceramic particulates (SiCp or B4Cp, respectively) was fabricated to increase the volume fraction of ceramics by a liquid pressing process, and its dynamic and ballistic properties were compared with those of monolithic Al-matrix composites reinforced with SiCp or B4Cp. The hybrid composite demonstrated a very high dynamic compressive strength (over 1.5 GPa), along with a good total strain of 11.7%, which readily reached an undiscovered strength area (far over 1.2 GPa) of typical composites. This was basically attributed to the highest ceramic fraction (60 vol%), together with strongly-bonded ceramic/Al interfaces and synergetic hybrid effects of SiCps and B4Cps. After the ballistic test, the hybrid composite was radially cracked with a small hole-mark and a few fallen-off debris, which indicated the higher ballistic properties than those of the SiCp- or B4Cp-reinforced composite because of outstanding dynamic compressive strength and strain.Graphical abstractImage 1
       
  • Strain rate effects on the dynamic compressive response and the failure
           behavior of polyester matrix
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Sonia Sassi, Mostapha Tarfaoui, Mourad Nachtane, Hamza Ben Yahia The dynamic compression behavior of the adhesively bonded composite glass/polyester composite joints at high strain rates was reported earlier by the authors. From this study, it was a question of investigating the dynamic behavior of each component of the adhesively composite joints (adhesive; polymer matrix and the laminate) for a better physical understanding of large deformations in composite assemblies. The results were interpreted here in the context of an experimental investigation of the high-strain-rate compressive behavior of the polyester resin matrix using the Split Hopkinson Pressure Bars (SHPB). The dynamic tests had been performed on the resin samples at similar dynamic conditions that the adhesively composite joints to demonstrate strain rate effects of the resin, as well as to study its own failure process. It was concluded that the dynamic parameters of the resin matrix depended strongly on strain rate due to the visco-plastic effect and the failure modes of the polymer. Based on the experimental results, empirical formulations including the strain-rate effects were developed, for modeling more faithfully the dynamic behavior of composites structures under the impact.
       
  • Functionalization of graphene oxide with poly(ε-caprolactone) for
           enhanced interfacial adhesion in polyamide 6 nanocomposites
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Jaroslav Minář, Jiří Brožek, Alena Michalcová, Romana Hadravová, Petr Slepička Because interfacial adhesion between polymer chains and a nanofiller strongly influences the properties of polyamide nanocomposites, various approaches have been described to improve it. Here, we investigate the covalent functionalization of graphene oxide (GO) with poly(ε-caprolactone) and its application for the in situ synthesis of polyamide 6 nanocomposites. For the functionalization, GO moieties were used to initiate the polymerization of ε-caprolactone, which was followed by the separation of ungrafted polymer chains. TGA and FTIR confirmed covalent bonding between the GO and poly(ε-caprolactone). The synthesis of the nanocomposites was carried out by the in situ polymerization of ε-caprolactam containing either untreated or functionalized GO. TEM and AFM images of the nanocomposites containing the functionalized GO revealed the presence of single exfoliated nanofiller layers. DMA showed that the functionalized GO had a higher reinforcing effect than the untreated one. Thus, the obtained results suggest that our method is simple and effective for enhancing the interfacial adhesion between GO and polyamide 6.Graphical abstractImage 1
       
  • Buckling analysis of composite lattice sandwich shells under uniaxial
           compression based on the effective analytical equivalent approach
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Davoud Shahgholian-Ghahfarokhi, Gholamhossein Rahimi In this paper, a new effective equivalent analytical approach is presented to compute the global buckling of composite lattice sandwich shells under uniaxial compression based on the first-order shear deformation theory (FSDT). The lattice core was transformed into a solid skin, as the middle skin of the sandwich shell by considering the transverse shear strains and the new force and moment effect analysis on the selected unit cell. The equivalent stiffness of the composite lattice sandwich shells is then calculated by superimposing the stiffness contribution of outer, middle and inner skins. Using the FSDT and Rayleigh-Ritz method, the related eigenvalue equations are solved, and the critical buckling load is obtained. Furthermore, a 3D finite element model is built using ABAQUS software for validation. For various test examples with different slenderness ratio, outer/inner thickness and ply stacking sequence, stiffener thickness and the number of unit cells, the efficiency and accuracy of the presented equivalent approach are confirmed by comparing the obtained results with FE and other work results. It is shown that for thick sandwich shells, the use of FSDT for determining their critical buckling load is necessary, more suitable and can give high computational efficiency.
       
  • The investigation of mechanical properties of a structural adhesive via
           digital image correlation (DIC) technic
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Elanur Çelebi Kavdir, Murat Demir Aydin The most important point to be taken into consideration in the use of bonding joints is the reliability of the joints created with the adhesive. Therefore, many analytical, experimental and numerical studies have been done to determine the mechanical properties of adhesives and to ensure the reliable use of adhesively bonding joints. This study presents the first stage of the two-stage study, which aims to determine the mechanical properties of the DP410 structural adhesive in the first stage and the mechanical behavior of the adhesively bonded single lap joints formed using the same adhesive in the second stage. In the study, mechanical properties of the DP410 structural adhesive were investigated experimentally via two dimensional Digital Image Correlation (DIC) technique. Bulk (tensile, Iosipescu and Arcan) and joint form (TAST) specimens were produced from structural bicomponent liquid adhesive (DP410) and subjected to uniaxial tensile and shear loads in the study. Mechanical properties of the DP410 bulk specimens were determined by two different measurement methods (DIC and video extensometer). It was observed upon comparing the results obtained that the DIC technique yielded reproducible results in the determination of the mechanical properties of adhesives and this method of optical measurement could be an alternative to other strain measurement methods. Shear mechanical properties of the DP410 adhesive were obtained via two different strain measurement methods, (DIC and contact extensometer) in the TAST specimens. When the results obtained from TAST specimens were examined, it was observed that the results obtained from DIC method were compatible with contact extensometer and it could be an alternative to contact extensometer. In addition, since local strain distributions can be obtained in the DIC method, it has been observed that this method allows to performe damage analysis of the specimens in bulk and joint form and to obtain the strain values at the desired positions. In this study, the accuracy of the results obtained from the 2D DIC analysis can be increased by using the software which allows to perform the 3D DIC analysis via high resolution cameras and by preparing the sample with the right methods.
       
  • Solution for cross- and angle-ply laminated Kirchhoff nano plates in
           bending using strain gradient theory
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): F. Cornacchia, N. Fantuzzi, R. Luciano, R. Penna The static analysis of Kirchhoff nano plates subjected to uniformly (UDL) and sinusoidally (SSL) distributed load is computed. The strain gradient nonlocal theory has been employed in order to involve the size effects of nanostructures in classical continuum theory. The governing equation of motion of Kirchhoff in weak form are applied to nano plates, involving second-order strain gradient nonlocal theory. Thus, the obtained partial differential equations have an increased order of derivation respect to the classical theory, from the fourth to the sixth. The displacements are carried out following the Navier procedure for simply supported boundary conditions. Isotropic and antisymmetric orthotropic laminates, both cross- and angle-ply are studied, for different layouts involving different material properties. Dimensionless outcomes in terms of transverse displacements, and normal and shear stresses, are given to changing aspect ratio and non local ratio, also making a comparison with the classical theory.
       
  • Reinforced concrete columns of square and rectangular section, confined
           with FRP – Prediction of stress and strain at failure
    • Abstract: Publication date: Available online 17 June 2019Source: Composites Part B: EngineeringAuthor(s): Theodora Fanaradell, Theodoros Rousakis, Athanasios Karabinis Fiber-reinforced polymer (FRP) confined concrete columns under axial compression reveal significantly enhanced axial strength and ductility compared to unconfined columns. Adequate FRP confinement provide hardening stress – strain behavior up to failure especially in columns of circular section. However, it is difficult to model and predict accurately the maximum stress and ultimate strain of the noncircular confined concrete columns in the presence of internal steel reinforcement, which is the real case for the majority of existing structures. Numerous experimental investigations have been carried out for axially loaded circular section concrete columns with or without internal steel reinforcement confined with FRP materials and other techniques. Also, a lot of predictive expressions of peak axial strength and strain and ultimate stress and strain, suitable for similar concrete sections, have been proposed. On the other hand, fewer studies concern reinforced concrete columns of square and rectangular section. The presented investigation gathers all the newest available test results on square and rectangular reinforced or plain concrete columns confined with composite reinforcements and assesses the performance of significant predictive expressions published in literature. The developed database includes these columns confined with FRP materials and other techniques and assesses the performance of 24 existing models proposed for the peak and ultimate conditions.
       
  • On the modeling of tensile behavior of ultra-high performance
           fiber-reinforced concrete with freezing-thawing actions
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Zhidong Zhou, Ruifeng Xie, Pizhong Qiao, Linjun Lu An analytical model is proposed to predict the tensile behavior of Ultra-High Performance fiber-reinforced Concrete (UHPC) with extended cyclic freezing-thawing (F-T) actions. Based on the work mechanisms of stress transfer at the matrix-fiber interface, the fiber pullout behavior is modeled, from which the combined effects of fiber orientation, fiber snubbing and matrix spalling on the tensile responses of UHPC are characterized with a fiber reinforcement efficiency function. The nanoindentation test results show that the interfacial transition zone (ITZ) between steel fiber and cementitious matrix deteriorates over the F-T period, and the thickness of this ITZ weak band gradually increases from 22 μm at 0 cycle to 60 μm at 1500 F-T cycles. A good agreement is achieved between the analytical and experimental tensile responses of UHPC at various F-T cycles, and the predictability of the model is improved by adjusting the coefficients that govern the softening branch of tensile stress-crack width curves. The proposed analytical model can be used to effectively predict the tensile behavior of UHPC and its degradation effect due to F-T actions.
       
  • Three-dimensional carbon fiber composite printer for CFRP repair
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Ho-Jin Kim, Hyung-Soo Kim, Gil-Yong Lee, Min-Soo Kim, Soo-Hong Min, Rusty Keller, Jeong-Beom Ihn, Sung-Hoon Ahn We developed a portable carbon fiber/epoxy printer that can be used to repair damaged carbon fiber reinforcement plastics (CFRPs). Conventionally, CFRP repair features grinding/excision of the damaged area, attachment of a prefabricated CFRP patch, and curing. The repair patch must match the ground/cut area, and is usually laid-up by hand. Our device prints epoxy-bound carbon fibers directly onto the ground/cut surface. We designed and fabricated a prototype printer and tested its repair capacity. We fabricated and compared simple samples with varying tensile strengths. We compared printer-repaired and hand-laid-up samples; the former samples exhibited higher stiffness. We used simple image processing to verify the differences between the samples.
       
  • Bond behavior of basalt textile meshes in ultra-high ductility
           cementitious composites
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Jiafei Jiang, Cheng Jiang, Benben Li, Peng Feng Textile reinforced mortar (TRM) is a composite used in engineering applications of fiber reinforced polymer (FRP) materials. Although TRM can solve the fire resistance and durability issues from epoxy resin, the brittle fracture of traditional mortar greatly influences the bond behavior between the matrix and fibers and subsequently causes a significant decrease in the efficiency of fibers/textiles. A new engineered cementitious composite (ECC), the ultra-high ductility cementitious composite (UHDCC), was recently proposed to replace the mortar in TRM and bond with the textile meshes (termed the TR-UHDCC). This material has the features of multi-microcracking, high strength and ductility under tension. Fundamentally, stress transfer from the textile to the matrix is accomplished through the bond properties, which affect the tensile behaviors of TR-UHDCCs. In this paper, an experimental study on the basalt textile mesh reinforced UHDCC is presented. Double-sided pull-out tests were carried out on 54 specimens. The bond performance was studied by varying the embedded length and mesh geometric properties (mesh spacing and mesh aspect ratio). The restraint of weft yarns was investigated in this study and considered in the bond-slip model for TR-UHDCCs with different textile meshes.
       
  • Strain rate effect on interfacial bond behaviour between BFRP sheets and
           steel fibre reinforced concrete
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Cheng Yuan, Wensu Chen, Thong M. Pham, Hong Hao, Cui Jian, Yanchao Shi Numerous studies have shown that using steel fibre reinforced concrete (SFRC) and retrofitting with Fibre-reinforced polymer (FRP) composites can improve the strength and ductility of RC structures against impact and explosive loadings. The interface between FRP and concrete has been identified as one of the weakest parts of the FRP strengthened structures subjected to dynamic loading, with debonding failure usually observed as the primary failure mode. In order to properly analysis and design of FRP strengthened reinforced concrete (RC) structures, it is important to understand the dynamic bonding strength between FRP and concrete. An experimental investigation regarding to the dynamic interfacial bond behaviour between basalt fibre (BFRP) sheets and SFRC is carried out in this study. Concrete prisms were made of short steel fibres with three volumetric fractions (i.e. Vf = 0.5%, 1.0%, and 1.5%) to improve the tensile strengths. To achieve different strain rates, the loading velocities varied from 8.33E-6 m/s, 0.1 m/s, 1 m/s, 3 m/s, to 8 m/s. Experimental results show the bond strength and bond-slip were sensitive to strain rate. The loading rate changed the debonding failure modes from concrete substrate failure to interfacial debonding. In addition, the shear resistance of the interface increased with the fibre volume under both quasi-static and dynamic loadings. Based on the testing data, an empirical bond-slip model, incorporating the volumetric fraction of steel fibre and strain rate, is established for FRP-strengthened SFRC structures.
       
  • On controlling aerogel microstructure by freeze casting
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Wang Liao, Hai-Bo Zhao, Zhiguo Liu, Shimei Xu, Yu-Zhong Wang Aerogels, the lightest solids with practicable mechanical properties and functionality, are rapidly expanding the family members and applications these years. The reason can be attributed to the simple and green preparation by freeze casting (FC) method and the excellent properties of the resultant materials. Although inorganic aerogels, metal aerogels, polymer aerogels and composite aerogels towards different goals, such as thermal isolation, sensors, electromagnetic interference shielding, absorbent, separation, life science, supercapacitor, catalysis, etc., have been fabricated by this methodology, the definition and influence factors during the FC process are not clarified in the literature and become a remarkable bottleneck for further development. This review differentiates three different types of freeze. And for the FC type, it collects the scattered factors in literature that influence the microstructure of aerogels and makes combinations and comments between the microstructure and the resulting performances. Three kinds of FC methods, i.e. traditional unidirectional freezing casting (UFC), recent bidirectional freeze casting (BFC) and orthogonal freeze casting (OFC), are clarified. We hope this review contribute the development of FC method and design of novel aerogels.
       
  • Copper matrix composites reinforced by rGO-MoS2 hybrid: Strengthening
           effect to enhancement of tribological properties
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Hemant Nautiyal, Sangita Kumari, Om P. Khatri, Rajnesh Tyagi The potential of reduced graphene oxide-molybdenum sulfide (rGO-MoS2) hybrid as a self-lubricating reinforcement in the Cu-based composites for enhancement of mechanical and tribological properties is presented. The rGO-MoS2 was synthesized by a hydrothermal approach using highly dispersed graphene oxide as a platform material to grow the MoS2 nanosheets. The Cu-rGO-MoS2 composites having 2 wt% of rGO-MoS2 were prepared at 600, 650, 700 and 750 °C to probe the effect of sintering temperature on mechanical and tribological properties. Microscopic images of Cu-rGO-MoS2 composites based on SEM and HRTEM measurements along with corresponding area elemental distribution suggested the nearly uniform dispersion of rGO-MoS2 hybrid in the copper matrix via multidimensional interactions. The composites exhibited significantly improved hardness compared to pure copper, and it was attributed to freezing of the movement of the dislocations by rGO-MoS2. Incorporation of rGO-MoS2 in Cu resulted in a remarkable reduction in both the coefficient of friction and the wear rate. The improved friction and wear performances of composites have been ascribed to the self-lubricating action of rGO-MoS2 hybrid and the formation of rGO-MoS2 containing tribo-film on the counter face steel ball which facilitated the sliding events and protected the tribo-pair against the wear.Graphical abstractImage 1
       
  • Mechanical properties, rheological behaviors, and phase morphologies of
           high-toughness PLA/PBAT blends by in-situ reactive compatibilization
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Xin Wang, Shaoxian Peng, Hao Chen, Xiaolei Yu, Xipo Zhao Different ratios of poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were prepared by melt blending in the presence of a multifunctional epoxy oligomers as reactive compatibilizer. During reactive blending, the compatibilizer could react with PLA and PBAT chains to increase melt elasticity, viscosity, and compatibility, as indicated by rheological curve and Han plot analyses. Adding the compatibilizer improved the tensile and impact toughness for all ratios of PLA/PBAT blends. The elongation at break and the notched impact strength of the blend reached 579.9% and 29.6 kJ/m2, respectively, which were 75.3 and 12.3 times that of neat PLA. The shear yield deformation of impact fractured surface and the fuzzy phase interface of cryo-fractured surface showed that the high toughness can be attributed to the reaction of the epoxy group of reactive compatibilizer with the terminal carboxyl and hydroxyl groups of PLA and PBAT to form a large number of branched copolymers. Thus, the improvement of the interfacial adhesion and compatibility of the two polymers induced that brittle-ductile transition occurred in the failure of the blend.Graphical abstractImage 1
       
  • Orientating carbon nanotube bundles and barium titanate nanofibers in
           tri-layer structure to develop high energy density epoxy resin composites
           with greatly improved dielectric constant and breakdown strength
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Dan Zhao, Li Yuan, Guozheng Liang, Aijuan Gu Developing a high dielectric constant (high-k) composite with high breakdown strength and big energy density is still an interesting challenge with great difficulty. Herein, a new type of tri-layer composite (A-B-A) with greatly increased dielectric constant, breakdown strength and energy density was reported. The orientation of functional fillers as well as the thickness ratio of layer A to layer B in A-B-A composites were systematically investigated and correlated to dielectric properties, breakdown strengths and storage densities of multi-layer composites. With the same composition, A-B-A composites have much better integrated dielectric properties than single-layer (ACB/PDA@BTnf/EP) composite. For example, when the volume fraction of layer B is 20 vol%, the resulting tri-layer composite (A-2B-A) has the highest dielectric constant (1080.9, 100 Hz) and biggest increase in breakdown strength (150%) among all high-k multi-layer composites reported so far. In addition, A-2B-A composite has very low dielectric loss (0.55, 100 Hz) and 17.8 times increase in energy density compared with that of ACB/PDA@BTnf/EP. This contribution proposes an efficient and promising method to prepare high-k composites for energy storage.
       
  • Optimization of thickness and delamination growth in composite laminates
           under multi-axial fatigue loading using NSGA-II
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Abbas Kamaloo, Mohsen Jabbari, Mehdi Yarmohammad Tooski, Mehrdad Javadi Employing NSGA-II, this paper aims to achieve a damage tolerant structure enjoying maximum delamination resistance and thinness; therefore, we simultaneously define minimization of laminate thickness and delamination growth as objective functions. Fiber orientation angle, ply thickness, and stacking sequence are chosen as design variables. The authors consider symmetric glass/epoxy laminates with middle layers containing a single matrix crack.By applying multi-axial fatigue loading, the initiation and growth of local delamination from the tip of the matrix crack in the damaged ply interface became possible. Finally, it is indicated that NSGA-II has good convergence with damage optimization in cracked glass/epoxy composite laminates.
       
  • Simulation of electrical conductivity for nanoparticles and nanotubes
           composite sensor according to geometrical properties of nanomaterials
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Soo-Hong Min, Tae Hun Lee, Sangwook Lee, Ji-Hyeon Song, Gil-Yong Lee, Daniel Zontar, Christian Brecher, Sung-Hoon Ahn The nanocomposite based on conductive nanoparticles and nanotubes are widely used for stretchable strain sensors application. Since electrical properties varies by the geometrical properties of nanomaterials, it is important to understand the effects of nanomaterials by strain to optimise the sensor performance. However, it is difficult to fabricate strain sensor using nanomaterials with exactly desired properties. Hence, in this study, we have developed a simulation method for conductive nanoparticles and nanotubes composite using Lennard-Jones potential model and the voter model. First, we optimised the distribution of nanocomposites using Lennard-Jones potential model in the boundary conditions according to external strain. Then, we counted the average attachment among nanomaterials by strain using the voter model which is directly influence electrical conductivity of strain sensors. Moreover, we validated proposed simulation method using experimental value of fabricated strain sensor with various nanocomposite composition ratio and packing ratio. Using the suggested method, the effect of geometrical properties of nanomaterials can be accurately estimated with low simulation cost. Finally, we obtained the simulation value for strain sensor performance by various diameter of nanoparticle, diameter of nanotube, and length of nanotube. We demonstrated that the diameter of nanoparticle is a primary factor for sensor performance while the diameter of nanotubes does not have great influence. Based on the simulation results, it was confirmed that the change of electrical conductivity according to the strain is the largest at small and uniform nanomaterials. The developed simulation method can be applied to the general analysis of electrical properties for nanocomposites.
       
  • Investigation of mechanical properties and shrinkage of ultra-high
           performance concrete: Influence of steel fiber content and shape
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Zemei Wu, Caijun Shi, Kamal Henri Khayat Use of steel fibers in ultra-high performance concrete (UHPC) plays a significant role in enhancing strength and toughness and restraining shrinkage. This paper investigates the effect of steel fiber content and shape on mechanical strength, toughness, and autogenous and drying shrinkage of UHPC. Three steel fiber shapes, including straight, corrugated, and hooked fibers, with volume fraction ranging from 0 to 3% were employed. Compressive, flexural, and fiber-matrix bond strengths were evaluated. A statistical quadratic model and the Composite Theory were employed to predict the flexural strength of UHPC. Test results indicated that the increase in fiber volume can enhance the compressive and flexural strengths of UHPC and reduce shrinkage. The optimum fiber content for strength and shrinkage was found at 2%, beyond which the strength was slightly increased and the shrinkage was slightly decreased. For a given fiber content, the use of hooked fibers was most efficient in improving fiber-matrix bond and flexural strengths and reducing shrinkage. The flexural strengths of UHPC made with various fiber contents and shapes can be predicted using the proposed quadratic model and the Composite Theory. The latter considers the primary parameters affecting performance, including bond strength, matrix properties, and fiber characteristics. Finally, several models were used to simulate autogenous shrinkage behavior of UHPC and optimal models were found.
       
  • A percolation network model to predict the electrical property of flexible
           CNT/PDMS composite films fabricated by spin coating technique
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Di Wu, Mengni Wei, Rong Li, Tao Xiao, Shen Gong, Zhu Xiao, Zhenghong Zhu, Zhou Li Carbon nanotubes (CNTs) based flexible films have great potential on the flexible electronics due to their relatively uniform electrical properties in the film and ease of fabrication technology. In this work, CNT/polydimethylsiloxane (PDMS) composite films with various film thickness was fabricated successfully. By introducing a percolation network model, this work reveals theoretically that the observed rapidly drops of conductivity in thin films mainly depends on the change of CNT network morphology during spin coating. Junctions formed by structural distorted tubes are also observed at the cross section of film samples. By considering both CNT re-orientation and CNT structural distortion into percolation network model, the simulation results are in good agreement with the experimental data. Furthermore, a comprehensive numerical investigation reveals the relationship between film conductivity and some core parameters including CNT loadings, CNT intrinsic conductivity and CNT aspect ratio.Graphical abstractImage 1
       
  • Insights into halloysite or kaolin role of BiVO4 hybrid pigments for
           applications in polymer matrix and surface coating
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Xiaowen Wang, Bin Mu, Zhe Zhang, Aiqin Wang Two highly thermal-stable clay mineral-based bismuth yellow hybrid pigments were facilely fabricated combining with precipitation and annealing processes using halloysite and kaolin, respectively. The color properties, crystalline phase, morphology, and thermal stability of hybrid pigments were studied. Incorporation of clay minerals not only greatly decreased the production cost of bismuth yellow, but also improved its color properties and thermal stability. After clay mineral-based bismuth yellow hybrid pigments were introduced into polypropylene, the obtained composites exhibited the good mechanical properties compared with polypropylene and polypropylene reinforced with bismuth yellow, which was mainly attributed to the synergistic effect between clay minerals and bismuth yellow. It suggested that the as-prepared bismuth yellow hybrid pigments could be simultaneously served as a promising colorant and toughening and strengthening materials to be applied in plastic. In addition, the bismuth yellow hybrid pigments also presented the outstanding flame retardancy after being coated on polyurethane foam.Graphical abstractImage 1
       
  • Conductive network formation in bacterial cellulose-based nanocomposite
           aerogels
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Hadi Hosseini, Mehrdad Kokabi, Seyyed Mohammad Mousavi In this work, the network formation of reduced graphene oxide (rGO) in comparison with multiwall carbon nanotubes (MWCNTs) in the in-situ biosynthesized bacterial cellulose (BC) matrix-based nanocomposite aerogels was investigated. A modified model was proposed for predicting the overall broadband dielectric properties (AC conductivity and dielectric permittivity) of BC-based nanocomposite aerogels that had a good agreement with experimental data. Broadband dielectric properties indicated higher percolation values for both BC/MWCNTs (0.7 wt%) and BC/rGO (0.9 wt%) nanocomposite aerogels in comparison to Dynamic mechanical thermal analysis (DMTA) findings. Fractal dimensions of 2.6 and 1.86 were obtained for rGO and MWCNTs networks, respectively.Graphical abstractImage 1
       
  • Curved masonry pillars reinforced with anchored CFRP sheets: An
           experimental analysis
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Tommaso Rotunno, Mario Fagone, Elisa Bertolesi, Ernesto Grande, Gabriele Milani An experimental program concerning the structural behaviour of anchored Carbon Fiber Reinforced Polymer (CFRP) externally applied reinforcements bonded to portions of masonry arches is described. Two different curvatures have been considered as well as two different positions of the reinforcement (intrados/extrados). The so-called Single Lap Shear Test Scheme was considered in the experimental program: the specimens were constrained at the upper and lower faces and were loaded by a force tangent to an end of the reinforcement. The experimental results allowed to evaluate the effectiveness of the anchored reinforcement with respect to its position (intrados/extrados) and to the curvature of the specimens. The contribute due to the anchor has been evaluated comparing the test results with a previous experimental program carried out on specimens having the same characteristics but reinforced by a CFRP sheet without anchor. The experimental outcomes showed that the curvature marginally affected the bond behaviour of the anchored reinforcements that, instead, was strongly influenced by the position of the reinforcement.
       
  • Comparing various toughening mechanisms occurred in nanomodified laminates
           under impact loading
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): H. Saghafi, G. Minak, A. Zucchelli, T.M. Brugo, H. Heidary Delamination is the most frequent failure mode in thermoset-based composite laminates which can be easily occurred under an impact loading. Applying nanofibers between composite layers is one of the attractive methods to decrease the influence of this phenomenon (delamination) on the operation of an engineering structure. In this study, various nanofibers were utilized to consider their effects on impact response of glass/epoxy laminates. The nanofibers were made of PA66, PCL, and their mixture (PA66/PCL) which their toughening mechanisms are different. The results showed that PA66 and PA66/PCL had the best effectiveness on damaged area caused by the impactor (reduction of 60%). According to these results and some other evidences, it is concluded that bridging between composite layers which was established by PA66 nanofibers is the best mechanism for toughening laminates. On the other hand, depending on the curing cycle, PCL can toughen the composite laminates with two various mechanisms: 1- bridging between the layers 2- phase separation. The evidences show that the first mechanism is much more effective than the second one.
       
  • Damage mapping using strain distribution of an optical fiber embedded in a
           composite cylinder after low-velocity impacts
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Bo-Hun Choi, Il-Bum Kwon Impact damage was mapped using the strain distributed in an optical fiber that was embedded in a composite cylinder after low-velocity impact. Three-dimensional strain images were obtained to allow damage inspection using the optical fiber as a distributed sensor for the first time. An acrylate-coated standard optical fiber was embedded in the hoop layer of the composite cylinder, [901/OF/901/+-201/903/+-201/903/+-202/EPDM]T, as a sensor. This sensing fiber was wound around the cylinder at intervals of 12 mm in the longitudinal direction. Impacts of varied energies that yield barely visible impact damage (BVID) were applied to the cylinder by a drop-weight impact machine with a hemispherical tip. The residual strain caused by external impact of the composite cylinder was measured by the sensing fiber with a Brillouin optical correlation domain analysis (BOCDA) sensor system using phase code modulation. To determine the impact damage location and severity, the strains of the sensing fiber were mapped to positions on the cylinder surface. In the first impact test, eight impacts were applied to the cylinder at energy levels of 10 and 20 J. After impact, the strain measurement using the BOCDA system gave well damage information via cylinder surface strain mapping. In the second impact test, five impacts were applied at four points with the energy of 40 J and at one point with that of 30 J. The strain mapping clearly identified the additional impact locations and severities. These results verified that impact damage to the composite cylinder could be accurately analyzed as mapping images by the buried sensing fiber and the BOCDA sensing system.
       
  • Modelling the size and strength benefits of optimised step/scarf joints
           and repairs in composite structures
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Robert S. Pierce, Brian G. Falzon Adhesive bonding offers a better load transfer between adherends, for the assembly and repair of composite structures, compared with mechanical fastening methods. One drawback of adhesive bonded repairs is the considerable amount of material which must be removed, around the damaged region, to ensure adequate load transfer. Optimised geometries that account for the highly-orthotropic properties of individual composite plies are investigated, including a novel ‘fibre-oriented’ scarf approach that is inspired by an existing fibre-oriented step design. These methods aim to reduce the length of joint and repair bonding regions by at least 36%, compared with conventional step and scarf geometries of a similar strength.Size-reduction benefits are predicted using a MATLAB tool that is applicable for any composite laminate, and parametric analysis used to assess the effect of ply thickness, the number of plies, stacking sequence and taper angle.Cohesive Zone Models of joints and repairs with conventional and fibre-oriented designs are used to predict and compare the ultimate strength of each configuration. The existing fibre-oriented step design appears to show no benefit over a conventional step design. However, the novel fibre-oriented scarf approach results in a 33–40% reduction in the size of the bonding region compared to a conventional scarf design with similar strength. Analysis further indicates a 17–22% increase in ultimate strength for joints and repairs with the same bonding region size that employ the optimised fibre-oriented scarf design.
       
  • Electrospun and hydrothermal techniques to synthesize the carbon-coated
           nickel sulfide microspheres/carbon nanofibers nanocomposite for high
           performance liquid-state solar cells
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Ling Li, Xue Zhang, Lishan Fu, Qiming Wang, Shaomin Ji, Mingxing Wu, Hongjie Wang, Wenming Zhang To achieve optimal electrochemical performance, a highly efficient and stable noble-metal-free catalyst which consists of carbon-coated nickel sulfide microspheres (Ni3S4@C) and carbon nanofibers (CNFs) are synthesized through the electrospinning and hydrothermal method. The optimized sample provides a large amount of active sites that benefit electron transfer which is further applied as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). A series of electrochemical measurements reveal that the resultant Ni3S4@C/CNFs show higher catalytic activity toward the reduction of I3− to I− in comparison to the benchmark Pt, Ni3S4@C, pure Ni3S4 and CNFs. As a result, the DSSC device assembled with Ni3S4@C/CNFs-based CE affords a decent power conversion efficiency (PCE) of 8.29%, which surpasses the corresponding values of the device using the commercial Pt (7.35%), Ni3S4@C(6.81%), pure Ni3S4(6.51%) and CNFs (6.11%) CE under identical conditions. This work unfolds a new strategy for developing low-cost and effective CE materials in DSSCs.Graphical abstractIn this work, we have developed a new cost-effective counter-electrode based on the carbon-coated nickel sulfide microspheres/carbon nanofibers (Ni3S4@C/CNFs), which synthesized by combining the advantages of electrospinning technology and hydrothermal method. The dye-sensitized solar cells fabricated using Ni3S4@C/CNFs nanocomposite as counter electrode exhibit an overall power conversion efficiency of 8.29% measured at 100 mWcm−2 illumination (AM 1.5G), which is significantly higher than that of the most commonly used but expensive Pt counterpart (7.35%).Image 1
       
  • Strengthening effect of melamine functionalized low-dimension carbon at
           
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Jaemin Cha, Joonhui Kim, Seongwoo Ryu, Soon H. Hong The strengthening mechanism of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) at general fiber reinforced polymer (FRP) composite were investigated by interlaminar shear failure. We proposed 6 steps of interlaminar shear behavior of laminates at FRPs impregnated with epoxy resins. The GNPs and CNTs were functionalized by melamine to form M-CNTs and M-GNPs, which improved their dispersion in the epoxy matrix of the CFRPs and enhanced the interfacial strength. As a result, the resistance to crack propagation at the interface of fiber and polymer matrix increased. The interlaminar shear deformation behavior was characterized performing an interlaminar shear strength (ILSS) test, and the six failure stages were observed by scanning electron microscopy. Differences between load–displacement curves and the effects of GNPs and CNTs on shear deformation were analyzed. The incorporation of 2 wt% of M-CNTs increased the ILSS value of the CF/M-CNT/epoxy nanocomposite by 61%. The same loading but with M-GNPs increased the ILSS of the CF/M-GNP/epoxy nanocomposite by 219%. The greater reinforcing effect of the M-GNPs than the M-CNTs was attributed to differences in delamination resistance at the interface between the fibers and the epoxy. The phenomenon of crack propagation was investigated and related to the improved ILSS values.
       
  • Investigation on energy director-less ultrasonic welding of polyetherimide
           (PEI)- to epoxy-based composites
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Eirini Tsiangou, Sofia Teixeira de Freitas, Irene Fernandez Villegas, Rinze Benedictus In ultrasonic welding of thermoplastic composites an energy director (ED) (i.e. neat thermoplastic film), is used between the two adherends to be welded, to promote frictional and viscoelastic heating. For welding of thermoset composites (TSC), a thermoplastic coupling layer is co-cured on the surface to be welded as typical procedure to make the TSC “weldable”. This study focuses on investigating whether a polyetherimide (PEI) coupling layer by itself has the potential to promote heat generation during ultrasonic welding of CF/epoxy and CF/PEI samples, without the need for a separate ED, and if so, what thickness should that coupling layer be. The main findings were that welding without a loose ED resulted in overheating of the CF/PEI adherend and/or coupling layer due to the inability of the latter to promote heat generation efficiently. However, welding of CF/epoxy and CF/PEI samples with the use of a loose ED resulted in high-strength welds.
       
  • Development of strain hardening cementitious composite (SHCC) reinforced
           with 3D printed polymeric reinforcement: Mechanical properties
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Yading Xu, Branko Šavija Cracking in concrete needs to be limited for esthetical and durability reasons. Currently, this is commonly done by using steel rebars in the structure or fiber reinforcement in the material. With certain fiber types and micromechanical design, it is even possible to create cement-based materials with steel like (i.e. quasi-plastic) properties – so called strain hardening cementitious composites (SHCCs). In this paper, an alternative approach for creating SHCC – through use of additive manufacturing to create polymeric reinforcement meshes – is proposed. Different designs are manufactured, casted in the cementitious matrix, and tested in four-point bending and uniaxial tension. It was found that, with proper designs, it is possible to create cementitious composites with deflection hardening or strain hardening properties. Furthermore, with proper design, multiple cracking behavior of conventional SHCC can be replicated. In addition, numerical simulations were performed using the Delft lattice model. Four point bending tests on mortar bars reinforced by two different mesh designs were simulated and the results show good agreement with the experiments. This research shows great potential of using additive manufacturing for creating SHCCs with customizable properties.
       
  • Viscoelastic damage behavior of fiber reinforced nanoparticle-filled epoxy
           nanocomposites: Multiscale modeling and experimental validation
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Behrouz Arash, Wibke Exner, Raimund Rolfes The development of a physically based constitutive model for glass fiber reinforced boehmite nanoparticle-filled epoxy nanocomposites undergoing finite strain is investigated. The constitutive model allows capturing the main features of the stress-strain relationship of the nanocomposites, including the nonlinear hyperelastic, time-dependent and softening behavior. A methodological framework based on molecular dynamics simulations and experimental tests is proposed to identify the material parameters required for the model. The fiber-matrix interaction is characterized by a composite model, which multiplicatively decomposes the deformation gradient into a uniaxial deformation along the fiber direction and a subsequent shear deformation. The effect of the nanoparticles on the stress–strain response is taken into account through the adoption of a modulus enhancement model. The Eyring model parametrized using molecular simulations is used to describe the rate-dependent viscoelastic deformation under loading. The stress softening behavior is captured by a monotonically increasing function of deformation, so-called softening variable. The results show that the model predictions of stress-strain relationships are in good agreement with experimental data at different fiber and nanoparticle weight fractions. Finally, the constitutive model is implemented in the finite element analysis and examined by means of a benchmark example. Experimental–numerical validation confirms the predictive capability of the present modeling framework, which provides a suitable tool for analyzing fiber reinforced nanoparticle/epoxy nanocomposites.
       
  • Dynamic and instability analyses of FG graphene-reinforced sandwich deep
           curved nanobeams with viscoelastic core under magnetic field effect
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Mohammed Sobhy, Mohammad Alakel Abazid Based on the nonlocal strain gradient theory, the effect of an axial magnetic field on the free vibration and mechanical buckling responses of an FG graphene-reinforced sandwich deep curved nanobeam with viscoelastic core embedded in a viscoelastic medium is elucidated in this paper. The curved beam is also assumed to be exposed to axial external compressions. The volume fraction of the constituents of the composite face layers are presumed to be functionally graded through the thickness according to a layer-wise law. The material properties are calculated in the framework of Halpin-Tsai micromechanical scheme. Lorentz magnetic force is deduced employing electro-dynamic Maxwell's relations for a conducting body. According to a refined shear and normal deformations curved beam theory, the motion equations are introduced in the polar coordinates. Analytical solutions are obtained for the natural frequencies and critical buckling load of the viscoelastic sandwich curved nanobeams. By comparing the present results with the available data in the literature, the developed formulations are validated. Furthermore, other several numerical examples are performed to show the effects of different parameters including viscoelastic core thickness, magnetic field, structural and foundation damping factor, opening angle and graphene concentration on the frequency and buckling load of the viscoelastic sandwich curved beams.
       
  • A high-efficiency photoelectrochemistry of Cu2O/TiO2 nanotubes based
           composite for hydrogen evolution under sunlight
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): T.N.Q. Trang, L.T.N. Tu, T.V. Man, M. Mathesh, N.D. Nam, V.T.H. Thu In present study, a series of single modified TiO2 nanotubes with varying amounts of Cu was synthesized via two-step chemical solution method and studied as photocatalyst for H2 production under sunlight irradiation. The results indicate significant improvement of photocatalytic activity for TiO2 nanotubes modified Cu nanoparticles compared with pristine TiO2 attributed by the formation of the p-n heterojunction between Cu2O and TiO2. This enhanced the photo-generated charge transfer properties, resulting in an improved H2 evolution performance. The modified TiO2 nanotubes with 1.5 wt% Cu (Cu1.5 -TNTs) showed highest photocatalytic activity for H2 generation under sunlight due to structural integrity and uniform distribution of cuprous oxide on the surface of photocatalyst. Additionally, recyclability study for the H2 production of Cu1.5-TNTs material slightly decreased after four times, due to the presence of CuO phase via the oxidation of Cu2O and agglomeration phenomena, rendering them inefficient for H2 evolution performance under sunlight. We believe, addressing these problems would eminently assist in steady-state H2 generation performance under sunlight. Also, expanding the regime of light absorption to visible region for TiO2 1-Dimensional structure decorated Cu2O has higher photocatalytic efficiency for H2 generation in comparison to current 2-Dimensional systems.Graphical abstractImage 1
       
  • Effect of elevated operating temperature on the dynamic mechanical
           performance of E-glass/epoxy composite
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): George Youssef, Geovana Pessoa, Somer Nacy The construction industry has seen a proliferation of continuous and discontinuous fiber-reinforced polymer composites due to their high strength-to-weight and stiffness-to-weight ratios while being resilience to harsh environmental and operating conditions. This paper reports a comparative experimental investigation of field-deployed E-glass/Epoxy composite panels with those freshly manufactured to elucidate the effect of deployment conditions on the performance of these panels. Samples extracted from underground vault after power-line explosion due to arcing fault were examined using optical and atomic force microscopes to assess the extent of the damage. The samples were also characterized using a dynamic mechanical analyzer to explain the change in the properties post-explosion quantitatively. Microscopy investigations show no significant change in morphology or topography of the panels as well as the absence of failure modes such as delamination, fiber-failure or core-failure. Nonetheless, surface contaminations due to service conditions were found to exaggerate the surface burn marks despite the fire retardation properties of the composite panels. The dynamic mechanical properties of the panels were found to change as a function of temperature and loading frequency slightly. A shift in transition temperatures (Tβ and Tg) was found to be within a few degrees Celsius. The storage modulus was reduced by 21%, while the overall complex modulus remained relatively constant when comparing fresh and field-deployed samples. A frequency and temperature dependent model was used to fit the dynamic data and found to provide insights into the microstructure evolution of the polymer matrix.
       
  • Cyclic elastic modulus and low cycle fatigue life of woven-type GFRP
           coated aluminum plates
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Nohjun Myung, Jihye Seo, Nak-Sam Choi In this study, the mechanical properties and low-cycle fatigue behavior of woven-type glass-fiber reinforced plastic (GFRP) coated on one side of an Al 6061 aluminum alloy plate are investigated based on the GFRP layer thickness. Tensile and fatigue tests are performed with one, three, and five plies of GFRP coating. The strain-life method and total strain energy density (TSED) method are used to evaluate the fatigue behavior and life expectancy of these materials. From the results of the tensile test, the maximum load of the GFRP-Al specimens increased with a thick coating layer; however, the yield stress and tensile elastic modulus decreased. The behavior of the cyclic elastic modulus in repeated strains was different from that of the tensile elastic modulus. The hysteresis behavior of GFRP-Al according to the strain magnitudes was virtually the same as that of the uncoated monolithic Al, and both materials seemed like a Masing behavior. The fatigue life was greater than that of the uncoated Al. Coating GFRP with three plies on the Al substrate demonstrated the highest fatigue performances despite the specimen thickness increase of approximately 14%. In the tensile test, an initial crack occurred in the GFRP coating layer leading to the fracture. However, the fatigue tests with low and high strains indicated an initial crack and fracture in the Al substrate as opposed to the tensile test result. The fatigue life test data of the GFRP-Al specimens and the predicted values obtained through the total strain energy density (TSED) method agreed well, indicating a value of R2 ≥ 0.92 in the linear regression analysis of strain versus life and TSED versus life data.
       
  • Evaluation of mechanical properties and morphology of seawater aged carbon
           and glass fiber reinforced polymer hybrid composites
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Dipak Kumar Jesthi, Ramesh Kumar Nayak The replacement of metallic components by carbon fiber reinforced polymer (CFRP) composites is inhibited due to expensive carbon fiber. This problem may be addressed through hybridization of carbon and glass fiber to reduce the cost and achieve desirable mechanical properties of the hybrid composites. In this article, the influence of stacking sequence of carbon and glass fiber on seawater diffusivity, tensile, flexural and impact strength of hybrid composites were evaluated. The composites were fabricated by hand layup technique and seawater aged for 90 days at room temperature. The results revealed that the flexural strength of [CG2CG]S type of hybrid composite was the highest, i.e. 490 MPa in dry condition. The seawater diffusivity of [CG2CG]S type hybrid composite was reduced by 44% as compared to that of plain glass fiber reinforced polymer composite. The retention of tensile, flexural and impact strength of seawater aged hybrid composite of [CG2CG]S type were about 95%, 82%, and 94% respectively. The failure modes of the hybrid composites in dry and seawater aged condition were observed by field emission scanning electron microscope (FE-SEM) to establish a possible structure properties co-relationship.
       
  • Optimization of graphite contents in PAEK composites for best combination
           of performance properties
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Jitendra Narayan Panda, Jayashree Bijwe, Raj K. Pandey Graphite is one of the most widely used solid lubricants in both, anti-friction and friction materials. The influence of particles in the composite mainly depends on its size, amount, its combination with fibers and other fillers etc. No efforts were done to optimize the amount of graphite to achieve very low friction and wear. A series of Polyaryl ether ketone (PAEK) composites with GF (short glass fibers) and increasing amount of graphite particles (10, 15, 20 and 25 wt %) were developed and characterized for various properties such as physical, mechanical, thermal along with adhesive wear performance in severe operating conditions (high pressure and velocity (PV)). Inclusion of graphite led to deterioration in strength and modulus but increase in thermal conductivity. The composites showed very low μ (friction coefficient) in the range of 0.04 and K0 (specific wear rate) (∼2 × 10−16 m3/Nm). Composite with 15 wt % graphite proved to be significantly superior by showing highest PVlimit value (154 MPa m/s) and very low μ (0.04) and K0 (1.91 × 10−16 m3/Nm). The typical inferences were supported by various techniques such as Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), 3D profilometer, Raman spectroscopy on the worn surfaces.
       
  • Relations between intralaminar micromechanisms and translaminar fracture
           behavior of unidirectional FRP supported by experimental micromechanics
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Sandip Haldar, Miguel Herráez, Fernando Naya, Carlos González, Cláudio S. Lopes The translaminar fracture behaviors of partially different unidirectional composite systems, constituted by the same carbon fibers but different (thermoset vs. thermoplastic) matrices, were characterized by means of compact tension fracture tests. The resulting crack resistance curves (R-curves) and fracture surfaces, were studied in detail and found to be rather different between those material systems, in spite of the same reinforcing fibers at similar volume fractions. In the attempt to justify this difference, the effects of the underlying micromechanisms were evaluated by employing experimental micromechanical measurements of the fracture characteristics of fibers, matrices and fiber/matrix interfaces. By means of a thorough analysis and quantification of the micromechanisms that contribute to the work of fracture, it was possible to decompose the translaminar fracture toughness of the composites into different contributions. Independently of the material considered, fibre bundle pull-out was found to be the mechanism that dissipates the highest amount of energy. Different patterns of bundle pull-out in different material systems were found to be the result of different outcomes from the competition of fracture micromechanims, and to be responsible for the differences between the translaminar fracture energies of both material systems. Moreover, it was realized that the energy dissipated in bundle pull-out, hence also the overall measured translaminar fracture toughness are strongly governed by in-situ effects, i.e. effects of specimen lamination features.
       
  • The key role of thread and needle selection towards ‘through-thickness
           reinforcement’ in tufted carbon fiber-epoxy laminates
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Kundan K. Verma, G. Padmakara, Kotresh M. Gaddikeri, S. Ramesh, S. Kumar, Suryasarathi Bose Tufting of dry preforms is one of the means of accomplishing through-thickness reinforcement (TTR) in a liquid composite molding process. Herein, once a preform is laid up, an automated robotic tufting setup is used to introduce the TTR. The selection of thread and needle for tufting process go hand-in-hand as tufting operation involves the act of penetrating preform by the needle as well as the trauma thread has to endure during this act. This paper explores the methodology of thread and needle selection through studies at different levels right from tufting of preforms to testing of tufted laminates. Glass, carbon and Kevlar threads in combination with a tufting needle and two different sewing needles are explored in this study. The effect of tufting speed on the quality of tuft is analyzed in terms of damage of fabric yarn, thread, and needle breakage. Layer-wise analysis of damage due to needle penetration in fabric yarns is carried out. Key mechanical properties of tufted composite samples are evaluated to determine the effect of tufting on the in-plane and out-of-plane properties.
       
  • Preparation of magnetically retrievable CoFe2O4@SiO2@Dy2Ce2O7
           nanocomposites as novel photocatalyst for highly efficient degradation of
           organic contaminants
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Sahar Zinatloo-Ajabshir, Masoud Salavati-Niasari CoFe2O4@SiO2@Dy2Ce2O7 magnetic nanocomposite as recyclable photocatalyst has been prepared for the first time. The cobalt ferrite component was produced through combustion route with the aid of grape juice as novel and green fuel, and the silica component was prepared through sol-gel route with the aid of 2,2-dimethyl-1,3-propanediamine as new basic agent as well as Dy2Ce2O7 component has been synthesized through a modified Pechini route with the aid of 2,2-dimethyl-1,3-propanediamine as novel pH regulator. The as-fabricated CoFe2O4@SiO2@Dy2Ce2O7 nanostructures were characterized by FESEM, DRS, TEM, EDX, XRD, VSM and BET. This is the first try on the survey of photocatalytic efficiency of CoFe2O4@SiO2@Dy2Ce2O7 nanostructures. Role of kind of irradiation source, catalyst loading and kind of contaminant has been described upon improving performance of CoFe2O4@SiO2@Dy2Ce2O7 nanostructures. The results indicated that the fabricated CoFe2O4@SiO2@Dy2Ce2O7 could be potentially utilized as efficient and favorable kind of recyclable photocatalyst for removal of water contaminants.Graphical abstractImage 1
       
  • Printability region for 3D concrete printing using slump and slump flow
           test
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Yi Wei Daniel Tay, Ye Qian, Ming Jen Tan Rheological studies are important for successful 3D concrete printing. The main challenge for successful 3D concrete printing is the complex characteristic the materials should possess. It should be flowable enough to be pumped and extruded through the hose, as well as gaining sufficient strength and stiffness for buildability after the layer by layer deposition. Existing literature has various mixtures proposed for successful 3D concrete printing. Most of these studies used rheometers to measure the dynamic yield stress and plastic viscosity. As the measurement with rheometer is sensitive to the protocols and is controlled by the rheologists, as well as data processing if non-standardized measuring geometries are used, results could vary significantly. This study used standardized field-friendly protocols to measure the slump and slump-flow of the mortars. The pumpability and buildability are evaluated in terms of the pumpability index and maximum height printed before collapsing. These result together with the slump and slump-flow values are used to define the printable region.
       
  • Fracture modeling of fiber reinforced concrete in a multiscale approach
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Marcello Congro, Eleazar Cristian Mejía Sanchez, Deane Roehl, Ederli Marangon This paper proposes numerical models for the study of fracture of fiber reinforced concrete. The composite material behavior is described at the macroscale and at the mesoscale. The macroscale model considers homogeneous equivalent continuum properties taken from experimental curves of the composite. In order to reproduce the effect of the random distribution of steel fibers within the cementitious matrix, random values of equivalent elasticity modulus and equivalent tensile strength are assigned to solid and cohesive elements, respectively. The mesoscale model represents the fiber explicitly inside the concrete matrix through cohesive interface elements with steel properties. In this case, fibers are located and oriented randomly in the matrix. In addition, to allow matrix fracture, cohesive elements with softening constitutive behavior are placed at the edges of the solid elements in the meso and macroscale models. The numerical models were applied to the simulation of a direct tensile laboratory test for a steel fiber reinforced concrete. The macroscale model uses probability functions to define the mechanical properties for each element. The predicted fracture paths and load capacity present satisfactory results when compared to those obtained experimentally. In the mesoscale model, distinct mechanical properties are applied for the steel fibers and for the cementitious matrix. The results from the mesoscale approach reinforce the concept that fiber dispersion and orientation affect the structural load capacity and matrix brittleness. In addition, cohesive interface elements proved to be an attractive approach to predict fracture propagation in the composite material.
       
  • Freeze-thaw cycling effect on tensile properties of unidirectional flax
           fiber reinforced polymers
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Kenneth Mak, Amir Fam Natural fibre-reinforced polymers (FRP) research has grown over the years. With interest in retrofitting reinforced concrete, flax-FRP (FFRP) was investigated across 300 freeze-thaw cycles, while varying fibre type, resin type, manufacturing method and exposure conditions. Vacuum bag moulded FFRP exhibited the most severe degradation at a 8% strength reduction and 10% stiffness reduction. Damage initiation began after 100 cycles. Conversely, wet lay-up moulded specimens’ higher resin content protected the flax from moisture. Equivalent glass-FRP showed no damage. FRP with epoxy and epoxidized pine oil blends (EPO) showed no initial mechanical difference. After exposure, epoxy showed signs of hydrolysis, whereas EPO showed further cross-linking.
       
  • A low-voltage graphene/Ag-based phase transition-controlled force actuator
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Ying Huang, Wei Hu, Xinli Wang, Xiaohui Guo, Chao Hao, Yunong Zhao, Xiao Zeng, Ping Liu A phase transition-controlled force actuator based on graphene/Ag/SR (silicone rubber) has been designed and fabricated. This actuator is based on the principles of phase transition. The actuator with an enclosed cavity, which consisted of a latex film and a graphene/Ag/SR-based electrothermal substrate, and then injecting ethanol into the cavity. The actuator can operate at a low voltage (6 V), and the magnitude of the feedback force can be controlled by applying a square wave signal which the duty cycle is adjustable. The minimal change in feedback force is 0.02 N. Owing to its simple fabrication, easy operation, lightweight (1.4 g), low driving voltage, large deformation and controllable force, manipulator, auto-injector and bionic fish have been made. Summarizing aforementioned experimental results, the manipulator can grip objects of different weights, and the auto-injector can inject a liquid and act as an injector. Furthermore, bionic fish can float and sink in the water. These devices showing that the phase transition actuator is expected to be widely used in soft robots, bionic devices design, and medical field. Also, this category of phase transition actuator could provide ideas for developing flexible actuator.
       
  • Effect of adding carbon nanotubes on the thermal conductivity of steel
           fiber-reinforced concrete
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Mohammad Kazem Hassanzadeh-Aghdam, Mohammad Javad Mahmoodi, Mohammad Safi A comprehensive analysis is performed to study the effect of adding carbon nanotubes (CNTs) on the thermal conductivity of short steel fiber (SSF)-reinforced concrete. The role of the CNT dispersion and the CNT/concrete interfacial thermal resistance in the SSF/CNT-reinforced concrete thermal conducting behavior is investigated. A good agreement is observed between the model predictions and available experiment. Also, the influences of the SSF aspect ratio, volume fraction and placement type; and the CNT volume fraction, length, diameter and directional behavior on the concrete thermal conductivities are examined. The results reveal that if the CNTs to be uniformly distributed, and the CNT/concrete interface bonding to be perfect, then the concrete effective thermal conductivity is significantly improved. The increasing both volume fraction and length of the CNT leads to the concrete thermal conductivity enhancement too. The CNT diameter and transverse thermal conductivity cannot affect the SSF/CNT-reinforced concrete thermal conducting behavior as well.
       
  • Developing high performance PA 11/cellulose nanocomposites for
           industrial-scale melt processing
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Priya Venkatraman, Anne M. Gohn, Alicyn M. Rhoades, E. Johan Foster This study presents methods of developing thermally stable polyamide 11 (PA 11), cellulose nanocrystal (CNCs) composites able to withstand high temperature processing for high performance applications. Thus far, it has been difficult to use cellulose-based composites in industrial applications due to the high temperatures at which the materials would need to be processed. Sulfated CNCs (S–CNCs), the most commercially available CNCs, perform the poorest with respect to being thermally stable at high temperatures. Direct mixing techniques typically used to make these nanocomposites at a lab-scale, even at low concentrations of CNCs, have resulted in poor dispersion and thermal stability of CNCs. However, this paper offers industrially viable methods of fabricating composites that shield these S–CNCs from excessive thermal degradation during processing. We set out to determine the effect of pre-mixing CNCs and the polymer to obtain homogeneous and thermally stable nanocomposites for high temperature processing methods such as compression molding and injection molding. For the PA 11/CNC composites, fabrication through both milling and compounding resulted in reinforcement of the polymer with increased storage modulus in the rubbery plateau, and increased Young's modulus while preserving the toughness of PA 11. Furthermore, the milled samples showed higher stiffness than the compounded samples and surface charge density of the CNCs played a great role in the mechanical properties of the composites as it directly correlates with how well dispersed the composites were. Overall, this work shows the potential of pre-mixing methods to obtain high performance nanocellulose based composites through industrial manufacturing processes.Graphical abstractFigure showing milling (Mi) and compounding (Co) as two methods of pre-mixing cellulose nanocrystals (CNCs) and PA 11 to produce homogeneously dispersed composite films with their corresponding mechanical properties. PA 11-BG-CNC Mi provided for comparison to indicates a film with poor CNC dispersion due to lower surface charge density. BG refers to CNCs obtained from BlueGoose.Image 1
       
  • Influence of environmental aging in two polymer-reinforced composites
           using different hybridization methods: Glass/Kevlar fiber hybrid strands
           and in the weft and warp alternating Kevlar and glass fiber strands
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): R.C.T.S. Felipe, R.N.B. Felipe, A.C.M.C. Batista, E.M.F. Aquino This study is based on research into the effect of accelerated environmental aging (alternate cycles of UV radiation and moisture, hot steam) in two polymer composite laminates developed using Kevlar 49 and glass E fibers with different hybrid fabrics. One uses a bidirectional textile with hybrid strands and the other with Kevlar and glass fiber strands in the weft and warp. Both use polyester resin as matrix. After exposure, the specimens underwent structural integrity assessment, followed by uniaxial tensile and three-point bending tests and evaluation of fracture characteristics. All the aged laminates were submitted to photo-oxidation, leading to a loss of mechanical properties, demonstrated by the severe damage after aging in both tests. The laminate with hybrid strands experienced the highest losses, especially in strain, but managed to retain 75% of flexural strain and 84% of tensile strain and delamination between layers.
       
  • Theoretical and numerical analyses of the structural stability of the
           pipe-grout-liner system with a crown void subjected to external pressure
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Zhaochao Li, Ronglu Wang, Yizheng Chen The thin-walled polymer liner is widely used to rehabilitate the deteriorated underground pipe. Although the liner is installed close-fitting in the lining procedure, an annular shrinkage gap is inevitable between the liner and the pipe. The grouting technique is commonly employed to eliminate the small gap and often results in a small crown void between the liner and the pipe. Therefore, a pipe-grout-liner system generates. This paper focuses on the structural stability of the pipe-grout-liner system with a crown void subjected to external pressure. It is found that the radially-inward out-of-roundness imperfection results in a single-lobe deformation and the radially-outward out-of-roundness imperfection results in a double-lobe deformation, respectively. The critical buckling pressure is derived and obtained theoretically, and then verified by developing a two-dimensional finite element model. The numerical result shows very close agreement with the analytical solution and other closed-form expressions for both single-lobe and double-lobe cases, respectively. Finally, the effect of the crown void is examined. It is found that the system with a small crown void can sustain the same buckling pressure as the perfectly-confined liner without void. However, a significant reduction of the critical buckling pressure was observed when the crown void is larger than the small size level.
       
  • Development of biocompatibility in the orthodontic brackets based on
           MgAl2O4/ Si3N4 nanocomposites
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): M.R. Loghman-Estarki, Ehsan Mohammad Sharifi, Hassan Sheikh, Amir Alhaji, Mehdi Naderi Orthodontic brackets based on transparent ceramics in the visible area (especially magnesium aluminate, MgAl2O4) are considered for high strength, but the most important drawback of transparent magnesium aluminate is the lack of fracture toughness. In this research, the silicon nitride nanoparticles as a reinforcing phase were used to improve the fracture toughness of magnesium aluminate orthodontic brackets. For this purpose, firstly, MgAl2O4 reinforced with 2% Si3N4 nanostructured granules were prepared using the spray drying method. Then, the nanostructured granules were spark plasma sintered (SPS) at 1400 °C under pressure of 100 MPa. Finally, with the help of the diamond cutting tool, the heat-treated sample was cut into an orthodontic bracket. The results of the tetrazolium-based colorimetric assay (MTT test) showed that the produced orthodontic brackets have excellent biocompatibility with human osteoblasts cell.
       
  • Effects of aging on asphalt binders modified with microencapsulated phase
           change material
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Muhammad Rafiq Kakar, Zakariaa Refaa, Jörg Worlitschek, Anastasia Stamatiou, Manfred N. Partl, Moises Bueno Temperature and chemical composition are governing parameters for the mechanical behavior of asphalt binders. During extreme low and high temperatures, asphalt binders can suffer thermal cracking as well as permanent deformation, respectively. The use of phase change materials (PCM) can provide asphalt binder with thermal energy storage properties for reducing the impacts of pavement temperature rise and decrease during seasonal and diurnal cycles. Studying the feasibility of using microencapsulated PCM in asphalt binders is the mean aim of this study. Accordingly, different penetration grade binders modified with microencapsulated PCM were characterized and their blends artificially aged using Rolling Thin Film Oven (RTFO) and Pressure Ageing Vessel (PAV) devices. This study also covers different size distributions of microcapsules. The thermal and rheological properties of both modified and unmodified asphalt binder under different aging conditions were analyzed using dynamic scanning calorimetry (DSC) and dynamic shear rheometer (DSR). It was found that the melting enthalpy of modified asphalt binder reduces upon aging and the reduction is dependent also on the type of binder. The results elucidate that the survival of microencapsulated PCM in asphalt binder depends on both the type of binder and the microcapsules used. Moreover, the rheological properties of modified asphalt binder determined with DSR improve due to the thermal energy released by PCM crystallization during cooling.Graphical abstractImage 1
       
  • Reinforcement of the optical, thermal and electrical properties of PEO
           based on MWCNTs/Au hybrid fillers: Nanodielectric materials for
           organoelectronic devices
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): M.A. Morsi, A. Rajeh, A.A. Al-Muntaser Polymer nanocomposite samples of polyethylene oxide (PEO) embedded with multi-walled carbon nanotubes and gold nanoparticles (MWCNTs/Au NPs) were prepared through the casting method The polymer–nanoparticle interactions had been examined by Fourier transform infrared (FT-IR) measurement. X-ray diffraction (XRD) analysis depicted that these samples were semi-crystalline and the crystalline phases of PEO were reduced due to the incorporation of MWCNTS/Au NPs. The TEM micrographs indicated that the diameter range of MWCNTs is 10–25 nm and the shape of Au NPs was spherical with size range 2–25 nm. The redshift of absorption edge in the spectra of ultraviolet/visible (UV–Vis.) spectroscopy for the nanocomposite samples indicated a good reactivity between the polymer matrix and the nanofillers which in turn the decrement of optical energy gap value was expected, which was calculated from Tauc's relation. The thermal stability of nanocomposite samples was improved as indicated by the thermogravimetric analysis (TGA) technique. The electrical and dielectric spectra of these samples had been measured using broadband dielectric spectroscopy. The electrical and dielectric measurements realize the favorable uses of these nanocomposite samples in the production of electroactive materials and further their use as the electrical insulating polymeric nanodielectrics in the production of organoelectronic devices. The Mechanical properties of the prepared samples were calculated by the tensile universal testing machine.Graphical abstractImage 1
       
  • Super-hydrophobic graphene oxide-azobenzene hybrids for improved
           hydrophobicity of polyurethane
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Karthika M, Hong Chi, Tianduo Li, Hongjuan Wang, Sabu Thomas A super-hydrophobic graphene oxide (GO)-azobenzene (Azo) hybrid material was synthesized through a covalent grafting of amide linkage. Fourier transforms infrared spectra (FTIR) and UV–visible (UV–vis) spectra confirmed the successful formation of GO-Azo hybrid material. The GO-Azo exhibited high water repellence with water contact angle of ∼152°. As a new kind of filler material, the scope GO-Azo in improving the hydrophobicity of polyurethane was investigated through contact angle measurements of polyurethane films with varying amount of GO-Azo. Mechanical and thermal studies showed improved stability and rigidity of the composite film as well at doping ratio of only 3 wt% the of the filler.Graphical abstractImage 1
       
  • Additive manufacturing of natural fiber reinforced polymer composites:
           Processing and prospects
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Vamsi Krishna Balla, Kunal H. Kate, Jagannadh Satyavolu, Paramjot Singh, Jogi Ganesh Dattatreya Tadimeti Throughout the world there have been alarming concerns over the use of nonrenewable resources during manufacturing of goods and associated environmental legislations. Therefore, the use of natural materials and fabrication of composites therefrom, particularly, development of natural fiber reinforced polymer composites is gaining significant attention. Although natural fiber reinforced composites (NFRCs) show strong application prospects, various materials and processing related challenges needs to be addressed to achieve long-term stability and performance. In this review, we attempted to provide an overview of different types of natural fibers, their characteristics and properties enabling them to be used as reinforcing agents in different polymers. Then the unique requirement of fiber surface modification to achieve enhanced fiber-matrix bonding is discussed. The article also discusses conventional processing routes and critical issues associated with NFRCs processing. The use of different additive manufacturing (AM) technologies in processing polymer composites is also discussed. At the end, we have critically analyzed the challenges and opportunities associated with AM of NFRCs.
       
  • Behavior of steel I-beam embedded in normal and steel fiber reinforced
           concrete incorporating demountable bolted connectors
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Ahmed Hamoda, Mohamed Emara, Walid Mansour This paper investigates experimentally and numerically behavior of steel I-beams with/without high strength bolted connectors embedded in normal/Steel Fiber-Reinforced concrete (SFRC). Composite action between embedded steel I-beam and concrete can be achieved through studs or bolted connectors. Studs connectors are widely used; however, short bolted counterparts may be considered for elements with small cross section. Composite action can be existed not only in composite structures but also when casing critical joints with bolted connectors. Use of SFRC in composite section may enhance cracking behavior, ultimate capacity and failure mode. Twenty-four push-out tests were implemented under axial monotonic static loading up to collapse. The main parameters were: concrete type, roughness of I-beam surface, number of bolts and closed stirrups. Nonlinear three-dimensional Finite Element Models (FEMs) were created identically simulating to those tested experimentally. Numerical outcomes were verified by experimental observations leading to an acceptable FEM, only variation about 8%, that can be qualified for studying composite section with short demountable bolts. Results showed that studied parameters could significantly affect load-slip behavior and failure mode which was push-out with/without insignificant splitting hair cracks. Numerical and experimental results were employed to propose formula could estimate ultimate shear bearing capacity with push-out failure mode.
       
  • Various polymeric monomers derived from renewable rosin for the
           modification of fast-growing poplar wood
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Youming Dong, Wei Zhang, MarK Hughes, Miao Wu, Shifeng Zhang, Jianzhang Li The incorporation of polymers derived from renewable resources is more desirable in the preparation of wood composites due to its sustainability. As biomass feedstock, rosin has been used for the preparation of wood-based composite material. However, the high leachability and non-reactive with wood limit its application. Three kinds of rosin derivatives synthesized with reactive groups in the current study were confirmed by 13C NMR and Fourier transform infrared spectroscopy. The polymerization process and polymer properties of the derivatives were studied by the differential scanning calorimetry and gel permeation chromatography. The poplar wood was impregnated by rosin derivatives solution and then oven heated to induce in situ polymerization. The results indicated that the derivatives could penetrate into wood structures, polymerize in both wood cell walls and lumina, and efficiently improve the physical properties and surface hardness of wood. Moreover, the extraction indicated that rosin derivatives could permanently bulk wood structure through the formation of polymers. Our studies provide a new approach to modify fast-growing wood using renewable resources.Graphical abstractImage 1
       
  • Review on mechanical properties evaluation of pineapple leaf fibre (PALF)
           reinforced polymer composites
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Santosh Sadashiv Todkar, Suresh A. Patil The environmental problems associated with the production, disposal and recycling of synthetic fibre based polymer composites has prompted the development of eco-friendly natural fibres. It involves use of kenaf, jute, oil palm, cotton, flax, banana, hemp, sisal and pineapple leaf fibre (PALF) for various applications such as automotive, infrastructure, biomedical, furniture, packaging etc. PALF will be important in material development for structural and non structural industrial products with other natural and synthetic fibres with different matrix. This review paper deals with the mechanical properties evaluation of PALF and several factors influencing properties such as type of variety, fibre length, matrix type, fibre orientation, voids and porosity content. Recent research in the advancement of mechanical properties of PALF as reinforcement in thermoset, thermoplastic and biodegradable resins are briefly provided. Attempts have been made to characterize PALF as a hybrid composite with other natural and synthetic fibres. Surface treatments to improve the interfacial and interphasial PALF - matrix interaction with consideration of coupling agents for mechanical strength improving requirements are discussed. Along with limitations, technical solutions to the traditional problems of natural fibre composite processing, tensile properties improvement, durability, thermal stability and interfacial incompatibility enhancement are discussed. Overall, this review article investigates highlights and identifies gaps in the earlier research work. It provides the resourceful tabulated data for continuing future research in various streams with PALF as reinforcement.
       
  • High-performance polyphenylene sulfide composites with ultra-high content
           of glass fiber fabrics
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Liang Zhao, Yan Yu, Hao Huang, Xianze Yin, Jiashun Peng, Jiuxiao Sun, Leping Huang, Youhong Tang, Luoxin Wang In this work, the high strength and rigidity composites composed of ultra-high content of glass fiber fabrics (GFF) and polyphenylene sulfide (PPS) nonwovens were successfully fabricated by a facile thermo-compression lamination method. The mechanical property, wettability, crystalline behavior, rheological behavior and dynamic mechanical properties were systematically characterized. These results show that the optimum formula of 80 wt% GFF content (∼70 vol%) can achieve the best mechanical properties of the composite with excellent wettability among PPS and glass fibers. The tensile strength, fracture elongation, elastic modulus, flexural strength, flexural modulus, ILSS and un-notched impact strength can reach to 850.6 MPa, 10.5%, 910.5 MPa, 78.5 GPa, 67.4 MPa and 215.2 kJ/m2, respectively, which are elevated by 108.8%, 38.2%, 52.8%, 82.6%, 230.4% and 136.5% in comparation to those of GFF/PPS composites with 60 wt% GFFs. The increasing interfacial layers and riveting effect among GFFs effectively prevent the crack propagation, which are the main reasons for the enhancing mechanical properties of PPS composites with ultra-high content GFF. It is established that the GFF/PPS composite fabricated in this work has the characteristic of the highest mechanical performance and the highest content of GFFs in comparison with the reported PPS-based composites. This GFF/PPS composite is an ideal substitute for traditional metal and GF/epoxy composites.
       
  • Synthesis and characterization of 3D flower-like nickel oxide entrapped on
           boron doped carbon nitride nanocomposite: An efficient catalyst for the
           electrochemical detection of nitrofurantoin
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Thangavelu Kokulnathan, Tzyy-Jiann Wang It is a great challenge to design and develop a new kind of cost-effective electrode with excellent activity and high stability for the electrochemical sensors. In this presented research, an eco-friendly sonochemical route was utilized to synthesize the flower-like nickel oxide entrapped on boron doped carbon nitride (NiO/BCN) nanocomposite for the application towards electrochemical detection of nitrofurantoin (NFT). The as-synthesized NiO/BCN nanocomposite was detailedly characterized by FESEM, TEM, elemental mapping, EDX, XRD and FT-IR analysis. The electrochemical studies presented that the new sensing probe using the NiO/BCN modified electrode possesses rapid mass transport, superior electrocatalytic activity and high electrical conductivity for the detection of NFT. Furthermore, the NiO/BCN nanocomposite on a glassy carbon electrode displayed a wide dynamic linear response range (0.05–230 μM), very low detection limit (10 nM) and good sensitivity (1.15 μA μM−1 cm2) with excellent selectivity. The proposed electrochemical sensor has been successfully applied to the determination of NFT in biological samples with satisfactory results.Graphical abstractImage 1
       
  • Characterization of polypropylene composites using yerba mate fibers as
           reinforcing filler
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): André Luis Catto, Marcos Aurélio Dahlem Júnior, Betina Hansen, Edson Luiz Francisquetti, Cleide Borsoi This study presents the preparation of polypropylene (PP) composites filled with yerba mate (YM) stick particles. Neat and post-consumer PP are used as the polymer matrices with 20, 30 and 40 wt% (w/w) YM fiber. Mechanical properties, including tensile, flexural and impact resistance, are determined, in addition to chemical and morphological analyses. The main findings show that the addition of filler from YM fiber increased the tensile and flexural strength of the neat and post-consumer PP composites up to a 30 wt% fiber content. The neat PP composites show better results than those with recycled PP, with PP20YM and PP30YM composites showing the best results. There is a gradual reduction in impact resistance with increasing YM content. Scanning electron microscopy shows a better adhesion between the matrix and filler in composites with 20 and 30 wt% YM, corroborating the tensile and flexural strength results.
       
  • The porosity, microstructure, and hardness of Al-Mg composites reinforced
           with micro particle SiC/Al2O3 produced using powder metallurgy
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Gul Tosun, Mehmet Kurt In this study, Al-Mg metal matrix composite (MMC) materials reinforced with micro-sized SiC, Al2O3 particles were manufactured using powder metallurgy. SiC and Al2O3 particles with 1 μm size were added to the Al-Mg matrix at different volume ratios (15–30%). A mixture of Al, Mg, reinforcement (SiC, Al2O3) powders was mixed at a speed of 16 rpm over a 24 h-time period for a homogeneous dispersion. The mixed powders were pressed at 300 and 600 MPa. Composite materials produced at different pressures were sintered under for 30, 60, 90 min and at 300, 400, 500 °C and allowed to cool in the furnace. The microhardness, porosity, microstructure of Al-Mg/SiC and Al-Mg/Al2O3 composites were investigated and characterized. The highest porosity ratio for all test conditions was measured as being 17% in the Al-Mg composite reinforced with 15% SiC produced at 300 MPa and 400 °C for 90 min. The lowest porosity ratio was measured as being 5.4% in the Al-Mg composite reinforced with 15% SiC produced at 600 MPa and 500 °C for 90 min. In their microstructure studies, a generally homogeneous microstructure was observed.
       
  • Optimization of triboelectric energy harvesting from falling water droplet
           onto wrinkled polydimethylsiloxane-reduced graphene oxide nanocomposite
           surface
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Abu Naushad Parvez, Md Habibur Rahaman, Hyeon Cheol Kim, Kyoung Kwan Ahn This study investigates the triboelectric energy harvesting phenomenon of falling water droplets on a novel nanocomposite surface, chemically synthesized from reduced graphene oxide (rGO) and polydimethylsiloxane (PDMS) polymer. The prime concern of this work is to synthesize such a triboelectric nanocomposite film, which will pose optimized hydrophobicity along with ameliorated dielectric properties through proper optimization of filler quantity inclusion in PDMS matrix. Therefore, six samples including one pristine PDMS and five nanocomposites (PDMS-rGO) have been prepared by varying filler concentration. Optimization has been explained based on determination of several parameters and nano-characterization techniques such as thickness of rGO flakes, thickness of polymer and nanocomposite samples, water contact angles, dielectric properties, triboelectric outputs, FE-SEM, EDX, FTIR, XPS and Raman spectroscopic analyses. After analyzing the outputs of a single electrode mode triboelectric nanogenerator (SEM-TENG) based on Pristine PDMS and nanocomposite samples, it has been found that 0.5 mg rGO incorporated PDMS matrix of 141 μm thickness revealed highest water contact angle i.e.116.9°. Besides, highest output potential difference (VOC) of ∼2 V and close circuit current (ISC) of ∼2 nA have been obtained upon contact and separation of rolling water droplet over the same nanocomposite surface. This work demonstrates a unique way to get an optimized thin triboelectric nanocomposite film, which is able to harvest the kinetic energy of a tiny moving water droplet. Hence, we hope that this work may serve as a convenient platform for triboelectric energy harvesting from natural raindrops, fountains or any real-life phenomenon involving the movement of droplet.
       
  • Organic versus inorganic matrix composites for bond-critical strengthening
           applications of RC structures – State-of-the-art review
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Hussein M. Elsanadedy, Husain Abbas, Tarek H. Almusallam, Yousef A. Al-Salloum The usage of organic matrix composites such as fiber reinforced polymers (FRP) in retrofitting of structures is increasingly becoming popular among structural designers, which is credited to varied attractive top features of these materials, such as: corrosion resistance, higher strength to weight ratio, ease and speed of application, and almost no section enlargement. However, FRP strengthening technique is not completely free of problems. The organic resins employed as binders have many disadvantages such as (a) relatively expensive resins; (b) poor response at temperature ranges above the glass transition temperature; (c) potential risks for the workers; (d) difficulty in application on moist areas or at low temperature ranges; (e) difficulty of reversibility (inability to undo the repair without damaging the original structural member); and (f) non-compatibility between resins and substrates. One possible solution for alleviating these difficulties is the substitution of the organic with the inorganic binder, such as cementitious mortars. A new class of material was then developed and used for structural strengthening applications. In this material, fibers are replaced by textile or fabric and organic matrix is replaced by cementitious matrix such as mortars and is usually called textile reinforced mortar (TRM). This paper presents a critical review of existing research on comparison between FRP and TRM composites used for strengthening of structural concrete members, identifies gaps in current knowledge, and outlines directions for future research. It briefly presents material characterization in terms of constituents and stress-strain behavior in tension, and also describes concisely methods of installation for both organic and inorganic composite systems. Available literature on bond behavior at composites-to-concrete interface at ambient and elevated temperatures are summarized. It also enlists available research on use of TRM composites in comparison with FRP composites for flexural and shear strengthening of RC beams.
       
  • Static and dynamic analyses of cracked functionally graded structural
           components: A review
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Debabrata Gayen, Rajiv Tiwari, D. Chakraborty Performances of conventional fiber reinforced composites are challenged in thermomechanical loading, when development of interlaminar stresses at the interface becomes the weakest link of the components. Development of functionally graded materials (FGMs) could lead to the reduction of such interlaminar failures, especially at high temperature applications. Therefore, these FGMs have a huge potential for use in many structural applications, particularly under thermomechanical loading. There has been a large number of works already reported on FGM components, starting from manufacturing to stress analysis of such components. Cracks in such FGM components may develop due to variety of reasons during service and need to be addressed while analyzing the performances of such components. This paper reviews the progress made till date on the analysis of structural components made of FGMs with a special emphasis on the analysis of cracked FGM components. In view of the potential use of components made of FGMs in a wide range of applications, it is important to understand the state of the art in this area. This paper thus provides a critical review of works reported in this area with an objective of providing the key challenges and future scopes of development in the direction of analysis of such structure for assessing safety in the presence of cracks.Graphical abstractImage 1
       
  • A novel method to produce kiss-bonds in composites components for NDI and
           characterisation purposes
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): R. Telford, A. O'Carroll, R.S. Pierce, T.M. Young Kiss-bonds (kissing bonds) are a defect type that feature a localised loss of structural continuity within the material, yet the material remains in intimate contact across the defect. Typically, shear and normal tensile stresses cannot be conducted across such defects (although, pure compressive stresses are possible). Kiss-bond defects are difficult to detect reliably – both within the bulk of the material (interlaminar) and within bond-lines of adhesively bonded joints or repairs – using conventional Non-Destructive Inspection (NDI) techniques. Compounding this issue is the lack of a reliable technique to create representative kiss-bond defects in a controlled fashion for the purpose of NDI equipment calibration or development, or scientific investigation.A novel method for manufacturing composite material test panels with kiss-bond defects (for research or NDI calibration, for example) in a controlled and repeatable fashion has been developed. Small areas of two adjacent pre-preg plies were pre-cured before being incorporated within a laminate. During consolidation, no bonding occurs between the pre-cured areas, thus creating a kiss-bond defect of known geometry. Test panels with 6 × 6 mm and 10 × 10 mm kiss-bond defects were manufactured. The robustness of the technique was verified using ultrasonic and laser shearography NDI methods; 7 of the 10 manufactured defects were classified as kiss-bonds, with the remaining 3 identified as dis-bonds.
       
  • Effect of seawater ageing with different temperatures and concentrations
           on static/dynamic mechanical properties of carbon fiber reinforced polymer
           composites
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Hailin Li, Kaifu Zhang, Xintian Fan, Hui Cheng, Guanhua Xu, Haoyuan Suo The aim of this paper was to investigate the static/dynamic mechanical properties and failure mechanism of carbon fiber reinforced polymer composites (CFRP) in seawater environments. The prepared specimens were immersed in artificial seawater with different temperatures and NaCl concentrations for 7 months. Quasi-static tensile and dynamic mechanical analysis (DMA) tests were carried out to evaluate the tensile and damping properties. Ageing damage and fracture morphology were observed by using scanning electron microscope (SEM) technology. The results show that tensile strength was sensitive to ageing time and environmental temperature but non-sensitive to NaCl concentration. In addition, the failure mode was changed.
       
  • Vibration analysis of multi-scale hybrid nanocomposite plates based on a
           Halpin-Tsai homogenization model
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Farzad Ebrahimi, Ali Dabbagh An analytical answer to the natural vibration problem of a composite plate consisted of multi-scale hybrid nanocomposites, is presented here for the first time. In this paper, the constituent material of the structure is made of an epoxy matrix which is reinforced by both macro- and nano-size reinforcements, namely carbon fiber (CF) and carbon nanotube (CNT). The effective material properties like Young's modulus or density are derived utilizing a micromechanical scheme incorporated with the Halpin-Tsai model. To present a more realistic problem, the plate is placed on a two-parameter elastic substrate. Then, on the basis of an energy-based Hamiltonian approach, the equations of motion are derived using the classical theory of plates. Finally, the governing equations will be solved analytically to obtain the natural frequency of the system's oscillation. Afterward, the normalized form of the results will be presented to put emphasis on the impact of each parameter on the dimensionless frequency of nanocomposite plates. It is worth mentioning that the effects of various boundary conditions on the frequency of the plate are covered, too. To show the efficiency of presented modeling, the results of this article are compared to those of former attempts. Numerical results declare that plates fabricated from the hybrid nanocomposites can endure higher frequencies compared with those consisted of conventional composites.
       
  • Experimental and numerical investigation of the residual strength of
           steel-composites bonded joints: Effect of media and aging condition
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Sugiman Sugiman, Paryanto Dwi Setyawan, Salman Salman, Hilton Ahmad This paper presents the experimental and numerical investigation of the residual strength of steel-composites joints aged in distilled and salt water under steady and fluctuating conditions at a temperature of 45 °C. The adhesive and the composites adherend had been characterized to obtain water absorption behavior and water-dependent mechanical properties. It was found that under the steady condition, the residual strength of the joints aged in distilled water was lower than that aged in salt water; however, under the fluctuating condition, the residual strength of the joints aged in salt water was lower than that aged in distilled water. Overall, the residual strength of the joints aged in salt water under the fluctuating condition was the lowest. Sequentially water diffusion and progressive damage finite element modeling of the joints considering the failure mode have been undertaken. The predicted residual strengths included the cohesive and interfacial failures were in reasonably agreement with the experimental results.
       
  • Energy analysis of fabric impregnated by shear thickening fluid in yarn
           pullout test
    • Abstract: Publication date: Available online 5 June 2019Source: Composites Part B: EngineeringAuthor(s): Ruixiang Bai, Yu Ma, Zhenkun Lei, Yang Feng, Chen Liu Impregnating fabrics with shear thickening fluid (STF) to form bi-phase composite is a potential method to improve the bulletproof resistance of flexible fabrics. In this study, a planetary ball milling method was used to prepare STF with 62, 65 and 70 wt% mass fraction using silica (SiO2) as dispersing phase and ethylene glycol as dispersant. The Kevlar 49 plain woven fabric was impregnated to form bi-phase composite. The yarn pull-out tests of neat fabrics and STF impregnated fabrics with loading speeds of 100, 500 and 1000 mm/min were carried out respectively. The experimental results show that STF impregnated fabrics have higher yarn pull-out loads than neat fabrics, and show a correlation of yarn pullout speed. A new energy absorption model is proposed to analyze the energy absorption mechanism in yarn pullout test. It is concluded that the work done by external force in yarn pull-out test can be equivalent to the energy dissipation of friction between yarns. The friction energy dissipation of STF impregnated fabrics is obviously increased compared with that of neat fabrics.
       
  • Graphene oxide-coated Poly(vinyl alcohol) fibers for enhanced
           fiber-reinforced cementitious composites
    • Abstract: Publication date: Available online 4 June 2019Source: Composites Part B: EngineeringAuthor(s): Xupei Yao, Ezzatollah Shamsaei, Shujian Chen, Qian Hui Zhang, Felipe Basquiroto de Souza, Kwesi Sagoe-Crentsil, Wenhui Duan The interface properties between fiber and matrix predominantly influence the mechanical performance of fiber reinforced cementitious composites (FRCCs). In this study, the interface between polyvinyl alcohol (PVA) fibers and mortar was modified by coating graphene oxide (GO) on the fiber surface. Experimental results showed the GO@ PVA fibers improved the tensile strength of FRCCs by 35.6% compared to that of pristine PVA FRCCs. Theoretical analysis indicated this significant improvement was attributed to the enhancement of the chemical bond energy (Gd) at fiber/matrix interface. With GO surface modification, the Gd was increased more than 80 times, changing the failure mode at the interface from adhesive failure to cohesive failure.Graphical abstractImage 1
       
  • 3D-printed polymer composites with acoustically assembled multidimensional
           filler networks for accelerated heat dissipation
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Lu Lu, Zhifeng Zhang, Jie Xu, Yayue Pan Polymer composites containing thermally conductive fillers show great promise in solving the overheating issue which is critical for electronic devices. Recent successes in developing functional polymer composites rely on the excellent filler property and heavy loading. Yet the intensive filler loading leads to challenges in manufacturing and composite properties. This study reports an alternative method for functional particle-polymer composite design and fabrication: instead of heavy loading, a small amount of filler composes highly concentrated multidimensional network functioning as active paths for heat dissipation in the polymer matrix. A novel 3D printing technique named acoustic field-assisted projection stereolithography realizes the fabrication of such composites. The local filler weight ratio in the network is > 7 times of the feedstock filler loading. With the same feedstock, the patterned composite exhibits>10 times higher efficiency in heat dissipation, compared to the uniform composite. With the same amount of fillers embedded, the patterned composite accelerates the heat dissipation twice than the uniform composite. Moreover, 3D filler network outperforms 2D network, showing that the higher network dimension is conducive to multidirectional heat transfer. With a low filler consumption while higher design flexibility, this new composite material design and manufacturing approach overcomes restriction caused by filler loading.Graphical abstractImage 1
       
  • Comprehensive enhancement in overall properties of MWCNTs-COOH/epoxy
           composites by microwave: An efficient approach to strengthen interfacial
           bonding via localized superheating effect
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Xin Liu, Jintao Luo, Jinfeng Fan, Song Lin, Liying Jia, Xiaolong Jia, Qing Cai, Xiaoping Yang By applying microwave (MW), strengthening effect of carboxylated MWCNTs (MWCNTs-COOH) on mechanical, thermal and electrical properties of epoxy (EP)-based composites was systematically evaluated. The localized superheating effect under MW contributed much in improving the dispersibility and dispersion stability of MWCNTs-COOH in EP matrix. MWCNTs-COOH/EP compositesEα via MW curing (MWC) showed the inside-out solidification mode associated with lower activation energy (α) over the range of cure (). An unique feature of MW was to enhance stress transfer and the formation of uniform MWCNT conducting networks, thus leading to a comprehensive enhancement in overall properties of resulting composites.
       
  • Effect of starch nanoparticles on the crystallization kinetics and
           photodegradation of high density polyethylene
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Nicolás Amigo, Humberto Palza, Daniel Canales, Francesca Sepúlveda, Diego A. Vasco, Francisco Sepúlveda, Paula A. Zapata Starch nanoparticles (SNp) with a diameter of ca. 70 nm were synthesized and used as fillers to prepare high density polyethylene (PE) composites by in situ polymerization. The effect of these particles on the thermal degradation, isothermal and nonisothermal crystallization, and photodegradation of PE was studied. SNp decreased the thermal degradation temperature of PE as tested by thermogravimetric analysis and increased the relative crystallinity and crystallization rate under isothermal conditions. This nucleating agent effect was confirmed by nonisothermal crystallizations as composites presented higher crystallization temperatures than neat PE. The photodegradation tests under UV radiation during 28 days showed that NPp promoted the polymer degradation by increasing the amount of carbonyl groups and by forming cavities at the nanoparticle/PE interface. Our findings open up new strategies for using SNp as filler in PE matrices to increase not only its photodegradation, but also its thermal properties.
       
  • Heat treatment and quenching media effects on the thermodynamical,
           thermoelastical and structural characteristics of a new Cu-based
           quaternary shape memory alloy
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Canan Aksu Canbay, Oktay Karaduman, Nihan Ünlü, Sivar Aziz Baiz, İskender Özkul In this study, Cu-based shape memory alloy (a smart material) with a new quaternary Cu-22.78Al-2.59Fe-2.44Mn (at%) composition was produced by arc melting and the samples cut from this cast-ingot alloy were homogenized at 900 °C for 1 h and quenched in traditional iced-brine water. Then except keeping one as the reference the others were all heat-treated (aged) at 200 °C for 1 h and then quenched/cooled in several different media. To find out the effects of the aging and varied quenching/cooling media types on the characteristic martensitic transformation temperatures, thermodynamical parameters and structural properties of this CuAlFeMn shape memory alloy (SMA) the thermal and X-ray measurements were carried out. The differential scanning calorimetry (DSC) and differential thermal analysis (DTA) measurements were made at different heating/cooling rates for all of the different types of the alloy samples. Thermal results showed that the characteristic forward martensite to austenite and backward phase transitions occurred at varied temperatures in between 44 and 176 °C and the different samples had different characteristic transformation temperatures and hysteresis due to the different quenching media effects. All of the samples exhibited high temperature shape memory alloy (HTSMA) behavior since all of their austenite start temperatures came up over 100 °C. The highest average austenite phase finish temperature belonged to the sample quenched in boiling water and the lowest belonged to the sample quenched in liquid nitrogen. The least amount of transformation entalphy and entropy change values were found for the aged sample quenched in liquid nitrogen which is the fastest coolant medium among others and caused the neatest martensite and interface formations and this was also understood from this sample having the lowest Gibbs free energy difference (ΔG). The X-ray analyses of the CuAlFeMn SMA samples showed the formations of β1′(M18R) and γ1′(2H) in the alloy and a main peak plane change occurred by aging. Besides this, there has been an adverse magnitude ranking correspondency found between average crystallite size and entropy change values of the aged samples. The analyses showed that the characteristic thermodynamical, thermoelastical and structural parameters of the CuAlFeMn high temperature shape memory alloy are strongly affected from the conditions of composition, aging temperature and quenching/coolant medium type used and the different combinations of those conditions can lead to their own distinctive genuine consequences.
       
  • Nickel-cobalt phosphate/graphene foam as enhanced electrode for hybrid
           supercapacitor
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Abdulmajid Abdallah Mirghni, Kabir O. Oyedotun, Badr Ahmed Mahmoud, Abdulhakeem Bello, Sekhar C. Ray, Ncholu Manyala Nickel-cobalt phosphate/graphene foam (40 mg) (NiCo(PO4)3/GF) composite was synthesized via a hydrothermal process and used as electrode material for supercapacitors. This work was done based on the fact that the electrochemical behavior of cobalt phosphate is similar to EDLC, while nickel phosphate is purely faradaic. Interestingly, the advantages of these two different mechanisms reflected on the results of NiCo(PO4)3/GF as an electrode for supercapacitor. The crystal structure, morphology and texture of the synthesized materials were studied with XRD, Raman spectrum, SEM and BET. The electrochemical performance of the produced sample was investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. NiCo(PO4)3/GF_40 mg composite exhibited significantly improved specific capacity (86.4 mAh g−1) much higher than pristine NiCo(PO4)3 (64 mAh g−1) at 1 A g−1 due to the synergistic effect between the conductive GF and NiCo(PO4)3. Furthermore, the hybrid supercapacitor device (NiCo(PO4)3//AC) fabricated achieved the highest energy density of 34.8 Wh kg−1 and a power density of 377 W kg−1 at a specific current of 0.5 A g−1. The hybrid device also showed 95% of capacity retention after 10000 charge-discharge cycles at a specific current of 8 A g−1 and 90% efficiency at floating time over 110 h at 5 A g−1. These results make this composite to be a good candidate for electrochemical capacitors applications.Graphical abstractImage 1
       
  • Experimental and numerical determination of the thermal cycle performance
           of joints obtained with nanostructure-doped nanocomposite adhesives
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Salih Akpinar, Adnan Ozel Particularly findings from nanoscience influence materials and mechanical sciences deeply as well as other disciplines. Polymers containing nanostructures attracted attention as nanocomposite materials. This study involves the production of a new nano adhesive utilizing the advantageous parameters of carbon-nano-reinforced polymers used for adhesively bonded, particularly in aerospace applications, and the mechanical and thermal cycle performance of this new product. In this study, the tensile mechanical properties of single-lap joints (SLJs), which are the most widely used type of adhesive joint geometry, obtained by adding nano-particle to adhesive was investigated experimentally and numerically under ambient temperature and thermal cycle conditions. The experimental results of reinforced adhesive under ambient temperature conditions were taken from open literature. Adhesively bonded SLJs were produced using DP460 tough and DP125 flexible adhesive types as the adhesives; AA2024-T3 aluminum alloy was used as the adherend and 1 wt% Graphene-COOH, Carbon Nanotube-COOH and Fullerene C60 were used as the added nano-particles. The experimental results were compared with the results of numerical calculations that employ Cohesive Zone Model (CZM). Also six different thermal cycle loadings were applied on the SLJs. As a result, when the experimental failure loads were examined, the nanocomposite adhesives obtained by adding nano-particle were found to have increased the thermal cycle resistance of the joints. However, increase rate in the thermal cycle resistance changes depending on the structural features of the adhesive, the type of nano-particle and thermal cycle condition. It was also concluded that the results of numerical calculations matches the experimental results quite satisfactorily.
       
  • Production of geopolymer mortar system containing high calcium biomass
           wood ash as a partial substitution to fly ash: An early age evaluation
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Omar A. Abdulkareem, Mahyuddin Ramli, John C. Matthews This paper presents an investigation on the feasibility of inclusion of biomass wood ash (BWA) as a partial replacement material for fly ash (FA) in preparation of blended BWA-FA geopolymer mortars. The blended mortar systems for this study were prepared at three replacement ratios of FA by BWA of 10%, 20% and 30% by binder mass. The engineering properties of the BWA-FA geopolymer mortars were evaluated using compressive strength, flexural strength, water absorption and total porosity measurements. Microstructural and phase composition analysis were also conducted to assess the obtained results and compared with a control mortar mix containing 100% FA at different ages of 3, 7 and 28 days. The results showed the inclusion of BWA up to 20% resulted in higher strength and porosity characteristics than the control mix at age of 3 and 7 days. However, at age of 28 days, the geopolymer contains 10% BWA of the total binder was the only blended mixture that exhibited higher compressive strength and lower total porosity than the control mix. The phase composition results of the blended mixtures at 28 days confirmed the formation of calcium polysialate and calcium silicate hydrate gels coexisted with sodium polysialate phase.
       
  • Processing and characterization of robust carbon–carbon composites from
           inexpensive petroleum pitch without re-impregnation process
    • Abstract: Publication date: 1 October 2019Source: Composites Part B: Engineering, Volume 174Author(s): Shishobhan Sharma, Rasmika H. Patel Robust carbon/carbon composite were developed solely from inexpensive petroleum pitch matrix and chopped carbon fiber reinforcement without cyclic reimpregnation process and have been characterized. The paper emphasizes on investigating the properties and behaviors of the same. Hot compression molding of chemically treated pitch as a binder and thermally treated pitch as a base matrix was carried out followed by single step carbonization. Specimens were characterized by UTM, TGA, TMA, SEM, Polarized light optical microscope, Tribometer etc. For physical characterization viz. density and porosity analysis, standard methods were utilized. Satisfactory results have been obtained. Densities of the samples appeared in the range of 1.50–1.73 g/cc. Carbon/carbon composite showed an increasing trend in their properties as the reinforcement content increased along with exceptional compression loading. Overall, the specimens are robust and have performed well in mechanical tests. Reinforcing as well as dispersing phase have shown high compatibility.
       
  • Parametric excitation of Euler–Bernoulli nanobeams under
           thermo-magneto-mechanical loads: Nonlinear vibration and dynamic
           instability
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): Majid Ghadiri, S. Hamed S. Hosseini The nonlinear vibration behavior and dynamic instability of Euler–Bernoulli nanobeams under thermo-magneto-mechanical loads is the main objective of present paper. Firstly, a short Euler–Bernoulli nanobeam is modeled and exposed to an external parametric excitation. Based on the nonlocal continuum theory and nonlinear von Karman beam theory, the nonlinear governing differential equation of motion is derived. Secondly, to transport the partial differential equation to the ordinary differential equation, Galerkin method is applied. Then, multiple scales method, as an analytical approach, is used to solve the equation. At the end, modulation equation of Euler–Bernoulli nanobeams is obtained. Then, to evaluate the dynamic instability of the system, trivial and nontrivial steady-state solutions are discussed. Emphasizing the effect of parametric excitation, for considering the instability regions, bifurcation points are studied and investigated. As a results, it can be observed that the damping coefficient plays an effective role as well as parametric excitation in stability and frequency response of the system.
       
  • Characterization of hydroxyapatite from eggshell waste and
           polycaprolactone (PCL) composite for scaffold material
    • Abstract: Publication date: 15 September 2019Source: Composites Part B: Engineering, Volume 173Author(s): V. Trakoolwannachai, P. Kheolamai, S. Ummartyotin Hydroxyapatite was successfully synthesized from eggshell waste. In addition, 10, 20, and 30 wt% hydroxyapatite/polycaprolactone (PCL) composites were prepared. The composites were prepared by dispersing hydroxyapatite particles in PCL. The structural properties of the composites were characterized by Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The results confirmed the presence of hydroxyapatite in the samples. The FTIR spectra showed P–O stretching peaks; the XRD patterns revealed the formation of the hydroxyapatite crystalline phase. Moreover, the thermal stabilities of the hydroxyapatite/PCL composites were higher that of pristine PCL, as revealed by thermogravimetric analysis. The higher thermal stabilities of the composites were attributed to the presence of hydroxyapatite; the composites were stable up to 300 °C. The melting temperatures of the composites were slightly higher than that of pristine PCL. In addition, scanning electron microscopy and elemental mapping were performed to investigate the morphological properties of the composites and the presence of hydroxyapatite in them. The results revealed that hydroxyapatite was present on the surface of PCL. Moreover, compared to pristine PCL, the composite samples exhibited superior swelling behaviors and lower degradation percentages. Preliminary experiment of cell cytotoxicity was observed. It presented the excellent properties to Saos-2 cell.Graphical abstractImage 1
       
  • Comparative analysis of micromechanical models for the elastic composite
           laminae
    • Abstract: Publication date: Available online 31 May 2019Source: Composites Part B: EngineeringAuthor(s): Lucas L. Vignoli, Marcelo A. Savi, Pedro M.C.L. Pacheco, Alexander L. Kalamkarov This paper deals with the first step required for the analysis and design of composite materials and structures: estimation of the effective macromechanical properties according to the structure of composite, properties of constituent materials and their volume fractions. There exist many micromechanical models proposed in the literature to estimate these effective elastic properties. Each one of these models is based on hypotheses that are valid for certain types of composite structures. The present paper aims to highlight the main assumptions of these models and compare their predictions with a set of 188 experimental data, compiled from 25 references, assuming that just the constituents’ properties are available as input. The following nine major micromechanical models are evaluated: asymptotic homogenization with hexagonal unit cell; asymptotic homogenization with square unit cell; Bridging; Chamis; generalized self-consistent; Halpin-Tsai; modified Halpin-Tsai; Mori-Tanaka; and rule of mixture (ROM). Besides, a novel modified version of the rule of mixture allowing better agreement with the experimental data is also proposed. It is shown, in particular, that the newly proposed modified rule of mixture model provides the best correlation with the experimental data among the ROM-based models, while the asymptotic homogenization presents the best predictions among the elasticity-based models.
       
  • N-doped carbon quantum dots @ hexagonal porous copper oxide decorated
           multiwall carbon nanotubes: A hybrid composite material for an efficient
           ultra-sensitive determination of caffeic acid
    • Abstract: Publication date: Available online 31 May 2019Source: Composites Part B: EngineeringAuthor(s): Ganesan Muthusankar, Murugan Sethupathi, Shen-Ming Chen, Ramadhass Keerthika Devi, Rajendran Vinoth, Gopalakrishnan Gopu, Narayanasamy Anandhan, Nallathambi Sengottuvelan Herein, we report the nitrogen-doped carbon quantum dots (N-CQD) loaded hexagonal structured porous copper oxide (N-CQD/HP-Cu2O) composite for the first time. The composite was synthesized using a facile hydrothermal approach. The loading of N-CQD in N-CQD/HP-Cu2O composite plays a vital role in the structural formation, and the composite has been evaluated using Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron, and transmission electron microscopy. Hereafter, the composite was anchored with multiwall carbon nanotube (MWCNT) using ultrasonication method to construct the N-CQD/HP-Cu2O/MWCNT hybrid composite material and used as an electrode material for effective electrochemical detection of caffeic acid (CA). The sensing behaviour was examined using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. As a result, the developed N-CQD/HP-Cu2O/MWCNT/GCE sensor exhibits a lower detection limit of 0.004 μM and excellent sensitivity of 31.85 μA μM−1 cm−2 for the detection of CA. Thus, the hybrid composite could be a promising electrode modifier for the enhanced electrocatalytic applications. Finally, the developed sensor has applied for the detection of CA in red wine samples.Graphical abstractImage 1
       
  • Novel hybrid nanocomposite based on Poly(vinyl alcohol)/ carbon quantum
           dots/fullerene (PVA/CQDs/C60) for thermoelectric power applications
    • Abstract: Publication date: Available online 31 May 2019Source: Composites Part B: EngineeringAuthor(s): Ahmed gamal El-Shamy In this literature, hybrid polyvinyl alcohol/carbon quantum dots/fullerene (PVA/CQDs/C60) nanocomposite films were fabricated by using casting technique for the first time. Microwave synthesized carbon quantum dots (CQDs) and Fullerene (C60) were synergistically incorporated in poly vinyl alcohol matrix. Addition of the hybrid CQDs/C60 nanoparticles enhances the mechanical, thermal and thermo-mechanical parameters of the nanocomposite. CQDs nanoparticles were used here to enhance the electrical conductivity (σelectrical), while C60 was used to improve the Seebeck coefficient (Sseebeck), obstruct the thermal conductivity (Kthermal) and produce synergistic influence to improve the thermoelectric behaviour. With doping of the hybrid (CQDs/C60) nanoparticles into (PVA/CQDs/C60) nanocomposite, the electrical conductivity (σelectrical) increased from (100–690 S/cm), and thermal conductivity (Kthermal) changed from (0.35–0.64 W/m K2), while the Seebeck coefficient (Sseebeck) improved by 2 order. In addition, the nanocomposite demonstrated a power factor (PF) as high as (2.1 × 10−4 W/m K2) and a high figure of merit (ZT) (0.16) at a ratio (CQDs:C60 = 15:5) at 300 K. Finally, these nanocomposites have a potential prospective application in thermoelectric devices thanks to their promising thermoelectric properties and easy scaling up.Graphical abstractImage 1
       
  • Fatigue damage behavior in carbon fiber polymer composites under biaxial
           loading
    • Abstract: Publication date: Available online 30 May 2019Source: Composites Part B: EngineeringAuthor(s): Travis Skinner, Siddhant Datta, Aditi Chattopadhyay, Asha Hall An investigation into the damage accumulation and propagation behavior in carbon fiber reinforced polymer (CFRP) composites under complex in-phase biaxial fatigue loading has been conducted. The goal is to capture early stage damage and obtain an improved understanding of damage propagation and associated degradation in material properties. Both cross ply and quasi isotropic laminate configurations have been studied and the tests were conducted under constant amplitude in-phase biaxial loading. An optimization technique was used to design the cruciform specimens for each stacking sequence. To understand the propagation of damage from the micro-to the macroscale, the fractured surfaces were analyzed, during various stages of fatigue, using electron microscope assisted fractography and a high-resolution camera. Material property degradation was determined by measuring the change in specimen stiffness to analyze the progression of fatigue damage and is correlated to the micro- and macroscale damage mechanisms and the biaxial fatigue loading parameters. The results provide insight into the initiation and propagation of damage mechanisms in CFRP composites which is essential to understanding the fatigue behavior of composite materials under complex multiaxial loadings.
       
  • Comparative investigation on electronic properties of metal-semiconductor
           structures with variable ZnO thin film thickness for sensor applications
    • Abstract: Publication date: Available online 30 May 2019Source: Composites Part B: EngineeringAuthor(s): Osman Çiçek, Sedat Kurnaz, Atakan Bekar, Özgür Öztürk In this work, AuPd/n-GaAs and Ag/n-GaAs metal–semiconductor, which is known as Schottky Junction Structures (SJSs), with various ZnO thin film thickness (25–250 nm) classified as Group AuPd and Group Ag to investigate electronic properties on SJSs. The current-voltage (I–V) characteristics of SJSs operating in their forward and reverse regions operating at ±3V were measured at room temperature (295 K). The electronics parameters such as the series resistance (Rs), the shunt resistance (Rsh), the ideality factor (n) and the barrier height (ΦB0) were calculated by using thermionic emission (TE) theory, Ohm's law, Cheung and Cheung's function and modified Norde's function. Labview® based characterization tool developed to calculate the electronic parameters. The results were compared according to the various thicknesses and different rectifier contacts. Experimentally, if the results are analysed for each group, a (gradual) decrease in ZnO thicknesses is caused by an increase in the values of n, ФB0, RR. In addition, the Rsh values were significantly increased while the Rs values were almost close to each other. As the ΦB0 values, while compatible with the values found in the Cheung and Cheung's function, they are slightly higher than the values found in the TE theory. On the other hand, due to the voltage-dependent barrier height and nature of the used method, ФB0 values from modified Norde's function are a little higher than the TE theory. Finally, it can be clearly seen that electronic parameters of SJSs based on sensor applications can be arranged with various thicknesses according to extracted results.
       
  • Robust, self-cleaning, anti-fouling, superamphiphobic soy protein isolate
           composite films using spray-coating technique with fluorinated HNTs/SiO2
    • Abstract: Publication date: Available online 30 May 2019Source: Composites Part B: EngineeringAuthor(s): Xiaorong Liu, Kaili Wang, Wei Zhang, Jizhi Zhang, Jianzhang Li The practical applications of protein-based materials have so far been limited due to their natural hydrophilicity and high sensitivity to moisture. In this study, we developed a facile surface coating technique to prepare superamphiphobic soy protein isolate (SSPI) films materials. First, fluorinated superamphiphobic HNTs/SiO2 particles (HS-SH-F) were prepared through simple and efficient thiol-ene click reaction. Then, HS-SH-F particles were sprayed onto SPI films while Polydimethylsiloxane (PDMS) as a medium adhesive layer. The as-prepared SSPI films exhibited excellent repellent liquid (both water and oil) ability. To the best of our knowledge, this is the first time for exploring and achieving superamphiphobic property on protein-based films materials. The as-prepared superamphiphobic protein film can repel various liquids even with low surface tension (the n-heptane contact angle is 154.2°, and the slide angle is 9.5°). Moreover, the SSPI film retained great superamphiphobic performance after various harsh conditions tests, such as 20 times tape-peeling test, blade-scratch, strong acid/basic and organic solvents immersion, etc., indicating excellent mechanical robust and chemical durability. Such surface coating deservedly exhibits outstanding self-cleaning property and antifouling function. Therefore, it can be applied in various harsh environments, such as outdoor service and underwater materials. More importantly, this is a scalable approach for a wider range of materials other than protein-based materials.Graphical abstractImage 1
       
  • Tensile fatigue characterization of polyamide 66/carbon fiber
           direct/in-line compounded long fiber thermoplastic composites
    • Abstract: Publication date: Available online 30 May 2019Source: Composites Part B: EngineeringAuthor(s): M. Bondy, W. Rodgers, W. Altenhof Fiber reinforced polymer (FRP) composite materials can be advantageous alternatives to structural metals due to their high specific stiffness and strength. One potentially useful class of FRPs are Long-Fiber Thermoplastic composites (LFT) as these materials have significantly higher aspect ratios for the fibers, and possible lower cost variant of LFTs, Direct Long Fiber Thermoplastics (DLFT), where the long discontinuous fibers are created directly during the extrusion process from fiber rovings. The objective of this study was to determine the fatigue performance of DLFT composites. Therefore, tensile fatigue characterization was carried out for compression molded direct/in-line compounded (DLFT) 40% (by weight) carbon fiber/polyamide 66 composites. This characterization yielded fatigue life prediction curves (stress ratio of 0.1) for 0°, 45°, and 90° orientations with respect to flow. The evaluations showed a reasonable match to a power law approximation for the relationship of peak stress to number of cycles to failure for these materials under these test conditions (23 °C, dry as molded, R = 0.1, 3 Hz). Peak stresses at which the samples achieved 106 cycles were 105 MPa for samples oriented in the flow direction, 72 MPa for samples oriented 45° to the flow direction, and 53 MPa for samples oriented 90° to flow.
       
 
 
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