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Composites Part B : Engineering
Journal Prestige (SJR): 2.039
Citation Impact (citeScore): 5
Number of Followers: 263  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1359-8368
Published by Elsevier Homepage  [3162 journals]
  • Exact dynamic characteristic analysis of a double-beam system
           interconnected by a viscoelastic layer
    • Abstract: Publication date: Available online 12 November 2018Source: Composites Part B: EngineeringAuthor(s): Fei Han, Danhui Dan, Wei Cheng As an important composite beam structure, the double-beam system with a viscoelastic connection layer has a wide range of applications in engineering. Accurate analysis of its dynamic characteristics is an imperative requirement for the design, monitoring and evaluation, or vibration control of these structures. Existing researches usually introduce some simplifications or assumptions, and ignore the damping characteristics of the structure in most cases, which results in inaccurate dynamic analysis results of such double-beam structures and cannot meet the actual requirements. For this reason, a generalized mechanical model that can consider the damping factor is established in this paper to accurately simulate the double-beam system with a viscoelastic connection layer, and its dynamic characteristics are accurately analyzed by dynamic stiffness method. On this basis, the effects of structural parameters on the modal frequencies and mode shapes of the system are studied. The results show that the stiffness of the connection layer has little effect on the system mode; the modal frequencies of the double-beam system can be reduced by increasing the mass or damping coefficient of the connection layer, where the influence of damping on the low-order modes of the system is very significant, but its effect on the higher-order modes are clearly inferior to that of mass.
  • Models for estimating the thermal properties of electric heating concrete
           containing steel fiber and graphite
    • Abstract: Publication date: Available online 12 November 2018Source: Composites Part B: EngineeringAuthor(s): Rui Rao, Hanfa Wang, Haihong Wang, Christopher Y. Tuan, Mao Ye This paper presents an experimental investigation for thermal properties of a specialized electric heating concrete containing steel fiber and graphite (SGEHC) which is a specialized concrete used for outdoor snow melting and indoor radiant heating. Experiments were carried out to determine the density, special heat capacity and thermal conductivity of the SGEHC. It shows that the SGEHC is a porous material with 11.7% porosity ratio, which has a great influence on the density, thermal conductivity of the SGEHC but limited effect on its specific heat capacity. Accordingly, a density model and a thermal conductivity model were proposed by treating the SGEHC as a four phases composite made of steel fiber, graphite, regular concrete and air, which could conducts heat in both parallel and series. The results show that the predicted results are in good agreement with the experimental results.
  • Towards solution-processable, thermally robust, transparent
           polyimide-chain-end tethered organosilicate nanohybrids
    • Abstract: Publication date: Available online 12 November 2018Source: Composites Part B: EngineeringAuthor(s): Ki-Ho Nam, Jeong-un Jin, Dong Hoon Lee, Haksoo Han, Munju Goh, Jaesang Yu, Bon-Cheol Ku, Nam-Ho You The main challenge to developing future display substrates is to synthesize flexible substrate materials that also have excellent optical and thermal properties, and low thermal expansion number. In this study, a novel trifluoromethylated asymmetric aromatic diamine, 4-[[4-(4-amino-2-trifluoromethylphenoxy)phenyl]sulfonyl-3-(trifluoromethyl)]benzenamine (AFPSFB), was synthesized through nucleophilic substitution. Conventional two-step polycondensation of AFPSFB with commercially available tetracarboxylic dianhydrides enabled the fabrication of fully or semi-aromatic polyimides (PIs). The resulting PIs were highly soluble in polar aprotic solvents with good optical and thermal properties. Next, polyhedral oligomeric silsesquioxane containing an amine group (NH2-POSS) was reacted with the resulting soluble PI. All the PI-POSS nanohybrids displayed excellent optical properties, including high transparency (>91% at 400 nm), low refractive index (
  • Fatigue behavior of short carbon fiber reinforced epoxy composites
    • Abstract: Publication date: Available online 11 November 2018Source: Composites Part B: EngineeringAuthor(s): C. Capela, S.E. Oliveira, J.A.M. Ferreira This paper intends to contribute to a better understanding of the failure mechanisms on short fibers composites with high fiber volume fractions, for which relatively low values of stiffness and resistance efficiency are reached. For the aforementioned purpose, the current work used composite plates that were manufactured by compression molding and incorporating short carbon fibers reinforcements (0.5 mm in length with 5–20% volume fiber fraction) into an epoxy resin. For low volume fractions, the composites exhibit static mechanical properties nearly proportional with fiber content. However, for high volume fraction lower efficiency was observed for both tensile stiffness and strength. As expected, the strain at failure decreases with the increasing of the fiber content. Fatigue strength follows a similar behavior of static strength, increasing until the fiber content is of 17.5% in volume, but afterwards remains nearly constant. Fatigue life is mainly influenced by fiber dispersion and porosity.
  • Topology optimization-guided stiffening of composites realized through
           Automated Fiber Placement
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): L. Esposito, A. Cutolo, M. Barile, L. Lecce, G. Mensitieri, E. Sacco, M. Fraldi The paper proposes a mixed strain- and stress-based topology optimization method for designing the ideal geometry of carbon fibers in composite laminates subjected to either applied tractions or prescribed displacements. On the basis of standard micromechanical approaches, analytical elastic solutions for a single cell, assumed to be a Representative Volume Element (RVE), are ad hoc constructed by involving anisotropy induced by fiber orientation and volume fraction, also taking into account inter-laminar stresses and strains. The analytical solutions are then implemented in a Finite Element (FE) custom-made topology optimization-based procedure rewritten to have as output the best curves the reinforcing fibers have to draw in any composite laminate layer to maximize the overall panel stiffness or to minimize the elastic energy. To verify the effectiveness of the proposed strategy, different structures undergoing either in-plane or out-plane boundary conditions have been selected and theoretically investigated, determining the optimal fibers' maps and showing the related results in comparison to standard sequences of alternate fibers disposition for the same composites. Two optimized panels were at the end actually produced using an innovative Automated Fiber Placement (AFP) machine and consolidating the materials by means of autoclave curing processes, in this way replicating the fiber paths obtained from theoretical outcomes. As a control, two corresponding composite structures were also realized without employing the fiber optimization strategy. The panels have been tested in laboratory and the theoretical results have been compared with the experimental findings, showing a very good agreement with our predictions and confirming the capability of the proposed algorithm to suggest how to arrange the fibers to obtain enhanced mechanical performances. It is felt that the hybrid analytical-FE topology optimization strategy, in conjunction with the possibilities offered by AFP devices, could pave the way for a new generation of ultra-lightweight composites for aerospace, automotive and many industrial applications.
  • Stretchable and patchable composite electrode with trimethylolpropane
           formal acrylate-based polymer
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): Byungil Hwang, Tae Gwang Yun With the huge variety of wearable/stretchable electronic devices that require materials with different properties depending on the applications, securing the large reserves of stretchable material systems is crucial. In this study, trimethylolpropane formal acrylate (TFA)-based polymer films are explored to develop stretchable composite electrodes. The TFA resin containing 1-hydroxycyclohexyl phenyl ketone as a photoinitiator is UV curable and shows a high optical transmittance of ∼93.0 ± 0.3% and a low haze of ∼0.29 ± 0.03%. The TFA films can withstand a tensile strain up to 100% and show excellent mechanical reliability during 30 cycles of tensile tests. Furthermore, the elastomeric TFA films are attachable to polymer or glass substrates, and during multiple adhesion tests, show a lower degradation of the adhesion properties than that showed by typical adhesive materials such as scotch tapes. The electrodes fabricated by embedding Ag nanowires in the surface of the TFA films (TFA/Ag nanowire electrodes) function as stretchable/patchable conductors under severe mechanical deformation such as stretching and crumpling. Furthermore, a patchable/stretchable supercapacitor comprising the TFA/Ag nanowire electrodes as a current collector is demonstrated that shows a reliable electrochemical performance under bending, stretching, and twisting conditions.
  • Transient wave propagation in Cosserat-type shells
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): Yury A. Rossikhin, Marina V. Shitikova The aim of this paper is to find the magnitudes of velocities of transient waves which could be originated and propagate in thin shells made of Cosserate-type material in the form of surfaces of strong and weak discontinuity. Thus, starting from the 3D Cosserat continuum, the velocities of four transient waves propagating in a thin shell with micro-structure have been determined according to a wave theory for thin-walled plates and shells proposed recently by the authors. Using the expansion ray theory and conditions of compatibility for thin-walled structures, it has been found that (1) the velocities depend only on material constants, and (2) only one micropolar modulus α, which governs the asymmetry of the stress tensor, influences the velocity of the quasi-shear wave, while the Láme moduli λ and μ do not affect the velocities of Cosserat waves, which are generated due to micropolar rotations. This results to the fact that the mathematical theory due to Cosserat is not coupled one. The knowledge of the velocities of transient waves in thin shells made of Cosserat-type materials will allow one to solve boundary-value transient dynamic problems resulting in the propagation of surfaces of strong and weak discontinuity.
  • Improved knockdown factors for composite cylindrical shells with
           delamination and geometric imperfections
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): Bo Wang, Xiangtao Ma, Peng Hao, Yu Sun, Kuo Tian, Gang Li, Ke Zhang, Liangliang Jiang, Jie Guo For cylindrical shell structures under axial compression, it is crucial to provide high-fidelity knockdown factors (KDFs) in preliminary design for aerospace and civil structures. In this paper, numerical studies of buckling response for composite cylindrical shell with geometric imperfections and embedded delamination imperfections are performed to predict the lower-bound buckling loads. Results indicate that composite shells with single dimple-shape geometric imperfection exhibit similar lower bound trend and buckling behavior as those with embedded delamination imperfection. It is found that the lower-bound buckling loads are much less conservative than the corresponding design recommendation from NASA SP-8007. And the effect of geometric imperfections can envelope that of delamination imperfections. Therefore, the worst multiple perturbation load approach (WMPLA) is performed to find the worst combination of dimple-shape geometric imperfections to predict the lower-bound buckling load, and the efficient global optimization (EGO) is employed to improve the computational efficiency of WMPLA. It is demonstrated that the improved WMPLA can provide an improved KDF by examples in open literature. Based on the improved KDFs, it is possible to increase the load-bearing efficiency of composite structures in practical engineering.
  • Thermal properties of doubly reinforced fiberglass/epoxy composites with
           graphene nanoplatelets, graphene oxide and reduced-graphene oxide
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): M. Rafiee, F. Nitzsche, J. Laliberte, S. Hind, F. Robitaille, M.R. Labrosse A novel manufacturing method based on Vacuum Assisted Resin Transfer Molding (VARTM) was devised to incorporate carbon nanoparticles for the enhancement of thermal properties of multiscale laminates. Several graphene-based nanomaterials including graphene oxide (GO), reduced graphene oxide (rGO), graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWCNTs) were used to modify the epoxy matrix and the surface of glass fibers. The thermal, rheological and morphological properties of the resulting glass fiber-reinforced multiscale composites were investigated. The thermal properties of the epoxy/nanoparticle composites were studied through thermal conductivity measurements, differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). The thermal characterization results showed that the introduction of GNPs, GO, rGO, and MWCNTs enhanced thermal conductivity. Compared with the neat epoxy/fiberglass composite control results, improvement in thermal conductivity of fiberglass/epoxy modified with MWCNTs 0.3%, GNPs 1%, GO 2% and rGO 0.042% were 8.8%, 12.6%, 8.2% and 4.1%, respectively. It was concluded that for the same volume fraction of nanoparticles, the thermal conductivity improvement in graphene nanoplatelets-modified composites is more pronounced compared with other nanoparticles. A better dispersion of nanoparticles and a better interfacial interaction between nanoparticles and epoxy are essential in enhancing the thermal conductivity of nanocomposite materials.
  • A study of the influence of processing parameters on steering of carbon
           Fibre/PEEK tapes using laser-assisted tape placement
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): Gearóid Clancy, Daniël Peeters, Vincenzo Oliveri, David Jones, Ronan M. O'Higgins, Paul M. Weaver Laser-assisted Automated Tape Placement (LATP) in-situ consolidation of thermoplastic composites has significant potential to produce repeatable and accurate components more efficiently than conventional processing methods. In addition, LATP can process Variable Angle Tow (VAT) laminates, that allow modification of load paths within the laminate to result in more favourable stress distributions and improved laminate performance. Previous studies have reported dry fibre placement and thermoset pre-preg tape placement processed VAT laminates. This work investigates the processing parameters required to produce VAT laminates from carbon fibre (CF)/polyether ether ketone (PEEK) tapes using LATP. Testing was carried out to examine the effect of lay-down speed and steering radii on defect frequency and bond strength. Measurements showed that the width and thickness of the CF/PEEK tapes changed as a result of steering. In addition, bond strength, determined using a novel wedge peel rig for steered tape, was found to be a function of lay-down speed.
  • A computer simulation of stress transfer in carbon nanotube/polymer
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): Jiawei Zhao, Mo Song The reinforcing efficiency or stress transfer of carbon nanotubes (CNT) on polymers in polymer/CNT composites mainly is controlled by the polymer-CNT interface. Enhancement of polymer-CNT interactions and interfacial crystallisation is as an important way for improvement of the reinforcement experimentally. However, it is not clear about the crystallisation and orientation of polymer chains on the CNT surface, and how the interfacial crystallisation layer affects the failure of the composite. In this work, poly(vinyl alcohol)/CNT nanocomposites was selected as an example and based on the molecular dynamics simulation, the crystallisation process, failure behaviour and stress transfer in poly(vinyl alcohol)/CNT nanocomposites were analysed. The crystallisation temperature of the polymer chains on the CNT surface is slightly higher than the bulk crystallisation temperature. CNT induced crystallisation can be divided into three stages: chain folding, orientating and growing on the CNT surface. A slower crack growth was observed in the interfacial crystallised polymer/CNT systems, compare to relative amorphous systems. The effect of the interfacial crystalline layer on stress transfer is similar as enhanced polymer-CNT interaction systems. The change of the polymer-CNT surficial energy to strain has been used to analyse the interfacial failure and the stress transfer.Graphical abstractFinal configuration and enthalpy change of isothermal crystallisation reveal the crystallization process on CNT surface.Image 1
  • Large amplitude thermally induced vibrations of temperature dependent
           annular FGM plates
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): Mehran Javani, Yaser Kiani, M.R. Eslami Present research deals with the large amplitude thermally induced vibrations of an annular plate made of functionally graded materials (FGMs). One surface of the plate is subjected to rapid surface heating while the other surface is either thermally insulated or kept at reference temperature. The material properties of the constituents are assumed to be temperature dependent. The rule of mixtures is used to obtain the properties of the graded media. With the aid of the von Kármán kinematic assumptions and first order shear deformation theory, the governing equations of motion and the associated boundary conditions are obtained. With the aid of the generalized differential quadrature (GDQ) method, these equations are transformed into a set of nonlinear algebraic equations which are solved iteratively using the Newton-Raphson method and Newmark time marching scheme. The temperature profile across the plate thickness is also obtained using the iterative Crank-Nicolson and the GDQ methods. Numerical results are devoted to the effects of temperature dependency, plate thickness, power law index, and boundary conditions of the plate on the large amplitude thermally induced vibrations. It is shown that for thin plates thermally induced vibrations take place and the quasi-static response can not be considered as the true response of the plate under thermal shock.
  • New energy harvester with embedded piezoelectric stacks
    • Abstract: Publication date: Available online 10 November 2018Source: Composites Part B: EngineeringAuthor(s): Alireza Keshmiri, Xiaowei Deng, Nan Wu Mechanical energy harvesters are designed to capture the ambient energy and transform it into usable electrical energy. Power harvesting from mechanical vibrations is the fundamental step toward providing self-powered smart systems in the developing wireless and portable electronic devices marketplace. This paper presents a new design and an analytical model for the development of a composite energy harvester by using piezoelectric stacks. The in-plane polarization of the piezoelectric elements and the flexible electrode design using piezoelectric stacks are introduced to maximize the electrical voltage/charge output. The presented model is applicable to composite beams with structural strain rate damping and embedded piezoelectric stacks. The steady state vibration response of the composite harvester subjected to a harmonic base motion is obtained and electrical outputs are analytically derived. Moreover, a parametric study for the composite energy harvester with different embedded piezoelectric stacks number, length and thickness under the excitation in a wide frequency domain has been done. Finally, the new design is compared to a conventional unimorph harvester with identical geometrical and material properties to demonstrate the potential significant improvement in the electrical charge and voltage outputs.
  • New technique of friction-based filling stacking joining for metal and
    • Abstract: Publication date: Available online 9 November 2018Source: Composites Part B: EngineeringAuthor(s): Yongxian Huang, Xiangchen Meng, Yuming Xie, Junchen Li, Long Wan A novel technique named friction filling staking joining (FFSJ) was proposed to join 6082-T6 aluminum alloy and poly propylene (PP) polymer sheets. The FFSJ was realized with the filling of a pre-fabricated hole using an additional filling stud. The excellent FFSJ joint was achieved under the synthesis effects of frictional heat and thermo-mechanical behavior at the interface between the filling stud and polymer sheet. The intimate joining formed at the interface, while the pre-fabricated hole was completely filled with the stud. A macro mechanical interlocking formed between the metal and filling stud, attributing to the main joining mechanism. And the partial adhesive layer appeared between the re-solidified polymer and metal. The maximum tensile shear strength was comparable to that of state-of-the-art welding. The FFSJ combines the benefits of the improvement of assembly precision, simple process, short welding cycle and high strength compared with the state-of-the-art welding, indicating that the FFSJ technique has potential to join metal with polymer or polymer matrix composites.Graphical abstractImage 1
  • Prediction of strength and constitutive response of SiC/SiC composites
           considering fiber failure
    • Abstract: Publication date: Available online 9 November 2018Source: Composites Part B: EngineeringAuthor(s): Sheng Zhang, Xiguang Gao, Xiao Han, Hao Duan, Yingdong Song A constitutive model of SiC/SiC composites is developed which considers fiber failure and broken fibers’ load carrying capability. To obtain the in situ properties of SiC fibers, tensile tests are performed on the heat-treated fibers. A more universal fiber strength model is developed to describe the strength distribution of SiC fibers. In the constitutive model of SiC/SiC composites, the stress distribution of broken fibers is analyzed. To validate the in situ fiber strength distribution and the constitutive model, a tensile test is performed on SiC/SiC minicomposites. The predicted strength and stress-strain response of SiC/SiC minicomposites are in good agreement with the experimental results. The numerical calculations show that fiber failure nearly has no effect on the nonlinearity of SiC/SiC composites although the strength of composites will increase to infinity without fiber failure, and that the strength of the composites will decrease greatly if broken fibers do not carry the load.
  • Calibration of hyperelastic and hyperfoam constitutive models for an
           indentation event of rigid polyurethane foam
    • Abstract: Publication date: Available online 9 November 2018Source: Composites Part B: EngineeringAuthor(s): Sanghoon Kim, Hyunho Shin, Sungsoo Rhim, Kyong Yop Rhee Hyperelastic and hyperfoam constitutive models are calibrated for rigid polyurethane (PU) foam exhibiting the characteristics of both soft foam and rubber. Test data from uniaxial and volumetric compression are used for calibration of the models with the goal of simulating a compressive-loading event (a hemi-spherical indentation). When the indentation event is simulated using the calibrated models via finite element analysis, both models moderately predict the experimentally determined load–displacement curve: the fitting errors of the two models were 13.6% and 11.5%, respectively. The applicability and limitations of the models for describing the compressive behavior of the rigid PU foam are discussed.
  • Improvement in adhesion of cellulose fibers to the thermoplastic starch
           matrix by plasma treatment modification
    • Abstract: Publication date: Available online 9 November 2018Source: Composites Part B: EngineeringAuthor(s): Mahyar Fazeli, Jennifer Paola Florez, Renata Antoun Simão This work deals with provision and characterization of the biopolymer-based composites achieved by incorporation of cellulose fibers as the reinforcement within the glycerol plasticized matrix formed by thermoplastic cornstarch biopolymer. The function of starch-based polymers is limited due to poor mechanical properties. However, it is improved with forming a biocomposite of thermoplastic starch (TPS) as matrix and the cellulose fibers (CF) as reinforcement. The surface of cellulose fibers is successfully modified using the air plasma treatment with the aim of improving the matrix/fiber adhesion. The modified fibers are studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The TPS/CF composites are prepared using high friction and hot compression procedure. Tensile test results and SEM images of the fracture surfaces show significant improvement of adhesion between treated cellulose fibers and TPS matrix. Thermogravimetric analysis shows a considerable decomposition at approximately 250–350 °C. XRD proved the significant increase in crystallinity percentage of composites compared to TPS.
  • Interface model of the influence of particle size on the plastic
           deformation resistance of particle-reinforced metal-matrix composites
    • Abstract: Publication date: Available online 9 November 2018Source: Composites Part B: EngineeringAuthor(s): A. Fedotov An interface model is proposed for the analysis of the influence of particle size on the plastic properties of metal matrix composites (MMCs). Dimensional effects are considered through surface strains and shear stresses at the interphase boundary. In comparison with the theories of the gradient of plastic strain, the proposed model greatly simplifies the analysis of dimensional effects. To calculate the plastic deformation diagram of an MMCs with an arbitrary particle size, it is sufficient to know the experimental diagram with one basic particle size and a theoretical diagram of deformation. The theoretical diagram is calculated using one of the classical models of homogenization. The results of calculating the deformation diagrams are in good agreement with the experimental data for aluminum MMCs reinforced with silicon carbide particles of various sizes.
  • Mechanism of surface preparation on FRP-Concrete bond performance: A
           quantitative study
    • Abstract: Publication date: Available online 9 November 2018Source: Composites Part B: EngineeringAuthor(s): Cheng Chen, Xue Li, Debo Zhao, Zhenyu Huang, Lili Sui, Feng Xing, Yingwu Zhou This paper quantitatively investigates the mechanism of surface preparation on the bond behavior of FRP-concrete interface. Two factors –aggregate's area ratio and roughening depth-are selected to quantify the level of surface preparation. To experimentally evaluate the effect of these two factors on bond behavior, thirty-six concrete block specimens were loaded by direct pullout force until failure. For the normal-strength concrete specimens, the increase to roughening depth increased the bond strength of concrete (C) interface and switched the fracture surface from FRP-concrete (FC) interface to concrete interface. Meanwhile, the effective bond length was decreased. However, the opposite trend was found in high-strength concrete specimens. The effect of aggregate's area ratio was negligible as compared to that of the roughening depth. The quantitative image analysis (QIA) shows that the surface preparation drastically changes the local fracture interface and the pullout force increases with the percentage of C interfacial failure. A design equation is proposed to predict the pullout force of FRP-concrete interface with surface preparation, considering contributions from different failure interfaces. Finally, the bond strength of C interface is calibrated as function of concrete strength and roughening depth, showing satisfactory agreement with the experimental results.
  • Interlaminar fracture toughness of GLARE laminates based on asymmetric
           double cantilever beam (ADCB)
    • Abstract: Publication date: Available online 8 November 2018Source: Composites Part B: EngineeringAuthor(s): Xiaoge Hua, Huaguan Li, Yi Lu, Yujie Chen, Liangsheng Qiu, Jie Tao Interlaminar fracture toughness of GLARE laminates (Glass reinforced aluminum laminates) with different fiber orientation, such as cross-plies/0ºand unidirectional-plies/0°, were investigated by the combination of experiments and finite element analyses. The Beam Theory and Fracture mechanics theory were used to calculate the proportion of Mode I and Mode II and further to predict the interlaminar fracture toughness of GLARE laminates. Also, the effect of loading rates (1 mm/min, 5 mm/min and 10 mm/min) on the interlaminar fracture properties was studied. Finite element analyses were carried out based on cohesive zone model (CZM) to numerically simulate delamination propagation by using the above experimental GIC. The results showed that the interlaminar fracture toughness in cross-plies/0° laminates(0.248 kJ/m2) was higher than that in unidirectional-plies/0° laminates(0.093 kJ/m2), and the interlaminar fracture toughness was increased with the growth of the loading rates. The numerical results agreed well with the experiments at crack initiation and furthermore supported the absence of mode mixity. The deviation between theoretical calculations and experimental results gradually increased with the crack propagation. Meanwhile, they were conformed to the linear function for unidirectional-plies/0° and cross-plies/0° laminates, respectively. Besides, the experimental data are highly consistent with both theoretical calculation and numerical simulation results.
  • Thermomechanical and dynamic mechanical properties of bamboo/woven kenaf
           mat reinforecd epoxy hybrid composites
    • Abstract: Publication date: Available online 7 November 2018Source: Composites Part B: EngineeringAuthor(s): Siew Sand Chee, Mohammad Jawaid, M.T.H. Sultan, Othman Y. Alothman, Luqman Chuah Abdullah The dimensional stability and dynamic mechanical properties on bamboo (non woven mat)/kenaf (woven mat) hybrid composites was carried out in this study. The hybridization effect of bamboo (B) and kenaf (K) fibers at different weight ratio were studied at B:K:70:30, and B:K:30:70 while maintaning total fiber loading of 40% by weight. The coeffiecient of thermal expansion (CTE) and dynamic mechanical properies of composites were analyzed by thermomechanical anlayzer (TMA), and dynamic mechanical analyzer (DMA), respectively. Positive hybridization effects were observed on B:K:50:50 hybrid composite with lowest CTE and higest dynamic mechanical properties among all composites. The dimensional stability were strongly influence by the fiber orientation where all composites shows prominent expansion in the transverse fibers direction but relatively low expansion in longitudinal fibers direction. Dynamic mechanical properties in term of complex modulus (E*), storage modulus (E′), loss modulus (E″), Tan delta and Cole-Cole plot were studied. DMA results reveal that B:K50:50 hybrid composite possess the highest complex modulus due to the strong fiber/matrix interfacial bonding which supported by the coefficient of effectiveness and Cole-Cole plot. Hence, it is concluded that 50:50 weight ratio of bamboo and kenaf fibers is the optimum mixing ratio to enhance both dimensional and dynamic mechanical properties of hybrid composites, and it can be utilized for automotive or building materials applications which demand high dimensional stability and dymanic mechanical properties.Graphical abstractImage 1
  • Magnesium-iron micro-composite for enhanced shielding of electromagnetic
    • Abstract: Publication date: Available online 7 November 2018Source: Composites Part B: EngineeringAuthor(s): Rachit Pandey, Sravya Tekumalla, Manoj Gupta All types of electronic equipment, especially microwave frequency ranged gears, experience the ill effects of electric and electromagnetic impedance. To electronic frameworks, such signals constitute a serious form of pollution. The impacts may go from simply irritating to catastrophic. To prevent such problem, this article aims at developing magnesium iron micro-composites; Mg/xFe (where x = 0, 5 and 15; denoting percentage of iron by weight) using disintegrated melt deposition (DMD) technique. This work studies the electrical conductivity, magnetic features, mechanical suitability, and electromagnetic interference shielding (EMI) capabilities of the composite. Observations were also made in reference to the impact of porosity on the shielding capability of the composite. The samples were tested in the X-band (8.2–12.4 GHz) to evaluate the properties. The results displayed an increased shielding capability with an increment in the amount of Fe microparticles. The study strives to accomplish that, with the addition of iron particulates of micron size, the electrical conductivity of the composites decreases and its magnetic strength increases. The ferromagnetic nature of the iron inclusions contributes critically towards the shielding mechanism of the composite.
  • Effects of Fe doping on the photoelectrochemical properties of CuO
    • Abstract: Publication date: Available online 7 November 2018Source: Composites Part B: EngineeringAuthor(s): Jaejin Oh, Hyukhyun Ryu, Won-Jae Lee In this study, CuO photoelectrodes doped with various iron concentrations were grown by using a modified chemical bath deposition method. We investigated the effects of the iron doping concentration on the morphological, structural, optical, electrical and photoelectrochemical properties of the CuO photoelectrode by using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectrophotometry (UV-Vis), electrochemical impedance spectroscopy (EIS) and potentiostatic/galvanostatic analysis, respectively. In this study, the smallest dislocation density, highest charge carrier density and lowest charge transfer resistance values were obtained from the sample with an Fe doping concentration of 2 at%. As a result, the maximum photocurrent density value of −1.44 mA/cm2 was obtained at −0.55 V (vs. SCE) from the photoelectrode with an Fe doping concentration of 2 at%, which was 53% higher than that of the undoped CuO photoelectrode.
  • Thermal conductivity enhancement of CNT/MoS2/graphene−epoxy
           nanocomposites based on structural synergistic effects and
           interpenetrating network
    • Abstract: Publication date: Available online 7 November 2018Source: Composites Part B: EngineeringAuthor(s): Chao Ji, Changzeng Yan, Ying Wang, Shuxian Xiong, Fengrui Zhou, Yayun Li, Rong Sun, Ching-Ping Wonga Efficient thermal management is becoming a global challenge with the rapid development of modern electronics. Therefore, conventional thermally conductive nanocomposites exhibit severe interfacial thermal resistance (ITR) generated at the interfaces of loaded thermally conductive components. Here, we design and synthesize a low-ITR carbon nanotube (CNT)/MoS2/graphene heterostructure in which the novel properties of highly thermally conductive CNTs, MoS2, and graphene are synergistically integrated into the final nanocomposite. During the hydrothermal reaction process, MoS2 and graphene are grown and wrapped on CNTs which ensure better interfacial contact. The CNTs act as a structural skeleton and heat transfer channel for effective heat collection from the large-surface-area MoS2 and graphene nanosheets. MoS2 which has good wetting properties further reduces the ITR between the heterostructure filler and polymer matrix; thus, a high−efficiency heat transfer channel of epoxy−graphene−MoS2−CNT is prepared. The synthesized CNT/MoS2/graphene−epoxy nanocomposite shows a much lower ITR of 8.3 × 106 K W−1 than a CNT-epoxy nanocomposite (3.98 × 107 K W−1) and a CNT/MoS2−epoxy nanocomposite (1.9 × 107 K W−1). Consequently, the thermal conductivity is improved from 2.0 W m−1 k−1 to 4.6 W m−1 k−1, which is 2300% of that of the pure epoxy resin. The factors affecting ITR and thermal conductive properties are analyzed. Our findings may contribute to the development of new types of high−performance thermal management materials.Graphical abstractImage 1
  • Hybrid effect of macro and micro steel fibers on the pullout and tensile
           behaviors of ultra-high-performance concrete
    • Abstract: Publication date: Available online 5 November 2018Source: Composites Part B: EngineeringAuthor(s): Booki Chun, Doo-Yeol Yoo This study aims to investigate the effect of hybrid use of macro and micro steel fibers on the pullout and tensile behaviors of ultra-high-performance concrete (UHPC). To this end, three different macro steel fibers (i.e., straight, hooked, and twisted fibers) and a single micro straight steel fiber were used, whereby a portion of the macro fibers was replaced with the micro fibers at the constant total volume fraction of 2%. In order to fabricate ultra-high-performance hybrid fiber-reinforced concrete (UHP–HFRC), five different replacement ratios of the macro fibers with the micro fiber were employed, including 0, 0.5, 1.0, 1.5, and 2.0%. The pullout behaviors of multiple aligned fibers embedded in UHPC were also compared with the tensile behaviors of UHP–HFRC to analyze their correlations. The test results indicated that the average bond strength and normalized pullout energy of the macro straight fibers in UHPC were improved after their replacement with micro fibers, whereas those of the hooked and twisted macro fibers were reduced according to the replacement ratio. Lower fiber efficiency ratios were obtained after the replacement of the macro fibers with the micro fibers in the hooked and twisted fiber cases, while similar ratios of approximately 0.3–0.4 were obtained in the cases of the macro straight fibers. In comparison, the post cracking tensile strength and energy absorption capacity of UHPC reinforced with macro straight fibers decreased, whereas those of UHPCs with hooked and twisted fibers increased when they were replaced by the micro fibers. The negative correlation between fiber pullout and tensile behaviors of all UHP–HFRCs occurred because the actual fiber orientation and bonding area in the composites could not be considered in the fiber pullout tests. Thus, it is concluded that the effects of the use of hybrid steel fibers on the tensile performance of the UHPC composites could not be predicted based on the pullout test results of the aligned fibers.
  • Geometrically nonlinear dynamic analysis of nanocomposite organic solar
           cell resting on Winkler-Pasternak elastic foundation under thermal
    • Abstract: Publication date: Available online 5 November 2018Source: Composites Part B: EngineeringAuthor(s): Qingya Li, Qihan Wang, Di Wu, Xiaojun Chen, Yuguo Yu, Wei Gao The nonlinear dynamic responses of a nanocomposite organic solar cell (NCOSC) are developed through the classical plate theory. The investigated NCOSC consists of five layers which are including Al, P3HT: PCBM, PEDOT: PSS, IOT and glass. A uniformly distributed external excitation is exerted on the simply supported NCOSC. The impacts of the Winkler-Pasternak elastic foundation, thermal environment and damping on the nonlinear dynamic responses of the NCOSC are investigated. The equations of motion and geometric compatibility of the NCOSC with the consideration of the von Kármán nonlinearity are derived. The governing equation of the dynamic system is formulated by employed the Galerkin and the fourth-order Runge-Kutta methods. Several numerical experiments are thoroughly presented to report the effects of damping ratio, temperature variations, and elastic foundation parameters on the frequency–amplitude curves and nonlinear dynamic response of the NCOSC. The numerical studies indicate that the existence of the Winkler-Pasternak elastic foundation effectively reduces the dynamic response of the NCOSC. In addition, the damping and thermal variation depress the vibration of the NCOSC but with relatively less efficiency compared with the Winkler- Pasternak elastic foundation.
  • Novel non-destructive evaluation technique for the detection of poor
           dispersion of carbon nanotubes in nanocomposites
    • Abstract: Publication date: Available online 5 November 2018Source: Composites Part B: EngineeringAuthor(s): Antonio Pantano, Nicola Montinaro, Donatella Cerniglia, Federico Micciulla, Silvia Bistarelli, Antonino Cataldo, Stefano Bellucci A wide use of advanced carbon nanotube polymer composites can be boosted by new non-destructive evaluation (NDE) techniques that can test the quality of the products to ensure that their specifications are met. It is well known in literature that the parameter that far more than others can affect the enhancing capabilities of the carbon nanotubes is their dispersion. Here we have presented a novel NDE technique based on infrared thermography able to evaluate the dispersion of the added nanoparticles in polymer nanocomposites. The NDE technique was used to compare pairs of samples whose difference is represented only by the level of dispersion. It was found a significant difference in the thermal response to heat transfer transients. Thus, the thermal response of a nanocomposite allows one to identify consistently good levels of dispersion with respect to lower levels of dispersion. A reference product, which has the expected dispersion level and achieves the desired design performance, can be used to test the thermal behaviour of other products coming out of the production process and those with poor dispersion can be identified. The physical phenomena that can explain the effects of multi-walled carbon nanotubes (MWCNTs) dispersion on the thermal response of the nanocomposites to the heat transfer transients were also identified.
  • Prismatic RC columns externally confined with FRP sheets and pre-tensioned
           basalt fiber ropes under cyclic axial load
    • Abstract: Publication date: Available online 5 November 2018Source: Composites Part B: EngineeringAuthor(s): Theodoros C. Rousakis, Georgios D. Panagiotakis, Emmanouela E. Archontaki, Alexandros K. Kostopoulos This experimental investigation addresses the use of transversely placed composite ropes made of basalt as external standalone confining reinforcement in cases of reinforced concrete columns with square section or combined with already applied FRP sheets. Non bonded, non impregnated basalt fiber rope is wrapped around the columns by hand in 1 or 2 layers or is pre-tensioned with special mechanical devices. The efficiency of wrapped columns is compared with identical columns confined with polypropylene fiber ropes. Further, the columns are wrapped with externally bonded GFRP sheets and then with non bonded basalt fiber ropes in a hybrid scheme. The columns are subjected to multiple cycles of increasing compressive deformation to simulate seismic actions. The columns wrapped with two layers of basalt composite ropes (pre-tensioned or not) present an ever increasing stress-strain response for concrete axial strains higher than 5.6%, even for very high rope pretension level, without rope fracture. Both the polypropylene and basalt ropes reveal a high potential for strain redistribution around the variably damaged concrete core. In the cases of hybrid FRP – basalt rope confinement the strain redistribution potential of the rope is similarly remarkable, controlling the dilation of the column even after the multiple fracture of the GFRP sheet. The rope could increase the axial strain sustained by the concrete from 2.21% to beyond 5.1%, without rope fracture.
  • Comparison to mechanical properties of epoxy nanocomposites reinforced by
           functionalized carbon nanotubes and graphene nanoplatelets
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Jaemin Cha, Joonhui Kim, Seongwoo Ryu, Soon H. Hong Low-dimension carbon nanomaterials, such as carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), are effective mechanical reinforcements in polymer composites. Epoxy matrix composites were fabricated by functionalizing CNT and GNP nanofillers using melamine and nondestructive ball milling. This noncovalent functionalization prevents agglomeration of nanofiller and produces direct C-N bonds with the epoxy matrix. Compared to pristine CNTs and GNPs/epoxy nanocomposites, melamine-functionalized CNT (M-CNT)/epoxy and melamine-functionalized GNP (M-GNP)/epoxy nanocomposites exhibited considerably higher tensile strengths and fracture toughness (single edge notch bending, SENB). At 2 wt%, both M-CNT/epoxy and M-GNP/epoxy nanocomposites exhibited enhanced Young's modulus values (M-CNT: 64% and M-GNP: 71%) and ultimate tensile strengths (M- CNT: 22% and M-GNP: 23%). Fracture toughness increased by 95% with the 2 wt% M-CNT/epoxy and by 124% with the 2 wt% M-GNP/epoxy nanocomposite. The reinforcing effects of the two-dimensional M-GNPs were greater than those of the one-dimensional M-CNTs due to differences in pull-out mechanisms and bridging effects. Crack propagation in the nanocomposites, as it relates to fracture toughness, was also investigated.
  • Failure mechanism of bonded joints with similar and dissimilar material
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Seyyed Mohammad Hasheminia, Beom Chul Park, Heoung-Jae Chun, Jong-Chan Park, Hong Suk Chang Adhesive joints with dissimilar materials have gained substantial attention recently due to their lighter specific weight compared to the joints with similar metallic components. In particular, dissimilar material joints with a structure such as composite materials combined with light-weight metals have been widely used in the automobile industries to overcome the issue of fuel efficiency and weight reduction. Therefore, accurate analysis and study about the mechanical behavior of dissimilar materials joints are fundamentally required. In this study, the experiments and finite elements analysis were performed on single lap-shear bonded joints with metal-composite, similar composites and dissimilar composites components to investigate the factors that affect the joint failure load.
  • Effect of early age curing carbonation on the mechanical properties and
           durability of high initial strength Portland cement and lime-pozolan
           composites reinforced with long sisal fibres
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Alex Neves Junior, Saulo Rocha Ferreira, Romildo Dias Toledo Filho, Eduardo de Moraes Rego Fairbairn, Jo Dweck This paper presents the results of a study about the mechanical behaviour, before and after aging, of two cement-based composites reinforced with long sisal fibres cured at early age in a CO2 environment. After curing, samples of both composite systems were submitted to wetting and drying cycles to accelerate the aging of the materials allowing the evaluating of the efficiency of the CO2 treatment. Besides promoting CO2 capture, the used cure also allowed the increase in the durability of the sisal fibre-cement based composites by the Calcium Hydroxide (CH) consumption and pH decrease promoted by the carbonation reactions. The lime-pozzolanic material composite was also treated with CO2 at early stages of formation, with the carbonation and pozzolanic reactions acting simultaneously to deplete the Ca(OH)2 thus improving its durability. Four-point bending test, thermogravimetry analysis of the matrix and SEM analysis of the fibres were done before and after aging to study the durability mechanisms of the composites. The obtained results showed that the CH free cement-based composite containing metakaolin and fly ash presented the best mechanical behaviour before and after accelerated aging. The early age carbonation of the lime-pozolan composites improved its mechanical response, before and after accelerated aging, when compared with the non-carbonated samples. The thermogravimetry test showed that the increase of the carbonation time of the reference Portland cement-based composite consumed the CSH, compromising the ductility and strain capacity of this composite family after aging. The SEM pictures showed petrified fibre effect by the migration of hydrated products after 10 and 20 cycles of ageing for this composite system.
  • Shear strength components of adjustable hybrid bonded CFRP
           shear-strengthened RC beams
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Yingwu Zhou, Menghuan Guo, Lili Sui, Feng Xing, Biao Hu, Zhenyu Huang, Yanchun Yun This paper presents an experimental study on shear behavior of full-scale rectangular reinforced concrete (RC) beams under shear-strengthening of carbon fiber-reinforced polymer (CFRP) U-strips. The test involved five RC beams with transverse reinforcement, including one control beam, one shear-strengthened by externally bonded (EB) CFRP U-strips only, and the remaining three strengthened in shear by a hybrid bonded (HB) CFRP system under different normal pressures applied on the CFRP U-strips. The transverse reinforcing steel bars and CFRP U-strips were extensively instrumented with strain gauges, which enabled the accurate quantitative assessment of shear strength contributions from CFRP (Vf), stirrups (Vs) and concrete (Vc) during the whole loading process of a shear test. Further, by comparing Vs and Vc for beams with and without CFRP strengthening, the interactions can be evaluated and clarified. In addition, key features of shear behaviors, e.g. failure mode, load-deflection curves, shear capacity and ductility, shear crack angle, and strain development and distribution of stirrups as well as CFRP strips, are presented, compared and analyzed.
  • Experimental investigation of nonlinear behavior of macroscopic materials
           and microscopic void volume fraction change for porous materials under
           uniaxial compression
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Eun Sun Lee, Tae Sik Goh, Jung Sub Lee, Jin-Young Heo, Gi-Baek Kim, Chi-Seung Lee The purpose of this study was to simultaneously analyze the nonlinear behavior and the void volume fraction change of polyurethane foam (PUF) under a uniaxial compressive load through micro-scale and macro-scale viewpoints. The influence of micro-scale factors on the macroscopic properties of PUF was analyzed, along with the interrelationships between micro-scale and macroscopic properties. The microstructure of PUF was observed by analyzing the density. Various micro-analyses were also conducted, including those for energy absorption, Young's modulus, and recovery behaviors. Internal structure changes such as those in density and degree of compressive strain were analyzed by measuring the void volume fraction of each region in the specimen under a uniaxial compressive load. The elastic, plateau, densification, and fracture regions of the compressive test stress-strain curve were divided, analyzed, and compared with microscopic analysis results. Based on the results of the macro-micro-scale experiment, we analyzed influence and change process of microstructures on the compressive behavior of the PUF specimen in detail. This study shows that internal and overall changes in the compression process of various porous materials can be predicted under a uniaxial compressive load.
  • Anomalous dichroism of cellulose nanowhisker embedded
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Composite Film, Hyun Kyung Lee, Young Seok Song While natural nanoparticles are currently being investigated in a wide range of applications due to their compelling strong potential, they have yet to be employed for practical engineering material systems. Here, we demonstrate a dichroic nanocomposite film that shows outstanding optical properties by introducing cellulose nanowhiskers (CNWs) into PVA iodine complex. CNWs were isolated via acid hydrolysis and the nanocomposite film was elongated and dyed with iodine. The significantly reduced extension and treatment time of iodine were applied for the alignment of iodine and PVA molecules in the film. The results revealed that the degree of polarization and transmittance were enhanced as the draw ratio and the content of the CNWs increased. We expect that this material system can offer a new pathway for designing and processing more advanced engineering materials with high performances by using various natural biomaterials.
  • Effect of styrene-butadiene rubber latex on the rheological behavior and
           pore structure of cement paste
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Keke Sun, Shuping Wang, Lu Zeng, Xiaoqin Peng Styrene-butadiene rubber (SBR) latex is beneficial to the workability of cement-based materials, but the mechanism remains unclear. This study aims to investigate the effect of SBR latex on the rheological property and pore structure of cement paste. The results showed that the fluidity of the modified cement-based material was improved, and a significant linear relation was obtained between the air content and the fluidity of the cement paste. The yield stress and viscosity of the paste decreased with increasing SBR latex content, and the modified cement paste exhibited shear-thinning behavior. In addition, the SBR latex can deteriorate the pore structure of the hardened cement paste at 3 days due to the hydrophobic groups easily trapping the air into the paste. Compared with that of the ordinary Portland cement paste, the number of pores (size range of 0.1 μm–1 μm and 10 μm-200 μm) in the SBR-modified cement paste was clearly increased. However, the lowest porosity was achieved at 28 days, when 2% SBR was used due to the filling effect of the hydration products and polymer particles. The throat/pore ratio and fractal dimension increased with the SBR latex content, illustrating the increasing of ink-bottle pores with a rough surface.
  • Facile preparation and high capacitance performance of copper sulfide
           microspheres as supercapacitor electrode material
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Tingkai Zhao, Xiarong Peng, Xin Zhao, Jingtian Hu, Wenbo Yang, Tiehu Li, Ishaq Ahmad Khan Copper sulfide (Cu2S) microspheres were easily prepared by reducing copper sulphate with ascorbic acid in sodium thiosulfate solution at room temperature and employed copper sulphate and sodium thiosulfate as Cu and S sources, respectively. The as-prepared Cu2S microspheres were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties including cyclic voltammetry, galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy were also investigated. The experimental results showed that the as-prepared Cu2S microspheres based on the three-electrode test system exhibited a maximum specific capacitance of 444.2 F g−1, and the energy density was up to 25.4 Wh·kg−1 with high power density of 4.1 kW kg−1 at the current density of 1 A g−1. Furthermore, Cu2S microspheres also showed outstanding long-term cycling stability with more than 87% capacitance retention over 6000 cycles due to their microspheres structure, which facilitate efficient charge transport and promote electrolyte diffusion. The Cu2S-1:1.5 was used as a positive electrode for the fabrication of asymmetric supercapacitor along with reduced GO as the negative electrode, which delivered the high energy density up to 18.6 Wh·kg−1 along with long cycling life and retains up to 89% specific capacitance after 6000 cycles. The excellent results suggest that the Cu2S microsphere is a promising candidate as electrode material for high performance supercapacitors.
  • Role of interface formation versus fibres properties in the mechanical
           behaviour of bio-based composites manufactured by Liquid Composite Molding
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Pierre-Jacques Liotier, Monica Francesca Pucci, Antoine Le Duigou, Antoine Kervoelen, Jacopo Tirilló, Fabrizio Sarasini, Sylvain Drapier The aim of this work was to study the effect of free surface energy modification of flax fibres by a thermal treatment on the mechanical behaviour of bio-based composites. It has been proved that this modification enhances the wettability of flax fibres by liquid epoxy resin and results in a lower porosity amount in composites. Tests to evaluate mechanical properties of elementary fibres, yarns and composites have been performed. The main outcome of this multiscale study, even if elementary fibres and yarns have been embrittled and interface properties have been lowered after thermal treatment, is that the mechanical behaviour of composites manufactured by Liquid Composite Molding (LCM) is better with treated fibres.
  • Stress-strain model for FRP-confined concrete subject to arbitrary load
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Pengda Li, Yu-Fei Wu, Yingwu Zhou, Feng Xing Most existing stress-strain models for fiber reinforced polymer (FRP) confined concrete are applicable to monotonic loading or complete cyclic loading where unloading/reloading is a continuous process between envelope curve and zero stress. However, load cycling is mostly incomplete or partial in practical problems where reverse of loading occurs before the previous load cycle is completed, and this unloading and reloading process is random. Cyclic model allowing for random partial load cycling is rare, if any, due to the lack of experimental data, and the insufficient understanding on the behavior of confined concrete under partial cyclic loading. In this study, FRP confined concrete cylinders were tested under six typical cyclic load patterns. The test results reveal that the partial cyclic stress-strain behavior is different from that under full cyclic loading. The key parameters determining unloading/reloading curves, such as reloading modulus, plastic strain, and tangent unloading modulus are related to loading history and axial stress level. It is found that the key parameters will change, or accumulative damage to concrete will occur, only under certain condition which is defined as effective partial cyclic loading in this work. A simple method is proposed to define the effective partial cyclic loading. Based on an existing complete cyclic model, a stress-strain model for FRP confined concrete under random partial cyclic loading is developed in this work. The proposed model performs well under different load patterns.
  • Thermal and mechanical properties of copper-graphite and copper-reduced
           graphene oxide composites
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Faisal Nazeer, Zhuang Ma, Lihong Gao, Fuchi Wang, Muhammad Abubaker Khan, Abdul Malik Graphene and its derivatives have a high value of thermal conductivity and good mechanical properties. Rare studies focused on the anisotropic thermal conductivity, while anisotropic thermal conductivity and hardness of reduced graphene oxide/metal are still far behind the expected values. In this work, different mesh sizes of graphite and graphene oxide were used for making copper-graphite and copper-reduced graphene oxide composites with the powder metallurgy technique. Raman, XRD, XPS and SEM were performed to evaluate the disorder, phase analysis, surface morphology and microstructure evolution of the composites as well as synthesized graphene oxide. Anisotropic thermal conductivity and Vickers hardness of the composites were characterized to check the effects of different mesh size on copper-graphite and copper-reduced graphene oxide composite. Results show that anisotropic thermal conductivity in-plane and through-plane ratio (1.68) and hardness (71.2 HV) which is 80% and 61% greater than pure copper were attained at only 1 wt% graphene oxide mesh size 3500 μm copper-reduced graphene oxide composite. Moreover, graphite and graphene oxide mesh size (3500 μm) gave good results compared with mesh sizes 500 μm and 1000 μm. The good anisotropic thermal conductivity and high hardness suggest that it may be ideal materials as heat sinks in thermal packaging.Graphical abstractImage 1
  • Chemically modified Sb2O3, a new member of high solar-reflective material
           family, incorporating with ASA (acrylonitrile-styrene-acrylate copolymer)
           for fabrication of cooling composite with lower wetting behavior
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Yanli Qi, Jun Zhang In this study, it is observed that antimony trioxide (Sb2O3) performs great potential as new solar-reflective additive to cool materials with higher security for its synergistic flame-retarding application. The optimal content of Sb2O3 into poly (acrylonitrile-styrene-butyl acrylate) (ASA) resin has been investigated, accompanied with the investigation of the effect of hydrophobic modification on Sb2O3 on the composite surface wettability. The cooling effect of the composite incorporated with the addition of 10 wt% modified Sb2O3, which has a solar reflectance of 68.4%, is estimated to be 13 °C higher than uncovered device on a summer sunny day. Simultaneously, the water contact angle of the abovementioned sample increases to 97°, which is 19° higher than that of the sample introduced with 10 wt% unmodified Sb2O3. It is envisioned that widely applicable composited cool materials can be achieved with the assistance of modified Sb2O3 particles.
  • Preparation and characterization of short kenaf fiber-based biocomposites
           reinforced with multi-walled carbon nanotubes
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Hessameddin Yaghoobi, Abdolhossein Fereidoon This paper presents the experimental study on the mechanical and thermal properties of nano-biocomposite made of polypropylene/kenaf fiber/polypropylene-grafted maleic anhydride (PP/kenaf/PP-g-MA) biocomposite and multiwall carbon nanotubes (MWCNTs). To meet this objective, the specimens were produced with different contents of MWCNTs (0, 0.5, 1, 1.5 and 2 wt%) by melt blending process in an internal mixer and in the following the standard form of specimens were made by compression molding. The amounts of chopped kenaf fiber loading and PP-g-MA compatibilizer were fixed at 30 wt% and 5 wt% for all formulations based on the preliminary studies. Tensile strength and modulus, flexural strength and modulus and notched Izod impact strength of the nano-biocomposites were evaluated, which obviously found that the mechanical properties of PP/kenaf/PP-g-MA biocomposites were enhanced by the addition of MWCNTs. The optimum in mechanical strengths was detected at 1 wt% MWCNTs. Thermogravimetric analysis (TGA) was carried out to investigate the thermal stability of nano-biocomposites. The results illustrated that the values of the different weight loss temperatures and second decomposition peak temperatures increased after incorporation of MWCNTs due to barrier effect of the MWCNTs. Morphological study which characterized using scanning electron microscopy (SEM) technique verified that a good and homogeneous distribution of MWCNTs through the biocomposites. However, some aggregates were revealed at higher MWCNT content. Fourier transform infrared (FTIR) spectroscopy analysis did not show any chemical interaction between MWCNTs and the PP/kenaf/PP-g-MA biocomposites.
  • Improvement of thermal behaviors of biodegradable poly(lactic acid)
           polymer: A review
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Fan-Long Jin, Rong-Rong Hu, Soo-Jin Park Owing to its excellent mechanical properties, processability, and biodegradability, poly(lactic acid) (PLA) has been widely investigated in the past few decades as a biomaterial. However, the poor heat resistance of PLA severely limits its applicability. In this review, several heat resistance modification methods, such as nucleating agent addition, fiber reinforcement, compounding, blending, stereoisomer complexation, and chemical modification, have been reviewed and their related mechanisms have been discussed in brief.
  • Improving the mechanical properties, UV and hydrothermal aging resistance
           of PIPD fiber using MXene (Ti3C2(OH)2) nanosheets
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Nadia Taloub, Abdelkhalek Henniche, Li Liu, Jun Li, Nahla Rahoui, Mohammad Hegazy, Yudong Huang The pursuit of improving the performance of rigid-rod polymeric fibers using a new inorganic nano-materials and efficient methods is very attractive topic. The combination of the unusual properties of both materials could definitely produce an outstanding final product. Herein, we proposed a simple grafting method of a graphene-like titanium carbides Ti3C2 (OH) 2 nanosheets (MXene) onto PIPD surface via covalent bond by using (3-Aminopropyl) triethoxysilane (APTES) as a bridging agent. The surface morphology and element compositions of PIPD fiber before and after grafting were characterized, and the effect of such treatment on the mechanical properties was also evaluated. The IFSS of the PIPD-Ti3C2(OH)2 was highly increased by 61.54% because of the significant improvement the fiber/epoxy interaction and surface wettability. Though the tensile strength (TS) was slightly decreased by only 5%. Furthermore, the experiment results showed a great enhancement of UV and hydrothermal aging resistance of the grafted fibers comparing with untreated ones by 33% and 25% respectively.
  • Thermal conductivity of shape memory polymer nanocomposites containing
           carbon nanotubes: A micromechanical approach
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): M.K. Hassanzadeh-Aghdam, R. Ansari A new micromechanical formulation based on a unit cell model is developed to predict the effective thermal conductivities of carbon nanotube (CNT)-shape memory polymer (SMP) nanocomposites. Model predictions considering interfacial thermal resistance between the CNT and SMP, agglomerated state of CNTs into the SMP matrix and CNT non-straight shape are in reasonable agreement with the experiment reported in the literature. It is found that the CNT agglomeration must be removed to obtain a maximum level of thermal conductivities of SMP nanocomposites. The effects of volume fraction, diameter, cross-section shape, arrangement type and waviness factors of CNTs as well as interfacial thermal resistance on the axial and transverse thermal conductivities of aligned CNT-reinforced SMP nanocomposites are extensively investigated. The results show that the alignment of CNTs into the SMP nanocomposites along the thermal loading can be an efficient way to dissipate the heat. When the CNT waviness increases, a nonlinear decrease in the axial thermal conductivity is occurred, however, the nanocomposite thermal conductivity along the transverse direction quickly rises. It is observed that the interfacial thermal resistance, cross-section shape and arrangement type of CNTs do not affect the axial thermal conductivity of CNT-SMP nanocomposites. But, the interfacial thermal resistance can play a key role in the transverse nanocomposite thermal conductivity. The present fundamental study is very important for understanding the thermal conducting behavior of CNT-SMP nanocomposites which may have a wide range of applications in temperature sensing elements and biological micro-electro-mechanical systems.
  • Pultruded GFRP square hollow columns with bolted sleeve joints under
           eccentric compression
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Lei Xie, Yu Bai, Yujun Qi, Hao Wang This paper presents an investigation into the performance of pultruded glass fibre reinforced polymer (GFRP) square hollow columns subjected to both compression and bending. Eccentric compression experiments were performed on slender GFRP column specimens at different eccentricities. Bolted sleeve joint was employed to connect the GFRP column specimens and loading end plates. The relationship between the load-bearing capacities of GFRP columns and the eccentricities was received and discussed. The interaction curve between compression load and bending moment due to eccentricity (P-M curve) was obtained from experiments and compared with finite element (FE) and design approaches. Results revealed that the compression performance of GFRP columns was significantly affected by the eccentricity and the moment capacity of bolted sleeve joint. Splitting failure developed from the initiative longitudinal cracks in the bolted sleeve joint region at the end of the columns was found as the ultimate failure, after the large lateral deformation. FE analysis presented satisfactory agreements with experimental results; furthermore, the stress analysis in the critical bolted sleeve joint region indicated that the in-plane shear stress was the dominant component leading to the splitting failure.
  • Strain transfer analysis of fiber Bragg grating sensor assembled composite
           structures subjected to thermal loading
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Huaping Wang, Jian-Guo Dai Optical fiber sensing technology has been widely used for thermal strain detection of civil structures subjected to the environmental temperature variations. Due to the fragile material nature, bare optical fibers are seldom used in practice, as they cannot resist the harsh service environment. A packaging measure is usually required to enhance the durability of optical fiber-based sensors for reliable long-term detection. However, the existence of packaging and bonding materials brings about strain transfer loss, which makes the optical fiber readings not accurately represent the actual strains of the host material. This paper presents a combined experimental and theoretical study on a four-layer optical fiber sensing composites (i.e., the host material, an adhesive bonding layer, the sensing fiber, and its protection layer) subjected to thermal loading to correct the above-mentioned strain transfer error. Aluminum and polypropylene (PP) plates with different thermal expansion coefficients were surface-bonded with fiber Bragg grating (FBG) sensors and then exposed to various temperatures (30–70 °C). Theoretical study was developed to investigate how the strain measurement error was influenced by the thermal deformation incompatibility of multiple contacted layers (i.e., the optical fiber, the protective layer, the adhesive layer and the hosting material) with different thermal expansion coefficients. The accuracy and effectiveness of the proposed strain transfer function was then validated through comparisons with the test results. Based on the theoretical analysis, the sensitivity of the relevant material and geometrical parameters on the strain transfer efficiency was discussed to instruct the design of FBG based sensors. The proposed error-modification formula can be used to effectively improve the strain measurement accuracy and instruct the optimum design of FBG based sensors applied to civil structures under thermal loading.
  • Mechanical property of re-entrant anti-trichiral honeycombs under large
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): L.L. Hu, Z.R. Luo, Z.Y. Zhang, M.K. Lian, L.S. Huang The quasi-static mechanical properties of re-entrant anti-trichiral honeycombs made from ABS polymer are studied by both experiments and theoretical analysis. The experimental results show that the deformation of honeycomb is dominated by the bending of ligaments, the rotation of ligaments around the plastic hinges and the rigid rotation of cylinders. Based on the deformation mechanism of the cell structures exhibiting in experiments, the collapse process of the honeycomb is divided into several stages. Theoretical formulas are deduced to predict the crushing stress of the re-entrant anti-trichiral honeycombs in each stage, which are functions of the honeycomb's global strain, the cells' geometry parameters and the properties of the base material. The analytical predictions are in good agreement with the experimental results. It is revealed that the crushing stress of the honeycomb increases with the global strain and the cell-wall thickness while decreases with the ligament-length ratio. An optimal value of the cylinders' radius is found which will result in the maximum load-carrying capacity of the honeycomb. The present work is supposed to shed light on the design and fabrication of re-entrant anti-trichiral honeycombs.Graphical abstractImage 1
  • Metal organic framework (ZIF-67)-derived hollow CoS2/N-doped carbon
           nanotube composites for extraordinary electromagnetic wave absorption
    • Abstract: Publication date: Available online 2 November 2018Source: Composites Part B: EngineeringAuthor(s): Jing Yan, Ying Huang, Xiaopeng Han, Xiaogang Gao, Panbo Liu The hierarchical hollow framework involving interconnected highly conductive N-doped carbon nanotube networks and CoS2 particles were successfully prepared by metal-organic framework (MOF) derived method. After the two pyrolysis process in the atmosphere of reducing gas and inert gases, numerous carbon nanotubes interlaced on the surface of framework and CoS2 nanoparticles also attached on the surface. The electromagnetic parameters of CoS2/NCNTs composites can be well controlled by regulating the loadings of sample in sample-paraffin mixture. The results demonstrate that CoS2/NCNTs with 50% loadings show superior electromagnetic wave absorption properties in the wide frequency range, almost covering the whole X bands (8–12 GHz) only with a relative thin thickness of 1.6 mm. Hierarchical hollow structure and better impedance matching performance between N-doped carbon nanocube and CoS2 nanoparticles contribute to the enhancement of microwave absorption ability. Our work confirms that hollow framework CoS2/NCNTs composites can provide a novel idea for designing high-absorbability microwave absorbers.
  • Effects of several bolt parameters on the bearing capacity of a composite
           multi-drum stone column under an earthquake
    • Abstract: Publication date: Available online 2 November 2018Source: Composites Part B: EngineeringAuthor(s): A. Buzov, J. Radnić, N. Grgić The paper presents some results of a shake-table study on the effects of several bolt parameters on the bearing capacity of a composite free-standing multi-drum stone column under an earthquake. In each test, a small-scale column with six blocks per height was exposed to different horizontal base accelerations until the column collapsed. Firstly, the effect of five different materials for the bolts were investigated on the column bearing capacity. Then, the effects of bolt length, bolt diameter and the ratio of the hole diameter to the bolt diameter on the column bearing capacity were investigated. Based on the test results, the main conclusions of the study are presented.
  • A hysteresis energy dissipation based model for multiple loading damage in
           continuous fiber-reinforced ceramic-matrix composites
    • Abstract: Publication date: Available online 2 November 2018Source: Composites Part B: EngineeringAuthor(s): Li Longbiao In this paper, a hysteresis energy dissipation based damage model for fiber-reinforced ceramic-matrix composites (CMCs) subjected to multiple loading stress levels is developed. Considering the combination effects of multiple loading sequences and multiple fatigue damage mechanisms, i.e., matrix cracking, fiber/matrix interface debonding and interface wear, the evolution of the fiber/matrix interface debonding and sliding, fatigue hysteresis loops, fatigue hysteresis dissipated energy and fatigue hysteresis modulus changing with increasing applied cycles are analyzed. The effects of fiber volume fraction, matrix crack spacing, fatigue peak stress and fatigue stress range on the damage development inside of CMCs are discussed. The difference of the fiber/matrix interface shear stress existed between the interface wear region and new interface debonded region affects the fiber/matrix interface debonded length and loading carrying ability of intact and broken fibers. The damage evolution for C/SiC and SiC/SiC composites subjected to multiple fatigue loading sequences are predicted using the hysteresis energy dissipation damage model. Under multiple loading stress, the fatigue hysteresis dissipated energy increases when high peak stress and stress range increases due to the increase of fiber/matrix interface sliding range. However, when the low peak stress increases, the evolution of fatigue hysteresis dissipated energy depends on the interface debonding and sliding state.Graphical abstractImage 1
  • Mechanical comparison of new composite materials for aerospace
    • Abstract: Publication date: Available online 1 November 2018Source: Composites Part B: EngineeringAuthor(s): C. Barile, C. Casavola, F. De Cillis Composite materials are becoming the most useful material for aircraft structures. Their main advantage is connected to the possibility of deeply reducing weight and costs by maintaining high performances in terms of strength and security. The second major advantage in using this them depends on the possibility they could be proper designed to guarantee services they are made to. Many ways to combine them lead to the necessity of planning experimental tests in order to evaluate the real both elastic and plastic mechanical properties and to compare their variability as function of the fiber type, matrix type and manufacturing technology involved for realizing them. In this paper, a comparison between two innovative Carbon Fiber Reinforced Plastic materials was done. They differ, one from each other, for the matrix type (PEEK and BENZOXAZINE) and for the manufacturing process used to assemble the matrix with the reinforcement (Compression Molding and Resin Transfer Molding). On the other hand, the resin percentage weight content of both materials is maintained constant for all the tests: it is 42% for PEEK matrix and 64% for BENZOXAZINE matrix. The aim of the work is to critically analyze the results in order to get useful information for choosing the best one intended for designing and making the back section of fuselage of a regional aircraft. The component will consist of a front portion with structural aims (zoom phase) and a back part able to withstand to elevated temperatures.
  • Models of flow behaviour and fibre distribution of injected moulded
           polypropylene reinforced with natural fibre composites
    • Abstract: Publication date: Available online 1 November 2018Source: Composites Part B: EngineeringAuthor(s): Ahmed Elsabbagh, Amna Ramzy, Leif Steuernagel, Gerhard Ziegmann Flowability of thermoplastics reinforced with natural fibres represents a major problem for the injection moulding of these composites. Flowability of natural fibre polypropylene composites is evaluated using the injection moulding in an Archimedean spiral mould. The influence of the following process parameters is studied in terms of flowability: injection temperature of 180–220 °C, injection pressure of 500–1000 bar and mould temperature of 25 and 80 °C. Additionally, different fibre shapes are investigated namely; non-branched straight cellulose fibres and branched hemp fibres with low flexural stiffness. Chopped cellulose fibres length of 0.5 and 1.5 mm are tried. Fibre contents of 10 and 30 wt% are also studied. The results showed that the effect of the investigated parameters namely; Pressure, temperature and mould temperature is significant on the flowability in a descending order.The homogeneity of fibre weight content along the injection moulded spirals represents an important quality feature. Therefore, samples are drawn at even distances from the spiral length. The cut samples are dissolved to extract fibres and calculate the fibre content for each segment. Fibre content was found to be variable and the deviation from the nominal value where measurements can reach up to almost 30% deviation. The results show that the phenomenon of fibres’ separation takes place by low pressure and low injection temperature. The deviation in fibre content is found to follow a cyclic trend. The frequency of the cyclic behaviour increases with more temperature and pressure but with lower variation amplitude.At low pressure and temperature; change in fibre length behaves in a similar pattern like fibre content. Fibre length is measured by QICPIC system (dynamic image analysis). It is found that the increase in the measured fibre length is accompanied by an increase in the measured fibre content. However, more understanding, based on fundamentals of fluid mechanics, is needed for establishing robust simulation models.
  • Strength and ductility improvement of recycled aggregate concrete by
           polyester FRP-PVC tube confinement
    • Abstract: Publication date: Available online 1 November 2018Source: Composites Part B: EngineeringAuthor(s): Chang Gao, Liang Huang, Libo Yan, Ruoyu Jin, Bohumil Kasal In literature, studies on recycled aggregate concrete (RAC) with recycled aggregates (RAs) originated from clay brick waste are rare, which is mainly attributed to the much lower compressive strength of the RAC with recycled clay brick aggregates (RAC-RCBA) when comparing with its normal aggregate concrete (NAC) counterpart. Nowadays it is well known that fiber reinforced polymer (FRP) composites as lateral confining materials can improve the strength and ductility of NAC significantly. In this study, FRP confining materials were used to improve the compressive strength and ductility of the RAC-RCBA. Compared with conventional synthetic glass or carbon FRP composites, polyester FRP (PFRP) and Polyvinyl chloride (PVC) are much cheaper and show much larger tensile deformation capacity. Therefore, this study investigated the axial compressive behavior of PFRP and PVC hybrid tube encased RAC-RCBA (i.e., shortened as PFRP-PVC-RAC-RCBA) structure. This PFRP-PVC-RAC-RCBA system consisted of an RAC-RCBA core, encased by a PVC tube directly and the PVC tube was further confined with a PFRP tube (i.e. PFRP tube-PVC-RAC-RCBA specimen) or PFRP strips (i.e. PFRP strip-PVC-RAC-RCBA) at the outermost layer. Uniaxial compression tests were performed on 33 PFRP-PVC-RAC-RCBA and 39 unconfined RAC-RCBA specimens to evaluate and compare the axial compressive behavior of PVC tube encased RAC-RCBA, PFRP tube encased RAC-RCBA, PFRP tube-PVC-RAC-RCBA and PFRP strip-PVC-RAC-RCBA columns. The tested variables included the number of PFRP layers (3-, 6- and 9-layer), the type of PFRP confinement (in the configuration of tube or strips) and the spacing of the PFRP strips (25 and 50 mm). The tested results demonstrated that the PFRP-PVC hybrid confining system enhanced the compressive strength and axial and lateral deformations of the RAC-RCBA pronouncedly, e.g. the increase in strength ranged from 4.5% to 39.6%. The enhancement in strength and deformations was increased with a thicker PFRP tube or strip. Both the PFRP tube-PVC-RAC-RCBA and PFRP strip-PVC-RAC-RCBA showed the similar axial compressive stress-stain behaviors. In addition, the comparison of PFRP tube-PVC-RAC-RCBA with the glass/carbon FRP tube-RAC-RCBA indicated that the GFRP and CFRP tube confinement resulted in much larger enhancement in ultimate compressive strength of RAC-RCBA due to the much larger tensile modulus and strength of these G/CFRP composites. However, PFRP-PVC tube confinement led to much larger axial deformation of the RAC-RCBA compared with the G/CFRP tube confinement due to the much larger tensile strain of the PFRP and PVC material. Furthermore, design-oriented compressive stress-strain models were developed for PFRP-PVC-RAC-RCBA specimens.
  • High tribology performance of Poly(vinylidene fluoride) composites based
           on three-dimensional mesoporous magnesium oxide nanosheets
    • Abstract: Publication date: Available online 1 November 2018Source: Composites Part B: EngineeringAuthor(s): Min Su Park, Hyeong-Seok Sung, Cheol Hun Park, Tong-Seok Han, Jong Hak Kim Three-dimensional mesoporous MgO nanosheets (MgO_NS) were synthesized by a facile non-hydrothermal method for the improvement of the tribological properties of poly(vinylidene fluoride) (PVDF) composites. The interactions and structural properties of the MgO_NS composites were systematically compared with those of commercially available MgO beads (MgO_B). It was found that the incorporation of MgO_NS decreased the polar β phase of the PVDF crystallinity owing to an intimate contact and good interactions between the mesoporous MgO_NS filler and PVDF matrix. Recipro-mode tribology tester results for a long measurement time of 3 h showed that the friction coefficients of the PVDF composites decreased with the increasing filler content for both MgO_B and MgO_NS, indicating an important role of MgO as a self-lubricating material. In particular, the PVDF/MgO_NS 5.0% composite exhibited an outstanding initial friction coefficient of 0.091 and specific wear rate of 1.8 × 10−5 mm3/N m as compared with MgO_B, this performance being among the best for PVDF-based composites. The results indicated that mesoporous MgO_NS composites with their small crystal size, large surface area, good dispersion, and intimate contact with the PVDF matrix were more effective than randomly organized MgO_B.Graphical abstractImage 1
  • Characterization of the electromagnetic parameter uncertainty in
           single-ply unidirectional carbon-fiber-reinforced-polymer laminas
    • Abstract: Publication date: Available online 31 October 2018Source: Composites Part B: EngineeringAuthor(s): Elliot J. Riley, Kevin L. Koudela, Ram M. Narayanan This paper characterizes the variation in electromagnetic properties of single-ply unidirectional carbon-fiber-reinforced-polymer (CFRP) laminas between samples fabricated using the same material. The variation is referred to as the electromagnetic-parameter uncertainty (EPU). The resulting EPU from both wet-layup and pre-preg fabrication techniques were investigated. A free-space materials characterization system operating from 4 to 18 GHz was used to characterize the electromagnetic properties with respect to the main fiber direction. A surface-impedance representation was calculated from the measured data to expose the EPU. Finally, the effects of the EPU on the reflectivity properties of electromagnetic-absorber designs using unidirectional CFRP were determined.
  • Multifunctional application of carbon fiber reinforced polymer composites:
    • Abstract: Publication date: Available online 31 October 2018Source: Composites Part B: EngineeringAuthor(s): N. Forintos, T. Czigány In most areas where weight reduction is crucial, carbon fiber reinforced composites (CFRPs) are an excellent choice. Carbon fiber, besides its structural role, can be applied for several secondary functions as well, based on its electrical properties; for example, it can be used for crosslinking, welding, as a sensor and it can also facilitate self-healing. By merging these functions, a multifunctional part or structure can be created. In this article, we review multifunctional application examples of reinforcing carbon fiber. The focus is on utilization: which additional function and what physical layout can be used with CFRP. In a summarizing table (Table 1), we classified the presented examples according to their secondary function, the material used and the physical layout. With the combination of different functions, important materials can be created for the energy and transportation industry, for autonomous vehicles and for Industry 4.0.
  • Improved fracture toughness and ductility of PLA composites by
    • Abstract: Publication date: Available online 30 October 2018Source: Composites Part B: EngineeringAuthor(s): Ying Wang, Yuan Mei, Qiang Wang, Wei Wei, Fei Huang, Ying Li, Jinyang Li, Zuowan Zhou To overcome the brittleness of poly (lactic acid) (PLA), worm-like helical carbon nanotubes (HCNTs) were selected as a novel additive to PLA in this work due to their unique morphology. To enhance the interfacial interaction with PLA matrix, a silane-coupling agent (3-aminopropyltriethoxysilane, KH550) is chemically grafted onto the HCNTs. Interestingly, a remarkable improvement in the ductility of poly (lactic acid) (PLA) composites is achieved by adding a small amount of KH550-treated HCNTs. The elongation at break and the impact strength of HCNT-KH550/PLA composite are 205% and 30% higher than those of pure PLA, respectively. The high orientation of PLA molecular chains and crystals is responsible for the remarkable enhancement in the tensile ductility. This strategy is believed to offer more possibilities for optimizing the mechanical properties of PLA composites.
  • NURBS-based modeling of laminated composite beams with isogeometric
           displacement-only theory
    • Abstract: Publication date: Available online 30 October 2018Source: Composites Part B: EngineeringAuthor(s): Shirko Faroughi, Erfan Shafei, Anders Eriksson This paper develops a formulation for displacement-only beam elements based on isogeometric analysis, with intended application to laminated composite members. The main purpose of the current study was to overcome some deficiencies of commonly used beam theories, such as shear-locking, the lacking relevance of isotropic materials for multi-layer composites, the incompatibility with other continuum elements, and the limited continuity in interpolation. A bi-variable non-uniform rational B-spline (NURBS) beam element with complete plane-stress elasticity terms and geometrical expressions was developed. Shear-locking, interlaminar stresses, the deep-beam situation, and vibration features were evaluated for several aspect ratios, ply orientations, and NURBS degrees, in order to verify the efficiency and accuracy. h-, p- and k-refinements were used to improve the displacement field. The validity of the solutions was measured based on results from plane-stress finite element analysis, and compared to the alternative Carrera unified formulation. Results show that the isogeometric displacement-only beam theory can provide the interlaminar stress distribution, gives high accuracy for mid and high-range eigen-frequencies, and avoids the shear-locking phenomenon.
  • Micromechanical analysis of bioresorbable PLLA/Mg composites coated with
           MgO: Effects of particle weight fraction, particle/matrix interface
           bonding strength and interphase
    • Abstract: Publication date: Available online 29 October 2018Source: Composites Part B: EngineeringAuthor(s): Hozhabr Mozafari, Pengfei Dong, Kewei Ren, Xinwei Han, Linxia Gu Magnesium (Mg) particles has been recently introduced in a poly-l-lactic acid (PLLA) matrix to enhance to its mechanical properties. The coating of Mg particles could also regulate its degradation rate. The mechanical behavior of PLLA/Mg composite was characterized using a three dimensional Representative Volume Element model. The influences of Mg weight fraction, imperfect bonding between particle and polymer matrix, and the interphase layer on the mechanical behaviors of the composites were quantified. Results clearly demonstrated that the effective Young's modulus and yield strength of the composite was enhanced by the Mg particles, as well as its MgO coating. In addition, the imperfect interfacial bonding between the Mg particle and PLLA weakened the mechanical advantage of the composite, which was in good agreement with the documented experimental observations. This work might shed some light on the optimal design and manufacturing of the bioresorbable composites.
  • A comparison of the effects of pozzolanic binders on the hardened-state
           properties of high-strength cementitious composites reinforced with waste
           tire fibers
    • Abstract: Publication date: Available online 29 October 2018Source: Composites Part B: EngineeringAuthor(s): M. Mastali, A. Dalvand, A.R. Sattarifard, Z. Abdollahnejad, B. Nematollahi, J.G. Sanjayan, M. Illikainen Experimental and statistical analyses were conducted to examine the effects of partially replacing ordinary Portland cement (OPC) with pozzolanic binders (silica fume and fly ash) on the hardened-state characteristics of high-strength cementitious concrete reinforced with steel fibers recovered from waste tires. The variables used in the analyses were the concentration of recycled steel fibers (volume fraction = 0.5% and 1%) and the proportion of silica fume or fly ash used to replace OPC (weight = 10%, 20%, and 40%). The effects of combining fibers at two volume fractions with pozzolanic binders in 14 mixtures were investigated through an experimental program carried out in two stages. First, the effects of replacing OPC with silica fume or fly ash on the matrix were determined by assessing the heat of hydration, the formation of the crystalline phases using X-ray diffraction analysis, the gel structure and mass loss at elevated temperatures with thermogravimetric, and differential thermogravimetry analyses, and porosity structures of pastes with using the mercury intrusion porosimetry test. Second, the effects of adding recycled steel fibers on the hardened-state properties of OPC-based concretes containing pozzolans were explored by evaluating the water absorption by immersion and capillary rise, ultrasonic pulse velocity, compressive strength, splitting tensile strength, flexural strength, and impact resistance of the reinforced mixtures. The experimental results were subjected to linear regression and statistical analysis to correlate the mechanical and impact properties of the mixtures and identify probability distributions, respectively.The findings showed that using pozzolanic binders enhanced the mechanical and impact properties of the mixtures reinforced with fibers from waste tires, thereby affecting the fibers’ frictional pull-out behavior. Therefore, significant differences on the impacts of fiber content were found on the post-peak responses of the mixtures under flexural loading. In general, using silica fume had higher impact on enhancing the hardened-state characterizations than fly ash. The greatest enhancement in mechanical properties was observed when OPC was replaced with 40% silica fume.The analytical results confirmed that silica fume was better fitted to the normal distribution than fly ash, while fly ash produced a higher coefficient of correlation between mechanical and impact resistance than did silica fume.
  • The effect of nanoperlite and its silane treatment on thermal properties
           and degradation of polypropylene/nanoperlite nanocomposite films
    • Abstract: Publication date: Available online 29 October 2018Source: Composites Part B: EngineeringAuthor(s): Razi Sahraeian, Seyed Mohammad Davachi, Behzad Shiroud Heidari The main goal of this study is to observe the exact effect of nanoperlite and its silane treatment on thermal behavior and degradation mechanism as well as thermomechanical properties of nanocomposites. In this regard, polypropylene (PP) with various contents of untreated nanoperlite and silane treated nanoperlite were prepared using a twin-screw extruder and an extrusion film blew machine. Regardless of the type, the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) tests show no chemical reaction between PP and nanoperlite and relatively good dispersion of nanoparticles was obtained in the system. The results of thermal studies represent a reduction in all the properties of nanoperlite/PP nanocomposites including thermal stability, while, the addition of silane treated nanoperlite shows less reduction and better thermal stability. Based on Flynn-Wall-Ozawa method, thermal degradation kinetics and mean activation energies of the untreated nanoperlite filled nanocomposites show higher values. Finally based on thermomechanical studies, treated nanoperlite-filled nanocomposites show lower values for tan D comparing to untreated nanoperlite-filled nanocomposites, as the storage modulus is reinforced and the loss modulus decreased. Overall, nanocomposites with 2–4% of treated nanoperlite showed nearly the same behavior of 4–6% of untreated nanoperlite filled nanocomposites and due to better dispersion, thermal and morphological properties, these films can be proper alternatives for packaging industries.
  • Bionic design and 3D printing of porous titanium alloy scaffolds for bone
           tissue repair
    • Abstract: Publication date: Available online 29 October 2018Source: Composites Part B: EngineeringAuthor(s): Li Zhao, Xuan Pei, Lihua Jiang, Cheng Hu, Jianxun Sun, Fei Xing, Changchun Zhou, Yujiang Fan, Xingdong Zhang Bone defect and osteoporosis are common in clinic which are seriously harmful for public health. Bionic bone tissue engineering scaffolds are very important for bone tissue repair and reconstruction. In this study, different bionic bone tissue engineering scaffolds were constructed by computer-aided design and fabricated by selected laser melting. Novel porous structures were designed by using parameterization modeling. The accurate models with key characteristics such as porosity and the mechanical property of scaffolds were studied. Compared with the designed model, the error of the selective laser melting (SLM) printed scaffold porosity was less than 2.73%. The mechanical properties of the prepared scaffold can be calculated by finite element analysis of 3D models, and the mechanical properties of the 3D printed samples were consistent with the model design. Through the design, manufacture, characterization and evaluation of the scaffold porous structures, the parametric modeling of porous titanium bone tissue engineering scaffold with good mechanical and biological properties was realized. Optimized design and precisely manufactured implants are very important for bone tissue repair and reconstruction.
  • On the stainless steel flakes reinforcement of polymer matrix particulate
    • Abstract: Publication date: Available online 29 October 2018Source: Composites Part B: EngineeringAuthor(s): G.V. Seretis, D.E. Manolakos, C.G. Provatidis The present paper is dealing with the reinforcement of epoxy and high density polyethylene (HDPE) matrices using stainless steel flakes (SSFs). Particulate composite specimens of different wt SSFs contents up to 10% were produced for each case of polymer matrix. The so-obtained SSFs/epoxy and SSFs/HDPE composites underwent tensile, three-point bending and compression tests. The tensile and flexural performance of the composites of both matrices seemed to be negatively affected by the SSF loading. However, the response on plastic deformation under tensile loading for the SSFs/HDPE composites was considerably enhanced for low SSFs contents. The compression response was enhanced in the case of SSFs/HDPE composites as well. The tensile, flexural and compression performance is being explained on the basis of the microstructural observations for each case of reinforced matrix.
  • Energy-absorption characteristics of a bionic honeycomb tubular nested
           structure inspired by bamboo under axial crushing
    • Abstract: Publication date: Available online 29 October 2018Source: Composites Part B: EngineeringAuthor(s): Dayong Hu, Yongzhen Wang, Bin Song, Linwei Dang, Zhiqiang Zhang Geometric configurations in nature could be mimicked in order to develop novel materials and structures with desirable properties. Lots of bio-inspired configurations had been introduced to tubal structures in promoting the energy-absorption performance of thin-walled structures. Nevertheless, these existing studies largely focused on hierarchical hexagonal honeycombs, and the bio-inspired hierarchical circular thin-walled structures under the out-of-plane crushing loads had not been well studied experimentally, numerically and analytically for energy absorption to date. In this study, the bionic honeycomb tubular nested structure (BHTNS) was first inspired by the micro-architecture of bamboo vascular bundles, which could be mimicked by connecting a central circular tube to other six circular tubes in a hexagonal arrangement, regardless of size or choice of materials. The energy-absorption characteristics of BHTNS under axial crushing were systematically studied by drop-weight experiment, numerical simulation, and theoretical analysis. Dynamic drop-weight impact experiments were conducted and the results showed that the specific energy absorption (SEA) of BHTNS was as high as 29.3 J/g. Furthermore, the parametric numerical simulation revealed the influence of diverse mean diameter D of the circular tube and length L of the junction plate on the energy-absorption characteristics. Finally, a theoretical model was also developed to predict the mean crush force Pm, which was in good agreement with the numerical simulation. This work could provide a reference for an energy-absorber design with high efficiency.
  • Mechanism of distributed composite GFRP bars in circular concrete members
           with and without spirals under shear
    • Abstract: Publication date: Available online 29 October 2018Source: Composites Part B: EngineeringAuthor(s): Hamdy M. Mohamed, Ahmed H. Ali, Brahim Benmokrane This paper presents experimental data and theoretical studies on the effect of distributed glass fiber-reinforced-polymer (GFRP) bars in circular concrete members. Th experimental program reports the test results of eight full-scale circular reinforced-concrete (RC) specimens with a total length of 3020 mm and a diameter of 508 mm were constructed and tested under shear load up to failure. The test specimens comprised three specimens reinforced with GFRP bars and spirals, three specimens with only longitudinal GFRP bars, and two reference specimens reinforced with conventional steel bars, with and without steel spirals. The various experimental parameters included the longitudinal reinforcement ratio, the type of reinforcement (GFRP versus steel), and presence of shear reinforcement. The shear strengths of GFRP circular concrete specimens, obtained from the experimental results, were compared to current codes and design guidelines as well as to the recently available shear design equations on circular concrete members in the literature. The test results indicate that the use of more GFRP bars distributed uniformly in the cross section, of the specimens with and without spirals, reduces the loss of flexural stiffness after cracking and increase the shear strength. The comparison indicates that some of the available design methods provide reasonable predictions.
  • Effects of hybridization on the mechanical properties of composites
           reinforced by piassava fibers tissue
    • Abstract: Publication date: Available online 29 October 2018Source: Composites Part B: EngineeringAuthor(s): Genilson Cunha de Oliveira Filho, Rui Carlos de Sousa Mota, Ana Claudia Rangel da Conceicao, Mirtania Antunes Leao, Oscar Olimpio de Araujo Filho The gradual replacement of conventional materials by composite materials becomes reality when specific properties cannot be achieved by the former. Also, the search for new composites that use natural fibers or a mixture of natural fibers with synthetic fibers as reinforcement is being carried out. Thus, a research was made on the development of two composite laminates, one based on piassava fiber fabric and the other a hybrid composite based on piassava fiber and glass-E fabrics, in order to compare the mechanical behavior of both. The laminate plates were prepared and were processed for specimen manufacture in accordance with the specifications of ASTM D3039 - Uniaxial Tensile Test, and ASTM D790 - Three-point Bending Test standards. Scanning Electron Microscopy (SEM) was also performed to analyze the mechanisms of damage of the specimens. The analysis of the results of the tested specimens show they are satisfactory, as they are very akin to the results of other materials already researched by academy.
  • Synthesis of silver nanoparticles decorated on core-shell structured
           tannic acid coated iron oxide nanospheres for excellent electrochemical
           detection and efficient catalytic reduction of hazardous 4-nitrophenol
    • Abstract: Publication date: Available online 28 October 2018Source: Composites Part B: EngineeringAuthor(s): Arumugam Sangili, Muthaiah Annalakshmi, Shen-Ming Chen, Paramasivam Balasubramanian, Mahalingam Sundrarajan In this research, synthesis of silver nanoparticles (Ag NPs) decorated on tannic acid (TA) covered magnetite (Fe3O4) (TA@Fe3O4-Ag NPs) nanohybrid is reported. TA (carbon-shell) on Fe3O4 nanospheres (core) acted as a green reducing and stabilizing agent for the reduction of Ag ions into Ag NPs. The as-synthesized TA@Fe3O4-AgNPs core-shell nanohybrid was employed as an efficient nanomaterial for the electrochemical detection and catalytic reduction of ecotoxic 4-nitrophenol (4-NP). TA@Fe3O4-AgNPs nanohybrid modified glassy carbon electrode (GCE) displayed a higher cathodic current response at a very lower over potential of −0.39 V toward 4-NP detection. Under optimized condition, TA@Fe3O4-AgNPs nanohybrid based sensor showed a broad working range from 0.1 to 680.1 μM, with a lower limit of detection of 33 nM for the detection of 4-NP. In addition, TA@Fe3O4-AgNPs nanohybrid exhibited a tremendous catalytic reduction activity for 4-NP, when compared to TA@Fe3O4 and Fe3O4. The results demonstrated that the TA@Fe3O4-AgNPs nanohybrid could be a promising nanocatalyst for the electrochemical detection and catalytic reduction of 4-NP.Graphical abstractImage 1
  • Polyamide 6/graphene oxide-g-hindered phenol antioxidant nano-composites:
           Intercalation structure and synergistic thermal oxidative stabilization
    • Abstract: Publication date: Available online 28 October 2018Source: Composites Part B: EngineeringAuthor(s): Ruiguang Li, Kaihua Shi, Lin Ye, Guangxian Li The hindered phenol antioxidant (HP) was grafted onto graphene oxide (GO) surface, and polyamide 6 (PA6)/GO-HP nano-composite was manufactured via melt processing. More efficient grafting of PA6 molecules onto GO surface was realized by forming hydrogen bonding, and GO was exfoliated and uniformly distributed in matrix. Compared with PA6/HP and PA6/GO, the oxidation induction time, thermal degradation temperature and Ea of PA6/GO-HP composite increased significantly, retention of reduced viscosity and tensile strength were improved, revealing GO-HP hybrid was more efficient than HP or GO to resist thermal oxidation degradation of PA6. Such synergistic thermal oxidative stabilization mechanism was further revealed.
  • Behavior and modeling of FRP-confined ultra-lightweight cement composites
           under monotonic axial compression
    • Abstract: Publication date: Available online 28 October 2018Source: Composites Part B: EngineeringAuthor(s): Yingwu Zhou, Yaowei Zheng, Lili Sui, Feng Xing, Jingjing Hu, Pengda Li Ultra-lightweight cement composite (ULCC) has low densities of less than 1400 kg/m3 with a compressive strength up to 60 MPa, making them ideal for use in structures where material weight is critical. However, these applications were limited by its brittleness and low ductility. Wrapping ULCC with fiber reinforced polymer (FRP) can enhance its ultimate strain and compressive strength. This premier study and model of FRP-confined ULCC under axial compression tested 21 FRP-confined ULCC cylinders. Strength and FRP thickness were the primary variables. Test results indicated that the bearing capacity and ductility of ULCC are considerably improved by FRP jackets, which is similar to FRP-confined normal concrete (NC). It also is shown that the lateral dilation behavior of FRP-confined ULCC differs significantly from that of FRP-confined NC because the former has lower elastic modulus and more brittle feature than the latter; this difference reveals the post-peak strain hardening-softening mechanism of confined concrete. In addition, this paper introduces a new strength model with an improved stress-strain relationship for FRP-confined ULCC columns. Compared with the existing models, the proposed model can predict the stress-strain behavior of FRP-confined ULCC with better accuracy.
  • Wave propagation in smart laminated composite cylindrical shells
           reinforced with carbon nanotubes in hygrothermal environments
    • Abstract: Publication date: Available online 27 October 2018Source: Composites Part B: EngineeringAuthor(s): Hossein Kh. Bisheh, Nan Wu Wave propagation problem is solved in smart laminated carbon nanotube (CNT)-reinforced composite cylindrical shells coupled with piezoelectric layers on the top and bottom surfaces in hygrothermal environments for the first time. The motion equations are derived based on the first-order shear deformation shell theory considering the transverse shear effects and rotary inertia. The hygrothermal effects are also included in the mathematical modeling and the effective material properties of a CNT-reinforced composite shell are estimated through the Mori-Tanaka micromechanical model. Dispersion solutions are obtained by solving an eigenvalue problem. Parametric studies are carried out to investigate the effects of temperature/moisture variation, CNT volume fraction and orientation, piezoelectricity, shell geometry, stacking sequence, and material properties of the host substrate laminated composite shell at different axial and circumferential wave numbers. The results show that the temperature/moisture variation influences moderately on the dispersion solutions of smart laminated CNT-reinforced composite shells. The presented methodology and results can be used in wave propagation analysis of smart laminated CNT-reinforced composite shells affected by hygrothermal environmental conditions.
  • Experimental investigation on bending behavior of honeycomb sandwich panel
           with ceramic tile face-sheet
    • Abstract: Publication date: Available online 26 October 2018Source: Composites Part B: EngineeringAuthor(s): Zhonggang Wang, Zhendong Li, Wei Xiong Honeycomb sandwich structures are widely employed in the engineering field, due to their light weight, strong rigidity and high strength. In this study, the bending resistance performance of the honeycomb sandwich panel with ceramic tile face-sheet (short as ceramic sandwich) was investigated through three-point bending experiments. Their differences between the present ceramic sandwich and the conventional ones were reported and discussed in terms of deformation mode, load-deflection history and bending resistance. As the experiments turned out that differing from the conventional sandwich panel, the present ceramic one performs different collapse modes when undergoing 3-point bending load. The results demonstrated that the bending behavior of the present ceramic sandwich was largely promoted due to the ceramic tile face-sheet. Besides, the mechanical influence of the ceramic tile face-sheet and the cell length of honeycomb core were determined. These achievements pave a way of designing composited superb bending resistant sandwich structures.
  • Periodic boundary condition and its numerical implementation algorithm for
           the evaluation of effective mechanical properties of the composites with
           complicated micro-structures
    • Abstract: Publication date: Available online 26 October 2018Source: Composites Part B: EngineeringAuthor(s): Wenlong Tian, Lehua Qi, Xujiang Chao, Junhao Liang, Mingwang Fu To evaluate the effective mechanical properties of the composites with complicated micro-structures, the RVE based FE homogenization method with the periodic boundary condition is introduced and implemented in this paper, and the emphasis is on the periodic boundary condition and its numerical implementation algorithm. The pre-processing (such as the generation of geometry model and application of periodic boundary condition), FE analysis and post-processing (such as the average of stress and strain and stress contouring of the surface nodes) concerning the evaluation of the effective mechanical properties of the composites with complicated micro-structures are conducted in the FE package ABAQUS through the Python Interface. Numerical results show that the proposed numerical implementation algorithm of the periodic boundary condition guarantees the stress and strain continuities and uniaxial deformation constraints of the RVEs for the composites with complicated micro-structures. Compared with the Halpin-Tsai model and two-step M-T/Voigt mean-field homogenization method, the RVE based FE homogenization method with the periodic boundary condition is verified to accurately predict the effective elastic properties and elasto-plastic responses of the composites with the complicated micro-structures.
  • A nonlinear dynamic model of fiber-reinforced composite thin plate with
           temperature dependence in thermal environment
    • Abstract: Publication date: Available online 26 October 2018Source: Composites Part B: EngineeringAuthor(s): Hui li, Huaishuai Wu, Tinan Zhang, Bangchun Wen, Zhongwei Guan In this paper, the material nonlinearity induced by the high temperature is introduced in the modeling of fiber-reinforced composite thin plate structure, and a nonlinear dynamic model in thermal environment is established using Hamilton's principle in conjunction with the classical laminated plate theory, complex modulus method and strain energy method. The nonlinear relationships between the elastic moduli, Poisson's ratios and loss factors and temperature change are expressed by the polynomial method. Then, the dynamic equations in the high temperature environment are derived to solve the inherent characteristics, dynamic responses and damping parameters with considering temperature dependent property. Also, the identification principle of concerned fitting coefficients in the theoretical model is illustrated. As an example to demonstrate the feasibility of the developed model, the experimental test of a TC500 carbon/epoxy composite thin plate is implemented. The results of the developed model and experimental test show a good consistency, and both indicate that the high temperature has complicated influence on its dynamic characteristics, especially on damping property.
  • Porous germanium enabled high areal capacity anode for lithium-ion
    • Abstract: Publication date: Available online 25 October 2018Source: Composites Part B: EngineeringAuthor(s): Kuber Mishra, Xiao-Chen Liu, Fu-Sheng Ke, Xiao-Dong Zhou The role of different mass loadings on the corresponding areal capacities, capacity retention, and rate performance in high-capacity Ge electrodes was studied. Micro-sized porous Ge powders were synthesized from a facile single-step process. The porous Ge electrode exhibited a high capacity retention over 1800 cycles at 8 A/g (∼73% retention) at the low loading of 0.56 mg/cm2. Even with the high loading of 4.45 mg/cm2, high areal capacity (>3 mAh/cm2) for over 100 cycles were observed. Excellent electrochemical stability for a full cell was also observed for about 180 cycles with a LiCoO2 cathode. Post cycling analysis reveals that the stability of the porous electrode stems from the ability of the grains to maintain their electrical contacts with each other even after undergoing transformation in the morphology and crystallinity.
  • Plasma synthesis of nanodiamonds in ethanol
    • Abstract: Publication date: Available online 25 October 2018Source: Composites Part B: EngineeringAuthor(s): Chen-Hon Nee, Ming Chuan Lee, Hun Seng Poh, Seong-Ling Yap, Teck-Yong Tou, Seong-Shan Yap In this work, we examined the characteristics of the plasma formed by fs laser filamentation in ethanol that affected the nanodiamonds formation by optical emission spectroscopy. Molecular and atomic C species were detected in the plasma as the precursors to the nanodiamonds formed; above the threshold laser energy of 360 μJ. Thus, the generation of homogeneous nanodiamonds was identified to be occurred within laser energy of 360–550 μJ where atomic C, ionized C and C2 clusters coexisted. The process of fs laser filamentation is monitored with in-situ absorbance measurement of ethanol. The intensity of the absorbance peak of the sample at ∼228 nm, corresponds to intrinsic absorbance of diamond (σ→ σ* transition) was observed to increase with irradiation time. The prepared samples are characterized by using Raman spectroscopy, XPS and TEM. Nanodiamonds of
  • A novel approach on the study of cure kinetics for rheological isothermal
           and non-isothermal methods
    • Abstract: Publication date: Available online 24 October 2018Source: Composites Part B: EngineeringAuthor(s): Ma Zhongliang, Qi Le, He Wei, He Liming The cure kinetics of GAP (glycidyl azide polymer) special propellant have been studied by rheological isothermal and non-isothermal methods. Arrhenius equation has been proposed to describe the dependence of storage modulus on the temperature. Thus, one can distinguish cure effect from temperature effect resulting in storage modulus change. The conversion a has been calculated by a novel method, according to which rheological non-isothermal test can be applied and the isothermal test can be optimized. Apparent activation energy has similar trends and similar values of parameters has been concluded for isothermal and non-isothermal tests. New kinetic equations had been established and showed great agreement with experimental data both in isothermal and non-isothermal tests. Altogether, the temperature effect should be distinguished while calculating the conversion degree a. Rheological isothermal and non-isothermal method should be used to investigate the mechanism and kinetics of thermosetting reactions, especially for heterogrnerous reactions. The obtained knowledge of the curing kinetics will form a contribution to the study of heterogrnerous reactions.
  • Assessment of failure toughening mechanisms in continuous glass fiber
           thermoplastic laminates subjected to cyclic loading
    • Abstract: Publication date: Available online 24 October 2018Source: Composites Part B: EngineeringAuthor(s): M. Nikforooz, J. Montesano, M. Golzar, M.M. Shokrieh Tensile fatigue behaviour of glass fiber/polyamide composites, including unidirectional ([0]8, [90]8) and cross-ply ([02/902]s, [04/904]s and [904/04]s) laminates, was studied and compared to that of similar glass fiber/epoxy composites. The fatigue resistance of cross-ply glass/polyamide was greater than that of glass/epoxy while also exhibiting lower stiffness reduction. To explain this key observation, residual stiffness and residual strength fatigue tests were performed on cross-ply laminates, while optical microscopy was used to measure ply crack density during the different stages of cycling. Testing of the cross-ply laminates at lower peak stresses of 50% of the ultimate tensile strength (i.e., high cycle fatigue regime) revealed partial cracks that did not propagate completely through the width and thickness of plies due to high matrix toughness and other observed toughening mechanisms such as matrix bridging. A micromechanical finite element model with explicit ply cracks was also used to predict laminate stiffness degradation corresponding to observed ply crack densities, revealing that stiffness degradation was overpredicted when cracks were assumed to span the entire specimen width. Additional finite element simulations with partial cracks showed notably less stiffness reduction. These observations suggest glass/polyamide is inherently more damage tolerant than glass/epoxy and may be a suitable replacement for fatigue critical structures.
  • A unified solution for the vibration analysis of functionally graded
           porous (FGP) shallow shells with general boundary conditions
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Fei Xie, Ailun Wang, Cijun Shuai, Jinyuan Tang, Qingshan Wang The main purpose of this paper is to illustrate the vibration characteristics of functionally graded porous (FGP) shallow shells with general boundary conditions for the first time. The general boundary condition of FGP shallow shells is realized by the virtual spring technique. The imposing procedures of the boundary conditions are simplified so that a certain kind of restraints can be easily achieved by merely setting different stiffness of the springs. It is assumed that the distributions of porosity are uniform or non-uniformly along a certain direction and three types of the porosity distribution are considered, among which material property of two non-uniform porous distributions are expressed as the simple cosine. The size of the pore in a shallow shell is determined by the porosity coefficients. Based on the first-order shear deformation theory (FSDT), all kinetic energy and potential energy of FGP shallow shells are expressed by displacement admissible function. On this basis, the author describes the displacement admissible function of the FGP shallow shells by using the modified Fourier series which increases the auxiliary function, so that the auxiliary function can be used to eliminate the discontinuity or jumping of the traditional Fourier series at the edges. Lastly, the natural frequencies as well as the associated mode shapes of FGP shallow shells are achieved by replacing the modified Fourier series into the above energy expression and using the variational operation for unknown expansion coefficients. Several numerical examples are carried out to demonstrate the validity and accuracy of the present solution by comparing with the results obtained by other researchers. In addition, a series of innovative results are also highlighted in the text, which may provide basic data for other algorithm research in the future.
  • A meshfree boundary-domain integral equation method for free vibration
           analysis of the functionally graded beams with open edged cracks
    • Abstract: Publication date: Available online 24 August 2018Source: Composites Part B: EngineeringAuthor(s): K.P. Kou, Y. Yang A dynamic analysis may be required either because a crack is excited by time dependent loads or because a crack under static loading conditions propagates so rapidly that the effects of the inertia forces are important and the inertia effects cannot be neglected. In this paper, free vibration of the functionally graded beams with open edged cracks are analyzed by a meshfree boundary-domain integral equation method. Elastostatic fundamental solutions are used as weight functions to generate the weighted residual statements of the equations of motion. Fundamental solutions are obtained by considering the inhomogeneous and inertia effects. Numerical results compared well with that of the analytical methods. Comprehensive parametric study investigates the effects of the material gradients and directions, crack length and depth ratios, as well as boundary conditions on the free vibration responses on the cracked FG beams, which demonstrate the present method states high efficiency and accuracy. Besides, the developed method can be used to identify the crack size and location of the FG beams.
  • Thermal performance of an alkali activated paste for bonding fibre sheets
           with concrete
    • Abstract: Publication date: Available online 19 October 2018Source: Composites Part B: EngineeringAuthor(s): Subhra Majhi, Abhijit Mukherjee, Anthony F. Spadacini Fibre Reinforced Polymers are widely used for retrofitting and strengthening of structures. The integrity of fibre matrix system in FRP system would be severely compromised in situations where the system is exposed to elevated temperatures. In this paper, an Alkali Activated Siliceous Paste (AASP) has been developed as a temperature tolerant adhesive for FRP systems. AASP has been compared with the conventional fibre-epoxy system and the fibre-epoxy system. It has also been tested as a thermal insulation overlay on the epoxy. The test has been performed by applying three-point flexure. Simultaneously, Acoustic Emission events have been recorded to understand the failure characteristics in each case. To understand the microstructural effect scanning electron micrographs and energy dispersive X-ray analysis have been performed. The conventional epoxy system suffered loss in integrity after the glass transition temperature of epoxy. AASP specimens offered considerably improved thermal performance but the bonding with concrete was variable due to inadequate penetration into the fibre sheet. AASP overlays prevented visual degradation of the epoxy from elevated temperature but couldn't help prevent development of heat gradient. AASP has a great potential to be developed as a temperature tolerant adhesive but its rheology must be improved for ensuring reliable bonding between the fibres and concrete.
  • Branch point algorithm for structural irregularity determination of
    • Abstract: Publication date: Available online 19 October 2018Source: Composites Part B: EngineeringAuthor(s): Can Cui, Zhonggang Wang, Wei Zhou, Yongjun Wu, Wanhui Wei Recently, more and more attentions have been paid to structural defect suppression. In this study, branch point algorithm was first constructed for structural irregularity determination of honeycomb structure, so as to identify the geometric defect of similar cellular structures. Detailed principle and process were presented with key steps as image binarization, smoothing & noise suppression, skeletonization, vertex identification and cell reconstruction. A representative illustration was given. Afterwards, the routine difference has been discussed between the present method and classic Harris algorithm. Some examples in different cases were presented. As the findings turning out that, the branch point algorithm efficiently identifies the vertices of each cell with high precision, even in cases of poor images with low resolution. All these achievements pave a way for high standard honeycomb structure in consistency, reliability and homogeneity.
  • Aluminum-sulfur composites for Li-S batteries with high-rate performance
    • Abstract: Publication date: Available online 25 September 2018Source: Composites Part B: EngineeringAuthor(s): Sophia P. Zhou, Yanqiu Lu, Shouyu Shen, Shao-Jian Zhang, Xiao-Dong Zhou, Jun-Tao Li, Lin Huang, Shi-Gang Sun Over the past few years, lithium sulfur (Li-S) batteries have attracted attention as an enabling technology because of their high energy density. The limitations to commercialize Li-S batteries originate from the intrinsic properties of sulfur: its poor electronic conductivity and the polysulfide shuttle. The aim of this research is to address these challenges by developing an additive for Li-S batteries. Al-powders prepared from soda-cans were mixed with S to form a composite with a mass loading of S up to 90 wt%. The electrochemical performance shows that the Al-S composite in Li-S cells exhibits a reasonable retention after 200 cycles and a remarkable ability to stabilize quickly (
  • Expression of normal stress difference and relaxation modulus for ternary
           nanocomposites containing biodegradable polymers and carbon nanotubes by
           storage and loss modulus data
    • Abstract: Publication date: Available online 25 September 2018Source: Composites Part B: EngineeringAuthor(s): Yasser Zare, Kyong Yop Rhee In this paper, the first normal stress differences (N1) and the relaxation modulus (G (t)) are predicted for prepared poly (lactic acid) (PLA)/poly (ethylene oxide) (PEO)/carbon nanotubes (CNT) nanocomposites using the experimental results of storage and loss moduli. N1 and G (t) are calculated for these samples as a function of shear rate. Moreover, the effects of various parameters on N1 and G (t) are revealed to validate the equations. N1 increases by shear rate, but it shows a plateau at low shear rates. The addition of nanoparticles to the blends increases N1 demonstrating that the nanoparticles enhance the elasticity. G (t) decreases upon increasing in the shear rate in all samples and the addition of CNT to polymer blends causes a high G (t). A high storage modulus and small loss modulus enhance N1 and G (t), whereas poor storage modulus lowers N1 and G (t). Additionally, G (t) improves significantly at small strain and high N1. This work presents useful guidelines for calculation of N1 and G (t) and understanding the origin of these terms in polymer systems.
  • PBO/graphene added β-PVDF piezoelectric composite nanofiber
    • Abstract: Publication date: Available online 23 September 2018Source: Composites Part B: EngineeringAuthor(s): Rabia Barstuğan, Mücahid Barstuğan, İlkay Özaytekin In this study, composite nanofibrous piezoelectric materials were produced. A solution of polybenzoxazole (PBO) with hydroxamoyl chloride was prepared with the sol-gel method using PBO, PVDF, and graphene. Composite nanofibrous materials were then fabricated from the produced solution using the electro-spinning method. The subsequent characterization of the piezoelectric materials was conducted using XRD and FTIR analysis. The mean radius of the fibers was calculated using SEM. Based on TGA and DSC analysis, it was found that the thermal resistance increased by around 20 °C with the addition of PBO. The surface morphology of the fibers was examined using AFM analysis. Even when pressing and polarization were not applied to the fibers, electricity was able to be generated. The oscilloscope showed that fibers 0.02 mm and 0.06 mm generated maximum 60 V and 9.68 V of electricity, respectively. An electric circuit was designed and an LED light run using the generated electricity.
  • Shear strengthening of reinforced concrete beams with PBO-FRCM composites
           with anchorage
    • Abstract: Publication date: Available online 23 September 2018Source: Composites Part B: EngineeringAuthor(s): Dorota Marcinczak, Tomasz Trapko, Michał Musiał In this paper results of tests carried out on beams strengthened in shear with PBO-FRCM composites were presented and compared with theoretical calculations according to the ACI549.4R-13 standard. PBO-FRCM (Fibre Reinforced Cementitious Matrix) composites consist of mineral mortar and PBO (p-Phenylene Benzobis Oxazole) composite fibres. The mineral mortar makes them a good alternative to the commonly used FRP composites, especially in structures exposed to high temperatures and in historic buildings. FRCM composites mostly fail due to the debonding (without rupture) of the fibres from the mineral mortar. Proper anchorage should be employed to prevent the premature debonding of the composite and to increase the effectiveness of the FRCM reinforcements. As part of this research tests were carried out on 10 RC T-beams strengthened in shear with PBO-FRCM composites with different anchorage system. The mechanisms of failure of the beams were analysed and described. A theoretical model based on ACI549.4R-13 (the only existing standard for FRCM composites) was described. Shear capacity was calculated on basis of the characteristics of the materials and elements used in the tests. The results of the calculations based on ACI549.4R-13 showed the shear capacity of the T-beams with transverse steel reinforcement and anchored composites to be considerably underestimated. The theoretical model needs to be refined and verified on a larger number of elements. The results and the probable causes of the discrepancies between the experimental results and the analytical ones are discussed.
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