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Journal Cover
Composites Part B : Engineering
Journal Prestige (SJR): 2.039
Citation Impact (citeScore): 5
Number of Followers: 262  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1359-8368
Published by Elsevier Homepage  [3162 journals]
  • Influence of FRP thickness and confining effect on flexural performance of
           HB-strengthened RC beams
    • Abstract: Publication date: Available online 18 October 2018Source: Composites Part B: EngineeringAuthor(s): Cheng Chen, Xiaowei Wang, Lili Sui, Feng Xing, Xilong Chen, Yingwu Zhou This paper presents details of an experimental study and an analytical model that investigates the influence of fiber reinforced polymer (FRP) thickness and confining effect on the flexural performance of hybrid bonded (HB) FRP strengthened reinforced concrete (RC) beams. In the experimental study, a total of ten 150 × 250 × 2400-mm RC beams, with and without HB strengthening, were tested under four-point bending. Each specimen varied in the thickness of FRP plate and the confining effects of HB fastener. Fastener detachment and FRP rupture were identified as the dominant failure modes. The load-carrying capacity increased when thicker FRP plate and higher confining effect were used. The best ductility performance was reached when the fastener detachment and the FRP rupture occurred simultaneously. An analytical model is developed to predict the load-carrying capacity of HB-strengthened RC beams, showing satisfactory precision as compared to the experimental data. The parametric study shows that increasing the FRP thickness increases the load-carrying capacity when the failure mode is FRP rupture, whereas increasing the confining effect increases the load-carrying capacity when the failure mode is FRP rupture. A design method is proposed to obtain satisfactory load-carrying capacity and ductility performance.
  • Biopolymer nanofiber/reduced graphene oxide aerogels for tunable and
           broadband high-performance microwave absorption
    • Abstract: Publication date: Available online 17 October 2018Source: Composites Part B: EngineeringAuthor(s): Boya Kuang, Mingqiang Ning, Lin Wang, Jingbo Li, Chengzhi Wang, Zhiling Hou, Yongjie Zhao, Haibo Jin Natural biopolymer cellulose nanofiber (CNF)/reduced graphene oxide (rGO) hybrid aerogels are developed for light-weight and high-efficiency microwave absorption (MA) materials. To evaluate the MA performance, CNF/rGO composites with different rGO/CNF ratios are fabricated, and the microstructure of CNF/rGO composites is tuned by changing the concentration of CNF precursor solution. It demonstrates that the MA performance is determined by not only the rGO addition but also the concentration of CNF aqueous precursor solution, evidencing the important role of microstructure of CNF/rGO composites in MA performance. The CNF/10% rGO composite prepared by 0.75% CNF solution exhibits superior MA performance with the maximum reflection loss (RL) of −40.64 dB and effective absorption bandwidth (EAB) (RL 
  • Space-confined growth of novel self-supporting carbon-based nanotube array
    • Abstract: Publication date: Available online 17 October 2018Source: Composites Part B: EngineeringAuthor(s): Liyun Dang, Yubin Hou, Chuang Song, Qingyi Lu, Ze Wang, Qiyuan Feng, Qingyou Lu, Feng Gao Tube-like nanostructure, especially carbon nanotube, usually has distinguished properties, making itself useful substrate for producing hybrid and composite materials with various applications. In this study, we proposed a space-confined self-oriented reaction in a single-ended reactor for the directional-induced decomposition of plate-like Zn-Fe double metal cyanide nanostructure. Two novel different kinds of magnetic self-supported carbon-based nanocomposites, FeC nanoparticle@ZnCN2 nanotube composite and austenite/Fe nanoparticle@carbon nanotube composite, were respectively synthesized. These nanotubes subjected to the plate-like precursor were short and non-intertwined, unlike most carbon nanotubes reported before. It was found that reactor geometry plays key roles in the self-oriented growth of these carbon-based nanoarrays and fine tubular reactors with different reducing aspect ratio (AR) values result in different nanocomposite products.
  • Scalable sonochemical synthesis of petal-like MnO2/Graphene hierarchical
           composites for high-performance supercapacitors
    • Abstract: Publication date: Available online 17 October 2018Source: Composites Part B: EngineeringAuthor(s): Shengqiang Qiu, Ran Li, Zhiyong Huang, Zhenjia Huang, Chi Pong Tsui, Chengen He, Xiaoyan Han, Yingkui Yang The past decade has witnessed substantial achievements on electrochemical energy storage in employing graphene-based composites; however, of which have been usually produced on a laboratory scale with a limited compatibility with future industrialization. Herein a facile, cheap, and scalable sonochemical method was developed to prepare MnO2/graphene composite electrodes for supercapacitors. Petal-like MnO2 arrays were densely grown on the surface of graphene oxide followed by annealing at 220 °C under an air atmosphere. The as-fabricated MnO2/graphene hierarchical composite electrodes deliver 292.9 and 156.1 F/g at 5 and 100 mV/s, respectively, showing higher specific capacitance and better rate capability compared to the MnO2 electrode. An excellent cyclability with a capacitance retention as high as 91.5% was also achieved for the composite electrodes after running 1000 cycles. Such excellent electrochemical performances are ascribed to the robust composite structure and synergetic contribution from petal-like MnO2 arrays and conductive graphene sheets.
  • Microwave-assisted synthesis of europium(III) oxide decorated reduced
           graphene oxide nanocomposite for detection of chloramphenicol in food
    • Abstract: Publication date: Available online 17 October 2018Source: Composites Part B: EngineeringAuthor(s): Rajaji Umamaheswari, Shaktivel Manavalan, Shen-Ming Chen, Mani Govindasamy, Tse-Wei Chen, T. Maiyalagan Herein, we describe an amperometric sensor for chloramphenicol (CAP) by using Eu2O3 nanoparticles decorated reduced graphene oxide. A simple microwave-assisted synthetical route was employed to prepare Eu2O3 NPs@RGO. it's structure and properties were characterized by x-ray diffraction pattern, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Field emission scanning electron microscope, High resolution transmission electron microscope. The electrical conductivity and cyclic voltammetry studies indicated the Eu2O3 NPs@RGO modified electrode exhibited the best performance electrocatalytic sensing of CAP. An amperometric CAP sensor was found to be good sensitive and reproducible which able to detect concentration as low as 1.32 nM. The fabricated sensor worked well even applied in honey and fresh milk samples with appreciable recovery.
  • Size-dependent analysis of FG microplates with temperature-dependent
           material properties using modified strain gradient theory and isogeometric
    • Abstract: Publication date: Available online 17 October 2018Source: Composites Part B: EngineeringAuthor(s): Amir Farzam, Behrooz Hassani This paper investigates the static bending and buckling behaviors of functionally graded microplates under mechanical and thermal loads by using isogeometric analysis (IGA) and modified strain gradient theory (MSGT). The material properties are assumed to be temperature-dependent and three different temperature rise patterns including uniform, linear and non-linear are considered. The material properties vary through the plate thickness based on the rule of mixture scheme. A refined hyperbolic shear deformation theory with four independent unknowns is used for analysis, which doesn't need a shear factor correction. For analysis the IGA using B-Spline or Non-Uniform Rational B-Spline (NURBS) functions can easily meet the C2 continuity requirement. Various parameters are dealt with including power index, material length scale parameter, temperature rise patterns and material combination. The MSGT results are also compared with those obtained by modified couple stress and classical theories. The obtained results indicate that the two studied types of functionally graded microplates show different behaviors under thermal load and the type of functionally graded material is an important factor for thermal analysis.
  • Modeling and analysis of composite laminates in the presence of
    • Abstract: Publication date: Available online 17 October 2018Source: Composites Part B: EngineeringAuthor(s): Mashhour A. Alazwari, Singiresu S. Rao The basic or primitive parameters of composite laminates, such as the constituent materials properties, the thickness of each ply, the ply orientations and the applied loads, exhibit variabilities, hence, the response of the laminated composites also exhibits some degree of variability. Thus, the accuracy and reliability of the laminates cannot be assured if the variabilities present in the basic parameters are ignored. In the past decades, the probabilistic approach has been used widely to simulate the uncertainties in the macromechanics of composite laminates. However, the exact probability distributions of the primitive parameters are not known in most of the applications. This work, for the first time, models the uncertainties in the macromechanics of composite laminates using the interval analysis and the universal grey system theory by representing the primitive parameters as intervals. Also, for comparison, a probabilistic approach is presented with plus/minus three standard deviations about the mean of the response. Due to the so-called dependency problem, the interval analysis predicts wider and inaccurate ranges. Thus, a truncation-based interval analysis procedure with a suitable truncation parameter is used to overcome the limitation associated with the original interval analysis. Specifically, in this work, the uncertainties in the in-plane and flexural engineering constants and laminae stresses are studied. The environmental effects on the laminae stresses are also investigated. Numerical examples are presented to demonstrate the application of the three interval-based uncertainty methods for the behavior of composite laminates by considering different stacking sequences of graphite/epoxy and glass/epoxy laminates.
  • Frequency-dependent forced vibration analysis of nanocomposite sandwich
           plate under thermo-mechanical loads
    • Abstract: Publication date: Available online 17 October 2018Source: Composites Part B: EngineeringAuthor(s): Babak Safaei, Rasool Moradi-Dastjerdi, Zhaoye Qin, Fulei Chu In this paper, the effect of loading frequency on the dynamic behavior of nanocomposite sandwich plates under periodic thermo-mechanical loadings has been investigated. The utilized sandwich plates are made of an isotropic polymer material and two symmetric face sheets reinforced by functionally graded (FG) distributions of carbon nanotube (CNT) agglomerations. In addition to periodic mechanical loads, these structures are also subjected to thermal gradient loads. Steady state response of the plates under thermal gradient load was assumed like a pre-stress for dynamic equations in conducting timeline vibrations of the structure. The material properties of polymeric matrix and CNTs were assumed to be temperature-dependent and the overall material properties of nanocomposites were estimated using Eshelby-Mori-Tanaka's approach. In order to achieve accurate results, a mesh-free method based on higher order shear deformation theory (HSDT) was utilized. The effects of mechanical loading frequency and thermal gradient load as well as CNTs cluster characterizations, essential boundary conditions and elastic foundation on forced vibration, resonance and phenomenon of beats behaviors were investigated. It was observed that thermal gradient loads and the formation of CNT agglomerations have significant effects on the amplitudes of vibrations in nanocomposite sandwich plates.
  • A thermomechanical model of multi-shape memory effect for amorphous
           polymer with tunable segment compositions
    • Abstract: Publication date: Available online 17 October 2018Source: Composites Part B: EngineeringAuthor(s): Xiaodong Wang, Haibao Lu, Xiaojuan Shi, Kai Yu, Yong Qing Fu Multi-shape memory effect (multi-SME) in amorphous polymers has attracted great attention due to their complex thermal transitions and multi-step recovery behavior. Many experimental studies have been reported for synthesis, characterization, testing and demonstration of the multi-SME. However, theoretical approaches have seldom been applied although they are critically needed to understand the principles and predict the behavior of the multi-SME in various amorphous polymers. In this study, a new thermomechanical model was proposed to describe the thermo-/chemo-responsive multi-SME of amorphous polymers with tunable segment compositions. Based on the Weibull statistical model, a new constitutive framework was established to describe temperature-, stretch ratio- and strain-dependent behaviors of thermo-/chemo-responsive multi-SME. Finally, this newly proposed model was applied to quantitatively identify the crucial factors for the thermo-/chemo-responsive shape recovery behaviors, which have been verified by the reported experimental data.
  • Impact-induced nonlinear damped vibration of fabric membrane structure:
           Theory, analysis, experiment and parametric study
    • Abstract: Publication date: 15 February 2019Source: Composites Part B: Engineering, Volume 159Author(s): Changjiang Liu, Xiaowei Deng, Jian Liu, Zhoulian Zheng Fabric membrane, a typical composite material, is widely applied in building structures, agricultural facilities, packaging engineering, and aeronautical engineering, etc. However, it may fail subject to large-amplitude vibration induced by impact due to its lightweight and small stiffness properties. Herein, the nonlinear damped vibration of a pretensioned rectangular orthotropic membrane structure under impact loading is studied by analytical, numerical and experimental methods. The governing equation is derived based on the von Kármán large deflection theory, and the analytical solution is obtained by the Bubnov-Galerkin method and the Krylov-Bogolubov-Mitropolsky (KBM) perturbation method. Meanwhile, the numerical and experimental analysis are carried out for validation of analytical model and good agreement is achieved. Furthermore, parametric study is also performed to find the sensitivity of the design parameters to the vibration response. The results obtained in the paper lay solid foundation for the vibration control and dynamic design of orthotropic membrane structures.
  • Reinforcement and workability aspects of graphene-oxide-reinforced cement
    • Abstract: Publication date: Available online 16 October 2018Source: Composites Part B: EngineeringAuthor(s): Matan Birenboim, Roey Nadiv, Amr Alatawna, Matat Buzaglo, Gal Schahar, Jounghoon Lee, Gunsoo Kim, Alva Peled, Oren Regev We explored the mechanical and the rheological properties of cement reinforced with graphene oxide (GO) in the presence of a superplasticizer. The GO enhanced the compressive and flexural strengths of the cement matrix by 40% and 70%, respectively, at extremely low GO concentrations (
  • Optimization of the pore structure of PAN-based carbon fibers for enhanced
           supercapacitor performances via electrospinning
    • Abstract: Publication date: Available online 16 October 2018Source: Composites Part B: EngineeringAuthor(s): Young-Jung Heo, Hyo In Lee, Ji Won Lee, Mira Park, Kyong Yop Rhee, Soo-Jin Park Activated microporous polyacrylonitrile-based carbon nanofibers (APCFs) were synthesized by a sequential process of electrospinning, carbonization, and KOH activation. The porosity and surface chemistry of the APCFs strongly depended on the activation temperature. The specific surface area and pore volume varied from 15 to 1886 m2 g−1 and 0.021–1.196 cm3 g−1, respectively, as the activation temperature increased; this was accompanied by morphology changes at high temperature. The dominant microstructure and minor mesostructure improved the capacitance of carbon. Compared to the other samples, APCFs activated at an optimum temperature of 1000 °C showed the highest specific capacitance of 103.01 F g−1 at 1 A g−1 in 1 mol L−1 Na2SO4 aqueous electrolyte, and an excellent cycling durability up to 3000 cycles. The improved electrochemical efficiency could be explained by the high specific surface area, suitable pore size, and influence of heteroatoms relative to the increased electrical double-layers. The change in the pore size distribution with activation temperature is also discussed in detail.
  • Graphene oxide encapsulated 3D porous chalcopyrite (CuFeS2) nanocomposite
           as an emerging electrocatalyst for agro-hazardous (methyl paraoxon)
           detection in vegetables
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Umamaheswari Rajaji, Keerthi Murugan, Shen-Ming Chen, Mani Govindasamy, Tse-Wei Chen, Pei Hung Lin, P. Lakshmi prabha Methyl paraoxon (MOX) is a highly toxic organophosphate pesticide. It is recently reported that, MOX can enter the human body through ingestion, inhalation, or by dermal penetration. Due to its high non-degradability, it can bind to the tissues of fruits and vegetables. When it is consumed, it can imposes sub-chronic and chronic diseases, by the inhibition of acetylcholinesterase in human metabolism. Therefore, for the first time, we reported a detection of non-enzymatic electrochemical sensor based on 3D porous phase graphene oxide sheets encapsulated chalcopyrite (GOS@CuFeS2) nanocomposite. Hence, the development of reliable sensors for the real-time detection of pesticides is imperative to overcome practical limitations encountered in conventional methodologies. As synthesized GOS@CuFeS2 nanocomposite film screen-printed carbon modified electrode (SPCE) displays excellent electrocatalytic ability towards MOX. Under optimized working conditions, the modified electrode provides linear response range from 0.073 to 801.5 μM. The detection limit was obtained as 4.5 nM. The sensor displayed outstanding sensitivity as 17.97 μA μM−1 cm−2. This composite could be a promising electrode modifier for electrocatalysis. Finally, the GOS@CuFeS2 nanocomposite modified electrode shows greater real-time practicality in vegetable real samples. The obtained moral parameters from the developed method were compared with the authenticated HPLC results.
  • Loading rate and temperature dependence of flexural behavior in
           injection-molded glass fiber reinforced polypropylene composites
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Lichao Yu, Yan Ma This paper is concerned with the influence of loading rate/temperature and frequency/temperature on static flexural behavior and dynamic mechanical properties of injection molded glass fiber reinforced polypropylene (GFPP) composites, respectively. Furthermore, the mechanism of long-term durability of PP and GFPP was investigated by the master curve of storage modulus constructed based on the Time-Temperature-Superposition (TTSP) method. Three-point bending tests at various loading rates/temperatures and dynamic mechanical analysis (DMA) at various frequencies/temperatures are performed. The time-temperature dependence of static flexural properties (modulus, E, and strength, σ) and dynamic properties (storage modulus, E’) in PP and GFPP is discussed. The results show that both static flexural behavior and dynamic mechanical behavior of PP and GFPP have significant time-temperature dependent phenomenon, which conforms to the time-temperature equivalence principle. The long-term durability of GFPP depends on the matrix resin rather than the GF reinforcement and its interface at temperatures above the glass transition temperature (Tg).
  • Dynamically vulcanized PP/EPDM blends with balanced stiffness and
           toughness via in-situ compatibilization of MAA and excess ZnO
           nanoparticles: Preparation, structure and properties
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Chuanhui Xu, Zhongjie Zheng, Wenchao Wu, Zhiwei Wang, Lihua Fu It is a challenge to simultaneously improve the stiffness and toughness of polymer blends due to that the stiffness and toughness are two mutually exclusive attributes. In this paper, we successfully prepared dynamically vulcanized polypropylene/ethylene-propylene-diene rubber (PP/EPDM) blends with balanced stiffness and toughness through in-situ compatibilization of in-situ formed zinc dimethacrylate (i-ZDMA). The i-ZDMA came from the neutralization of methacrylic acid (MAA) and excess zinc oxide (ZnO) nanoparticles. With i-ZDMA, strong PP/EPDM interface and size reduction of EPDM particles were achieved during peroxide-induced dynamic vulcanization. The average size of EPDM particles was reduced to 260–280 nm, which significantly enlarged PP/EPDM interfacial surfaces. At the same time, the residual excess ZnO nanoparticles migrated into PP phase and served as nucleating agents to increase the crystallinity of PP phase. When the MAA/ZnO reached 2/1.3, the Izod impact strength was increased to 80.1 kJ/m2, nearly 1.6 times that of the blend without i-ZDMA and 22 times that of neat PP, while the Young's modulus and yield stress were increased to 373 MPa and 14.8 MPa, respectively, showing an improved rigidness of blend.
  • Synergistic delamination toughening of composites using multi-scale carbon
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Anil R. Ravindran, Raj B. Ladani, Chun H. Wang, Adrian P. Mouritz Multi-scale toughening is a key strategy employed by biological systems, made of intrinsically brittle constituents, to achieve high damage tolerance. This paper presents an investigation of the synergistic enhancements to the mode I interlaminar fracture toughness of fibre-polymer composite laminates using multi-scale carbon reinforcements. By combining carbon nanofibres (CNFs) dispersed in the matrix and z-pins in the laminate thickness at various contents, an extra mechanism of energy dissipation occurs. This additional mechanism synergistically improves the laminate's resistance to delamination growth under mode I loading. Addition of the nanofibres in the matrix increases the interfacial strength and frictional energy dissipation during z-pin pull-out, thus generating a greater-than-additive toughening effect that would not have existed should either the nanofibres or the z-pins been deployed alone. The results reveal that the magnitude of the synergistic toughening effect was dependent on the volume fraction and combinations of CNFs and z-pins used; where synergy values ranged between 24 and 69% over the expected additive toughness value. A numerical model was developed to successfully predict the crack growth resistance and the synergistic toughening effect with filler content of the multi-scale composites.
  • Investigation of mechanical performance of 3D woven spacer sandwich
           composites with different cell geometries
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Ghanshyam Neje, Bijoya Kumar Behera In this research, woven spacer fabrics with woven cross-links and having different cell geometries viz. rectangular, trapezoidal and triangular were produced, along with one spacer structure connected with core piles which were subsequently converted to their composite forms using vacuum assisted resin infusion molding (VARIM). The sandwich composites produced were analyzed for their quasi-static lateral compression and flexural performance to compare their load bearing capacity and energy absorbency. The rectangular spacer structure with double layer wall construction (RECTDL) sustained maximum specific compressive load among all the structures, followed by spacer structure connected with pile yarns (SPY). For structures with single layer wall constructions, rectangular spacer (RECTSL) had higher specific compressive load compared to triangular (TR) and trapezoidal (TPZ) spacer structures. The energy per unit volume absorbed by these structures was in the order of RECTDL > RECTSL > TR > TPZ. The specific bending load for these structures was in the order of RECTDL > RECTSL > SPY > TR > TPZ structures, and flexural stress for sandwich structures with woven cross-links was higher than the one connected with core piles. These results can be used to engineer woven cross-linked spacer fabric based sandwich composite structures with specific load bearing capability.
  • Toughening of brittle polyester with functionalized halloysite
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): M.T. Albdiry, B.F. Yousif This study presents the role of pristine halloysite nanotubes (HNT) and silane-functionalised halloysite (s-HNT) on toughening mechanisms and initiating plastic deformation in unsaturated polyester (UPE) nanocomposite. The critical stress intensity factor (KIc) and the critical strain energy release rate (GIc) as fracture toughness indications were measured and the relationship between the morphological structures and toughening mechanisms was identified. The results indicated that the fracture toughness values exhibited a steady-state increasing trend with the incorporation of up to 5 wt. % HNT or s-HNT into the UPE resin. The 3% HNT or 3% s-HNT composites were found to obtain the highest toughness values supported with uniformly dispersed particles. The SEM observations showed different energy dissipation mechanisms are; zone shielding and shear yielding with a presence of full particle debonding with the HNT addition; and river line patterns, a tail-like structure and the formation of micro-cracks mechanisms were observed with the addition of s-HNT.
  • Arc erosion behavior of the Al2O3-Cu/(W, Cr)
           electrical contacts
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Xiaohui Zhang, Yi Zhang, Baohong Tian, Junchao An, Zhuan Zhao, Alex A. Volinsky, Yong Liu, Kexing Song Al2O3-Cu/(25)W(5)Cr and Al2O3-Cu/(35)W(5)Cr electrical contact materials were fabricated by vacuum hot-pressing sintering and internal oxidation. The relative density, electrical conductivity, and Brinell hardness were measured. The microstructure was analyzed by scanning electron microscopy and transmission electron microscopy. JF04C electrical contact testing apparatus were used to investigate the electrical contact performance of composites. Arc erosion morphologies were analyzed by scanning electron microscopy and three-dimensional profilometer. The material transfer as well as electrical contact performance were studied during contact make and break operations at 30 V DC with current between 10 and 30 A. It indicates that the nano-Al2O3 particles pinned dislocations. Material transfers from the cathode to the anode. With the melting, evaporation, and sputtering of Cu during arcing, W particles gather and generate needle-shaped skeletons. Finally, liquid droplets, needle-like structures, craters, and bulges were formed on electrode surfaces after arc erosion. Furthermore, their quantity and morphology are affected by tungsten content. When the content of W in the dispersed copper matrix increases from 25 wt% to 35 wt%, welding force is reduced during the steady operations. In addition, when the arc duration is greater than 8.86 ms, the Al2O3-Cu/(35)W(5)Cr contact material has a shorter average arc duration than Al2O3-Cu/(25)W(5)Cr at the same arc energy.Graphical abstractLiquid droplets, needle-like structures, craters, and bulges were formed on the electrode surfaces after arc erosion.Image 1
  • Design and characterisation of cellular composite structures for
           automotive crash-boxes manufactured by out of die ultraviolet cured
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): I. Saenz-Dominguez, I. Tena, A. Esnaola, M. Sarrionandia, J. Torre, J. Aurrekoetxea The present paper analyses the feasibility of designing a honeycomb-like crash-box, as a cellular structure, based on data obtained from the characterisation of the building block. In order to generalise the conclusions of the study, different thicknesses and testing velocities have been analysed. The main conclusion is that, if the same thickness and testing velocity are used, the specific energy absorption (SEA) and peak load values are similar for the building block and the crash-box. Consequently, the design of the complex structure can be validated by simplifying the test procedure. However, special attention must be put on the testing velocity, since the broken fibre percentage is higher in quasi-static conditions. Thus, SEA in quasi-static conditions is higher than in dynamic conditions, 64 kJ/kg and 45 kJ/kg respectively.
  • Preparation of high dielectric constant of lanthanum strontium nickelate
           oxide-resin composites for application in fingerprint recognition
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Tzu Hsuan Chiang, Jhen-Kai Wong, Sideny Huang, Chu-Tsun Wu This study investigates the preparation of a composite material composed of lanthanum strontium nickelate oxide (LSNO) and a resin to be used as fingerprint identification materials. The study showed that the dielectric constants of the composites influence fingerprint discriminability. The highest dielectric constant was 112 at 1 MHz, and the lowest impedance of the composites was obtained from the LSNO powders prepared using La:Sr:Ni of 1:3:1 and subjected to 1200 °C calcining temperature for 1 h. Composites with 50% of the LSNO powders (La:Sr:Ni = 1:3:1) exhibited the highest fingerprint discriminability.Graphical abstractImage 1
  • Amine-assisted synthesis of FeWO4 nanorod g-C3N4 for enhanced visible
           light-driven Z-scheme photocatalysis
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Devi Prashad Ojha, Hem Prakash Karki, Jun Hee Song, Han Joo Kim Highly crystalline FeWO4 nanorods (FWO NRs) were prepared using an amine in a hydrothermal reaction. A photocatalyst active to visible light was designed by preparing 5FWO/g-CN heterostructures via in-situ hydrothermal methods. Fabricated heterostructures were analyzed using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), BET measurements, transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), and Fourier transform spectroscopy (FTIR). The photocatalytic activity toward the degradation of salicylic acid (SA) was investigated under visible light irradiation. The active species trapping experiments showed that the holes, as well as the electrons, exhibited an obvious influence on the photocatalytic degradation process. Examinations of the mechanism showed that the enhanced photocatalytic activity was mainly ascribed to reduced recombination rate and band gap broadening in a Z-scheme mechanism, which enhance the efficient transfer and the oxidation potential of the holes.Graphical abstractImage 1
  • Strain rate effect on mechanical properties of 3D needle-punched C/C
           composites at different temperatures
    • Abstract: Publication date: Available online 15 October 2018Source: Composites Part B: EngineeringAuthor(s): Xiaochao Jin, Cheng Hou, Chunling Li, Xiaobin Wang, Xueling Fan Carbon/carbon (C/C) composites are considered as one of the most promising materials in structural applications owing to their excellent mechanical properties at room and high temperature. Considering their service environments, investigations on the quasi-static and dynamic mechanical properties of C/C composites at different temperatures are of great importance. In this work, the compressive strengths and failure modes of C/C composites under different strain rates and at different temperatures were studied in detail. The experiments were conducted at room temperature and 300 °C with the strain rate controlled over a wide span of 2.08 × 10−4 −1862.09 s−1. Results showed that the failure modes of the C/C composites were obviously influenced by the strain rate and temperature, and the compressive strength of the C/C composites significantly increased with the increase of strain rate or temperature. In addition, relationships between the dimensionless compressive strength and strain rate were first established for C/C composites by using a bilinear fitting algorithm at different temperatures. The results can be conveniently used to predict the compressive strength of C/C composites in engineering applications.
  • Numerical calculation model performance analysis for aluminum alloy
           mortise-and-tenon structural joints used in electric vehicles
    • Abstract: Publication date: Available online 14 October 2018Source: Composites Part B: EngineeringAuthor(s): Huiyuan Xiong, Zhirong Tan, Ronghui Zhang, Zhijian Zong, Zhipeng Luo In this paper, several numerical calculation models for aluminum alloy MT joints are presented through experiments and simulation, which is applied to the joint deformation and failure process, compares with moment-corner curve in the joint deformation process. Besides, the characteristic points are figured out, characteristic double broken line curve and numerical hybrid beam element model are established based on spring element. The results show that finite element model for solid elements is available. The model can simulate joint failure process better. The error is 3.8% during deformation process simulation. For numerical model based on mixed spring beam element, its calculation speed is 530 times faster than that of the solid element model, but its error is 5.1%. It guarantees calculation accuracy and greatly improves the calculation speed. The two models provide a theoretical basis for such metallic composite material structures used in electric vehicles based on characteristic analysis, framework and overall structure design. It is also give a useful reference to other metallic composite material design and calculation.
  • Evolution of mechanical properties of steel fiber-reinforced rubberized
           concrete (FR-RC)
    • Abstract: Publication date: Available online 14 October 2018Source: Composites Part B: EngineeringAuthor(s): Chuanqing Fu, Hailong Ye, Kejin Wang, Kaiqi Zhu, Caiyi He In this work, the evolution of strength (compressive, tensile, and flexural) and toughness of steel fiber-reinforced rubberized concrete (FR-RC) with various fiber dosages and rubber contents was studied. The toughness of FR-RC was investigated using both four-point bending unnotched beams and three-point bending of notched beams. The toughness characteristics were quantified using toughness indexes proposed in ASTM C1018 and doubleK fracture model. The results show that the compressive strength of FR-RC is dependent on both rubber content and fiber dosage, while the flexural and tensile strengths are dominated by the fiber dosage. Although steel fiber can slightly increase the modulus of elasticity of FR-RC, it is mainly controlled by the rubber content. In addition, the first peak strength of FR-RC is influenced by both rubber and steel fiber inclusion, which is in agreement with its strength development. The steel fiber controls the straining hardening and softening behaviors of FR-RC. According to the double-K fracture model, it is found that the rubber content dominates the initial fracture toughness, while the steel fiber dominates the unstable fracture toughness.
  • Lightweight, high electrical and thermal conducting carbon-rGO composites
           foam for superior electromagnetic interference shielding
    • Abstract: Publication date: Available online 14 October 2018Source: Composites Part B: EngineeringAuthor(s): Pinki Rani Agrawal, Rajeev Kumar, Satish Teotia, Saroj Kumari, D.P. Mondal, Sanjay R. Dhakate Lightweight and high strength carbon-rGO composite foams were inventively fabricated by simple sacrificial template technique using reduced graphene oxide (rGO) and phenolic resin as a carbon source. The carbon-rGO composite foams were fabricated by two different routes. In one case, rGO was incorporated in phenolic resin and carbon foam developed by several heat treatments. In the other case, graphene oxide (GO) was decorated over carbon foam and converted into rGO decorated carbon foam by heat treatment. The EMI shielding of carbon-rGO composite foams was measured in the X-band frequency range (8.2–12.4 GHz) and mechanisms were systematically studied with respect to the rGO and porous structure. The EMI SE of carbon foams was increased from −23.2 to −50.7 dB by the decoration of 1.0 wt. % rGO. The thermal conductivity achieves as high as 1.4 W/(m K) by incorporation of 4.0 wt. % rGO in carbon foam. All the results indicated that this effort provided a novel, simple, low-cost concept for fabricating lightweight, high electrical and thermal conducting carbon-rGO composite foam for high-performance EMI shielding applications.Graphical abstractA lightweight carbon-rGO foam composites is fabricated by simple cost effective sacrificial template technique. It is shown that decoration of rGO in phenolic resin based carbon matrix exhibit absorption dominating improved EMI shielding value of −50.7 dB at 2.0 mm thickness in X-band (8.2–12.4 GHz).Image 1
  • High frequency electromagnetic energy phenomena in chiral dielectric
           structures with distributed and localized conductive insertions
    • Abstract: Publication date: Available online 14 October 2018Source: Composites Part B: EngineeringAuthor(s): Romeo Ciobanu, Cristina Schreiner, Radu Damian Chiral dielectric structures with conductive insertions have the tendency to peculiarly concentrate the electromagnetic energy, subject to their specific architecture. The study analyses the associated heating effect at high transmission levels at GHz frequency, for the applications related to electromagnetic shielding. The favorable shielding structure can suffer, in well defined situations, a mechanical stress and/or an acceleration of aging mechanisms.
  • Effect of bagasse ash filled epoxy composites reinforced with hybrid plant
           fibres for mechanical and thermal properties
    • Abstract: Publication date: Available online 14 October 2018Source: Composites Part B: EngineeringAuthor(s): S. Vivek, K. Kanthavel Bagasse ash (BGA) filled bio-composite were developed with the reinforced hybrid natural fibres sisal, flax, banana and kenaf to improve mechanical and thermal properties. The vacuum bag assisted resin transfer method is used to develop hybrid natural fibres reinforced epoxy composites in combination of banana/flax (HBF), banana/kenaf (HBK), sisal/flax (HSF), and sisal/kenaf (HSK). A ball milled BGA of size 350 nm with a combination of 1, 3 and 5 wt% were incorporated in bio-composites to study its effects in thermal and mechanical properties. Characterization of BGA samples for its chemical composition were done through X-ray fluorescence spectroscopy and X-ray diffraction, thermal analysis through thermo-gravimetric and derivative thermo-gravimetric analysis results contemplated the application of BGA-B as filler in epoxy composites. Mechanical testing and thermogravimetric analysis were conducted to ascertain mechanical properties and thermal stability of composites. The significant improvement in flexural, tensile and impact strength was observed for HBF composite filled up to 3 wt% of BGA. Interestingly maximum flexural and tensile strength was observed for HBK composite filled up to 5 wt% of BGA. The enhanced impact strength was determined for HSF and HSK composites filled with 1 wt% of BGA. The highest thermal stability was ascertained for HBK composites filled up to 3 wt% BGA and HSK composites with 5 wt% BGA. Morphological analysis was performed to study the fractured surface of the specimen using a scanning electron microscope.
  • Stochastic low-velocity impact on functionally graded plates:
           Probabilistic and non-probabilistic uncertainty quantification
    • Abstract: Publication date: Available online 28 September 2018Source: Composites Part B: EngineeringAuthor(s): P.K. Karsh, T. Mukhopadhyay, S. Dey This paper quantifies the compound effect of source-uncertainties on low-velocity impact of functionally graded material (FGM) plates following a coupled surrogate based finite element simulation approach. The power law is employed to evaluate the material properties of FGM plate at different points, while the modified Hertzian contact law is implemented to determine the contact force and other parameters in a stochastic framework. The time dependent equations are solved by Newmark's time integration scheme. Insightful results are presented by investigating the effects of degree of stochasticity, oblique impact angle, thickness of plate, temperature, power law index, and initial velocity of impactor following both probabilistic and non-probabilistic approaches along with in-depth deterministic analyses. A detail probabilistic analysis leading to complete probabilistic characterization of the structural responses can be carried out when the statistical distribution of the stochastic input parameters are available. However, in many cases concerning FGM, these statistical distributions may remain unavailable due to the restriction of performing large number of experiments. In such situations, a fuzzy-based non-probabilistic approach could be appropriate to characterize the effect of uncertainty. A surrogate based approach based on artificial neural network coupled with the finite element model for low-velocity impact analysis of FGM plates is developed for achieving computational efficiency. The numerical results reveal that the low-velocity impact on FGM plates is significantly influenced by the effect of inevitable source-uncertainty associated with the stochastic system parameters, whereby the importance of adopting an inclusive design paradigm considering the effect of source-uncertainties in the impact analysis is established.
  • 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.
  • Durability of adhesively bonded joints between pultruded GFRP adherends
           under hygrothermal and natural ageing
    • Abstract: Publication date: Available online 23 September 2018Source: Composites Part B: EngineeringAuthor(s): J.M. Sousa, J.R. Correia, J. Gonilha, S. Cabral-Fonseca, J.P. Firmo, T. Keller This paper presents an experimental and numerical study about the durability of adhesively bonded joints between pultruded glass fibre reinforced polymer (GFRP) adherends for civil engineering applications. Single lap joint (SLJ) specimens were manufactured using either epoxy (EP) or polyurethane (PUR) adhesives and exposed to the following hygrothermal and outdoor ageing conditions for up to 730 days: water and salt water immersion at 20 °C and 40 °C, continuous condensation at 40 °C, salt fog spray at 35 °C, and outdoor ageing in Lisbon, Portugal. At predetermined times, the mechanical behaviour of the SLJs was assessed through shear tests, after drying the specimens to constant mass. Results obtained show that hygrothermal ageing detrimentally affected the failure load and stiffness of the SLJs made with both adhesives, although this degradation was balanced to some extent by post-curing effects and the desorption period (recovery after drying). The magnitude of such degradation was not significantly influenced by the immersion media, but was largely affected by temperature. Outdoor ageing did not cause significant changes in terms of stiffness; for both adhesives, failure load presented a moderate increasing trend, with cyclic pattern, reflecting the effects of seasonal changes in weather. For both adhesives, failure always initiated in one of the GFRP adherends, regardless of the ageing process. However, ageing seemed to affect the portion of bond area with either (light) fibre-tear or adhesive failure: in EP-GFRP specimens, the area with adhesive failure (initially null) increased due to ageing, while in PUR-GFRP specimens (significant in unaged joints) it decreased. The final part of the paper presents linear finite element (FE) models of the SLJs exposed to the harsher ageing environment; these models were developed to numerically simulate the mechanical performance of the joints and to assess the evolution of the internal stresses developed in the SLJs due to the effects of hygrothermal ageing in the constituent materials.
  • Nonlocal free and forced vibration of a graded Timoshenko nanobeam resting
           on a nonlinear elastic foundation
    • Abstract: Publication date: Available online 4 September 2018Source: Composites Part B: EngineeringAuthor(s): M. Trabelssi, S. El-Borgi, R. Fernandes, L.-L. Ke The free and forced vibration of a nonlocal Timoshenko graded nanobeam resting on a nonlinear elastic foundation is investigated in this paper. The Timoshenko beam theory along with the von Kármán geometric nonlinearity is formulated while accounting for Eringen's nonlocal elasticity differential model. A power-law distribution is used to model the material distribution along the beam thickness. The equations of motion are derived using Hamilton's principle and then solved analytically using the Method of Multiple Scale (MMS) and numerically using the Differential Quadrature Method (DQM) and the Harmonic Quadrature Method (HQM). The considered boundary conditions include both Hinged-Hinged and Clamped-Clamped. The obtained nonlocal nonlinear frequencies of the nanobeam are first validated based on published analytical results that use linear mode shapes. A frequency response analysis is also conducted utilizing both MMS and DQM. The time discretization in DQM solution is performed using Spectral Method (SPM) and HQM. The primary objective of this study is to investigate the effects of the nonlocal parameter, power-law index, linear and nonlinear stiffnesses of the elastic foundation as well as the boundary conditions on the dynamic response of the nanobeam.
  • A novel method of vibration modes selection for improving accuracy of
           frequency-based damage detection
    • Abstract: Publication date: Available online 30 August 2018Source: Composites Part B: EngineeringAuthor(s): Jingwen Pan, Zhifang Zhang, Jiurong Wu, Karthik Ram Ramakrishnan, Hemant Kumar Singh Frequency-based damage detection techniques have been widely applied to structural health monitoring. By analysing the changes (shifts) in natural frequencies in a structure with and without damage, these techniques solve the inverse problem of determining size and location of damage. In the existing literature, the first few or random modes of frequency shifts are given to the inverse algorithms as inputs in order to predict the damage parameters. These frequency shifts can be either numerical or measured. While the accuracy of prediction in the former (numerical) case has been found to be satisfactory, the use of measured frequencies has often shown large errors. This can be attributed to unavoidable noise in frequencies, including the mismatch between FEM model and real structure, as well as the noise in the measurement itself. Previous research has shown that the noise in frequency will actually be magnified in the discrepancy of frequency shifts, and thus affect the damage prediction accuracy. And moreover, a same level's noise added to different modes of frequency of a damaged case will lead to the different levels of deviation in different modes of frequency shifts. This observation indicates that potentially some modes of frequency shifts are less affected by the noise than others for a given case. However, so far, there has been no studies that attempt to identify particular vibration modes of frequency shifts that are (a) less affected by the noise for all damage cases and (b) result in a more accurate prediction of damage. In this study, a novel concept of Noise Response Rate (NRR) is proposed to evaluate the sensitivity of each mode of the frequency shift to noise. Further, it is shown that selecting the vibration modes with low NRR values improves the prediction accuracy of frequency-based damage detection. The efficacy of NRR is demonstrated through a case study on a composite curved plate compared with the conventional method for damage detection.
  • 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.
  • Preparation and characterization of cellulose nanofibers and nanocrystals
           from liquefied banana pseudo-stem residue
    • Abstract: Publication date: Available online 21 August 2018Source: Composites Part B: EngineeringAuthor(s): Fanrong Meng, Guoqing Wang, Xueyu Du, Zhifen Wang, Shuying Xu, Yucang Zhang This work aimed to extraction of nanocellulose from banana pseudo-stems (BPs) via energy-saving method for reinforcing polymeric matrix materials. BPs was initially subjected to an atmospheric liquefaction process to remove waxes, pectin, hemicellulose and partly lignin. Bleaching treatment was further conducted to eliminate residual lignin and polycondensate in the liquefied residues. Cellulose nanofibers (CNF) were subsequently obtained by a two-stage TEMPO-mediated oxidation and high-intensity ultrasonic treatment. TEMPO-oxidized cellulose (TOC) thus produced were acid hydrolyzed into nanocrystals (CNC). Results show that liquefied residue content as well as its constituent varied with respect to liquefaction time. Scanning electron microscopy (SEM) and fourier transform infrared (FTIR) demonstrate that the progressive removal of non-cellulosic impurities. Results of transmission electron microscopy (TEM) and atomic force microscopy (AFM) exhibit that CNF present a range of 3–5 nm in diameter and 400–500 nm in length, while CNC have average diameter of 2.24 ± 0.57 nm and a length of 125 ± 28 nm. X-ray diffraction (XRD) analysis indicates that the cellulose crystal type of TOC would stay unchanged and the CNCs have a high crystallinity (75%). Thermogravimetric analysis (TGA) was also used to investigate the thermal stability of the residues and nanocelluloses.
  • The static and dynamic analyses of warping included composite exact
           conical helix by mixed FEM
    • Abstract: Publication date: Available online 13 October 2018Source: Composites Part B: EngineeringAuthor(s): Umit N. Aribas, Merve Ermis, Nihal Eratli, Mehmet H. Omurtag The objective of this study is to investigate the combined influence of two important topics on the precision of static and dynamic analyses of non-circular composite helical bars, namely, exact helix geometry and the warping effect. Sometimes a conical helix over logarithmic spiral planar curve is formed by a degenerated plane curve. The most important goal of this study is to determine the range of the geometric parameters in which the degenerated plane curve lacks the precision necessary for the structural analysis of the conical helix compare to using an exact logarithmic spiral function. Another important topic on the precision of the results is the warping of non-circular composite sections. In this study, first, a parametric analysis is carried out in order to determine the maximum influence of warping on the torsional rigidity of non-circular sandwich/composite cross-sections. Then, some benchmark examples are employed to consider the combined influence of the two topics mentioned above. The analysis is performed over a curved mixed finite element formulation based on Timoshenko beam theory by considering the shear influence, rotary inertia and the warping included torsional rigidity. The curved element consists of two nodes and 24° of freedom in total.
  • Effect of moisture exposure and elevated temperatures on impact response
           of Pennisetum purpureum/glass-reinforced epoxy (PGRE) hybrid composites
    • Abstract: Publication date: Available online 12 October 2018Source: Composites Part B: EngineeringAuthor(s): M.J.M. Ridzuan, M.S. Abdul Majid, A. Khasri, K.S. Basaruddin, A.G. Gibson A Pennisetum purpureum/glass-reinforced epoxy (PGRE) hybrid composites was comprehensively characterised to assess its impact response behaviour at room temperature (RT), under moisture exposure, and elevated temperatures. The untreated, 5 and 10% alkali-treated PGRE composites were fabricated using hybridised Pennisetum purpureum/woven E-glass fibres and epoxy resin. An instrumented IMATEK IM10 drop weight impact tester was utilised to characterise the impact responses of the prepared hybrid composites. The specimens were subjected to water exposure for 50, 100, 200, and 400 h and before arranged with a low-velocity impact test. In addition, the tests were repeated at 40, 60, and 80 °C to examine the effects of elevated temperatures. The results indicate that the untreated PGRE composite yielded the highest peak load impact response at all energy levels. The stiffness of the composites found to decrease substantially with increasing temperatures, which increases the absorbed energy and peak deflection causing extensive damage to the specimens.
  • Investigation of wave propagation in piezoelectric helical waveguides with
           the spectral finite element method
    • Abstract: Publication date: Available online 12 October 2018Source: Composites Part B: EngineeringAuthor(s): Yingjing Liang, Yiyi Li, Yijie Liu, Qiang Han, Dianzi Liu The dispersion behaviors of wave propagation in waveguides of piezoelectric helical structures are investigated. By using the tensor analysis in the helical curve coordinate, the general strain − displacement relationship of piezoelectric helix is firstly considered. This paper's formulation is based on the spectral finite element which just requires the discretization of the cross-section with high-order spectral elements. The eigenvalue matrix of the dispersion relationship between wavenumbers and frequencies is obtained. Numerical examples on PZT5A and Ba2NaNb5O15 helical waveguides of a wide range of lay angles are presented. The effects of the piezoelectric on the dispersive properties and the variation tendency of dispersion curves on helix angles are shown. The mechanism of mode separation in piezoelectric helical waveguides is further analyzed through studying waves structures of the flexural modes.
  • Effectiveness of some technical standards for debonding analysis in
           FRP-concrete systems
    • Abstract: Publication date: Available online 12 October 2018Source: Composites Part B: EngineeringAuthor(s): Elisabetta Monaldo, Francesca Nerilli, Giuseppe Vairo Debonding failure is a key issue in strengthening and retrofitting of existing concrete structures via fiber-reinforced polymers (FRP). In this paper, strength models proposed by different technical guidelines for predicting the debonding load and the effective bond length in FRP-concrete systems are consistently summarized and compared. By referring to the recent specialized literature, a wide database of experimental data - collected from debonding tests associated to FRP based on carbon, glass and basalt fibers - is defined and analyzed. As a result, soundness and effectiveness of some available technical indications are critically assessed, by highlighting the influence of both FRP stiffness (mainly related to the fiber type) and FRP application system. Moreover, a least-square-fitting calibration of theoretical predictions with respect to the experimental evidence is proposed and applied, resulting in the definition of a novel set of values for the empirical correction coefficients occurring in the analyzed strength models. Accordingly, proposed results pave the way towards the effective refinement of actual technical standards for debonding analysis in FRP-concrete systems.
  • Enhanced mechanical and electrical properties of super-aligned carbon
           nanotubes reinforced copper by severe plastic deformation
    • Abstract: Publication date: Available online 12 October 2018Source: Composites Part B: EngineeringAuthor(s): Lunqiao Xiong, Jing Shuai, Kangwei Liu, Zecheng Hou, Lin Zhu, Wenzhen Li For conducting materials, achieving both high strength and high electrical conductivity has remained challenging due to the mutual exclusivity between these two properties. Here, we demonstrate the possibility of adjusting dislocation distribution by severe plastic deformation (SPD) at room temperature to improve both mechanical strength and electrical conductivity of super-aligned carbon nanotubes (SACNTs) reinforced copper matrix composites. After rolling, a high tensile strength (470 MPa) combined with a high electrical conductivity (98% IACS) was achieved. Strain hardening, which mainly resulted from dislocation accumulation, is the major strengthening mechanism after rolling. The increase of electrical conductivity of composites is a result of a combined effects of the elongated grains, repressed dislocation generation and regulated dislocations distribution. The formation of ultra-low dislocation density regions in the rolling direction, which can be attributed to the strengthening effect of SACNTs during rolling, provided a much more efficient channel for conducting electrons. Scalable production of composites with high mechanical strength and high electrical conductivity can be achieved by using this method.
  • Free vibration analysis of functionally graded carbon nanotube reinforced
           composite truncated conical panels with general boundary conditions
    • Abstract: Publication date: Available online 12 October 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Kwangnam Choe, Cijun Shuai, Ailun Wang, Qingshan Wang This paper presents the free vibration analysis of functionally graded carbon nanotube reinforced composite truncated conical panels with general boundary conditions for the first time. Based on the modified Fourier series method for the field variables, the Ritz method is employed to obtain the frequency parameters associated with the mode shapes. The truncated conical panels are reinforced by single-walled carbon nanotubes (SWCNTs) which are assumed to be graded through the thickness direction with different types of distributions. The effective material properties of the FG-CNTRC truncated conical panels are estimated through a micromechanical model based on the extended rule of mixture. In the present study, the artificial spring boundary technique is adopted here to implement the general boundary condition. Several examples are given to demonstrate the convergence, accuracy and flexibility of the present method. The effects of the volume fractions of CNTs, distribution type of CNTs, boundary restraint parameters and geometrical parameters on the vibration behavior of the FG-CNTRC truncated conical panels are presented.
  • Shear behavior of a strain hardening cementitious composites
           (SHCC)-Grooved steel composite deck
    • Abstract: Publication date: Available online 11 October 2018Source: Composites Part B: EngineeringAuthor(s): Liqiang Yin, Changwang Yan, Shuguang Liu, Ju Zhang, Mingyang Liang The deterioration and premature failure of an orthotropic steel deck pavement during its service period is a pressing issue. Strain hardening cementitious composites (SHCC) possess an extreme tensile ductility, in the range of 3%–5% (about 300–500 times that of concrete). Using SHCC as a steel deck pavement can enhance the overall stiffness of a deck system. In this paper, an SHCC-grooved steel composite structure is the research object, and the tooth spacing, tooth width, and tooth height are the parameters. The shear behavior of an SHCC-grooved steel composite structure was studied using a compression shear test and the digital image correlation method. The response surface method was used to analyze the significant influence of the test parameters on the shear capacity, and the response model of the shear capacity was established. The calculation formula of the shear capacity of an SHCC-grooved steel composite structure was established based on the theory of the diagonal compression strut. The experimental results show that the cracking of a shear diagonal SHCC leads to the ultimate failure of an SHCC-grooved steel composite structure. The angle between the main crack and the shear load direction ranges from 30 to 45°. The failure process of the composite structure can be divided into 4 stages: linear elasticity, elastic-plastic, slip hardening, and instability failure. The order of the influence of the test parameters on the shear capacity is the tooth spacing > tooth height > tooth width. The response surface model can optimize and predict the shear capacity of the composite structure under different parameters within a certain range. The calculated values of the shear capacity model based on the theory of the diagonal compression strut agree well with the experimental values, and the calculated values are favorable for safety. This research can provide a reference for the shear design of an SHCC-grooved steel composite structure.
  • Improvement in the mechanical properties of carbon and aramid composites
           by fiber surface modification using polydopamine
    • Abstract: Publication date: Available online 11 October 2018Source: Composites Part B: EngineeringAuthor(s): Han Joo Kim, Jun Hee Song To improve the interfacial properties of super fabrics, the effect of surface treatment on the dopamine monomer concentration was investigated. Carbon and aramid composites were manufactured with the same lamination structures using VARTM. The mechanical strength and stiffness of the fiber composite materials with polydopamine surface treatment were investigated. The surface treatment improved the mechanical properties of carbon and aramid fabric composites. The composites showed the highest tensile strength and stiffness at the dopamine and tris(hydroxymethyl) aminomethane (TRIS) concentrations of 1.5 g/L and 40 mM, respectively. For surface treatment with 1 g/L polydopamine and 40 mM TRIS, the bending strength was the best and improved by more than 11%.
  • Analytical approach for global load-slip behaviour of FRP plates
           externally bonded to brittle substrates with anchors
    • Abstract: Publication date: Available online 11 October 2018Source: Composites Part B: EngineeringAuthor(s): A.B. Sturm, P. Visintin, J. Vaculik, D.J. Oehlers, R. Seracino, S.T. Smith A partial interaction procedure is developed for obtaining analytical solutions for the global load-slip behaviour of fibre-reinforced polymer plates adhesively bonded and mechanically anchored to brittle substrates. This is performed by adopting a matrix approach where the slip and slip strain at any point is given by the product of a solution matrix which is a function of: the position; the zone of solution - whether it is elastic, softening or debonding; and a coefficient vector. It is shown that the procedure can be used as a convenient research tool for extracting the material bond properties from standard experimental pull-push tests, or for use in advanced numerical simulations to develop anchorage systems for structures retrofitted with fibre-reinforced polymer (FRP) composites.
  • Tribological characteristics of cast polyamide 6 (PA6G) matrix and their
           composite (PA6G SL) under normal and overload conditions using dynamic
           pin-on-plate system
    • Abstract: Publication date: Available online 10 October 2018Source: Composites Part B: EngineeringAuthor(s): Robert Keresztes, Miklos Odrobina, Rajini Nagarajan, Karthikeyan Subramanian, Gabor Kalacska, Jacob Sukumaran The current study addresses the tribological characteristics of Cast Polyamide 6 (PA 6 G) matrix and its composite filled with polyethylene (PE) solid lubricant (PA 6 G SL). Tribological tests under different contact kinematics (1) traditional pin-on-disc (PoD) and (2) dynamic pin-on-plate (PoP). Tribotests revealed that the PA 6 G SL composite showed increased wear resistance and reduction in heat generation as compared to the virgin PA 6 G matrix. The difference in tribological characteristics was analyzed with respect to morphology (primary and secondary layer) of the transfer layer formed on the counter material. In summary, the solid lubricant alters the tribological process by means of altering the surface response by introducing a limitation in the wear particle generation.
  • An enhanced method to control the residual vibrations of a single-link
           flexible glass fabric reinforced epoxy-glass composite manipulator
    • Abstract: Publication date: Available online 9 October 2018Source: Composites Part B: EngineeringAuthor(s): Şahin Yavuz Lighter manipulators are used due to reducing power consumption and reaching higher speeds for applications. Composite manipulators can be more desirable for this purpose because they are light weight and have high strength. As it is well known that using flexible manipulators causes high amplitude vibrations and this affects the accuracy of end-point positioning. In this study, a single-link flexible glass fabric reinforced epoxy-glass composite manipulator is analyzed in ANSYS and the residual vibrations are controlled with a new method. The finite element vibration analysis is performed and an experimental system is introduced to verify simulation results. [0/90] lay-up and two different velocity profiles are studied for different case studies. An exponential-harmonic velocity excitation is applied after the end of the trapezoidal velocity profile to control the residual vibrations. It is known that the vibration amplitudes of a system decrease when the system is excited at higher frequency than the natural frequencies. The effect of the amplitude, frequency, the duration of the application and the exponential decay factor on the suppression of the residual vibration are analyzed. Both simulation and experimental analyses are performed and the results are in good agreement. It is concluded that the residual vibration amplitudes of the flexible composite manipulator are suppressed with the proposed method up to 99% for all velocity inputs.
  • Mechanical response and microstructure of 2D carbon fiber reinforced CMCs
           containing Cu-Si alloy exposed to fatigue stresses
    • Abstract: Publication date: Available online 9 October 2018Source: Composites Part B: EngineeringAuthor(s): Wei Zhou, Yang Li Microstructures, mechanical properties of reactive melt infiltration (RMI) derived C/C-SiC-Cu3Si composites with plain-weave fiber fabrics as reinforcement before and after exposure to tensile fatigue stresses have been investigated. Results show that C/C-SiC-Cu3Si composites have good resistance with fatigue limit of 65 MPa, about 72% of quasi-static tensile strength of virgin specimens. Moreover, strength enhancement at expense of slightly decreased elastic modulus is observed in post-fatigue specimens during quasi-static loading. Residual tensile strength after fatigue loadings with 65 MPa for 105 cycles increases to 104 MPa, about 15.5% higher than that of virgin specimens. Microstructural analysis regarding to crack density and fractured surface indicates that crack multiplication and propagation together with interfacial debonding as the most pronounced fatigue damages are responsible for the higher strength after fatigue tests.
  • Enhanced rules-of-mixture for natural fibre reinforced polymer
           matrix(NFRP) composites (comment on Lau et al. in volume 136)
    • Abstract: Publication date: Available online 9 October 2018Source: Composites Part B: EngineeringAuthor(s): John Summerscales, Amandeep Singh Virk, Wayne Hall The use of rules-of-mixture to predict the elastic modulus and strength of natural fibre-reinforced composites is often compromised by the fibre properties used in the calculations being derived with an assumption of circular cross-section, when real fibres have polygonal cross-section. A fibre area correction factor (FACF) has been proposed to address this inaccuracy and has been demonstrated to improve the predictions.
  • Bond behaviour of sand coated GFRP bars to concrete at elevated
           temperature – Definition of bond vs. slip relations
    • Abstract: Publication date: Available online 9 October 2018Source: Composites Part B: EngineeringAuthor(s): I.C. Rosa, J.P. Firmo, J.R. Correia, J.A.O. Barros The use of glass fibre reinforced polymer (GFRP) bars as internal reinforcement of concrete structures has been growing, mainly due to the advantages they present over steel reinforcement, namely their low weight, high strength and corrosion resistance. However, at moderately elevated temperatures, especially when approaching the glass transition temperature (Tg) of the polymeric matrix (usually between 65 and 150 °C), the stiffness, strength and bond properties of these rebars are known to be significantly degraded. The first part of this paper presents an experimental investigation comprising tensile and pull-out tests on sand coated GFRP rebars at elevated temperatures under steady-state conditions; the tensile tests were carried out up to 300 °C, whereas the pull-out tests were performed up to 140 °C (measured at the GFRP-concrete interface); two embedment lengths of the rebars were considered. The obtained results confirmed that the stiffness and strength of the GFRP-concrete interface are significantly reduced with temperature increase, especially when the Tg of the GFRP rebars is approached and exceeded. In the second part of the paper, analytical bond vs. slip relations for the GFRP-concrete interface are proposed for each of the tested temperatures; the defining parameters of these local laws were calibrated with the experimental data from the pull-out tests. Moreover, the accuracy of two empirical (relaxation) models in predicting the GFRP-concrete bond strength reduction with temperature was also assessed.
  • Synergistic effect of graphene/multiwalled carbon nanotube hybrid fillers
           on mechanical, electrical and EMI shielding properties of
           polycarbonate/ethylene methyl acrylate nanocomposites
    • Abstract: Publication date: Available online 7 October 2018Source: Composites Part B: EngineeringAuthor(s): Nisha Bagotia, Veena Choudhary, D.K. Sharma This paper describes the preparation of polycarbonate/ethylene methyl acrylate (95/5 w/w) nanocomposites using graphene: MWCNT hybrid filler in varying ratios (1:1, 1:3 and 3:1) by melt blending process. The effect of graphene/MWCNT hybrid filler on electrical, mechanical, thermal and electromagnetic interference shielding properties of nanocomposites was investigated. Morphology of these composites was characterized by scanning and transmission electron microscopy. Composites with 10 phr loading of hybrid filler (graphene: MWCNT ratio of 1:3) show the highest tensile strength and tensile modulus as compared to the composites based on graphene or MWCNT at the same loading. The maximum electrical conductivity (1.91 × 10−1 S/cm) was also achieved at a loading of 10 phr of hybrid filler (graphene: MWCNT in the ratio of 1:3), which is higher as compared to the composite prepared using either of the filler alone at the same loading. This significant enhancement in electrical conductivity is responsible to attain up to −34 dB EMI shielding effectiveness in frequency range of 8.2–12.4 GHz (X-band). An increase in mechanical properties, electrical conductivity and EMI shielding for composites having hybrid filler (graphene: MWCNT in ratio 1:3) shows the synergistic effects when such fillers are used in combination.
  • Material optimization of functionally graded plates using deep neural
           network and modified symbiotic organisms search for eigenvalue problems
    • Abstract: Publication date: Available online 5 October 2018Source: Composites Part B: EngineeringAuthor(s): Dieu.T.T. Do, Dongkyu Lee, Jaehong Lee The paper is aimed at improving computational cost enhanced by a new combination of deep neural network (DNN) and modified symbiotic organisms search (mSOS) algorithm for optimal material distribution of functionally graded (FG) plates. The material distribution is described by control points, in which coordinates of these points are located along the plate thickness using B-spline basis functions. In addition, DNN is used as an analysis tool to supersede finite element analysis (FEA). By using DNN, solutions can directly be predicted by an optimal mapping which is defined by learning relationship between input and output data of a dataset in training process. Each of dataset is randomly created from analysis through iterations by using isogeometric analysis (IGA). The mSOS being a robust metaheuristic algorithm is employed to solve two optimization problems: buckling and free vibration with various volume constraints. Moreover, the power of mSOS is verified by comparing to other algorithms in the open literature. Finally, optimal results in all examples generated by the proposed method are compared to those of a combination of IGA and mSOS to demonstrate its effectiveness and robustness.
  • Two-scale constitutive modeling of a lattice core sandwich beam
    • Abstract: Publication date: Available online 5 October 2018Source: Composites Part B: EngineeringAuthor(s): Anssi T. Karttunen, J.N. Reddy, Jani Romanoff Constitutive equations are derived for a 1-D micropolar Timoshenko beam made of a web-core lattice material. First, a web-core unit cell is modeled by discrete classical constituents, i.e., the Euler–Bernoulli beam finite elements (FE). A discrete-to-continuum transformation is applied to the microscale unit cell and its strain energy density is expressed in terms of the macroscale 1-D beam kinematics. Then the constitutive equations for the micropolar web-core beam are derived assuming strain energy equivalence between the microscale unit cell and the macroscale beam. A micropolar beam FE model for static and dynamic problems is developed using a general solution of the beam equilibrium equations. A localization method for the calculation of periodic classical beam responses from micropolar results is given. The 1-D beam model is used in linear bending and vibration problems of 2-D web-core sandwich panels that have flexible joints. Localized 1-D results are shown to be in good agreement with experimental and 2-D FE beam frame results.
  • Experimental study on shear behavior of high strength bolt connection in
           prefabricated steel-concrete composite beam
    • Abstract: Publication date: Available online 5 October 2018Source: Composites Part B: EngineeringAuthor(s): Yujie Zhang, Bingcong Chen, Airong Liu, Yong-lin Pi, Junping Zhang, Yang Wang, Licong Zhong In order to study the shear behavior of high strength bolt connection in prefabricated steel-concrete composite beam, eleven push-out specimens with different parameters were experimented. In the experiments, two failure modes in the specimens were observed. For the specimens with the concrete strength of larger than 50 MPa and the bolt diameter of less than 20 mm, the bolts failed in shear fracture. For the other specimens, the concrete near the bolts crashed with the bolts bending yield failure. The load-slip curves of the connectors had four distinctive stages corresponding to four different loading state of bolts. The shear bearing capacity of the bolted connector was mainly depended on the bolt diameter, the bolt tensile strength and the concrete strength. Finite element models verified by the experimental results were also developed, which were used to conduct parametric analysis for achieving the effect of those parameters involving in the bolt pretension, the bolt diameter, the bolt tensile strength and the compressive strength of concrete, on the failure mode, the load-slip characteristics and the ultimate strength of the bolt connectors. Finally, based on the experiment results and FEA, design formulas for predicting the shear bearing capacity of bolt connections under different failure modes were proposed, which could be referred to guide the design of high strength bolt connections in composite structures.
  • Extracting elastic modulus at different strain rates and temperatures from
           dynamic mechanical analysis data: A study on nanocomposites
    • Abstract: Publication date: Available online 5 October 2018Source: Composites Part B: EngineeringAuthor(s): Xianbo Xu, Chrys Koomson, Mrityunjay Doddamani, Rakesh Kumar Behera, Nikhil Gupta Viscoelastic nature of polymers makes their properties strongly dependent on temperature and strain rate. Characterization of material properties over a wide range of strain rates and temperatures requires an expensive and time consuming experimental campaign. While viscoelastic properties of materials are widely tested using dynamic mechanical analysis (DMA) method, the frequency dependent component of the measured properties is underutilized due to a lack of correlation between frequency, temperature, and strain rate. The present work develops a method that can extract elastic modulus over a range of strain rates and temperatures from the DMA data for nanocomposites. Carbon nanofiber (CNF) reinforced high-density polyethylene (HDPE) matrix nanocomposites are taken as the study material. Four different compositions of CNF/HDPE nanocomposites are tested using DMA from 40 to 120 °C at 1–100 Hz frequency. First, time-temperature superposition (TTS) principle is used to develop an extrapolation for the results beyond the test parameter range. Then the TTS curve is transformed to a time domain relaxation function using integral relations of viscoelasticity. Finally, the strain rate sensitive elastic modulus is extracted and extrapolated to room temperature. The transform results are validated with tensile test results and the error found to be below 13.4% in the strain rate range 10−5 to 10−3 for all four nanocomposites. Since, the materials are tested with the aim of finding a correlation among the test methods, the quality of the material is not a study parameter and the transform should yield accurate results for any material regardless of composition and quality.
  • Performance study of ultrasonic assisted processing of CNT
           nanopaper/solventless epoxy composite
    • Abstract: Publication date: Available online 5 October 2018Source: Composites Part B: EngineeringAuthor(s): Dan Zhang, Maria G. Villarreal, Eusebio Cabrera, Avraham Benatar, L. James Lee, Jose M. Castro This work presents an innovative ultrasonic-assisted process for the fast infiltration of solventless epoxy into carbon nanotube (CNT) nanopaper (NP) (50 μm thick thin film) to fabricate prepregs and composites. The effect of process parameters including: ultrasonic time (infiltration time), ultrasonic amplitude, pressure, and mold temperature on the resin impregnation quality and composite mechanical properties were evaluated. Nanopapers made of multi wall carbon nanotube (MWNT) or single wall carbon nanotube (SWNT) were used in this work. Homogeneous resin impregnation was achieved in the MWNT NP/epoxy composite with 30.5 wt. % MWNT loading. For coating applications, the MWNT NP/epoxy composite showed 167% improvement in sand erosion resistance compared to glass fiber/epoxy composite. NPs with different MWNT wt. % and SWNT wt. % were fabricated. Although non-uniform resin impregnation was observed in SWNT NP/epoxy composites, there was still 142% improvement in tensile strength compared to pure epoxy due to the rigid SWNT NP structure. The EMI shielding of SWNT NP reached 57 dB, which was higher than commercial carbon fiber preform (51 dB). The CNT NP/epoxy composites offer multi-functional properties, and demonstrate promising coating applications in wind energy, automotive and sporting goods industries.
  • Preparation and characterization of carbon black/pitch-based carbon fiber
           paper composites for gas diffusion layers
    • Abstract: Publication date: Available online 4 October 2018Source: Composites Part B: EngineeringAuthor(s): Young-Jung Heo, Mira Park, Woo-Seok Kang, Kyong Yop Rhee, Soo-Jin Park We prepared carbon Ketjenblack (KB)/carbon fiber papers (CFPs) from pitch-based carbon fibers (CFs) by web-laid processing, and the electrical conductivity and mechanical properties of the CFPs were investigated according to the structure and morphology of the CFs by the addition of KB as a conductive filler at different carbonization temperatures. The wet-laid processing fabrication method for CFPs consisted of four steps: dispersion of CFs, preparation of a CF web, impregnation of phenol resin, and heat treatment. The results showed that the electrical resistance and tensile strength of the CFPs were low at high-heat-treatment temperatures. Notably, CFPs with a thickness of 190 μm, porosities of 86.7%, and specific resistance of 7.795 × 10−2 Ω cm were obtained by after adding 6 wt.% of KB at a carbonization temperature of 800 °C.
  • On the validity of LEFM methods to investigate the fracture behavior of
           angle-ply laminates
    • Abstract: Publication date: Available online 4 October 2018Source: Composites Part B: EngineeringAuthor(s): A.R. Shahani, R. Abolfathitabar, H. Shooshtar In this research, an experimental characterization of the interlaminar fracture behavior of unidirectional and multidirectional glass/epoxy laminates is presented under pure mode I loading. The delamination growth resistance curves are obtained by means of two different data reduction methods based on the LEFM and the J-integral approaches. The J-integral approach has great advantages over the standard LEFM approach. It removes the need for measurement of the delamination length. Moreover, it is not subjected to the strictly limited scope of LEFM, the validity of which is not guaranteed in the presence of damage mechanisms. This might be a great concern for multidirectional laminates where distributed damage in the form of matrix cracking is usually anticipated. The current standards do not provide any validity criteria for LEFM assumptions in multidirectional laminates. Any way, these data are often reduced with common standard methods. In this study it has been shown that the LEFM method provides comparable results with the J-based one for unidirectional laminates. However, it may grossly underestimate the fracture resistance of multidirectional laminates.
  • Wave propagation in piezoelectric cylindrical composite shells reinforced
           with angled and randomly oriented carbon nanotubes
    • Abstract: Publication date: Available online 4 October 2018Source: Composites Part B: EngineeringAuthor(s): Hossein Kh. Bisheh, Nan Wu Wave propagation behavior in piezoelectric cylindrical composite shells reinforced with angled and randomly oriented, straight carbon nanotubes (CNTs) is analytically investigated for the first time via the first-order shear deformation shell theory including the transverse shear effects and rotary inertia. The Mori-Tanaka method is used for micromechanical modeling. Dispersion solutions are computed by solving an eigenvalue problem. The effects of CNT orientation, CNT volume fraction, and shell geometry on the dispersion solutions are examined. Various orientations of CNTs lead to different dispersion behaviors; the variation of wave phase velocities is more significant at lower axial wave numbers; and the effects of CNT volume fraction and shell geometry on wave dispersion behaviors are more obvious at higher circumferential wave numbers. The presented model and analytical results of this study can be utilized in the wave propagation analysis of piezoelectric shells reinforced with CNTs for the design of new smart structures used in structural health monitoring and/or energy harvesting applications.
  • Dynamics analysis of functionally graded porous (FGP) circular, annular
           and sector plates with general elastic restraints
    • Abstract: Publication date: 15 February 2019Source: Composites Part B: Engineering, Volume 159Author(s): Jing Zhao, Fei Xie, Ailun Wang, Cijun Shuai, Jinyuan Tang, Qingshan Wang In this paper, the dynamics analysis of functionally graded porous (FGP) circular, annular and sector plates with general elastic restraints is performed in a unified form for the first time. The overall theoretical model is based on the first order shear deformation theory. The kinetic energy and potential energy function of the plates are unified representation of five kinds of displacement admissible function. Then, each of displacement admissible function is expanded as a modified Fourier series to obtain general elastic restraints. Lastly, the solutions are obtained by using the variational operation. The convergence and accuracy of the present modeling are validated by comparing its results with those available in the literature and FEM results. Based on that, a series of innovative results are also highlighted in the text, which may be as the basic data for other algorithm research in the future.
  • Strain rate effects on the compressive and tensile behavior of bundle-type
           polyamide fiber-reinforced cementitious composites
    • Abstract: Publication date: Available online 3 October 2018Source: Composites Part B: EngineeringAuthor(s): Hongseop Kim, Gyuyong Kim, Sangkyu Lee, Minjae Son, Gyeongcheol Choe, Jeongsoo Nam The compressive and tensile behavior of fiber-reinforced cementitious composites is significantly affected by the bonding and pull-out properties between matrix and reinforced fiber, as well as the fracture properties of the fibers. In addition, an increase in strain rate according to loading conditions influences the fracture behavior between the fiber and matrix. Steel fiber-reinforced cementitious composites with high flexural and tensile strength, toughness, and crack resistance are widely used in tunnels and plant structures. However, the high specific gravity and stiffness of steel fibers can cause rupture of concrete pump tubes, increase the rebound volume of shotcrete, and decrease durability by corrosion of fiber. Therefore, it is necessary to study the development and application of organic fiber which has similar mechanical properties to steel fiber and does not cause corrosion. In this study, polyamide fibers having the same aspect ratio as the hooked steel fibers, which are widely used as reinforcing fibers for concrete, have been developed. And strain rate effect on the compressive and tensile behaviors of bundle-type polyamide fiber-reinforced cementitious composite and hooked steel fiber-reinforced cementitious composite were evaluated. The results showed that the effect of strain rate over different fiber types influenced the tensile behavior more significantly than the compressive behavior. In polyamide fiber-reinforced cementitious composite (PAFRCC), a fracture behavior of fiber was observed regardless of a strain rate, and the tensile behavior of PAFRCC was influenced more by tensile strength of polyamide fiber itself than a bonding stress between fiber and matrix. In hooked steel fiber-reinforced cementitious composite (HSFRCC), a bonding stress between hooked steel fiber and matrix (frictional force at the interface between fiber and matrix, mechanical bond of the hooked part) influenced the tensile behavior significantly. Fracture properties that straightened pulled out the fiber from the matrix were observed at static tensile loading condition. However, non-straightened hooked steel fiber was observed along with the fracture of matrix due to an increase in mechanical bonding force of the hooked part and the bonding stress between the fiber and the matrix.
  • High temperature resistant polyimide/boron carbide composites for neutron
           radiation shielding
    • Abstract: Publication date: Available online 3 October 2018Source: Composites Part B: EngineeringAuthor(s): Xiaomin Li, Juying Wu, Changyu Tang, Zhoukun He, Ping Yuan, Yong Sun, Woon-ming Lau, Kai Zhang, Jun Mei, Yuhong Huang Boron carbide (B4C) is an important type of neutron radiation shielding material with relatively high efficiency due to the high content of 10B element. Incorporation of B4C particles into polymer to prepare high-performance neutron radiation shielding material has become more and more important for the safe operation of nuclear power in the defense industry and nuclear power plant. The polyimide/B4C composite films with different micro-sized B4C contents were successfully prepared by in-situ polymerization. Silane coupling agent KH550 was employed to functionalize B4C particles to improve the dispersion of B4C particles in the polyimide matrix with strengthened interfacial interaction. As shown that the micro-sized B4C functional particles can be well dispersed in the BPDA/ODA polyimide matrix. With the B4C content increase, thermal stability of the polyimide/B4C composite films can be significantly improved, even mechanical properties partly declined. Meanwhile, the polyimide/B4C composite films exhibit good thermal neutron radiation shielding properties. The neutron permeability I/I0 changes exponentially with the change of B4C content. When the B4C content is increased to 30 wt%, the polyimide/B4C composite films show optimum properties combination with thermal decomposition temperature (Td10) of 622 °C, neutron permeability (I/I0) of 0.24 (800 μm in thickness), and tensile strength of 406 MPa. The composite thus shows great potential for use in applications which require materials with high thermal stability and neutron radiation shielding ability, such as fusion reactor system and nuclear waste disposal.
  • Self-polarized electrospun polyvinylidene fluoride (PVDF) nanofiber for
           sensing applications
    • Abstract: Publication date: Available online 3 October 2018Source: Composites Part B: EngineeringAuthor(s): Ehsan Ghafari, Na Lu This study aimed at synthesizing a self-polarized electrospun PVDF which eliminates a need for the post treatment process. In addition, the feasibility of using an electrospun PVDF sensor for both active and passive sensing applications has been studied. The pitch-catch approach was considered for an active sensing approach while an acoustic emission monitoring was used as a passive method. Moreover, the experimental program involved studying the several parameters such as the transmitted signal amplitude, frequency and the distance on the received signal by PVDF sensor. The PVDF sensor was found to be effective in detecting the pulsed and continuous generated Lamb wave. The results indicate that the PVDF device is efficient in detecting the transmitted signal from 1-100 kHz, but less efficient either at a low-frequency range (100 kHz). The results clearly indicate that the sensor can detect different magnitudes of surface acoustic waves propagating on the surface.Graphical abstractImage 1
  • Realization of self-poled, high performance, flexible piezoelectric energy
           harvester by employing PDMS-rGO as sandwich layer between
           P(VDF-TrFE)-PMN-PT composite sheets
    • Abstract: Publication date: Available online 2 October 2018Source: Composites Part B: EngineeringAuthor(s): Usman Yaqoob, Rahaman Md Habibur, Muhammad Sheeraz, Hyeon Cheol Kim This study investigates the role of highly charged uniform electrostatic polydimethylsiloxane-reduced graphene oxide (PDMS-rGO) layer in achieving the self-poled piezoelectric energy harvester (PEEH) using P(VDF-TrFE)-PMN-PT composite sheets. To obtain the tri-layer structure the PDMS-rGO layer was sandwiched between two P(VDF-TrFE)-PMN-PT composite sheets using spin coating technique. From the X-ray diffraction pattern it was projected that the highly charged PDMS-rGO layer attracts the dipoles from upper and lower P(VDF-TrFE)-PMN-PT sheets and then facilitates them in aligning in one direction without any external electric field. The output performances of the self-poled tri-layer energy harvester (EH) was observed using finger tapping (∼2.5 N), the maximum open circuit voltage and short circuit current was measured around 8.5 Vpk-pk and 3 μApk-pk, respectively. Furthermore, the as-fabricated self-poled tri-layer energy harvester (EH) reveals the maximum power density of 6.1 μW/cm [2]. Finally, in order to realize its implementation in realistic application, it was attached on the insole of a shoe and on a bicycle. The device reveals good mechanical flexibility and stability during several times walking and running. Finally, our highly flexible, self-poled piezoelectric energy harvester can be a potential candidate for its employment is various futuristic portable electronics.Graphical abstractImage 1
  • Static and cyclic response of low-strength recycled aggregate concrete
           strengthened using fiber-reinforced polymer
    • Abstract: Publication date: Available online 2 October 2018Source: Composites Part B: EngineeringAuthor(s): Pengda Li, Lili Sui, Feng Xing, Yingwu Zhou Concrete production using recycled aggregates (RAs) from construction and demolition waste is known to have a lower strength performance than natural aggregate concrete. Many studies have been carried out to improve the strength properties of recycled aggregate concrete (RAC). One widely accepted strategy is to use fiber-reinforced polymer (FRP) jackets as external confinement material to enhance the compressive strength and ductility performance of RAC, especially in the seismic retrofit of RAC members. Most existing research has focused on normal strength concrete subjected to monotonic loading. However, retrofitting or repair work is more common for concrete structures with low concrete strength. In addition, cyclic behavior research focused on FRP-confined low-strength RAC is also rare due to the lack of sufficient experimental data. In this study, 29 concrete specimens were cast using varying proportions of RAs mixed with natural coarse aggregates. In this case, poor quality natural aggregates were selected to achieve a low concrete strength. Thickness of the carbon FRP (CFRP) jacket, loading types (monotonic or cyclic), and the RAs replacement ratio were the main test parameters of this experimental work. The mechanical properties of CFRP-confined RAC were analyzed and discussed from the failure mode perspective; these included peak strength, ultimate strain, and cyclic stress-strain relationships. Test results show that strength enhancement by FRP confinement was much more pronounced in lower strength RAC than in normal strength concrete, whereas the ductility improvement was almost consistent. Confinement rigidity and recycled aggregate replacement ratio had little effect on cyclic stress-strain behavior, in terms of unloading and reloading paths, as well as in plastic strain. The adhered cement mortar on RAs weakened the impact brought by confinement when repeated unloading and reloading were applied. This was especially true during cyclic loading, which generated a large deformation.
  • A closed form solution for free vibration of orthotropic circular
           cylindrical shells with general boundary conditions
    • Abstract: Publication date: Available online 2 October 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Kwangnam Choe, Yongkang Zhang, Ailun Wang, Chaohui Lin, Qingshan Wang In the past decades, the exact closed form solutions for the free vibration of thin orthotropic circular cylindrical shells have been merely restricted to some classical boundary conditions. Therefore, the target of the current paper is to present a new exact closed form solution for free vibration of orthotropic circular cylindrical shells with general boundary conditions by means of the method of reverberation-ray matrix (MRRM). Based on the Donnell–Mushtari shell theory, the wave solutions are constructed by the exact closed form solutions of the governing differential equations. The artificial spring technology is introduced to achieve the general boundary conditions of two end edges of shell. Hereby, the reverberation ray matrix can be easily obtained by using the MRRM together with the wave solutions, boundary conditions and dual coordinates of the orthotropic circular cylindrical shells. Then, the vibration results are obtained from the extrapolation method and golden section search (GSS) algorithm. By the comparison with other published methods and the finite element method, the accuracy of the present method is verified. On the basis of that, some new exact nature frequencies of the orthotropic circular cylindrical shells with general elastic restraints are shown which can serve as the benchmark data for the future computing method.
  • Three-dimensional exact solution for the free vibration of thick
           functionally graded annular sector plates with arbitrary boundary
    • Abstract: Publication date: Available online 2 October 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Yongkang Zhang, Kwangnam Choe, Xiaofei Qu, Ailun Wang, Qingshan Wang A new three-dimensional exact solution for the free vibrations of arbitrary thick functionally graded annular sector plates with arbitrary boundary conditions is presented. The three-dimensional elasticity theory is employed to formulate the theoretical model. According to a power law distribution of the volume of the constituents, the material properties change continuously through the thickness of the functionally graded annular sector plates. Each of displacements of the annular sector plates, regardless of boundary conditions, is expanded as a three-dimensional (3-D) Fourier cosine series supplemented with closed-form auxiliary functions introduced to eliminate all the relevant discontinuities with the displacements and its derivatives at the edges. Since the displacement fields are constructed adequately smooth throughout the entire solution domain, an exact solution is obtained based on the Ritz procedure by the energy functions of plate. The excellent accuracy and reliability of the current solutions are demonstrated by numerical examples and comparison of the present results with those available in the literature, and numerous new results for thick FG annular sector plates with elastic boundary conditions are presented. The effects of gradient indexes are also illustrated.
  • Structural deformation performance of glass fiber reinforced polymer
           composite beam actuated by embedded indented SMA wires
    • Abstract: Publication date: Available online 2 October 2018Source: Composites Part B: EngineeringAuthor(s): Guoqing Yuan, Yanjie Bai, Zhemin Jia, Kin-tak Lau, Pui-yan Hung Intelligent morphing wings have become a research hotspot due to their potential value. This paper is also an innovative basic research work to study it. The deformation performances of the GFRP(glass fiber reinforced polymer) composite beams embedded different pre-strained indented SMA wires were experimentally and numerically studied. The indentation SMA wire made by mechanical indentation method has better interface bonding strength than normal SMA wire. In this paper, the indented SMA wires acting as actuators, were embedded in a symmetrically GFRP laminated composite beam and located at the eccentric position of the laminate. The layering scheme of the laminated plate is as follows: [90°(4:1 fabric)/SMA/0°/0°/90°(4:1)]. The 0° direction is consistent with the direction of the axis of the SMA wire. The Finite element method is adopted to simulate the deformation of the beam with indented SMA wire in which the linear constitutive model of fully constrained SMA wires, together with considering their thermally-induced strain response, is used to describe the recoverable properties of SMA. The prediction from the numerical simulation agrees well with experimental measurements.
  • Seismic performance of steel plate reinforced high toughness concrete
           coupling beams with different plate ratios
    • Abstract: Publication date: Available online 29 September 2018Source: Composites Part B: EngineeringAuthor(s): Wei Hou, Shilang Xu, Dashuai Ji, Qinghua Li, Pan Zhang Embedded steel plate reinforced concrete (PRC) coupling beams are newly introduced into the family of coupling beams to improve the seismic behavior of reinforced concrete (RC) coupling beams. However, the brittle crush and spalling of concrete in these composite members noticeably reduce their deformation performance and energy-dissipating capacity which largely deteriorate the efficiency of this combination. Considering this noteworthy shortcoming, in this paper the authors propose a novel type of composite coupling beams, which is entitled steel plate reinforced high toughness concrete (PRHTC) coupling beam. This novel member replaces the conventional reinforced concrete with the high toughness concrete (HTC) which is a sort of pseudo strain-hardening cementitious composites exhibiting quasi-ductile behaviors. This study mainly investigates the seismic performance of PRHTC deep coupling beams (span-to-depth ratio, l/h = 1.5) with various steel plate reinforcement ratios. The test results indicate that the PRHTC coupling beams exhibit a ductile flexural failure mechanism with excellent energy dissipation capability. The high toughness concrete in this composite member displays multiple cracking pattern and maintains desirable integrity. All specimens attained high-level ductility factors exceeding 5.5, survived large rotations ranging from 0.064 to 0.078 rad, manifested superior stiffness retention capacity and strength retention capacity. The steel plate ratio ranging from 4.31% to 6.47% is proven to be appropriate and effective for maintaining high ductility and rotation deformability of the PRHTC coupling beams in this paper.
  • Multiscale modeling of the elastic moduli of CNT-reinforced polymers and
           fitting of efficiency parameters for the use of the extended
    • Abstract: Publication date: Available online 28 September 2018Source: Composites Part B: EngineeringAuthor(s): Enrique García-Macías, Carlos Felipe Guzmán, Erick I. Saavedra Flores, Rafael Castro-Triguero In this work, a bottom-up multiscale modeling approach is developed to estimate the effective elastic moduli of Carbon NanoTube (CNT)-reinforced polymer composites. The homogenization process comprises two successive steps, including an atomistic-based computational model and a micromechanics approach at the nano- and micro-scales, respectively. Firstly, the atomistic-based finite element model defines a cylindrical Representative Volume Element (RVE) that accounts for a carbon nanotube, the immediately surrounding matrix, and the CNT/polymer interface. The carbon-carbon bonds of the CNT are modeled using Timoshenko beams, whilst three-dimensional solid elements are used for the surrounding matrix. Through the application of four loading conditions, the RVEs are homogenized into transversely isotropic equivalent fibers by equating the associated strain energies. Secondly, the equivalent fibers are employed in a micromechanics approach to estimate the macroscopic response of non-dilute composites. This is performed using both the analytical Mori-Tanaka model and a computational RVE model with a hexagonal packing geometry. A wide spectrum of single- and multi-walled carbon nanotubes are studied, as well as two different polymeric matrices. Furthermore, the so-called efficiency parameters, imperative for the application of the simplified extended rule of mixtures, are characterized by polynomial expressions for practical filler contents. Finally, detailed parametric analyses are also provided to give insight into the sensitivity of the macroscopic response of CNT-reinforced polymer composites to microstructural features such as filler volume fraction, chirality or aspect ratio.
  • Hydrothermal-assisted synthesis of a porous polyaniline/reduced graphene
           oxide composite as a high-performance electrode material for
    • Abstract: Publication date: Available online 28 September 2018Source: Composites Part B: EngineeringAuthor(s): Adam Moyseowicz, Grażyna Gryglewicz We report a facile, two-step synthesis process for a porous polyaniline/reduced graphene oxide composite (PANI/rGO-HT) that involves the oxidative polymerization of aniline, followed by the hydrothermal treatment of polyaniline (PANI) and graphene oxide. The reduction of graphene oxide under hydrothermal conditions in the presence of PANI nanoparticles yields a three-dimensional porous composite with a specific surface area of 228 m2 g−1, which delivers high specific capacitances from 420 to 239 F g−1 at current densities of 0.2–20 A g−1. PANI/rGO-HT exhibits remarkable electrochemical stability due to the rGO, achieving a capacitance retention of 80% after 6000 cycles at a high current density of 2 A g−1, which unveils its promising potential for supercapacitor applications.Graphical abstractImage 1
  • Nano-cement composite with graphene oxide produced from epigenetic
           graphite deposit
    • Abstract: Publication date: Available online 28 September 2018Source: Composites Part B: EngineeringAuthor(s): Tanvir S. Qureshi, Daman K. Panesar, Boopathi Sidhureddy, Aicheng Chen, Peter C. Wood This study presents the development of a nano-cement composite with graphene oxide (GO) carbon-based nanomaterials synthesized from a high-purity epigenetic graphite deposit. Diamond drill sampled graphite mineralization was upgraded through beneficiation and purification to recover a high-purity graphite product (99.9% graphitic carbon “Cg”). An alternate and improved chemical oxidation process based on the Modified Hummers method was adopted for the synthesis of GO from high-purity graphite. Microstructural analysis were performed to characterise GO. The GO consists of OH, C=O, COOH, and C-O-C functional groups with a layer thickness of 1.2 nm, 2 to 3 layers of graphene, an interlayer distance of 0.89 nm and a Raman (ID/IG) ratio of 0.79. The effect of 0.02, 0.04, and 0.06 wt% GO of cement on the composite workability, hydration, microstructure, mechanical and transport properties was determined. Increasing the concentration of GO in the composite decreased the workability due to the hydrophilic nature of the 2D planar surface. The rate of hydration accelerated and the cumulative hydration heat increased with the increasing proportions of GO in the composite. GO dosages about 0.02 and 0.04 wt% of cement in the composites resulted the maximum enhancement of compressive and flexural strength by 83 and 26%, respectively, compared to the control mix (0 wt% GO). The microstructural investigation shows that GO enhanced the hydration of calcium hydroxide (CH) and calcium silicate hydrate (C-S-H) during the nucleation and growth stages, filled pores, bridged micro-cracks and created interlocking between the cement hydration products. Collectively, these effects ultimately improved the mechanical properties of the composites. Also, in this process, the 0.02 and 0.04 wt% GO cement composite increased the electrical resistivity by 11.5%, and decreased the sorptivity by 29%, respectively, both of which improved the overall performance of the composite.
  • Application of 3D printed ABS based conductive carbon black composite
           sensor in void fraction measurement
    • Abstract: Publication date: Available online 28 September 2018Source: Composites Part B: EngineeringAuthor(s): Jayanth N, Senthil P The application range of fused deposition modeling (FDM) process has been increased by the introduction of multifunctional materials. These materials exhibit enhanced mechanical and thermal properties. In addition to that, some materials like graphene, carbon nanotubes and carbon black have the conductive properties and can be used in electronic applications. In this research work acrylonitrile butadiene styrene (ABS) based carbon black (CB) filament is used for three dimensional (3D) printing the low cost concave capacitive sensor and it is used to measure the void fraction of the two-phase flow. The capacitance values for different void fractions are measured using 3D printed sensor and compared with the copper sensor. Also, the effect of parameters such as thickness and width of sensors on capacitance values are studied, and a prediction model using regression analysis is developed and validated to find the void fraction value. Analysis of variance (ANOVA) is done to find the significant factors affecting the capacitance values obtained for different void fraction values.Graphical abstractImage 1
  • Impact of hybrid composites based on rubber tyres particles and sugarcane
           bagasse fibres
    • Abstract: Publication date: Available online 28 September 2018Source: Composites Part B: EngineeringAuthor(s): Sérgio Luiz Moni Ribeiro Filho, Pablo Resende Oliveira, Tulio Hallak Panzera, Fabrizio Scarpa The paper describes the impact behaviour of hybrid composites made of sugarcane bagasse fibres and disposed rubber particles. The analysis was carried out using a full factorial design (25) on samples subjected to drop-tower testing. The effects of the bagasse fibre treatment, length and weight fraction were considered, as well as the rubber particles size and their amount. Higher weight fractions of coarse rubber particles led to an enhancement of the absorption. Sustained chemical treatments of the bagasse fibres provided an increase of the composites stiffness, reducing therefore the energy absorption. In contrast, higher energy absorption was obtained in composites made with untreated bagasse because of the enhanced fibre pull-out mechanism.
  • Effects of carbon nanotube inclusion into the carbon fiber reinforced
           laminated composites on flexural stiffness: A numerical and theoretical
    • Abstract: Publication date: Available online 22 September 2018Source: Composites Part B: EngineeringAuthor(s): Hamza Taş, Ibrahim Fadil Soykok Because of increased usage areas, and advances in characterization of the nanostructured materials, determination of the engineering properties of composites that includes carbon nanotubes has gained importance. It is possible to designate material properties of carbon nanotube based composites theoretically and experimentally. In this study, engineering constants of carbon nanotube based unidirectional carbon fiber reinforced composite lamina determined theoretically with two different approaches. Then, a composite plate whose laminas were stacked up as a [0°/+45°/-45°/90°]s layup was built up in ANSYS, ACP Module. Finally, three point bending analyzes were performed separately under concentrated and distributed load. The results showed that there were negligible differences between the engineering constants obtained from two different theoretical approaches. Engineering constants, E1, E2, G12 and G23, increased as the added carbon nanotube fraction is increased. Besides that, flexural rigidity of composite plate also showed ever-decreasingly increase, as carbon nanotube content is increased. The results of theoretical and numerical bending analyzes exhibited a good agreement with the maximum percentage relative error of 9.1.
  • Development of fire retardancy of natural fiber composite encouraged by a
           synergy between zinc borate and ammonium polyphosphate
    • Abstract: Publication date: Available online 19 September 2018Source: Composites Part B: EngineeringAuthor(s): Pooria Khalili, Xiaoling Liu, Kim Yeow Tshai, Chris Rudd, Xiaosu Yi, Ing Kong The current work investigated the effects of zinc borate (ZB), ammonium polyphosphate (APP)/ZB and alumina trihydrate (ATH)/ZB hybrids as flame retardants on the flammability, calorimetric, thermal and mechanical performances of empty fruit bunch (EFB) fiber reinforced epoxy composites. The formulations with concentration of 5, 10, 15 wt·% ZB and 15 wt·% APP/ZB, 15 wt·% ATH/ZB hybrids and the Control composite (EFB reinforced epoxy) were fabricated using resin infusion method. The composite containing 10 wt·% APP and 5 wt·% ZB was found to produce the highest flame retardancy in 12 s vertical Bunsen burner test and show promising results in terms of burn length, drip flame time and total flame time as obtained from 60 s vertical Bunsen burner. This could be attributed to the synergism that was created at this mass fraction between the hybrid of APP and ZB. Flexural properties did not change significantly with the inclusion of APP and ZB hybrid whereas tensile strength and elongation at break experienced an obvious reduction.
  • Analytical and experimental investigation of transverse loading on grid
           stiffened composite panels
    • Abstract: Publication date: Available online 19 September 2018Source: Composites Part B: EngineeringAuthor(s): Hamed Ahmadi, Gholamhossein Rahimi This paper investigates the behavior of grid stiffened composite panel (GSCP) subjected to transverse loading by analytical and experimental approach. An improved analytical model is proposed on the basis of smeared method to compute an equivalent stiffness matrix for the isogrid lattice of the GSCP. Hence, the panel can be considered as a laminate with different layers of specific stiffness. In this manner, the global deformation of GSCPs is studied in three types of transverse loading: three-point bending, quasi-static indentation and low-velocity impact. The model is verified by the same experimental tests on some fabricated glass/epoxy GSCPs. The results indicate the good compatibility of analytical model with experiments. Moreover, energy absorbing characterization and damage mechanisms of the tested GSCPs are studied experimentally. Observations indicate that if the skin and the lattice structure are fabricated simultaneously, debonding of ribs and facing would not happen until the main damage (central rib fracture) occurs. Also, micro buckling of skin laminas would not affect the global response significantly. So, the progressive damage and degradation of overall stiffness of the GSCPs have not considerable effect and the prediction of global response on the basis of equivalent stiffness matrix would be a high precision tool to design grid stiffened structures. Finally, based on the analytical model, a parametric study is performed to investigate the effect of changing some panel's variables and some optimum point is concluded.
  • Adsorption of metronidazole antibiotic using a new magnetic nanocomposite
           from simulated wastewater (isotherm, kinetic and thermodynamic studies)
    • Abstract: Publication date: Available online 19 September 2018Source: Composites Part B: EngineeringAuthor(s): Negin Nasseh, Behnam Barikbin, Lobat Taghavi, Mohammad Ali Nasseri This experimental study was conducted on a laboratory scale to synthesize a new magnetic nano-adsorbent and to examine its efficiency in removing metronidazole antibiotic from aqueous solutions. In this research, a new FeNi3/SiO2/CuS magnetic nanocomposite was first synthesized and its physical and structural characteristics were analyzed using FESEM, TEM, FTIR, XRD, VSM, and TGA techniques. To determine the thermodynamic parameters, the equilibrium isotherms, and adsorption process kinetics, the effect of parameters including pH (3–11), contact time (5–180 min), initial concentration of pollutant (10–30 mg/L), nanocomposite dose (0.005–0.1 g/L), and temperature (50-5 °C) were studied. Finally, the residual metronidazole concentration was determined using a UV–Vis spectrophotometer T80+ at a wavelength of 320 nm. The results related to the physical properties of the synthesized magnetic nanocomposite indicated that the particle size lied within the range of 20–65 nm and the structure of this new nano-absorbent was amorphous. Also, the FeNi3/SiO2/CuS nanocomposite had a good magnetism and its magnetic saturation was 18.42 emu/gr. Considering the efficiency of the newly synthesized nanocomposites in metronidazole absorption, the highest percentage of the pollutant adsorption was observed at pH = 7, contact time = 180 min, nanocomposite dose = 0.1 g/L, and temperature = 20 °C. With the increase in the synthesized nano-absorbent dose, the absorption percentage increased significantly (from 24.18 to 62.18). Similarly, with in the growth of the initial concentration of metronidazole from 10 to 30 mg/L, the absorption percentage declined from 85.26 to 44.6% due to the restriction of the absorption sites. Notably, as the temperature rose, the absorption percentage increased (from 37.73% to 65.15%), suggesting that the adsorption reaction was endothermic. The data obtained from Langmuir (R2 = 0.9991) and Freundlich (R2 = 0.8148) equilibrium isotherms revealed that the metronidazole absorption process through the synthesized magnetic nanocomposite was consistent with the Langmuir model. Also, the data obtained from the reaction kinetic calculations showed that the absorption of metronidazole by the adsorbent was described in accordance with a pseudo-second-order model. According to the results of the thermodynamic studies including the entropy changes (ΔS) (82.12% J/mol k), the enthalpy changes (ΔH) (0.056 kJ/mol) and the Gibbs negative free energy (ΔG), it could be concluded that the adsorption process was endothermic. In this study, the efficiency and the reusability of the synthesized magnetic nanoadsorbent were examined in the removal of metronidazole. The findings indicated that following five adsorption – desorption cycles, the efficiency of the nanoadsorbent in the removal process have a slight decrease. Regarding the results of this study, it is suggested that the magnetic nanocomposite (FeNi3/SiO2/CuS) can be a suitable new absorbent for absorption of metronidazole antibiotic from aqueous solutions. The reason is that in addition to its excellent efficiency, it can be separated from an in-vitro setting by an external magnetic field due to its great magnetic properties.Graphical abstractImage 1
  • Effect of temperature on the mechanical behaviours of a single-ply
           weave-reinforced shape memory polymer composite
    • Abstract: Publication date: Available online 17 September 2018Source: Composites Part B: EngineeringAuthor(s): Jifeng Gao, Wujun Chen, Pengxuan Fan, Bing Zhao, Jianhui Hu, Daxu Zhang, Guangqiang Fang, Fujun Peng Single-ply weave-reinforced shape memory polymer composites (SpWR_SMPCs) are promising materials for deployable space structures because they have high deformability, stiffness and strength and exhibit variable mechanical properties at different external temperatures. Thus, understanding their sensitivity to temperature has been a significant concern for better application. This paper presents comprehensive experimental investigations of temperature effects on the mechanical behaviours of a recently developed SpWR_SMPC. With the aid of newly modified compressive and shear test fixtures, the mechanical behaviours dissimilar to those of laminated composites were experimentally investigated: below the glass transition temperature (Tg), the composite was in a solid state, and the modulus relationship was observed as tension > compression > flexural > shear; however, above Tg, the relationship changed significantly due to the transition to a rubbery state and the obvious existence of weft skew. During tension and compression, a large geometric deformation was easily exhibited owing to the weave microstructure. All the mechanical properties showed decreasing trends with the rise in temperature, and the most decline was shown in the resin-dominated compressive and shear properties. Based on the test data, Correia's empirical formula was validated to characterize the thermo-mechanical behaviours as an explicit function of temperature. In general, the present work provides basic observations and comprehensive test guidelines for understanding the effects of temperature on the mechanical properties of SpWR_SMPCs.
  • Integrated design framework of next-generation 85-m wind turbine blade:
           Modelling, aeroelasticity and optimization
    • Abstract: Publication date: Available online 17 September 2018Source: Composites Part B: EngineeringAuthor(s): Xiao Wei Deng, Nan Wu, Kun Yang, Wing Lam Chan The National Energy Administration of China has promoted the use of wind energy to replace the conventional fossil energy, which provides an inexhaustible and eco-friendly alternative to the increasing energy demand. 10-MW wind turbine is the next-generation turbine with 85-m blade length, which poses great challenges in the engineering design, manufacturing, transportation, installation and maintenance. The paper aims to establish a numerical framework that integrates 3D full-scale modelling, analysis and parametric optimization. Isogeometric Analysis (IGA) enables seamless integration between structural modeling and computational analysis by using NURBS as basis functions. Aerodynamic forces and rotor power of blade subject to wind will be obtained by FAST. The Kirchhoff-Love shell element will be employed for 3D blade modeling to reduce rotational degrees of freedom and alleviate shear locking. The integrated framework residing within Rhino-based Grasshopper will be performed to model and analyze the wind turbine. Parametric optimization using pattern search algorithm targets at a family of turbines that satisfies the Tsai-Wu failure criterion and deformation constraint. The framework is deployed on a 10-MW turbine blade based on the initial design upscaled from the NREL 5-MW baseline model. The optimal blade design with shear webs has gained 20.9% improvement in performance.
  • Quantitative evaluation of fiber structure by using coherent terahertz
    • Abstract: Publication date: Available online 31 August 2018Source: Composites Part B: EngineeringAuthor(s): Chao Tang, Tadao Tanabe, Shitaro Yudate, Yutaka Oyama The structures of fiber, including the distance between fibers and the arrangement direction of fibers, were quantitatively investigated using coherent terahertz (THz) wave. Composite fibers with periodically arranged 57% silk and 43% nylon are measured, then the specific absorption spectra due to intermolecular vibration and interference effect are observed in terahertz frequency region. It is shown that, not only the period and direction of woven but also the type of material could be specified by the THz spectroscopy. This study enlightens a novel method for fiber nondestructive inspection beyond microscopy imaging, which has potential to be applied in quality control, infrastructure disaster prevention.
  • On the properties of magnetorheological elastomers in shear mode: Design,
           fabrication and characterization
    • Abstract: Publication date: Available online 27 September 2018Source: Composites Part B: EngineeringAuthor(s): Ashkan Dargahi, Ramin Sedaghati, Subhash Rakheja Magnetorheological elastomers (MREs) are novel class of magneto-active materials comprised of micron-sized ferromagnetic particles impregnated into an elastomeric matrix, which exhibit variable stiffness and damping properties in a reversible manner under the application of an external magnetic field. Characterization of highly complex behavior of these active composites is a fundamental necessity to design adaptive devices based on the MREs. This study is mainly concerned with in-depth experimental characterizations of static and dynamic properties of different types of MREs using methods defined in related standards. For this purpose, six different types of MRE samples with varying contents of rubber matrix and ferromagnetic particles were fabricated. The static characteristics of the samples were experimentally evaluated in shear mode as a function of the magnetic flux density. The particular MRE sample with highest iron particles content (40% volume fraction) was chosen for subsequent dynamic characterizations under broad ranges shear strain amplitude (2.5–20%), excitation frequency (0.1–50 Hz) and applied magnetic flux densities (0–450 mT). The results revealed nearly 1672% increase in the MRE storage modulus under the application of a magnetic flux of 450 mT, which confirms the potential of the novel fabricated MRE for control of vibration and noise in various engineering applications.
  • On the influence of moisture content on the fracture behaviour of notched
           short glass fibre reinforced polyamide 6
    • Abstract: Publication date: Available online 27 September 2018Source: Composites Part B: EngineeringAuthor(s): F.T. Ibáñez-Gutiérrez, S. Cicero, I.A. Carrascal The aim of this work is to analyse the influence of moisture content on the fracture behaviour of notched short glass fibre reinforced polyamide 6 (SGFR-PA6). For this purpose, the study combines two fibre contents (10 wt% and 50 wt%) with three different moisture contents (dry, 2% and 4–5%). Fracture tests were conducted on Single Edge Notched Bending (SENB) specimens, considering five notch radii (from 0 to 2 mm) for each combination of fibre and moisture content. Although notch effect is clearly observed in dry conditions, when the moisture content increases this effect tends to decrease for the notch radii considered here. The Line Method of the Theory of Critical Distances has been calibrated and validated for the conditions studied, providing a reasonable prediction of the apparent fracture toughness of the material in notched conditions. Concerning the fractographic observations, a Scanning Electron Microscopy analysis was performed, revealing the evolution of fracture micromechanisms when the moisture content increases.
  • Influence of processing parameters on the impact behaviour of
           glass/polyamide-6 composite
    • Abstract: Publication date: Available online 27 September 2018Source: Composites Part B: EngineeringAuthor(s): Venkateswaran Santhanakrishnan Balakrishnan, Kevin Wartig, Nikolas Tsombanis, Holger Seidlitz This study aims to investigate the low-velocity impact response and post-impact flexural behaviour of glass/polyamide-6 (G/PA-6) composite. G/PA-6 composites with a layup configuration of [02,902]s were prepared via press-forming technique. Composite samples were developed using four different processing conditions, by modifying compression pressure and heating temperature. Local variations of fiber volume and porosity fraction were noticed for samples developed in each processing conditions. On the investigated samples, damages were induced by using 35 joule of drop weight impact to investigate the impact resistance of samples with respect to different processing conditions. The damage behaviour and residual flexural strength was characterized using a micro-CT and three-point bending tests respectively. Furthermore, the influence of porosity fraction on the residual flexural strength were investigated. This paper will provide necessary fundamental knowledge for future selection of processing parameters in order to have enhanced impact performance.
  • Contribution rates of normal and shear strain energies to the natural
           frequencies of functionally graded shear deformation beams
    • Abstract: Publication date: Available online 26 September 2018Source: Composites Part B: EngineeringAuthor(s): Jung Woo Lee, Jung Youn Lee Based on the first-order shear deformation theory, this study investigated the effect of shear deformation on the contribution rates of normal and shear strain energies to the natural frequencies of functionally graded beams. This is a new analytical method to investigate the effect of shear deformation, and the analytical technique can more accurately evaluate the effect of shear deformation compared with those using the frequency ratio. The coupled axial-bending vibrations are considered, and the material properties of the structure are continuously varied according to power law distribution along the height of the cross section. Under these assumptions, the contribution rates of the related strain energies are predicted from the relationship between the maximum strain and kinetic energies. The shape function of the displacement required in the computation of the contribution rate is deduced by an exact transfer matrix method, and the developed method is used to obtain the exact eigenpairs and shape functions. The effect of shear deformation is examined for various boundary conditions, length-to-height ratios, and variations in the power law index. Therefore, the length-to-height ratios capable of ignoring these shear effects are analyzed for the first four bending-dominated frequencies of the functionally graded beams. The accuracy of the developed transfer matrix method is demonstrated via comparison with the results discussed in previous works; further, we successfully calculated the contribution rate. In addition, the axial-bending displacements coupled by the use of functionally graded materials are investigated to ascertain the reason for the decoupling phenomenon in homogeneous beams.
  • Sisal fiber reinforced high density polyethylene pre-preg for potential
           application in filament winding
    • Abstract: Publication date: Available online 26 September 2018Source: Composites Part B: EngineeringAuthor(s): Mengyuan Dun, Jianxiu Hao, Weihong Wang, Ge Wang, Haitao Cheng A thermoplastic-penetrated natural fiber belt was developed for potential application in filament winding. Discontinuous sisal fiber bundles were impregnated with high density polyethylene and then connected into continuous pre-pregs via hot-pressing. The interfacial bonding was improved by treating the fibers with sodium hydroxide (NaOH) and three types of coupling agents (NH2C3H6Si(OC2H5)3, C2H3Si(OC2H5)3 and C51H112O22P6Ti). Tensile properties of the fiber bundles, pre-pregs, and annular specimens were determined. The fiber surface microstructure and the pre-preg interfacial bonding were evaluated via scanning electron microscopy and Fourier transform infrared spectroscopy. Among the four treatments, 2% C2H3Si(OC2H5)3 yielded the most significant improvement in the tensile properties of the pre-pregs and annular specimens. The fiber bundle was less damaged by the coupling agents treatment comparing to NaOH treatment. When the overlap at the end of the sisal fibers was>11 mm, the presence of the joint had no effect on the tensile strength of the pre-preg. The pre-preg belt containing treated fibers, which was evaluated based on the requirements of filament winding applications, exhibited a high performance.
  • Free vibration study of multilayer sandwich spherical shell panels with
           viscoelastic core and isotropic/laminated face layers
    • Abstract: Publication date: Available online 26 September 2018Source: Composites Part B: EngineeringAuthor(s): Deepak Kumar Biswal, Sukeshs Mohanty The present work deals with the free vibration and damping characteristics study of multilayer sandwich spherical shell panels with viscoelastic material core layers and elastic face layers based on first order shear deformation theory. The displacements of the core layers are assumed to vary linearly along the thickness. Longitudinal and transverse deformations of the core layers are taken in to account with the consideration of independent transverse displacements of the elastic layers. The equation of motion is derived using Hamilton's principle in conjunction with the finite element method. Eight number of sandwich shell panels are studied mainly in two groups viz. sandwich panels with laminated base layer and isotropic base layer. Fundamental frequencies and associated system loss factors of different sandwich shell panels are deduced by solving the equation as an eigenvalue problem. The effect of thickness of the constraining layers, thickness of the core layers, viscoelastic material loss factor and aspect ratio on the natural frequencies and system loss factors of the sandwich structures are investigated.
  • Magnetic flux density effect on electrical properties and visco-elastic
           state of magnetoactive tissues
    • Abstract: Publication date: Available online 26 September 2018Source: Composites Part B: EngineeringAuthor(s): I. Bica, E.M. Anitas Magnetoactive tissues are prepared from a mixture of silicone oil (SO) and various volume concentrations Φ of carbonyl iron (CI) microparticles impregnated in a cotton cloth. The obtained tissues are examined as dielectric materials for manufacturing electrical capacitors. By using the plane capacitor method, we show that the relative dielectric permittivity, apparent viscosity, modulus of elasticity, and the components of deformations and of mechanical tensions can be sensibly influenced by an external magnetic field and by Φ. These effects make the obtained tissues versatile candidates for applications which require textiles consisting of conductive fillers, powders, yarns etc. embedded into non-conductive fabric fibers and with pre-established strength and flexibility. An immediate application is in fabrication of magnetic field sensors for detection of magnetic flux densities in the range 40÷180 mT.
  • Modified plastic-damage model for passively confined concrete based on
           triaxial tests
    • Abstract: Publication date: Available online 25 September 2018Source: Composites Part B: EngineeringAuthor(s): Mohsen Mohammadi, Yu-Fei Wu Plasticity-based models are used as the constitutive relationship of concrete under passive confinement of fiber reinforced polymers (FRPs). Triaxial cube tests are needed for adjusting the parameters included in a model. Most of the existing plasticity models are developed from actively confined tests or by uniform passively confined column tests. Methods for developing a plasticity model based on non-uniform passively confined concrete tests and applied to non-uniform passive confinement are rare and needed. This study reports more than one hundred triaxial concrete cube tests under uniform and non-uniform passive confinement. Six grades of concrete were tested under monotonic and cyclic compression loads. The lateral stiffness ratio was the main parameter for designing the tests. Using the reported tests, a new approach is devised for deriving parameters of a plastic-damage model for practical application to concrete structures under non-uniform passive confinement. The lateral stiffness ratio is found to be a key factor for plasticity model parameters involving dilation angle, hardening rule, and damage variable. Based on the test results and using finite element analysis (FEA), explicit empirical models are developed for the plasticity parameters. FEA analyses using the developed plasticity-damage model performs well compared with test results.
  • Quasi-static three-point bending and fatigue behavior of 3-D orthogonal
           woven composites
    • Abstract: Publication date: Available online 25 September 2018Source: Composites Part B: EngineeringAuthor(s): Xiaoping Gao, Nannan Tao, Xiaori Yang, Cong Wang, Fujun Xu 3-D orthogonal woven composites (3DOWC) have attracted great attention in the industrial and civil fields, due to their excellent mechanical properties. However, due to the mutual perpendicular yarns in three directions, its mechanical properties especially for fatigue behavior are very unique but critical for structural design in the practical applications. An experimental study was carried out for the quasi-static three-point bending and fatigue behavior of 3-D orthogonal woven composite (3DOWC). The 3-D orthogonal woven fabric (3DOWF) was reinforced with epoxy resin with the technique of Vacuum Assisted Resin Transfer Molding (VARTM). The damage process of specimens in quasi-static three-point bending tests was detected by acoustic emission (AE) detector. Simultaneously, the critical load levels i.e. the stress levels used in the bending fatigue experiments were also obtained according to AE results. The bending fatigue tests were performed at different stress levels, and the SN curves, stress-strain curves, stiffness degradation curves and residual strength of the composite specimens were also obtained. For the three-point bending fatigue loading condition, the characterizations of the three-stage failure process and crack propagation behavior were observed and illustrated. This study is the first time to systemically illustrate the fatigue stress level of 3-D orthogonal glass woven composites by acoustic emission (AE) detector and the detailed failure process are very important to guide the parameter and structural of the 3DOWC in real applications.
  • New 2D and quasi-3D shear deformation theories for free vibration of
           functionally graded plates on elastic foundations
    • Abstract: Publication date: Available online 25 September 2018Source: Composites Part B: EngineeringAuthor(s): Fatima Zohra Zaoui, Djamel Ouinas, Abdelouahed Tounsi The aim of this work is to establish a two dimensional (2D) and quasi three dimensional (quasi-3D) shear deformation theories, which can model the free vibration of FG plates resting on elastic foundations using a new shear strain shape function. The proposed theories have a novel displacement field which includes undetermined integral terms and contains fewer unknowns with taking into account the effects of both transverse shear and thickness stretching. The mechanical properties of the plates are assumed to vary through the thickness according to a power law distribution in terms of the volume fractions of the constituents. The elastic foundation parameters are introduced in the present formulation by following the Pasternak (two-parameter) mathematical model. Hamilton's principle is employed to determine the equations of motion. The closed form solutions are derived by using Navier's method and then fundamental frequencies are obtained by solving the results of eigenvalue problems. The efficiency of the proposed theory is ascertained by comparing the results of numerical examples with the different 2D, 3D and quasi-3D solutions found in literature.
  • Robust free vibration analysis of functionally graded structures with
           interval uncertainties
    • Abstract: Publication date: Available online 25 September 2018Source: Composites Part B: EngineeringAuthor(s): Di Wu, Qihan Wang, Airong Liu, Yuguo Yu, Zihua Zhang, Wei Gao In this paper, a robust interval free vibration analysis for 3D functionally graded frame type engineering structure is presented through the finite element method (FEM). Uncertain material properties, which are including the Young's modulus and material density, of the functionally graded material are considered. Unlike the conventional uncertainty quantification through stochastic approach, the uncertain system inputs are modelled by the interval approach. Instead of straining on the precise statistical information of the uncertain parameters, only upper and lower bounds of the uncertain system inputs are required for valid structural safety assessment. By implementing the mathematical programming approach combined with the intrinsic characteristics of the non-deficient engineering structures, the upper and lower bounds of the natural frequencies of 3D functionally graded frame structure can be explicitly formulated by two independent eigen-problems. The sharpness and physical feasibility of the interval natural frequencies of the functionally graded structure can be well preserved. To demonstrate the competence of the proposed method, two numerical examples have been thoroughly investigated. In addition, diverse numerical investigations have been conducted to explore the impacts of uncertain material properties and the power-law index of the functionally graded materials on the overall structural performance.
  • Two-dimensional analysis of interlaminar stresses in thin anisotropic
           composites subjected to inertial loads by regularized boundary integral
    • Abstract: Publication date: Available online 25 September 2018Source: Composites Part B: EngineeringAuthor(s): Y.C. Shiah, Kuo-Wei Hsu Evaluation of interlaminar stresses in composites plays a crucial role to ensure structural integrity. It is quite often to have composites consisting of very thin anisotropic multilayers. Traditional domain modeling of ultra-thin multilayers usually requires a tremendous amount of refined elements that might cause computation overloading. This article proposes an efficient computational methodology for evaluation of two-dimensional interlaminar stresses in thin anisotropic composites subjected to inertial loads. This analysis is by the regularized boundary integral equation (BIE) that employs only very coarse meshes. In the present work, the directly transformed boundary integral equation is regularized using the scheme of integration by parts and analytical integration. By the proposed approach, modeling of very thin layered composites can be performed simply by very coarse mesh. The obvious advantage of the present method over conventional methods is the much less modeling efforts that are required for analyzing very thin multi-layered composites. For verifications, a few benchmark examples are presented in the end.
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