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Composites Part B : Engineering
Journal Prestige (SJR): 2.039
Citation Impact (citeScore): 5
Number of Followers: 260  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1359-8368
Published by Elsevier Homepage  [3161 journals]
  • Puncture properties of a hybrid continuous-discontinuous sheet moulding
           compound for structural applications
    • Abstract: Publication date: Available online 18 September 2018Source: Composites Part B: EngineeringAuthor(s): A. Trauth, K.A. Weidenmann, W. AltenhofAbstractA novel two-step curing resin system and adapted moulding approach enables the manufacturing of hybrid continuous-discontinuous SMC in a one-shot process. Hybridization led to a significant increase of maximum force (+36%) and puncture energy (+35%) if specimens were punctured in a quasi-static manner. The effect of hybridization was less distinct under dynamic loading (increase of 13% and 7%, respectively), due to a negative rate dependency of the continuous carbon fibre SMC. An increase from 4.4·10−5 m s−1 to 4.4 m∙s− 1 resulted in a positive rate dependence of the hybrid SMC with increased maximum force (+33%) and puncture energy (+18%). Important failure mechanisms were inter-bundle and inter-fibre fracture of the continuous SMC and pseudo-delamination (intra-laminar) of the discontinuous component. Delamination took place at both considered loading rates but was more important if hybrid SMC was punctured in a dynamic manner.
  • 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 PengAbstractSingle-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.
  • Effect of fire-retardant ceram powder on the properties of phenolic-based
           GFRP composites
    • Abstract: Publication date: Available online 17 September 2018Source: Composites Part B: EngineeringAuthor(s): Wahid Ferdous, Tuan Duc Ngo, Kate T.Q. Nguyen, Abdallah Ghazlan, Priyan Mendis, Allan ManaloAbstractThis paper investigated the effect of ceram powder on the properties of composite laminates based on glass fibres and phenolic resin. The amount of ceram in the polymer matrix was varied between 30% and 50% of the weight of resin. The density, void ratio, tensile strength, interlaminar shear strength, bond strength, bending modulus and glass transition temperature were studied, and the effect of ceram on these properties was assessed. A systemic decision-making strategy is applied to evaluate the optimal amount of ceram in the polymer matrix. Results showed that while the increase of ceram decreased the strength properties of the composite laminates, the bulk density and bending modulus increased. Moreover, the glass transition temperature increased by 32 °C with the addition of 50% (by weight of resin) ceram powder. The strategic decision-making approach suggested that a good balance of physical, mechanical, and thermos-mechanical properties can be achieved when ceram is added at a fraction of 50% of the weight of resin, and this amount is considered as optimal for designing laminated fibre composites.
  • Significant improvement of thermal oxidative mechanical properties in
           phthalonitrile GFRP composites by introducing microsilica as complementary
    • Abstract: Publication date: Available online 17 September 2018Source: Composites Part B: EngineeringAuthor(s): Xulin Yang, Kui Li, Mingzhen Xu, Xiaobo LiuAbstractHigh performance composites are not only pursued with the high modulus, high strength and high service temperature, but also most of their mechanical performances should be maintained after the high-temperature thermal aging. To improve thermal oxidative mechanical properties of phthalonitrile (PPN) composites, microsilica (MS) as complementary reinforcement was introduced into PPN to form particle-filled GFRP (MS/PPN/GF) composite. DSC and DRA studies showed that the introduction of MS could lower the curing temperature and increase melt complex viscosity of MS/PPN prepolymers. Thermal oxidative stabilities of the MS/PPN composites with 16 wt% MS content were improved by 25.4 °C in T5%, 41.3 °C in T10% and 14.7% in char residue at 800 °C compared those of PPN matrix, respectively. Mechanical performances of MS/PPN/GF composites were significantly improved with the increasing MS content. More importantly, most of their mechanical performances could be maintained after being aged at 400 °C for various durations. After 400 °C/12 h thermal aging, all MS/PPN/GF composites showed a retention ratio of flexural modulus and strength higher than 90% and 70%, respectively. These improvements can be mainly attributed the complementary reinforcement of MS and better thermo-oxidative stabilities of the MS/PPN composites. Fracture surface images of MS/PPN/GF-8 composite reveal an obvious interfacial structure transformation as the thermal oxidative process goes. This study demonstrate that the introduction of particles like MS into polymer-based GFRP composite as complementary reinforcement can be an easy and effective way to improve the thermal oxidative mechanical properties.
  • 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 ChanAbstractThe 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.
  • 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 ZhangAbstractThis 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.
  • Facile fabrication of silver decorated polyarylene ether nitrile
           composites micro/nanospheres via microemulsion self-assembling
    • Abstract: Publication date: Available online 13 August 2018Source: Composites Part B: EngineeringAuthor(s): Dawei Zhang, Ruoyu Zhang, Xiaohong He, Kun Jia, Xiaobo LiuAbstractAlthough soft micro/nanoreactors obtained from amphiphilic block co-polyolefin are intensively used for metallic nanoparticle synthesis, the intricate crosslinking after self-assembling of copolymers is an indispensable step. In this work, an amphiphilic block copolymer made of aromatic macromolecular with rigid backbone structures (i.e. polyarylene ether nitrile, PEN) is explored to formulate a robust micro/nano-reactor for direct silver nanoparticles (Ag NPs) synthesis without any crosslinking step. We show that the polymeric micro/nanoreactors can be fabricated in both microemulsion and reverse microemulsion system. More importantly, Ag NPs with modulated morphology and optical properties can be in-situ synthesized using these PEN micro/nanoreactors, which is due to the coordination between Ag+ and pendant cyano/sulfonate groups of PEN. Interestingly, the anisotropic polygonal plate-like hybrid nanostructures are obtained via the optimization of nucleation and growth kinetics of Ag NPs using PEN nanoreactor in the water-in-oil W/O reverse microemulsion. Based on these results, the present work would open the way for the facile fabrication of soft micro/nanoreactors for plasmonic nanostructures synthesis using amphiphilic block-copolymers with rigid molecular structures.
  • The in situ laser-induced synthesis of the sensor-active microcomposites
           based on molybdenum and its oxides
    • Abstract: Publication date: Available online 9 August 2018Source: Composites Part B: EngineeringAuthor(s): Valeriia E. Baranauskaite, Maxim O. Novomlinskii, Ilya I. Tumkin, Evgeniia M. Khairullina, Andrey S. Mereshchenko, Irina A. Balova, Maxim S. Panov, Vladimir A. KochemirovskyIn the current paper, the in situ laser-induced synthesis of the sensor-active microcomposites based on molybdenum and its oxides has discussed. The influence of pH of the solutions used for deposition and the optical characteristics of the dielectric substrate on the electrical conductivity and the sensor properties of the synthesized deposits has studied. It was shown that the phase distribution in the synthesized materials is consistent with the temperature level in the thermal zones of the laser beam focused on the surface of a dielectric substrate of different type. In turn, highly developed surface area of the obtained deposits is directly responsible for their high sensitivity, short response time, and low temperature of regeneration with respect to hydrogen sulfide and ammonia. Indeed, the highest sensitivity was observed for detection of small concentration (≤50 ppm) of hydrogen sulfide at temperatures of 300–350 °C, whereas at temperatures of 300 °C or less the deposited structures are applicable for the ammonia sensing. The results obtained in this work demonstrate that the method of laser-induced metal deposition is a promising and perspective approach for fabrication of new effective standalone micro-sized gas sensors.Graphical abstractImage 1
  • Elastoplastic nonlinear FEM analysis of FGM shells of Cosserat type
    • Abstract: Publication date: Available online 25 July 2018Source: Composites Part B: EngineeringAuthor(s): Stanisław Burzyński, Jacek Chróścielewski, Karol Daszkiewicz, Wojciech WitkowskiAbstractThe paper is a continuation of [1] where the formulation of the elastic constitutive law for functionally graded materials (FGM) on the grounds of nonlinear 6-parameter shell theory with the 6th parameter (the drilling degree of freedom) was presented. Here the formulation is extended to the elasto-plastic range. The material law is based on J2 Cosserat plasticity and employs the well-known Tamura-Tomota-Ozawa (TTO) [2] mixture model with additional formulae for Cosserat material parameters. Formulation is verified by solving a set of demanding analyses of plates, curved and multi-branched shells, including geometry, thickness and material distribution variation parameter analyses.
  • Magnetic field effect on thermomechanical buckling and vibration of
           viscoelastic sandwich nanobeams with CNT reinforced face sheets on a
           viscoelastic substrate
    • Abstract: Publication date: Available online 15 September 2018Source: Composites Part B: EngineeringAuthor(s): Mohammed Sobhy, Ashraf M. ZenkourAbstractThis article investigates the effect of the magnetic field on the thermomechanical buckling and vibration of viscoelastic sandwich nanobeams in humid environment. The nanoscale beam is composed of a homogeneous core integrated with two functionally graded (FG) carbon nanotube (CNT) reinforced face sheets. The present sandwich nanobeam is subjected to in-plane compressive load as well as in-plane axial magnetic field and embedded in visco-Pasternak substrate that contains Kelvin-Voigt viscoelastic layer and Pasternak shear layer. The motion equations for the deformable sandwich nanobeam are deduced based on a shear and normal deformations beam theory incorporated with the modified couple stress theory that captures the size effect by involving a material length scale parameter. The present results are verified by comparing them with the previously published ones. Moreover, parametric studies have been performed to illustrate the impacts of material parameter, viscoelastic damping for the structure and the foundation, the magnetic field parameter, humidity concentration and other parameters on the buckling load and frequency of the FGCNT reinforced viscoelastic sandwich nanobeams.
  • RUC-based multi-scale model for braid-reinforced polymers: Application to
           coil springs
    • Abstract: Publication date: Available online 15 September 2018Source: Composites Part B: EngineeringAuthor(s): Marc Luger, Roland Traxl, Ulrich Hofer, Benjamin Hirzinger, Roman LacknerAbstractAs fiber- and braid-reinforced polymer components exhibit a vast number of additional design parameters compared to components made of monolithic materials, simulation methods are indispensable in the design and optimization process, accompanying or substituting experimental approaches. In respect thereof, we present a multi-scale approach comprising three observation scales: (i) the yarn scale considering fibers embedded in polymer, (ii) the braid scale capturing interwoven yarns, and (iii) the component scale. Information from one scale is transferred to the next higher scale by means of effective properties determined by finite element analysis of repetitive unit cell (RUC) models, subsequently applied for the determination of elastic properties on the yarn and braid scale. The depicted procedure allows the consideration of different types of braids (balanced and unbalanced regular braids) exhibiting arbitrary braid angles. Therefrom obtained effective properties enter the numerical model of the respective structural component. Finally, the multi-scale model is applied to the analysis of braid-reinforced polymer coil springs highlighting the potential of the proposed numerical approach. The obtained simulation results show excellent agreement with the respective experimental measurements and provide – additionally – insight into the stress distribution/loading within the coil as well as the sensitivity of design parameters with respect to the spring performance.
  • Large-scale preparation of segregated PLA/carbon nanotube composite with
           high efficient electromagnetic interference shielding and favourable
           mechanical properties
    • Abstract: Publication date: Available online 15 September 2018Source: Composites Part B: EngineeringAuthor(s): Fang Ren, Zhen Li, Ling Xu, Zhenfeng Sun, Penggang Ren, Dingxiang Yan, Zhongming LiEnvironment friendly conductive polymer composites (CPCs) with high electromagnetic interference (EMI) shielding performance and favourable mechanical properties were successfully produced on large scale from poly (l-lactid acid) (PLLA), poly (lactic acid) stereocomplex crystallite (PLASC) and multi-wall carbon nanotube (MWCNT). The morphology results indicated that the perfect segregated structure was easily manipulated by controlling the injection temperature. The prepared composite exhibits good conductivity and high EMI shielding effectiveness (EMI SE) under low MWCNT content due to the selective dispersion of the conductive MWCNT in the continuous PLLA phase. With the addition of only 3 wt% MWCNT, the composite exhibits high electrical conductivity of 6.42 S/m and outstanding EMI shielding performance of 31.02 dB at 8.2 GHz. Moreover, similar molecular structure between PLLA and PLAsc endowed excellent interfacial adhesion, thus results in favourable mechanical properties of composites. The work provides a novel idea for manufacting high EMI shielding materials with both toughness and degradation.Graphical abstractSegregated structure poly (lactic acid) (PLA) conductive composites with efficient electromagnetic interference (EMI) shielding performance and favourable mechanical properties were easily fabricated by injection molding from poly (l-lactid acid) (PLLA), poly (lactic acid) stereocomplex crystallite (PLASC) and multi-wall carbon nanotube (MWCNT). Due to the selective dispersion of conductive MWCNT filler in the continuous PLA phase, good conductivity and high EMI shielding effectiveness (EMI SE) were achieved under low MWCNT content.Image 1
  • Nanofibrous membrane constructed magnetic materials for high-efficiency
           electromagnetic wave absorption
    • Abstract: Publication date: Available online 15 September 2018Source: Composites Part B: EngineeringAuthor(s): Ibrahim Abdalla, Jianyong Yu, Zhaoling Li, Bin DingWith the rapid advancement of modern technology, electromagnetic (EM) wave absorption materials become more and more indispensable to daily life and even national strategic areas. However, how to fabricate such materials in a manner of high-efficiency and broad frequency range remains a challenge and highly desired. Here, we proposed a new route to produce high performance EM wave membranes by combined techniques of electrospinning, stabilization and carbonization processes. NiFe2O4 nanoparticles and multiwall carbon nanotubes (MWCNTs) were respectively selected as the effective magnetic material and dielectric material to construct the highly flexible NiFe2O4/MWCNTs doped carbon nanofibers (CNFs). The fabricated composite membrane exhibits superior EM wave absorption behavior in a wide frequency range. For the EM wave absorption performance in C-band (4–8 GHz), X-band (8–12 GHz) and Ku-band (12–18 GHz), the reflection loss (RL) exceeding −20 dB are obtained in the frequency range of 5.36–18 GHz at a sample thickness of 2–5 mm. Similarly, the RL value of 45.60 dB can be realized for NiFe2O4/MWCNTs CNFs with a bandwidth of 12.96 GHz at a thickness of 2.5 mm. The as-synthesized NiFe2O4/MWCNTs CNFs nanofibrous membrane can be a promising candidate for light-weight and excellent EM wave absorbers. This research will afford an alternative solution for the fabrication of EM wave absorbing materials for wide practical applications.Graphical abstractA new route is developed to fabricate the NiFe2O4/MWCNTs CNFs composite membranes for wide practical applications. The as-fabricated composite membranes exhibit excellent EM wave absorption properties in wide frequency range with a small absorber thickness compared with previously reported magnetic composites.Image 1
  • Acoustic emission of material damages in glass fibre-reinforced plastics
    • Abstract: Publication date: Available online 15 September 2018Source: Composites Part B: EngineeringAuthor(s): T. Bohmann, M. Schlamp, I. EhrlichAbstractThe aim of this study is to compare two different standardized testing procedures, tensile testing and Mode-I double cantilever beam (DCB) testing, to evaluate a possible correlation between the dominant failure in glass fibre-reinforced plastics and their according acoustic emissions (AE). AE is processed by using a burst collection of all recorded transient signals and is further analysed with the k-means clustering algorithm. To generate damage related AE, a series of experiments for tensile testing and Mode-I DCB testing is performed on 16-layer glass fibre/epoxy specimens with a cross-ply lay-up for tensile and an unidirectional lay-up for Mode-I DCB testing. Three sensors at tensile testing and one sensor at Mode-I DCB testing gather AE data. The results of clustered burst signals show a good accordance between both testing procedures, with a similar weighted peak frequency (WPF) range in each classified cluster. In total, three different clusters are determined. An assignment of these three clusters to the three dominant damage mechanisms, visually observed by microscopy, is suggested.
  • Numerical study on the mechanical behavior of a polyurethane adhesive
           under high strain rate
    • Abstract: Publication date: Available online 15 September 2018Source: Composites Part B: EngineeringAuthor(s): Zhemin Jia, Guoqing Yuan, Xiaoping Feng, Yun ZouAbstractThe cohesive parameters of a polyurethane (PU) adhesive are experimentally tested under different strain rate conditions. As the strain rate of this adhesive is constantly changing under the actual impact conditions, this paper proposes a method, called weighted average strain rate method, to determine the effective strain rate of the adhesive under the high strain rate condition for numerical simulation. Based on this method, the relationship between cohesive parameters and the determined effective strain rate is established and a strain rate-dependent cohesive constitutive model of the adhesive is developed and implemented into commercial finite element analysis software via a subroutine. The model is calibrated and verified against experimental data for double cantilever beam (DCB), end notched flexure (ENF) tests and thick adherend shear tests (TAST). Finally, impact tensile shear test and numerical analysis on composite single-lap joints at high loading rates are carried out to validate the reliability of the subroutine. By comparing the FEA results with experimental results, a good agreement is achieved which proves the effectiveness of the strain rate determination method and the subroutine.
  • The effect of amine functionalization of CuO and ZnO nanoparticles used as
           additives on the morphology and the permeation properties of
           polyethersulfone ultrafiltration nanocomposite membranes
    • Abstract: Publication date: Available online 14 September 2018Source: Composites Part B: EngineeringAuthor(s): Nazanin Nasrollahi, Soheil Aber, Vahid Vatanpour, Niyaz Mohammad MahmoodiAbstractNew polyethersulfone (PES) ultrafiltration blended membranes were prepared by doping them with different amine-functionalized CuO (FCN) and ZnO (FZN) nanostructures added at different concentrations (0–2 wt%). 3-(aminopropyl) trimetoxysilane was used as an amine precursor in a simple method for the amino-functionalization of the nanoparticles. Physicochemical properties of the synthesized nanoparticles before and after amino-functionalization were characterized by X-ray diffraction, SEM and FTIR techniques to confirm the correct synthesis. SEM, EDAX, AFM, and pore size distribution were utilized as the applied techniques to know more about the membrane morphology. Water contact angle measurement was used to determine the hydrophilicity of the membranes. All of the doped membranes showed a significant increase in porosity and hydrophilicity, resulted leading to considerable improvement in the pure water flux, as compared with the bare PES membrane. Comparison of FCN and FZN showed that the NH2CuO nanoparticles participation in the PES polymeric matrix had a more remarkable positive effect on permeability, reaching to 886.6 kg/m2h (0.5 wt% FCN/PES), as compared with the bare one (554.2 kg/m2h). By the addition of the nanoparticles in specific amounts, AFM results showed the remarkable reduction in the determined roughness. Moreover, the obtained results were in a good agreement with the antifouling modification of the amino-functionalized blended membranes. More roughness of the bare PES membrane, as compared to the mixed one, increased the possibility of fouling. The FRR of the blended membranes was improved. AFM and FRR results showed that the more roughness of the membrane surface increased the possibility of fouling.
  • Artificial lightning strike tests on PRSEUS panels
    • Abstract: Publication date: Available online 13 September 2018Source: Composites Part B: EngineeringAuthor(s): Juhyeong Lee, Pedram Gharghabi, Dounia Boushab, Trenton M. Ricks, Thomas E. Lacy, Charles U. Pittman, Michael S. Mazzola, Alex VelickiAbstractThe lightning damage resistance of Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panels was characterized experimentally. Two unprotected PRSEUS panels were subjected to standard impulse current waveforms (consistent with actual lightning strikes) with 50, 125, and 200 kA nominal peak currents at a variety of panel locations. Lightning-induced damage to the PRSEUS panels was a strong function of (1) the peak current, (2) the lightning attachment location (mid-bay, stringer, frame, etc.) that involved different through-thickness Vectran™ stitching, and (3) the presence of a surface finish paint.The sizes of the damaged regions increased as the peak current increased, since greater peak current leads to more Joule heating. The lightning-damaged PRSEUS panels exhibited unique damage features due to the presence of through-thickness Vectran™ stitches and warp-knitted fabrics. Through-thickness Vectran™ stitches constrained the development and spread of intense local damage in the vicinity of the lightning attachment point. The polyester warp-knit threads used to stitch the warp-knitted laminates together appeared to influence the development of widespread small-scale fiber damage in the region surrounding the strike. Consequently, the Vectran™ structural stitches, as well as the polyester knit threads holding the tows together, have a significant beneficial effect on both the size of the impingement region and the subsequent damage propagation within the laminate. In addition, damage to the painted panel was greater for each current level than for the sanded (unpainted) panel.
  • Thermoelastoplastic analysis of FGM rotating thick cylindrical pressure
           vessels in linear elastic-fully plastic condition
    • Abstract: Publication date: Available online 12 September 2018Source: Composites Part B: EngineeringAuthor(s): Mohammad Zamani Nejad, Negar Alamzadeh, Amin HadiAbstractIn this paper, exact solutions to purely elastic, partially plastic and fully plastic deformation and stresses of rotating functionally graded (FG) cylindrical pressure vessels under thermal load are obtained. The material properties are assumed to vary nonlinearly in the radial direction of the vessel whereas the Poisson's ratio due to slight variations in engineering materials is kept constant. To the best of the researchers' knowledge, in the literature, there is no study carried out exact solution for thermal stresses in elastic-plastic rotating FGM thick cylindrical pressure vessels. The novelty of the current work is to present a complete exact elastoplastic solution for thick cylindrical pressure vessels made of FGM under thermal loading, taking into account all stress regions. Assuming that the inner surface is exposed to an airstream, and that the outer surface is exposed to a uniform heat flux. The heat conduction equation for the one-dimensional problem in cylindrical coordinates is used to obtain temperature distribution in the vessel. Tresca's yield criterion and its associated flow rule are used to formulate six different plastic regions for an ideal plastic material. All these stages are studied in detail. It is shown that the thermo-elasto-plastic response of the functionally graded pressurized cylindrical vessel is affected notably by the radial variation of material properties.
  • Manufacturing and properties of r-PETG/PET fibre composite – Novel
           approach for recycling of PETG plastic scrap into engineering compound for
           injection moulding
    • Abstract: Publication date: Available online 12 September 2018Source: Composites Part B: EngineeringAuthor(s): P. Franciszczak, E. Piesowicz, K. KalniņšAbstractThe study proposes utilisation of recycled PETG foils as a matrix for manufacturing of a composite reinforced with short PET fibres. With 70/30 wt-% filling ratio its notched impact strength of ∼12.8 kJ/m2 is twice higher than native PETG, 6-fold higher than the r-PETG and on the level of PP reinforced with the same content of glass fibres. Its good mechanical properties allow it to be applied as an engineering compound for injection moulded goods. The reuse of PETG foils as a matrix reinforced with inexpensive PET fibres gives a cost advantage and proposes a smart solution for recycling of problematic waste material. In order to be able to reprocess the r-PETG, the molecular weight of matrix material is restored during compounding by means of an efficient epoxy chain extender. A simple manufacturing method allows it to be implemented at plastic processing plants using standard machinery without additional installation costs.
  • On buckling of porous double-layered FG nanoplates in the Pasternak
           elastic foundation based on nonlocal strain gradient elasticity
    • Abstract: Publication date: Available online 12 September 2018Source: Composites Part B: EngineeringAuthor(s): Nebojša RadićAbstractIn the present investigation, the buckling behaviours of porous double-layered functionally graded nanoplates in hygrothermal environment are presented for the first time. The nonlocal strain gradient theory with two material scale parameters is developed to examine buckling behaviour much accurately. Based on the new first order shear deformation theory the equations of equilibrium are obtained from the principle of minimum potential energy. To simplify the equations of equilibrium and removing the bending-extension coupling, the buckling behaviours of FG nanoplates are investigated based on physical neutral surface concept. The equations of equilibrium are solved for various boundary conditions using Galerkin's method. The obtained results are compared with the results available in the literature to valid the correctness of present solution method. The effects of nonlocal parameter, strain gradient parameter, porosity volume fraction, power-law index, temperature change, humidity change and boundary conditions on critical buckling load are presented.
  • Green cement composite concept reinforced by graphite nano-engineered
           particle suspension for infrastructure renewal material
    • Abstract: Publication date: Available online 11 September 2018Source: Composites Part B: EngineeringAuthor(s): Mehmet S. KirgizAbstractRenewal of infrastructure is significant concern in most countries around the globe. Sustainable renewal of infrastructure needs an innovative concept that is inexpensive, quickly hardened, and strength gained at the early age, such as green cement composite concept explained in the study. This article aims to present the physical properties of green cement composite concept reinforced by the graphite nano-engineered particle suspension (GNPS) by means of sustainability, stiffness, hydraulic lateral formwork pressure, and strength gain at early age. Results of numerous tests measured, such as the optical atomic absorbance spectra, the initial and final stiffness of time, the flow, and the early age compressive strength of green composite concept, are discussed. In all tests, the usability of GNPS is displayed as innovative original nano-engineered-suspension for infrastructure renewal material and for manufacturing of green cement composite concept effectively. For that reason, the results of this work could bring new materials to cement and concrete producers, specifiers, and end-users; and new market could emerge to provide the GNP and the GNPS in additive and admixture forms.
  • Free vibration analysis of laminated composite elliptic cylinders with
           general boundary conditions
    • Abstract: Publication date: Available online 11 September 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Kwangnam Choe, Cijun Shui, Ailun Wang, Qingshan WangAbstractIn this paper, a unified analysis model is proposed for the first time to study the free vibration of laminated composite elliptic cylinders with general boundary conditions including the classical boundary, elastic boundary and their combinations. The theoretical model is established by means of the modified variational principle and multilevel partition technique based on the first-order shear deformation theory. The interface continuity and boundary constraints are enforced by using the coupling and boundary spring technique. On the basis of that, the displacement components of each shell domain are expanded in the form of double Jacobi polynomials along the meridional and circumferential direction. The convergence and comparison analysis for laminated composite elliptic cylinders subject to different classical boundary conditions is conducted to show the reliability and accuracy of the present method. To make the research topic understood better, some mode shapes are also depicted. The present solutions show stable and rapid convergence characteristics, and the natural frequencies and mode shapes agree well with the Finite Element Analysis results. Some new vibration results and parameterized results are presented and may be as the reference data by other researchers in the future.
  • Peridynamic analysis of fibre-matrix debond and matrix failure mechanisms
           in composites under transverse tensile load by an energy-based damage
    • Abstract: Publication date: Available online 10 September 2018Source: Composites Part B: EngineeringAuthor(s): M. Rädel, C. Willberg, D. KrauseAbstractReliable simulation methods and failure criteria are required during the sizing of (FRPs). Peridynamics (PDs) is a promising numerical method to predict the evolution and interaction of damages. In the current text a novel energy-based failure criterion for linear peridynamic solid (LPS) materials is implemented and applied to the micromechanical damage of FRP structures. The novel criterion promises a more realistic reproduction of failure modes for ductile materials, a reduced mesh dependency and only requires physically measurable parameters. The results of the novel criterion are compared to a reference criterion and are evaluated against experimental observations.
  • Mechanical behaviors and failure mechanisms of Buried Polyethylene pipes
           crossing active strike-slip faults
    • Abstract: Publication date: Available online 7 September 2018Source: Composites Part B: EngineeringAuthor(s): Jie Zhang, Yao Xiao, Zheng LiangAbstractPolyethylene (PE) pipes are widely used in gas transmission projects due to their excellent performances. Earthquake is destructive and difficult to predicted, which is one of the major disasters caused PE pipe failure. The study was conducted on the mechanical behaviors and failure mechanisms of buried PE pipes under fault movement, and the effects of gas pressure, fault dislocation, soil and pipe size on the mechanical behavior of PE pipes were discussed. The study indicates that gas pressure has a less effect on the mechanical behavior of PE pipe. Under faults, the flatness curve of PE pipe is distributed symmetrically with respect to the fault plane. Deformation rules of PE pipe in different stratums are similar, while the pipe deformation is the largest in clay and it is smallest in sand. The greater the standard pipe size, the greater the diameter flatness coefficient is. The larger the diameter, the smaller the pipe diameter flattening parameter is. PE pipes with a larger the standard dimension ratio of a fitting (SDR) and a smaller diameter are prone to failure in fault zone. The results can provide the basis for gas pipe design, laying, testing, and evaluation.
  • Multi-scale response sensitivity analysis based on direct differentiation
           method for concrete structures
    • Abstract: Publication date: Available online 7 September 2018Source: Composites Part B: EngineeringAuthor(s): Quan Gu, Lei Wang, Yong Li, Xiaowei Deng, Chun LinAbstractAs traditional composite materials, concrete and reinforced concrete (RC) have been widely used for civil and military purposes. The multi-scale response analysis of concrete structures can be implemented by coupling the finite element and discrete element methods (FEM-DEM). To study the response sensitivities, this paper presents a novel approach by extending the direct differentiation method (DDM) to coupled FEM-DEM multi-scale method. The response and response sensitivity analysis methods are implemented by coupling an existing FEM framework, OpenSees, and DEM software, Yade, based on a client-server (CS) software integration technique. An application example is used to demonstrate the multi-scale response sensitivity method presented herein.
  • Simplification of finite element modeling for plates structures with
           constrained layer damping by using single-layer equivalent material
    • Abstract: Publication date: Available online 6 September 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Pak Kin Wong, Xinbo Ma, Zhengchao Xie, Jun Xu, V.A. CristinoAbstractAs an effective approach of suppressing vibrations, the constrained layer damping (CLD) has drawn wide attention from the automotive and aerospace industries. However, most of the existing investigations focus on the beam structures with CLD and few studies have been done on the plate structures with CLD. Considering the practical applications, this work studies the finite element (FE) modeling of plate structures with CLD by considering the shear and extension strains in all of three layers. To reduce the computational cost and ensure the accuracy, a simplified single-layer equivalent method is originally proposed to model the plate structure with CLD based on the equivalent material properties. In this method, the equivalent material properties are obtained by defining a new equation which includes the equivalent bending stiffness. By nonlinear regression of these responses at resonance frequencies, the equivalent bending stiffness can be obtained, and the plate structure with CLD can be regarded as a regular single-layer plate for modeling. The simulation result shows that the proposed simplified single-layer equivalent method using single-layer equivalent material properties is efficient and accurate for modeling plate structures with CLD.
  • A mixed-form solution to the macroscopic elastic properties of 2D
           triaxially braided composites based on a concentric cylinder model and the
           rule of mixture
    • Abstract: Publication date: Available online 6 September 2018Source: Composites Part B: EngineeringAuthor(s): Wei Ye, Wenbo Li, Yongbin Shan, Jian Wu, Huiming Ning, Dongyang Sun, Ning Hu, Shaoyun FuAbstractUnderstanding the elastic properties of 2D triaxially braided composites (2DTBCs) is fundamental for further analysis and design of structural components made from 2DTBCs. Based on a concentric cylinder model (CCM) and the rule of mixture (RoM), we reformulated the global stiffness of 2DTBCs for the anisotropic carbon fiber reinforcement to replace the currently available formulations for the isotropic glass fiber reinforcement with a replacement scheme. First, the global stiffness calculated from CCM, Quek's model and Shokrieh's model was compared for clarification. It was found that Shokrieh's model had the relatively worse performance under the same conditions. Second, the performances of Shokrieh's model, CCM, Quek's model and CCM+RoM (Reuss-type and Voigt-type) were compared using available experiments under various braiding configurations and our experiments on the hybrid carbon/glass fiber reinforced 2DTBCs, which revealed that Quek's model and CCM+RoM (Reuss-type) could yield equivalently great results, and CCM+RoM (Reuss-type) performed even better in some cases.
  • Soft and hard interface models for bonded elements
    • Abstract: Publication date: Available online 5 September 2018Source: Composites Part B: EngineeringAuthor(s): S. Dumont, R. Rizzoni, F. Lebon, E. SaccoAbstractThe present paper deals with the modeling of bonded interfaces adopting the asymptotic expansion technique. The equilibrium problem of a composite body made of two adherents issn perfect contact with an elastic interface is considered and a classical rescaling technique is introduced. The asymptotic expansion method is reviewed; in fact, the representation form for the displacement and stress vector fields are introduced and tsshe effect of higher order terms is taken into account. Using the classical scheme of matched asymptotic expansions, the interface conditions are obtained. The cases of hard and soft interfaces are considered: the first is derived assuming the elasticity coefficients independent of the adherent thickness, the second considers the elasticity properties linearly depending on the thickness. Numerical investigations are performed in the framework of the finite element method. In particular, comparisons of the results obtained by modeling the adhesive as a continuum material (discretized in finite elements even in the thickness) with the results carried out using hard, soft interface models at the first and higher order expansion are performed.
  • Reliability assessment for flexural FRP-Strengthened reinforced concrete
           beams based on Importance Sampling
    • Abstract: Publication date: Available online 5 September 2018Source: Composites Part B: EngineeringAuthor(s): Xiaoxu Huang, Lili Sui, Feng Xing, Yingwu Zhou, Yufei WuAbstractDue to the uncertainties raised by model error, materials (e.g., concrete, FRP and steel) and environment (e.g., loads), research aimed at reliability analysis and risk assessment of FRP-strengthened structures is necessary. In this paper, reliability analysis of flexural FRP-strengthened reinforced concrete (RC) beams with the ultimate limit state is studied. Four failure modes are considered: concrete crushing, FRP rupture, IC debonding and end debonding. First, the computational models for each failure type are assessed in terms of model error based on a comprehensive database that contains 624 FRP strengthened RC beams. Then, the stochastic information for mechanical properties of the FRP and concrete materials is further identified through a series of mechanical tests on 600 concrete compression blocks and 50 FRP tensile specimens. Subsequently, the reliability index is estimated by Importance Sampling (IS) for its satisfied accuracy and efficiency. The results show that: (1) The probability of failure is different for each failure mode. It is necessary to consider all the possible failure modes to provide a comprehensive guide in the design process. (2) Based on the partial safety factor design format, the effect of the FRP partial safety factor γf on the reliability index for concrete crushing, IC debonding and end debonding is negligible. The calibration of γf is only valid for FRP rupture in order to meet the target reliability index. (3) Based on the resistance reduction factor design format, it is effective to calibrate resistance reduction factor ϕ for concrete crushing, FRP rupture, IC debonding and end debonding. Each failure mode should be designed with corresponding ϕ. (4) Additional anchors can improve the reliability index for IC debonding and helps to transfer to other failure modes for end debonding.
  • Larch tannin-based rigid phenolic foam with high compressive strength, low
           friability, and low thermal conductivity reinforced by cork powder
    • Abstract: Publication date: Available online 5 September 2018Source: Composites Part B: EngineeringAuthor(s): Jiongjiong Li, Aibin Zhang, Shifeng Zhang, Qiang Gao, Wei Zhang, Jianzhang LiPhenolic foam (PF) has recently been spotlighted because of their excellent flame resistance, low smoke emission, and low production costs. However, PF is mainly prepared from petroleum-based products, and it exhibits poor mechanical strength and high friability. In this study, larch tannin-based rigid phenolic foams (LTPFs) and cork powder was used as filler to prepare cork powder-reinforced LTPFs (CLTPFs). The chemical structure, cell morphology, compressive mechanical properties, friability, thermal properties, and flame retardancy of the foams were evaluated. The results indicated that the LTPFs showed inferior cell morphology, compressive strength and thermal properties, high friability and high flame retardancy as compared with the neat PF. LTPF10 presented the maximal limiting oxygen index (LOI) of 47.8%. As compared with the unreinforced LTPFs, CLTPFs possessed excellent cell morphology, high compressive strength, low thermal conductivity, low friability, and good thermal properties. At a cork powder dosage of 1 wt%, the compressive strength and modulus of CLTPFs increased by 14.84% and 16.18%, respectively; the pulverization ratio and thermal conductivity of CLTPFs decreased by 18.4% and 32.29%, respectively, as compared with those of the LTPF. In addition, the introduction of cork powder improved the thermal stability of LTPFs. The LOI values of the CLTPFs were slightly lower than those of LTPFs. LTPF reinforced with 1 wt% cork powder exhibited the best combination of the features.Graphical abstractImage 1
  • A study on Mg and AlN composite in microstructural and electrochemical
           characterizations of extruded aluminum alloy
    • Abstract: Publication date: Available online 4 September 2018Source: Composites Part B: EngineeringAuthor(s): L.X. Bach, D.L. Son, M.P. Phong, L.V. Thang, M.Z. Bian, N.D. NamA combination of composites and metallic materials has been shown to be an effective way to modify the microstructure and thus enhance the corrosion properties. This study focuses on the development of a new aluminum alloy using Mg and AlN composite and the hot extrusion processing. The microstructures and electrochemical properties have been characterized using the advanced surface analysis and electrochemical techniques in a naturally-aerated 0.1 M chloride solution. Open circuit potential and potentiodynamic polarization results indicate that Mg and AlN composite additions could improve corrosion and pitting potentials as well as passive film quality formed on the alloy surface. Electrochemical impedance spectroscopy has confirmed that the addition of Mg and AlN composite also increases the passive film and charge transfer resistances, resulting in an improvement of passive film stability and pitting resistance. X-ray photoelectron spectroscopy suggests that Mg and AlN composite addition promotes the stable passive film formed on the aluminum alloy surfaces due to the existence of Mg oxides/hydroxides and AlN incorporating with Al oxides/hydroxides. The improved pitting resistance could be attributed to the reduction in the grain sizes and defects in the alloy matrix that are observed by electron backscatter diffraction and could directly relate to the alloy dissolution and passive film formation.Graphical abstractImage 1
  • 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. KeAbstractThe 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.
  • Bi-directional functionally graded beams: Asymmetric mode and nonlinear
           free vibration
    • Abstract: Publication date: Available online 3 September 2018Source: Composites Part B: EngineeringAuthor(s): Ye Tang, Xiaofei Lv, Tianzhi YangAbstractIn the paper, a novel model of Euler–Bernoulli beams made of bi-directional (2D) functionally graded materials (FGMs) is presented to study the nonlinear free vibration. We found that the 2D FGMs may induce asymmetric modes in free vibration, which is distinctly different from previous research. The Hamilton's principle is applied to derive the nonlinear governing equation of the beam and associated boundary conditions based on the geometric nonlinearity. The generalized differential quadrature method (GDQM) is used to predict the vibration modes. The closed-form solutions of the nonlinear free vibration of the beam are determined by the homotopy analysis method. The effects of the material distributions, length-thickness ratio and initial amplitude on the nonlinear free vibration are discussed in details. It is notable that the nonlinear dynamic properties are highly dependent on materials properties, which suggests that the vibration behaviors of the beam may be tailored/tuned by multi-direction FGMs.
  • 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 OyamaAbstractThe 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.
  • 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 SinghAbstractFrequency-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.
  • Wrinkling modelling of space membranes subject to solar radiation pressure
    • Abstract: Publication date: Available online 30 August 2018Source: Composites Part B: EngineeringAuthor(s): Xiaowei Deng, Y. Xu, C. ClarkeAbstractLarge, thin, prestressed membranes known as ‘gossamer’ structures have many applications in space, including light reflection and electromagnetic signal collection. The prestress forces applied to these structures usually causes some wrinkling of the membrane to occur, and the degree of wrinkling affects the reflective performance of the structure. The primary aim was to assess whether solar radiation pressure could affect the wrinkle pattern of gossamer structures, with a particular focus on solar sails. Several prestressed rectangular membranes with dimensions and material properties representative of current and future solar sails, a class of membrane structures typically made of Kapton, were modelled to investigate the effects of pressure on the wrinkle pattern. It was shown that increasing the pressure applied normal to the membrane surface increased the amplitude and decreased the wavelength of the wrinkles. However, no significant change in the wrinkle pattern was found to occur until the magnitude of the applied pressure was much greater than that likely to be experienced by gossamer structures due to solar radiation pressure. Therefore it was concluded that the effects of solar pressure will have no significant impact on the future development of larger and thinner gossamer structures than exist at present.
  • Deformations and stresses of multilayered plates with embedded
           functionally graded material layers using a layerwise mixed model
    • Abstract: Publication date: Available online 29 August 2018Source: Composites Part B: EngineeringAuthor(s): F. Moleiro, V.M. Franco Correia, A.L. Araújo, C.M. Mota Soares, A.J.M. Ferreira, J.N. ReddyAbstractThis work presents a new layerwise mixed model for the static analysis of multilayered plates with embedded functionally graded material (FGM) layers subjected to transverse mechanical loads. This model is capable to fully describe a two-constituent metal-ceramic FGM layer continuous variation of material properties in the thickness direction, using any given homogenized method to estimate its effective properties. The present model is based on a mixed least-squares formulation with a layerwise variable description for displacements, transverse stresses and in-plane strains, chosen as independent variables. This mixed formulation ensures that the interlaminar C0 continuity requirements at the layers interfaces, where the material properties actually change, are fully fulfilled a priori for all independent variables. The order of the in-plane two-dimensional finite element approximations and the order of the z-expansion through each layer thickness, as well as the number of layers, whether FGM layers or not, are considered free parameters. The full description of the FGM effective properties is achieved by applying to the z-continuous elastic coefficients a z-expansion through the layer thickness of a given order, set as an added free parameter, in a similar approach to finite element approximations. The numerical results consider both single-layer and multilayered functionally graded plates with different side-to-thickness ratios, using either Mori-Tanaka or the rule of mixtures estimates for the FGM effective properties with different material gradation profiles. The present model results are assessed by comparison with three-dimensional (3D) exact solutions and closed form solutions, which demonstrate its capability to predict a highly accurate quasi-3D description of the displacements and stresses distributions altogether.
  • Free vibration analysis of laminated and FGM composite annular sector
    • Abstract: Publication date: Available online 29 August 2018Source: Composites Part B: EngineeringAuthor(s): Ömer Civalek, Ali Kemal BaltacıogluAbstractIn this article, the authors used two different numerical approaches for frequency response of annular sector and sector plates with functionally graded materials and laminated composite cases. First-order shear deformation (FSDT) and Love's conical shell theories are used for obtaining the annular sector plate equations via some suitable angles and geometric parameters. The method of harmonic differential quadrature (HDQ) and discrete singular convolution (DSC) have been used for numerical solution of the resulting governing equations for modal analysis. Simple power-law and four-parameter power law distributions in terms of the volume fractions of constituents have been used for FGM composites. Comparison and convergence study for the present numeral methods have been made via existing results available in the literature for sector and annular sector plates. Frequencies values for annular sector/sector plates have been obtained for different material and geometric parameters, boundary conditions and sector angles.
  • Improved high-temperature mechanical property of carbon-phenolic
           composites by introducing titanium diboride particles
    • Abstract: Publication date: Available online 28 August 2018Source: Composites Part B: EngineeringAuthor(s): Jie Ding, Jiamin Sun, Zhixiong Huang, Yanbing WangAbstractThe effect of TiB2 on the thermal stability of phenolic and the role of TiB2 on the high-temperature mechanical property of carbon–phenolic composites are investigated by introducing TiB2 particles into phenolic, and then TiB2 particles into carbon–phenolic composites. The thermal stability of phenolic is enhanced by TiB2 additions. And the enhancement in thermal stability of phenolic exhibits a positive effect on improving the high-temperature mechanical property of carbon–phenolic composites. The flexural strength at 1000 °C of carbon–phenolic composites is increased by 148.2% after introducing 20 wt% TiB2 particles into phenolic matrix. In the heating stage before high-temperature mechanical test, TiB2 particles react with oxygen or oxygen-containing molecules released by phenolic pyrolysis. As a result, amorphous carbon coated with glassy B2O3 and ceramic particles forms a new compact matrix. The well-bonded interface provides TiB2 modified carbon–phenolic improved mechanical performance at high temperature.
  • A multi-physics framework model towards coupled fire-structure interaction
           for Flax/PP composite beams
    • Abstract: Publication date: Available online 28 August 2018Source: Composites Part B: EngineeringAuthor(s): Swagata Dutta, Raj Das, Debes BhattacharyyaAbstractIn this paper, a coupled fire-structure model combining the finite volume and finite element methods, which captures the essential physics of the problem has been developed. The model is based on a multi-physics framework where the essential physics pertaining to the combustion process of the fire and resultant thermo-mechanical response of the structure, in particular, of natural fibre reinforced composites, has been incorporated. In addition, a relatively new concept of adiabatic surface temperature has been introduced as a practical means to transfer data between fire and thermal/structural models at the gas-solid interface. The model predicts the temperature, stress distribution and deformation behaviour of composite beams under combined thermal and mechanical loads.
  • Gas-atomized copper-based particles encapsulated in graphene oxide for
           high wear-resistant composites
    • Abstract: Publication date: Available online 28 August 2018Source: Composites Part B: EngineeringAuthor(s): Wenzheng Zhai, Wenlong Lu, Youming Chen, Xiaojun Liu, Liping Zhou, Dong LinA novel architecture of graphene oxide wrapped copper spheres (Cu/GO) is proposed for fabricating high wear-resistant Cu-based composites. Tribological results indicate that GO shell layers present an exceptional strengthening efficiency surpassing conventional nanoparticle, fiber and nanosheet reinforcements for Cu-based materials reported to date. The friction torque of the composites shows a load-insensitive behavior stabilized at 0.26–0.41 Nm. Such good tribological performance is ascribed to integrated effects including strong metal/GO interfacial coupling, uniform distributed GO, and the GO-assisted tribofilm formed on ridges and asperities of wear tracks. The fabrication strategy is convenient, low cost, easily scalable, and can be expanded to the preparation of other metal/GO materials.Graphical abstractImage 1
  • Effects of sample orientation on the fire reaction properties of natural
           fibre composites
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Swagata Dutta, Nam Kyeun Kim, Raj Das, Debes BhattacharyyaAbstractIn this paper, comprehensive experimental and numerical analyses are carried out to compare the fire reaction properties of wool and flax based polypropylene composites under horizontal and vertical orientations. Moreover, extensive numerical analysis results on the fire reaction properties, burn time and surface temperature distribution have been reported. Fire Dynamics Simulator (FDS®) was employed to develop a numerical predictive model for the cone calorimeter. The study revealed that vertical samples ignited later compared to the horizontal ones. In addition, it has been shown that fibre type has a significant effect on the heat release rate in horizontal and vertical tests. The surface temperature distributions showed similar trends for both composites.
  • Effect of concrete creep on dynamic stability behavior of slender
           concrete-filled steel tubular column
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Y.Q. Huang, J.Y. Fu, A.R. Liu, Y.L. Pi, D. Wu, W. GaoAbstractAn analytical procedure for dynamic stability of CFST column accounting for the creep of concrete core is proposed. The long-term effect of creep of concrete core is formulated based on the creep model by the ACI 209 committee and the age-adjusted effective modulus method (AEMM). The equations of boundary frequencies accounting for the effects of concrete creep are derived by the Bolotin's theory and solved as a quadratic eigenvalue problem. The effectiveness of the proposed method and the characteristics of time-varying distribution of instability regions are numerically surveyed. It is shown that the CFST column becomes dynamically unstable even when the sum of the sustained static load and the amplitude of the dynamic excitation is much lower than the static instability load. It is also found that due to the time effects of concrete creep under the sustained static load, the same excitation, that cannot induce dynamic instability in the early stage of sustained loading, can induce the dynamic instability in a few days later. The critical amplitude and frequency of the dynamic excitation can decrease by 6% and 3% in 5 days, and 11% and 6% in 100 days.
  • Dispersion control of raw and modified silica particles in PMMA. Impact on
           mechanical properties, from experiments to modelling
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): A. Siot, R. Léger, C. Longuet, B. Otazaghine, A.S. Caro-Bretelle, N. AzémaStructure and properties of PMMA/silica composites were characterized by various methods including SEM, TGA, rheology, microscopic level evaluation of nano-reinforcement effect on properties. Static modulus and yield strength of PMMA are enhanced with silica incorporation regardless of their dispersion or functionalization. However, composites ultimate properties are strongly affected by fillers characteristics. As expected, better performances are associated to well-dispersed and functionalized silica.A finite element modelling with interface debonding through cohesive model and interfacial area is introduced to reproduce the sensibility of tensile test response to fillers surface functionalization. Experimental results confirmed this modelling: at constant low weight rate, ultimate composites properties are mostly affected by any microstructural changes. An analysis of local stress confirms the premature breakage of composite with pristine silica. Finally, by considering the expected properties, functionalization of silica is not always a necessity. Instead of particle functionalization, a dispersion protocol could be advantageously used to reach interesting composite properties.Graphical abstractImage 1
  • Towards “green” viscoelastically prestressed composites:
           Cellulose fibre reinforcement
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Yang Qin, Kevin S. FanceyAbstractWith growing concerns over environmental issues, fibre reinforced composites based on renewable, biodegradable low-cost cellulosic/cellulose fibres increasingly attract interest. This paper reports on the first study to produce viscoelastically prestressed polymeric matrix composites (VPPMCs) using regenerated cellulose/viscose continuous fibres. The aim was to demonstrate that this prestressing technique could improve the mechanical properties of a cellulose fibre reinforced composite without the need to increase section mass or thickness. By investigating the viscoelastic properties of cellulose yarn, a suitable load was applied to subject the fibres to tensile creep. The load was then released and the loose yarns were moulded into a polyester resin matrix. Following matrix solidification, the viscoelastically recovering fibres imparted compressive stresses to the matrix. The mechanical properties of these cellulose fibre VPPMCs were investigated by tensile, three-point flexural and Charpy impact tests. Under the creep conditions investigated, the VPPMC samples demonstrated up to 20% increase in tensile strength and modulus and a comparable improvement in flexural properties, compared with control (unstressed) counterparts. Nevertheless, the prestress effect reduced impact toughness by ∼30%, by impeding matrix crack formation and promoting fibre fracture. Based on findings from this paper, all-green VPPMCs may be achieved in the future by considering potentially suitable green resins.
  • 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 WangAbstractThe 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.
  • Experimentally informed micromechanical modelling of cement paste: An
           approach coupling X-ray computed tomography and statistical
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Hongzhi Zhang, Branko Šavija, Mladena Luković, Erik SchlangenAbstractThis work proposes a method for numerically investigating the fracture mechanism of cement paste at the microscale based on X-ray computed tomography and nanoindentation. For this purpose, greyscale level based digital microstructure was generated by X-ray microcomputed tomography with a resolution of 2 μm/voxel length. In addition, statistics based micromechanical properties (i.e. Young's modulus and hardness) were derived from the grid nanoindentation test which was set to have an interaction volume the same as the resolution of the digital microstructure. A linear relationship between the two probability density functions of greyscale level and local Young's modulus was assumed and verified by the two-sample Kolmogorov-Smirnov (K-S) statistic. Based on this assumption, the fracture and deformation of a digital cubic volume with a dimension of 100 μm under uniaxial tension was simulated using a lattice fracture model. In addition, the influence of heterogeneity on fracture response was studied. Furthermore, the proposed method was compared with the results obtained from a traditional approach used previously by the authors in which discrete phases (capillary pore, anhydrous cement clinker, outer and inner hydration products) were considered. The two methods show similar crack patterns and stress-strain responses. The proposed method is regarded more promising as it captures also the gradient of material properties (within the discrete phases) in the cement paste.
  • Dynamics analysis of functionally graded porous (FGP) circular, annular
           and sector plates with general elastic restraints
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Fei Xie, Ailun Wang, Cijun Shuai, Jinyuan Tang, Qingshan WangAbstractIn 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.
  • Monotonic and hysteretic in-plane behaviour of graphene through an
           atomistic FE model
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Diogo Galhofo, Nuno Silvestre, Bruno Faria, Cátia GuardaAbstractThis paper presents a computational study on the monotonic and hysteretic in-plane behaviour of graphene. With this purpose, atomistic finite element models of graphene were developed taking into account the degradation of stiffness and strength through an elastic-plastic model. The study extends the typical unidirectional tests (in armchair and zigzag directions) to the bidirectional test and the shear test, establishing a consistent and comprehensive set of both elastic and strength properties. The mechanical properties obtained from the monotonic analyses (elastic and strength properties) are validated from the comparison with those available in the literature (experimental, density functional theory, molecular dynamic simulations and finite element models). The strain-softening behavior of graphene is assessed through these atomistic models. The failure modes of graphene sheets in different loading tests are detailed and its load carrying capacity is explained. Finally, the hysteretic behaviour of graphene is discussed. The stress-strain curves and the variation of dissipated energy with the strain are given for different number of cycles. Then, some concluding remarks are drawn.
  • A critical assessment of multifunctional polymers with regard to their
           potential use in structural applications
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): P.V. Polydoropoulou, ChV. Katsiropoulos, SpG. Pantelakis, M. Raimondo, L. GuadagnoAbstractMulti Wall Carbon Nanotubes (MWCNTs) and Polyhedral Oligomeric Silsesquioxanes (POSS) are common additives to simultaneously enhance electrical conductivity and flame resistance. In the present work, the synergistic effect of the addition of MWCNTs and two different POSS compounds, DodecaPhenyl POSS (DPHPOSS) and Glycidyl POSS (GPOSS), on the mechanical behavior of multifunctional polymers subjected both to quasi-static as well as to fatigue loading was investigated. The results of the mechanical tests were discussed supported by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) analyses. The results showed that the incorporation of MWCNTs in the resin containing GPOSS determines a slight decrease in the flexural modulus compared to the unfilled resin. The material filled with MWCNTs and DPHPOSS shows a higher reduction of the flexural modulus as compared to the other analyzed materials. The same trend was observed also for the flexural strength; more than 50% decrease of the flexural strength of the material filled with MWCNTs and DPHPOSS is detected. As far as the fatigue is concerned, it seems that the incorporation of the flame retardants led to an appreciable decrease in the fatigue life. The decrease in the mechanical properties of the nanofilled resin loaded with DPHPOSS is most likely due to the presence of aggregates of DPHPOSS crystals in the matrix. This hypothesis is confirmed by EDX analysis which shows that DPHPOSS forms some small aggregates, whereas GPOSS, being molecularly solubilized in the epoxy formulation, shows mechanical performance more similar to the sample loaded only with carbon nanotubes.
  • Experimental study on effects of structural characteristics of C/E
           composite laminates on grinding temperature
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Tao Chen, Hongbo Li, Mengli Ye, Chao Xiang, Shenlin TianAbstractAs for ultrasonic vibration assisted grinding (UVAG) of carbon/epoxy (C/E) composites, the grinding temperature is greatly influenced by their structural characteristics (such as epoxy resin content and fiber directional angle (θ)). For revealing their relationship, C/E composite workpieces with various structural characteristics were designed and prepared; moreover, Fiber Bragg grating (FBG) sensors were embedded in each workpiece for measurement of the grinding temperature; in addition, various grinding parameters were set in UVAG experiments. Experimental results show that: 1). the grinding temperature is influenced very remarkably by the fiber directional angle of C/E composites and the grinding temperature along the direction of fibers is much higher than that reverse fiber direction; 2). the grinding temperature peaks under fiber directional angle (θ=90°); 3). on the premise of meeting the performance of workpieces, the grinding temperature raises with the increase of epoxy resin content; 4). the change of grinding parameters has nothing to do with the relationship (the grinding temperature vs. the structural characteristics of C/E composites).
  • Durability performance and long-term prediction models of sand-coated
           basalt FRP bars
    • Abstract: Publication date: Available online 27 August 2018Source: Composites Part B: EngineeringAuthor(s): Ahmed H. Ali, Hamdy M. Mohamed, Brahim Benmokrane, Adel ElSafty, Omar ChaallalAbstractBasalt-fiber-reinforced polymer (BFRP) bars are expected to provide benefits that are comparable or superior to other types of FRP while being significantly cost-effective. However, extensive investigations are needed to evaluate the long-term characteristics and durability performance of these bars. This article presents an experimental study that investigated the physical, mechanical, microstructural, and durability characteristics of newly developed basalt-fiber-reinforced polymer (BFRP) bars. The physical, mechanical properties and microstructural characteristics were evaluated first on the unconditioned BFRP bars. The durability performance of the BFRP bars was then assessed by conducting the mechanical tests, such as transverse-shear test, flexural test, and interlaminar-shear test, on the specimens after different exposure periods (1000; 3000; and 5000 h) at 60 °C. Thereafter, the BFRP bar properties were assessed and compared with the values obtained on the unconditioned specimens. The test parameter was conditioning time (1000; 3000; and 5000 h). The test results revealed that the unconditioned BFRP bars had the best physical properties. On the other hand, the long-term durability performance revealed that the transverse shear-strength, flexural-strength, and interlaminar shear-strength retention were decreased by 12%, 19%, and 21%, respectively.
  • Effect of food chemicals and temperature on mechanical reliability of
           bio-based glass fibers reinforced polyamide
    • Abstract: Publication date: Available online 26 August 2018Source: Composites Part B: EngineeringAuthor(s): Margherita Basso, Agnese Piselli, Michele Simonato, Riccardo Furlanetto, Liva Pupure, Roberts Joffe, Luigi De NardoAbstractThis paper presents an experimental study to assess the effects of food chemicals and temperature on the mechanical performance of glass fiber reinforced bio-based polyamide. The diffusion of food chemicals was mainly driven by thermal energy, following Arrhenius law in all tested environments. Degradation of mechanical properties and decrease in reliability were assessed, due to the plasticization of polymer matrix. Secondary but not negligible effect on flexural strength degradation is given by the different chemical interaction between polymeric chains and molecules of food chemicals. Colour change was measured and resulted to be positively correlated to diffusion.
  • Fabrication of a piezoelectric strain sensor based on SbSI nanowires as a
           structural element of a FRP laminate
    • Abstract: Publication date: Available online 25 August 2018Source: Composites Part B: EngineeringAuthor(s): Mateusz Kozioł, Bartłomiej Toroń, Piotr Szperlich, Marcin JesionekAbstractA research procedure involving the fabrication of deformation sensors integrated into a FRP (fiber reinforced polymer) laminate structure is presented in this manuscript. The sensors were made from a nanocomposite based on epoxy resin and antimony sulfur iodide (SbSI) nanowires. The nanocomposite was applied as an active layer, locally placed in the laminate structure. The piezoelectric performance of the sensors was evaluated by non-destructive bending tests. The obtained electrical characteristics showed that the sensor response allows us to determine both the deformation rate and the strain of the material. This gives a potential use for these types of sensors in structure monitoring systems. The presence of a sensor in the laminate's structure does not cause a significant decrease in the mechanical performance of the material.
  • Development of novel building composites based on hemp and
           multi-functional silica matrix
    • Abstract: Publication date: Available online 25 August 2018Source: Composites Part B: EngineeringAuthor(s): Atif Hussain, Juliana Calabria-Holley, Mike Lawrence, Martin P. Ansell, Yunhong Jiang, Diane Schorr, Pierre BlanchetAbstractThis study focuses on the development of novel bio-composites using a silica matrix that provides dual functionality: as a hydrophobic surface treatment and as a binder for hemp-shiv. The hydrophilic nature of hemp shiv, a plant based aggregate, results in composites having poor interfacial adhesion, weak mechanical properties and long drying times. In this work, sol-gel process has been utilised to manufacture durable low density hemp based composites. Morphological characterisation by scanning electron microscopy (SEM) showed that hemp shiv was embedded well in the matrix. Detailed chemical analysis using x-ray photoelectron spectroscopy (XPS) and gas chromatography-mass spectrometry (GC-MS) indicate the presence of water soluble and ethanol soluble extractives leached from the hemp shiv which are incorporated into the silica matrix inducing the binding effect. The composites were water resistant and showed good mechanical performance having the potential to develop novel thermal insulation building materials.
  • Experimental and analytical flexural performances of reinforced concrete
           beams strengthened with post-tensioned near surface mounted basalt
           composite laminates
    • Abstract: Publication date: Available online 24 August 2018Source: Composites Part B: EngineeringAuthor(s): Lluís Gil, Ernest Bernat, Christian EscrigAbstractNear surface mounted (NSM) is a technique that improves the strengthening capacity of composite laminates. The use of a post-tensioning technique modifies the performance of the strengthening because it is active bearing loads from the very beginning. This study compares the performances of three beams: one without strengthening, one with passive NSM laminate, and a third with post-tensioned NSM laminate. The experimental approach compares the pre-cracking and post-cracking performance until failures, showing that the post-tensioned solution withstands larger loads in pre-cracking and presents less deformation in post-cracking. Moreover, post-tensioning is an effective technique that can prevent loss of stiffness even after cracking. Finally, simple analytical equations based on the plane cross-section for pre-cracking and failure analysis are proposed, showing good agreement with the experimental results.
  • 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. YangAbstractA 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.
  • Surface characteristics of wood polypropylene nanocomposites reinforced
           with multi-walled carbon nanotubes
    • Abstract: Publication date: Available online 24 August 2018Source: Composites Part B: EngineeringAuthor(s): Alperen Kaymakci, Emre Birinci, Nadir AyrilmisAbstractEffect of multi-walled carbon nanotubes (MWCNT) content on the surface roughness, wettability, and scratch hardness properties of wood/polypropylene nanocomposites were investigated. To meet this objective, pine wood flour, polypropylene with and without coupling agent (maleic anhydride grafted polypropylene), and multi-walled carbon nanotube (0, 1, 3 or 5 wt%) were compounded in a twin screw co-rotating extruder. The mass ratio of the pine wood flour to polypropylene was 50/50 (w/w) in all the composite formulations. Test samples were manufactured using injection molding machine from the pellets. The surface roughness, wettability, and scratch hardness properties of the wood/polypropylene nanocomposites reinforced with multi-walled carbon nanotubes were determined. The surface roughness values of the nanocomposite specimens decreased with increasing MWCNT content. The MWCNT reinforced wood/polypropylene nanocomposites without coupling agent had higher surface roughness values than the ones with coupling agent. The wettability of the nanocomposite specimens decreased with increasing content of the MWCNT. The incorporation of the coupling agent into the wood/polypropylene nanocomposites decreased the wettability of the specimens. The scratch hardness values of the nanocomposite specimens improved with increasing MWCNT content.
  • Effect of thickness and reinforcement configuration on flexural and impact
           behaviour of GFRP laminates after exposure to elevated temperatures
    • Abstract: Publication date: Available online 24 August 2018Source: Composites Part B: EngineeringAuthor(s): Milad Bazli, Hamed Ashrafi, Armin Jafari, Xiao-Ling Zhao, Hamed Gholipour, Asghar Vatani OskoueiAbstractThis study investigates the flexural and impact behaviour of GFRP laminates after exposure to elevated temperatures. The effect of fibre's length and orientation, laminate's and exposing time is studied. A total number of 540 tests in terms of three-point bending and Charpy impact tests were conducted to obtain the mechanical properties. In addition, SEM analyses were carried out to investigate the degradation mechanisms. Finally, statistical study was conducted to investigate the contribution of each variable and developing probabilistic models using ANOVA and linear Bayesian regression method. The results showed that generally the flexural and impact properties of GFRP laminates decreases by increasing the temperature and time of exposing as well as decreasing the laminates' thickness. It is also observed that laminates with unidirectional fibres have the best performance under elevated temperatures, while laminates with randomly distributed fibres are the most vulnerable type. The performance of laminates with woven fibres are almost between those two other types. However, all types of the laminates lost almost all their flexural strength and impact energy absorption capacity at 300 °C.
  • Design and simulation of innovative foam-filled Lattice Composite Bumper
           System for bridge protection in ship collisions
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Lu Zhu, Weiqing Liu, Hai Fang, Jiye Chen, Yong Zhuang, Juan HanAbstractIn this paper, an innovative Foam-filled Lattice Composite Bumper System (FLCBS) with fiber-reinforced polymer (FRP) skins and a foam-web core is proposed as protective structures for bridge piers against ship collision. FLCBS consists of FRP face sheets, FRP lattice webs and polyurethane (PU) foam cores, which can be manufactured at the same time by vacuum assisted resin infusion process (VARIP). FLCBS exhibits good energy-absorbing and highly designable properties. The design, performance evaluation, manufacture and installation of FLCBS for a real prestressed concrete continuous girder bridge were introduced. A detailed numerical model for performance evaluation was developed with the explicit finite element (FE) software package ANSYS/LS-DYNA. An experimental study of two foam-filled lattice composite panels under low-velocity impact was conducted to verify the numerical model for FLCBS. The corresponding FE models of the composite panels generally showed good agreement, compared to the impact load history and mid-span deflection history of experimental results. Based on the validated numerical model, both head-on collision cases and lateral collision cases with and without FLCBS were investigated. Simulation of different impact angles, velocities and locations were carried out. Numerical results indicate the obvious advantages of FLCBS by comparing peak impact force and impact duration. Significantly decrement of the peak impact force and effectively prolonged impact process indicate the superior performance of FLCBS. The modular fabrication and replacement, easy and time-efficient installation and highly designable structure make FLCBS very attractive as bridge protection in ship collisions.
  • Novel method for improving fatigue behavior of carbon fiber reinforced
           epoxy composite
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Ajitanshu VedrtnamAbstractThe fatigue prone structures made of carbon fiber reinforced polymer composites (CFRPCs) are frequently used in aerospace, defense, structural, and automotive applications. In this work, a novel method was reported that increases the fatigue life of CFRPC (96.56% at an average) by interface strengthening. The fatigue life of CFRPC composite was evaluated using the standard bending cyclic fatigue test. The CFRPCs were prepared by the hand layup method using a specially designed compression molding setup. The waste glass powder and PVA adhesive were used for treating the carbon fibers (CFs). The statistical analysis was used to interpret the effect of the volume fraction variation of the treated/untreated CFs on the cyclic fatigue strength (CFS) of the CFRPC. The effect of treatment and the load ration (R) on CFS of CFRPC were reported. The finite element (FE) model was developed using the transient analysis in COMSOL multi-physics (Explicit Dynamics Module) to obtain the deformation and stresses for treated/untreated CFRPC made using single tow of the carbon fiber. The experimentation on treated and untreated single tow CFRPC was performed to validate and complement the FE model. The stress-deformation-life relations for CFRPC were established. The scanning electron microscopy (SEM) images were used to establish the structure-property relationship and explain the basis for increment in CFS of CFRPC. Analysis of variance was conducted to ensure the validity of the experimental results.
  • Shear properties of polyurethane ductile adhesive at low temperatures
           under high strain rate conditions
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Zhemin Jia, Guoqing Yuan, Xiaoping Feng, Yun Zou, Jingyan YuAbstractThe shear properties of the polyurethane adhesives at room temperature (RT) and low temperatures under different loading speeds were experimentally studied by thick adherend shear test (TAST) specimens. The shear strength of the polyurethane (PU) adhesive decreases with the temperature reducing at quasi-static conditions. The ultimate shear strain also shows a decreasing trend with the decrease of the temperature. With the loading speed increases, the shear strength of the adhesive increases significantly. When the loading speed increases to 1000 mm/s, compared with the data under quasi-static conditions, the strength of the adhesive increases by 177%. Under the impact conditions, the strength of the adhesive at low temperatures decreases a lot compared with that at RT. The mechanical behavior of the TAST specimens under impact loadings at different temperatures were reasonably predicted by the 3D finite elements method by ABAQUS. It is concluded that the shear strength of adhesive at RT under quasi-static cannot be used to design and analyze the adhesive joints at low temperatures under impact loading conditions.
  • Fabrication, morphology and thermal properties of octadecylamine-grafted
           graphene oxide-modified phase-change microcapsules for thermal energy
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Da-Zhu Chen, Si-Yin Qin, Gary CP. Tsui, Chak-yin Tang, Xing Ouyang, Jia-Hua Liu, Jiao-Ning Tang, Jian-Dong ZuoThe demands for achieving microencapsulated phase-change materials (MEPCMs) with high thermal-energy storage ability have motivated increasing research interest in inorganic filler-modified MEPCMs. However, challenges for such MEPCMs still exist in the pursuit of good compatibility of inorganic particles with the core or shell material. Here, a novel type of octadecylamine-grafted graphene oxide (GO-ODA) -modified MEPCMs using melamine-formaldehyde (MF) resin as the shell material and the mixture of GO-ODA and n-octadecane as the core material was fabricated via in-situ polymerization. The alkylated GO with a thickness of ∼1 nm was confirmed to be highly compatible with the core material. The as-prepared MEPCMs with a regular spherical shape were dispersed without any agglomeration, and the size decreased with increasing the filling amounts of GO-ODA. The incorporation of GO-ODA promoted the crystallization of n-octadecane, resulting in an observable reduction in supercooling degree. The encapsulation efficiency of MEPCMs was calculated to be over 88.0%, and the melting/freezing latent heats reached to a level as high as 207.2 J g−1 and 202.5 J g−1, respectively, even at a tiny loading level of 0.5%. Besides, the GO-ODA incorporated MEPCMs showed a good thermal cycling stability during a phase change. Moreover, a substantial enhancement in thermal transfer rate and a less marked heating effect for the MEPCMs containing GO-ODA were observed from the thermal conductivity tests and infrared thermography analysis. The findings suggested that the prepared MEPCMs are promising for applications in the fields of thermal energy storage and temperature regulation due to their enhanced thermal transfer performance and prominent phase-change enthalpy.Graphical abstractImage 1
  • Experimental and numerical investigation on the mechanical characteristics
           of polyethylenimine functionalized graphene oxide incorporated woven
           carbon fibre/epoxy composites
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Nitai Chandra Adak, Suman Chhetri, Naresh Chandra Murmu, Pranab Samanta, Tapas Kuila, Joong Hee LeeAbstractThe synergistic effects of polyethyleneimine functionalized graphene oxide (PEI-FGO) on the static and dynamic mechanical properties of the carbon fibre reinforced epoxy composites were investigated in detail. The functional groups of PEI-FGO, especially the NH2, experienced strong molecular interaction with the epoxy resin, and increased the load carrying capacity of the matrix, and the corresponding overall mechanical strength of the composites. The tensile and flexural strength of the 0.3 wt% PEI-FGO incorporated CF/epoxy composites was improved by ∼ ((58–62) and (65–70)) %, respectively as compared to the base CF/epoxy composites. The numerical analysis via Finite Element Method of the prepared composites was carried out to validate the experimental results. The numerical models showed linear behavior in the stress-strain diagram, whereas the experimental results expressed non-linear behavior, due to the fibre-matrix de-bonding. The effects of temperature and frequency on the dynamic mechanical properties of the prepared composites were meticulously studied. The broadening of the tan δ curve with increasing frequency also signified that PEI-FGO affects the molecular motions of the epoxy network.
  • Vibration behavior of the functionally graded porous (FGP) doubly-curved
           panels and shells of revolution by using a semi-analytical method
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Fei Xie, Ailun Wang, Cijun Shuai, Jinyuan Tang, Qingshan WangAbstractThe main goal of this article is to provide parameterization study for vibration behavior of functionally graded porous (FGP) doubly-curved panels and shells of revolution by using a semi-analytical method. Distribution of the porous through the thickness of structure may be uniform or non-uniform and three types of the porosity distributions are performed in this paper. Mechanical properties of materials are determined by open-cell metal foam. Energy expressions, including kinetic energy and potential energy, are expressed by displacement admissible function. Then, in order to obtain the general boundary conditions including the simply classical boundary conditions, elastic boundary constraint and their combinatorial boundary constraints, each of displacement admissible functions is expanded as a modified Fourier series of a standard cosine Fourier series with the auxiliary functions introduced to eliminate all potential discontinuities of the original displacement function and its derivatives at the edges. Lastly, the natural frequencies as well as the associated mode shapes of FGP doubly-curved panels and shells of revolution are achieved by replacing the modified Fourier series into the above energy expression and using the variational operation for unknown expansion coefficients. 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 provide basic data for other algorithm research in the future.
  • Self-healing epoxy nanocomposites via reversible hydrogen bonding
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): L. Guadagno, L. Vertuccio, C. Naddeo, E. Calabrese, G. Barra, M. Raimondo, A. Sorrentino, W.H. Binder, P. Michael, S. RanaThe development of high performance self-healing composites is still at an early stage due to the difficulty to integrate self-healing mechanisms in their structure by applying current manufacturing processes. Here, the authors propose structural self-healing resins based on dynamic hydrogen bonds capable to overcome many current industrial limitations. Hydrogen bonding moieties, such as barbiturate and thymine, able to act as reversible healing-elements by their simultaneous donor and acceptor character, can be covalently linked to multi-wall carbon nanotubes (MWCNTs) to generate self-healing nanocomposites. The so functionalized MWCNTs, embedded in a rubber-toughened epoxy formulation, lead to reversible MWCNTs-bridges through the matrix due to strong attractive interactions between the rubber phase, finely dispersed in the matrix, and MWCNT walls. Healing efficiencies have been assessed for the nanocharged epoxy formulation loaded with 0.5% wt/wt of MWCNTs decorated with barbituric acid and thymine groups. For both functional groups, healing efficiencies higher than 50% have been found. Dynamic mechanical analysis (DMA) evidences an enhancement in epoxy chains movements due to micro/nano domains of the rubber phase enabling self-healing behavior by recovering the critical fracture load. Results from this study may promote the wide development of safe and cost-efficient self-healing composites in aeronautical, automotive, civil engineering and wind power industries.Graphical abstractImage 1
  • Resistance of interfacial debonding failure of GFRP bars embedded in
           concrete reinforced with structural fibers under cycling loads
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): B. Kim, J.-Y. LeeAbstractGFRP rebars with different surface treatments such as helical wrapping and sand coating were evaluated under cyclic loads. The pull-out specimens were made from the addition of structural fibers (hooked end steel, PP, PVA fibers) with 1% of fiber volume fraction in a concrete matrix with expected change in interfacial bonding property as well as ductility improvement after first cracking. The experimental results were analyzed in terms of bond stress-slip curve, bond strength ratio, and energy dissipation. Severe failures in the interfacial layers of the GFRP rebars at the resin-bar fiber interface was observed as cycling loads increased. The addition of structural fibers to concrete generally showed significant changes for debonding failure mechanism since the strong bonding resulted in reduced energy dissipation as well as a sharp increase of load in the bond stress-slip curve. For the GFRP rebars, wedge effects from crushed or cracked particles due to repeated damage in the interfacial debonding zone affected the low dissipated energy. Abrupt pull-out bar failure was represented. The effect of fibers in the interfacial bonding layer confirmed that resistance of steel rebar to cycling debonding failures from rebar types showed the best performance. In particular, the addition of hooked steel fibers indicated the best performance regardless of rebar types.
  • Tensile behavior of basalt textile grid reinforced Engineering
           Cementitious Composite
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Benben Li, Haibei Xiong, Jiafei Jiang, Xiangxiang DouAbstractTo overcome the shortness of organic bonding in fiber-reinforced polymer (FRP) retrofitting, textile-reinforced mortar (TRM) has been studied as an alternative composite for retrofitting structural concrete. However, the brittleness of mortar brings the conflict between the efficient using of FRP and durability performance of TRM. To solve this problem, Engineering Cementitious Composite (ECC) can potentially be used to replace mortar in TRM, due to its “ductile” property. The new textile-reinforced composite is named as TR-ECC. In this paper, the tensile failure mechanism and mechanical properties of TR-ECC composite, which was composed of basalt textile grids and one kind of ECC, Ultra High Ductility Cementitious Composite (UHDCC) as the matrix, was investigated. The uniaxial tensile tests on 24 TR-ECC specimens (eight groups) were carried out. The variables include thickness of UHDCC per layer, textile grid geometry configuration and volumetric ratio of textile grids. The influence of variables on the failure pattern, initial elastic and hardening modulus, crack tensile stress, ultimate tensile strain and stress of TR-ECC were analyzed. Finally, the stress-strain behavior and strength of TR-ECC were compared with that of traditional TRM. The test and comparison results show that ECC can largely improve the textile reinforcement effect than the mortar and well control the cracking width.
  • The effect of different linear robot travel speed on mass flowrate of
           pineapple leaf fibre (PALF) automated spray up composite
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Z.M. Hanafee, Khalina Abdan, M. Norkhairunnisa, Z. Edi Syams, Liew Kan ErnAbstractThis paper investigates the effect of different linear robot travel speed on mass flowrate of bio composites automated spray up. The linear robot travel speed investigated are 0.5, 0.75, 1.0, 1.25 and 1.5 m/s. In this study, the manual chop spray gun is integrated with industrial robotic arm to produce random discontinuous fibre composite (DFC) from PALF roving (273 tex) and vinyl ester resin. Samples fabricated are tested for mechanical properties including tensile and flexural, and thermal properties including TGA and DMA. The results showed that the speed of 0.75 m/s yielded 28.70 MPa of tensile strength, tensile modulus of 3.17 GPa, with the lowest Coefficient of Variance (COV) of 9.51%, which denotes the best combination compared to all other robot speed. The flexural test depicted speed of 1.0 m/s to be the highest with 59.12 MPa with 18.10% COV, while speed 0.75 m/s produced the best COV of 12.67% despite lower flexural strength of 55.83 MPa. The TGA showed that the 0.75 m/s speed sample yielded the highest onset oxidation temperature (OOT) of 392.06 °C and highest maximum combustion temperature of 433.40 °C. The DMA depicted the highest Glass Transition Temperature (Tg) of 118.20 °C is also recorded by the 0.75 m/s robot speed composite sample.
  • Design properties of insulated precast concrete sandwich panels with
           composite shear connectors
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): Wonchang Choi, Seok-Joon Jang, Hyun-Do YunAbstractResearchers have developed various types of shear connectors to enhance shear transfer in insulated concrete sandwich panels. The shear transfer capacity of a precast concrete sandwich panel (PCSP) system that is composed of two precast reinforced concrete wythes separated by a layer of insulation wythe is influenced by the degree of composite behavior/action. This paper presents experimental results of push-out tests of concrete sandwich panels that use a grid type of glass fiber-reinforced polymer shear connector and then compares these results with previous research results that are based on corrugated shear connectors. A design equation (ICC-ES) was modified for this work to determine the shear strength of PCSPs with various configurations. For this study, 22 double-shear (push-out) specimens were fabricated and tested using two types of insulation materials, three insulation wythe thicknesses, and two grid spacings for the shear connectors as the variables. The test results were used to calculate toughness index and shear modulus values and to calibrate the modified ICC-ES equation. Increasing the thickness of the insulation wythe had a decreasing effect on the maximum shear flow and shear modulus of the PCSP system.
  • A design oriented multiaxial stress-based criterion for the strength
           assessment of adhesive layers
    • Abstract: Publication date: Available online 23 August 2018Source: Composites Part B: EngineeringAuthor(s): A. Spaggiari, D. Castagnetti, E. DragoniAbstractAdhesively bonded joints are becoming widespread in the composites industry and therefore there is a need for quantitative information on the mechanical strength of the material used. The great strength and stiffness of a composites structure may be strongly undermined by their weakest part, the bonded joint. Unfortunately, the testing of adhesives in bulk form may not be representative of their behaviour in a layered state, typically quite thin, because of differences in the polymerization process and lack of adhesive-adherend interfaces. The drawback of the test in thin layer is the stress concentration at the edges, typical in the single lap or t-peel joints, and also the chance of having the adhesive subjected both to a shear and predominant peel stress. This work deals with the characterization of adhesives in thin film under uniform distributions of multi-axial stresses, which is the typical application condition. The test exploits a tubular butt-bonded specimen, previously investigated by the authors, which guarantees a non-singular stress field over the adhesive layer both in shear and normal directions. According to the analytical prediction, in addition to the direct normal stress, both radial and circumferential secondary stresses arise in the adhesive, due to the constrained lateral contraction imposed by the adherends (Poisson's effect). The test campaign investigates two chemically different, commercial adhesives, an acrylic and an epoxy resin. By means of a biaxial testing machine, we applied to the specimens eight different combinations of normal and shear loads ranging from pure tensile to a shear-compressive stress state. As expected, both the pure shear stress and the compressive stresses lead to better performances of the adhesive layer with respect to tensile loading. The authors compare a variety of failure criteria from the literature and propose a simple multiaxial criterion to obtain a failure envelop of the experimental data. The applicability of the criterion is also assessed on experimental tests found in literature on different configurations and gives fairly good results. The outcome of study is a simple stress based, failure criterion, which can be used to predict the failure of several adhesive bonded joints, relying only on monoaxial experimental data.
  • On the additive manufacturing of an energy storage device from recycled
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): Rupinder Singh, Harpreet Singh, Ilenia Farina, Francesco Colangelo, Fernando FraternaliAbstractThe disposal/recycling of plastic materials are one of the biggest challenges of 21st century. Some studies have been reported in recent past on recycling of thermoplastics via three-dimensional (3D) printing as a novel technique under primary and secondary recycling. But hitherto no work has been reported on use of recycled/virgin thermoplastics for use as energy storage devices (ESD). In this paper an effort has been made to develop in house ESD in form of dry cell by printing with low cost fused deposition modeling (FDM) based commercial open source 3D printer. The feed stock filament of FDM has been prepared by twin screw extrusion (TSE) comprising of advanced composite materials (thermoplastic: acrylonitrile butadiene styrene (ABS) matrix, reinforced with different proportions of chemicals/salts namely: MnO2, ZnCl2, NH4Cl and graphite), which has been used to print dry cell for energy storage applications. The commercial dry cell consists of four zones/sections and feed stock filaments for three zones have been prepared separately on TSE (with different proportions of ABS and reinforcement of chemical/salts) and fourth zone (of Zn metal) has been casted with conventional sand casting route. Finally, all four zones have been assembled in series to develop fully functional prototype of ESD. This study highlights that with the proposed methodology, dry cell comprising of minimum 40% by weight recycled thermoplastics can be prepared successfully having voltage potential at par with commercial dry cell. Another major advantage of using this novel route is that the ESD prepared is more thermally stable (confirmed by differential scanning calorimetry (DSC) analysis) and can operate up to 95 °C temperature. Along with this the ESD so prepared has better rheological, mechanical properties (tensile, surface hardness) ensuring it to be useable under severe loading conditions. The results are also supported by photomicrographs.
  • Temperature dependent thermoelectric properties of cuprous delafossite
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): Yining Feng, Aline Elquist, Yuepeng Zhang, Kaizhong Gao, Ian Ferguson, Athanasios Tzempelikos, Na LuAbstractThe use of nanostructured delafossite oxides in thermoelectric (TE) applications has attracted a great interest due to their high performance and long-term stability at elevated temperatures. Cuprous delafossites, CuMO2 (M = Al, Cr, Fe, Ga, Mn), compared to conventional TE materials, such as Bi2Te3, PbTe and SiGe, are non-toxic and more earth abundant. In particular, CuAlO2 compound shows a great potential for high performance thermoelectric materials.In this work, a systematic study of temperature dependent TE properties of cuprous delafossite materials, CuAlO2, is reported. The optimization of the TE properties has been realized by controlling nanostructure size around 80 nm CuAlO2 powder was prepared using a solid-state synthesis method at ∼1373 K in nitrogen/air atmosphere. The nanostructure size was controlled by a high energy ball milling process. Reducing the particle size of nanostructured bulk materials decouples interdependent electron and phonon transport and results in a lattice thermal conductivity decrease without deteriorating electrical conductivity. The high effective mass plays a dominant role in the high Seebeck coefficient and low electrical conductivity. The power factor reached ∼0.78 × 10−5 W/mK2 at 780 K. Temperature dependent TE properties, including Seebeck coefficient, electrical conductivity, and thermal conductivity are analyzed. The processing-structure-property correlation of these materials are discussed.
  • Production feasibility and performance of carbon fibre reinforced glulam
           beams manufactured with polyurethane adhesive
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): Michele Brunetti, Ioannis P. Christovasilis, Michelangelo Micheloni, Michela Nocetti, Benedetto PizzoAbstractWood is a structural material traditional and modern at the same time. It can be used as solid timber or combined with adhesives to form engineered wood products with enhanced mechanical properties, opening several opportunities for the development of the wood building sector in the construction industry. Here, the feasibility of producing glulam beams reinforced with carbon fabric applied using mono-component polyurethane glue was analysed. The same adhesive was utilized during beam manufacturing; thus, carbon-reinforced elements were produced with a unique assembling procedure. Unreinforced glulam beams were compared with strengthened elements; the factors analysed were the thickness of the carbon fabric and the adhesive type used at the fabric-timber interface, comparing the polyurethane adhesive with an epoxy resin. Both bending tests and numerical modelling have been performed in the study. Tests showed that the general performance of the strengthened elements with polyurethane glue, in terms of strength and stiffness, was equivalent with the one obtained with the epoxy adhesive used as a reference, thus confirming that polyurethane can be fully suitable and efficient for industrial production. The carbon fabric considerably improved the bending strength of the original element (between 45% and 57%); the quantity of fibres did not influence the strength, but it significantly affected the stiffness (increased from 12% to 22% for carbon fabric of 500 and 1000 g/m2 weight, respectively, compared to unreinforced beams). The modelling evidenced that the effective modulus of elasticity of the reinforcement, as a system of carbon fabric and adhesive, was on average higher and with lower variability for the specimens with polyurethane adhesive compared to the ones with the same carbon fibre quantity but glued with epoxy resins.
  • Perforated shear + reinforcement bar connectors in a timber-concrete
           composite solution. Analytical and numerical approach
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): Félix Suárez-Riestra, Javier Estévez-Cimadevila, Emilio Martín-Gutierrez, Dolores Otero-ChansAbstractThis paper presents a study of a novel shear connector in a timber-concrete composite solution, focussing on the determination of an analytical expression that makes it possible to predict its behaviour and a numerical analysis that describes it accurately. The shear connector is composed of a perforated steel plate inserted into a slot within the timber rib and glued, in combination with reinforcing corrugated steel bars affixed to the top of the plate. Previous tests made it possible to establish failure mode in different T composite section plate-rebar configurations. These results determine the effectiveness of the system in terms of force-slip behaviour, with systematic failure in the timber section. A simple predictive model is proposed to determine the ultimate capacity of the joint, taking into account the mechanical properties of timber in relation with the fracture plane and the timber-adhesive interface. This model makes it possible to apply a design process that is able to predict the stiffness of the connection.FEM models were analysed for each configuration in a variable load process equal to that used in the test, according to the standard procedure. A variable friction coefficient in contact definition made it possible to achieve an accurate descriptive model in association with the test procedure.
  • Characterization of Al2O3/Ni composites manufactured via CSC technique in
           magnetic field
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): Justyna Zygmuntowicz, Marcin Wachowski, Aleksandra Miazga, Katarzyna Konopka, Waldemar KaszuwaraIn the case of this article, the research were involved an innovative concept of forming composites materials. The goal of this study was to determine the possibility of forming microstructure of Al2O3/Ni composites with a gradient structure by new method combining centrifugal casting with the action of magnetic force. By using this innovative method, it was possible to obtain a composite material with a zone structure. The use of the magnetic field resulted in the characteristic distribution of the metallic phase in the ceramic matrix. The material was characterized by negligible porosity due to the application of centrifugal force. Gradient structure was confirmed by SEM observation, EDS measurements and XRD analysis. In addition, selected mechanical properties (hardness, compression strength) were characterized.Graphical abstractImage 1
  • Extreme enhancement of the nonlinear elastic response of elastomer
           nanoparticulate composites via interphases
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): Amira B. Meddeb, Tim Tighe, Zoubeida Ounaies, Oscar Lopez-PamiesOver the last two decades, it has become increasingly unarguable that the addition of a small amount of nanoparticles to elastomers can lead to a drastic enhancement of their elastic response not only at small deformations but, more importantly, at large deformations. Yet, because of the experimental difficulties of conducting direct quantitative measurements of mechanical properties at the length scale of the nanoparticles together with the mathematical challenges associated with the analysis of large deformations in the presence of nanoscale heterogeneities, the precise mechanisms responsible for such an enhancement have remained unresolved. This paper reports a combined experimental/theoretical investigation aimed at revealing and quantifying the precise mechanisms behind the enhanced elastic properties of a prototypical class of elastomer nanoparticulate composites: polydimethylsiloxane (PDMS) filled with an isotropic distribution of TiO2 nanoparticles. The synthesized composites exhibit drastically enhanced stress-stretch responses, featuring up to about a 10-fold increase with respect to the response of the unfilled PDMS elastomer, over the entire spectrum of small and large deformations considered. Inter alia, it is found that the “bulk” PDMS elastomer — i.e., the regions of the PDMS elastomer not immediately surrounding the nanoparticle aggregates formed during the synthesis process — is softer than the unfilled PDMS elastomer, while the “interphasial” PDMS elastomer surrounding the aggregates is significantly stiffer. The latter mechanism is found to rule over the former and to constitute the dominant mechanism behind the drastic enhancements in the macroscopic elastic properties of the composites.Graphical abstractImage 1
  • Mechanical properties and simulation of nanographene/polyvinylidene
           fluoride composite films
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): Qiong Wu, Dong-jian Xie, Yi-du Zhang, Zhe-min Jia, Hua-zhao ZhangNanographene possesses unique mechanical and electrical properties. The mechanical properties of nanographene/polyvinylidene fluoride (PVDF) composite films are studied by experiment and simulation analysis in this paper. Different amounts of nanographene/PVDF samples were prepared to obtain general field emission scanning electron microscopy overviews and perform tensile experiments for obtaining the equivalent elastic moduli. Materials Studio was used to establish nanographene microscopic models to obtain linear elasticity data. The digital simulation models were established using ANSYS to conduct the finite element simulation for the equivalent elastic modulus of the composites in different graphene contents and assumptions.Results of the experiments and simulations showed that the equivalent elastic modulus of the composites increases first with increasing graphene content and then decreases after the mass fraction of graphene reaches 10%. The change in the mechanical properties of nanographene/PVDF composites is due to graphene aggregation. The agglomeration phenomenon increases with the increase in graphene.Graphical abstractImage 1
  • On the porosification of LTCC substrates with sodium hydroxide
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): Ali Hajian, Doruk Müftüoglu, Thomas Konegger, Michael Schneider, Ulrich SchmidAbstractOutstanding material properties of low temperature co-fired ceramics (LTCC) make them the technology of choice when targeting the realization of robust, highly integrated substrates or packaging solutions for micromachined devices. However, the relatively high permittivity limits their utilization in high-frequency applications, as in addition defined areas with reduced permittivity in one single LTCC layer would be most beneficial. The wet-chemical porosification method under alkaline conditions is a novel and most advantageous approach which can be applied for permittivity reduction through locally embedding air into the LTCC surface in its as-fired state with low impact on the surface characteristics. The resulting porosity of the LTCC substrates after the etching process is strongly affected by the LTCC tape composition as well as the etch parameters. Since the chemical composition of the tape is desired to be unaltered, optimizing the etching parameters, namely etchant concentration, etching time, and bath temperature is a reasonable procedure which allows tailoring the porosification process for the LTCC tapes in their as-fired state.In this work the etching behavior and surface morphology of the LTCC substrates have been studied, both qualitatively and quantitatively, and detailed gravimetric and roughness measurements, as well as porosification depth investigations, were carried out. The conducted analyses suggest a dominating reaction-controlled mechanism for the etching process. In addition to generating a tailored porosity in the surface-near region, overall thickness reduction of the LTCC through the overall dissolution of the LTCC surface under a defined etching condition was also possible. The experimental results were finally fitted into a nonlinear polynomial model for providing an experimental basis in order to identify the most crucial parameters to achieve a tailored porosity.
  • About an approach to the determination of the critical time of
           viscoelastic functionally graded cylindrical shells
    • Abstract: Publication date: Available online 22 August 2018Source: Composites Part B: EngineeringAuthor(s): A.H. SofiyevAbstractIn this study the dynamic stability of viscoelastic functionally graded cylindrical shells (VEFGCSs) under an axial load with different initial conditions is investigated. Mathematical models are constructed for the problem of dynamic stability of the VEFGCSs, which is characterized simultaneously by taking into account both viscoelastic and FGM features. The basic equations of VEFGCSs are described by integro-differential equations using the linear viscoelasticity theory. An approach is developed to the determination of the critical times (CTs) for VEFGCSs with different initial conditions. Finally, the numerical analyzes are performed to demonstrate the influences of the initial conditions, the FGM profiles and the rheological parameter on the critical times for various geometric characteristics of the cylindrical shells.
  • Accelerated thermal ageing behaviour of bagasse fibers reinforced Poly
           (Lactic Acid) based biocomposites
    • Abstract: Publication date: Available online 21 August 2018Source: Composites Part B: EngineeringAuthor(s): Manish Kumar Lila, Kartikeya Shukla, Ujendra Kumar Komal, Inderdeep SinghAbstractAgeing behavior is one of the crucial factors for selection of material by designers and engineers, mainly for structural applications. Investigation of the ageing effect on biocomposites would supplement current knowledge and may help in encouraging their uses in real life applications. The current experimental investigation aims to determine the variation in various properties of Bagasse fibers reinforced Poly Lactic Acid (PLA) biocomposites during accelerated thermal ageing. Specimens of biocomposite were fabricated and exposed to temperature cycles of −20 °C and 65 °C (12 h each) for 12 weeks and characterized after every 4 weeks of exposure. Tensile and flexural properties exhibited steady improvement on exposure up to 8 weeks, followed by a reduction after ageing for 12 weeks. It can be concluded from X-ray diffraction (XRD) and dynamic mechanical analysis (DMA) that significant change in crystalline and glass transition behavior happens during the exposure period.
  • Adhesion properties of poly(ethylene oxide)-lignin blend for nanocellulose
    • Abstract: Publication date: Available online 21 August 2018Source: Composites Part B: EngineeringAuthor(s): Tippabattini Jayaramudu, Hyun-U. Ko, Hyun Chan Kim, Jung Woong Kim, Eun Sik Choi, Jaehwan KimAbstractIn this paper, poly(ethylene oxide)-lignin (PEO-L) blends were prepared for eco-friendly nanocellulose composites and the effect of lignin content on its adhesion property was studied by using single lap joint test. The PEO-L blends were prepared by blending method using 60% methanol. Cellulose nanofiber (CNF) film, chosen as an adherent material of eco-friendly nanocellulose composites, was prepared by casting CNF emulsion, followed by vacuum filtration and drying. The successful formation of PEO-L blends was confirmed from FTIR, DSC and XRD studies. The shear strength of PEO-L blend increased with the lignin content and the 30% lignin case (442 kPa) showed 189% larger shear strength than the pure PEO (835 kPa). This shear strength improvement is associated with enhanced hydrogen bonds between lignin/PEO and CNF film.
  • Simplification and development of McLachlan model for electrical
           conductivity of polymer carbon nanotubes nanocomposites assuming the
           networking of interphase regions
    • Abstract: Publication date: Available online 20 August 2018Source: Composites Part B: EngineeringAuthor(s): Yasser Zare, Kyong Yop RheeAbstractThis paper simplifies and develops the conventional model suggested by McLachlan for electrical conductivity of polymer CNT nanocomposites. The original model expresses the conductivity as a function of filler concentration, filler conductivity, filler percolation threshold and an exponent. However, this model is developed by considering the roles of interfacial tension between polymer matrix and nanoparticles, tunneling distance between adjacent nanotubes, interphase regions around nanoparticles and waviness of CNT. The experimental results of conductivity for some samples and the analysis of the effects of various parameters on the conductivity evaluate the developed model. The predictions demonstrate fine agreement with the experimental results and the parameters show acceptable roles in the conductivity of nanocomposites. A large tunneling distance significantly decreases the conductivity to zero. Likewise, the higher and slighter surface energies of the polymer matrix and filler, respectively cause an improved conductivity. A thin interphase produces very low conductivity, while a thick interphase and a low waviness improve the conductivity.
  • Synthesis of PAN/PVDF nanofiber composites-based carbon adsorbents for
           CO2 capture
    • Abstract: Publication date: Available online 20 August 2018Source: Composites Part B: EngineeringAuthor(s): Young-Jung Heo, Yifan Zhang, Kyong Yop Rhee, Soo-Jin ParkAbstractIn this work, we have prepared PAN/PVDF hybrid composites via electrospinning. And, the carbonization and activation process were performed to obtain the porous carbons for CO2 capture. The features and morphologies were observed by HR-SEM, and the surface properties were investigated by XPS. The textural properties were analyzed by N2 adsorption/desorption isotherms at 77 K. The CO2 adsorption/desorption isotherms were measured at 298 K and practical use on CO2 capture processes of the samples were performed under 15% CO2 in N2 as flue gas in fossil fuel power plants through temperature swing adsorption process. The effect of steam activation in electrospun PVDF/PAN nanofibers was investigated in relation to textural properties and CO2 capture. The A-PAN/PVDF nanofibers attained a high CO2 uptake of 2.21 wt%, and exhibited reversible CO2 capturing performances under flue gas condition. These results indicate that the effects of hybridization and steam activation on the CO2 adsorption were confirmed, and the capture performances of the adsorbents were maximized under practical conditions.
  • Free vibration of nonlocal Timoshenko beams made of functionally graded
           materials by Symplectic method
    • Abstract: Publication date: Available online 20 August 2018Source: Composites Part B: EngineeringAuthor(s): Kai Zhang, Meng-Hua Ge, Cheng Zhao, Zi-Chen Deng, Xiao-Jian XuAbstractThe aim of this paper is to numerically investigate the size-dependent vibration behavior of the nano-beam made of functionally graded materials (FGMs). The material properties of the FGMs are considered to vary throughout the thickness direction of the beams. Based on the non-local theory and the material and dimensions of the beams, the total energy including the potential and kinetic energy of the FGMs beams is obtained. The first-order governing differential equations in the Hamilton systems of the beam are constructed by introducing the dual variables and with the help of the variational principle. A precise-constant method and extended Wittrick-Williams algorithm are applied to obtain the structural frequencies of the nano-beams with the clamped-free and clamped-clamped boundary conditions. The model is verified by comparing the results with the data available in the literature. In the following, a study is carried out to find the effects of the nonlocal parameter, power index, and aspect ratio on the vibration of the FGMs nano-beams with the clamped-free and clamped-clamped boundary conditions respectively. The results show the soft effect of the nonlocal parameter on the structural vibration and the increase of the nonlocal parameter leads to the decrease of the frequency. The power index and aspect ratio also have significant effects on the vibration of the beams. The increase of the power index can increase the ceramic volume fraction in the FGMs, which leads to the increase of structural frequencies. The vibration of the beams can be controlled by choosing proper values of the power index and aspect ratio.
  • Modeling of viscosity and complex modulus for poly (lactic acid)/poly
           (ethylene oxide)/carbon nanotubes nanocomposites assuming yield stress and
           network breaking time
    • Abstract: Publication date: Available online 20 August 2018Source: Composites Part B: EngineeringAuthor(s): Yasser Zare, Kyong Yop RheeAbstractIn this paper, the blends and nanocomposites containing poly (lactic acid) (PLA), poly (ethylene oxide) (PEO) and carbon nanotubes (CNT) are prepared and the viscosity of samples is measured at different frequency ranges. After that, a suitable model proposed by Zhu group is applied to predict the viscosity and the viscoelastic parameters of prepared samples. Moreover, this model is developed to suggest the complex modulus as a function of zero viscosity, yield stress, relaxation time and network breaking time. The roles of different parameters in the viscosity and complex modulus are clarified to justify the suggested models. All predictions show good agreements with experimental data at all frequency ranges. The addition of CNT to blend increases the zero viscosity, yield stress, relaxation time and network breaking time. The zero viscosity directly handles the viscosity, but the role of relaxation time in the viscosity depends on the extents of other parameter. Moreover, the low values of yield stress and network breaking time reduce the viscosity, whereas only high yield stress is enough to improve the viscosity. Additionally, high zero viscosity, high yield stress and short relaxation time grow the complex modulus of polymer systems.
  • Flexural behavior of composite sandwich beams with different kinds of GFRP
           ribs in flatwise and edgewise positions
    • Abstract: Publication date: Available online 19 August 2018Source: Composites Part B: EngineeringAuthor(s): Fubin Zhang, Weiqing Liu, Hai Fang, Zhemin JiaAbstractThis paper investigated the flexural behavior of composite sandwich beams, composed of glass fiber reinforced polymer (GFRP) skins and a polyurethane (PU) foam core with different kinds of GFRP ribs reinforcement, in flatwise and edgewise positions. The GFRP ribs, consisted of longitudinal, transverse and horizontal ribs, respectively, were embedded inside of the PU foam core. Twenty specimens were tested under four-point bending to verify the influence of the GFRP ribs and beam orientation on the bending stiffness, ultimate bending strength, and failure modes of sandwich beams. It was found that changing the beam orientation from flatwise to edgewise change the beam failure mode from foam core shear failure to skin compressive failure. The sandwich beam's high stiffness and ultimate bending strength can be efficiently utilized by placing them in edgewise position, and the longitudinal ribs played a major role on the bending stiffness and ultimate bending strength compared with the transverse and horizontal ribs in flatwise position. Furthermore, an analytical model accounting for shear and flexural rigidities was proposed to predict the deflection and ultimate bending strength of composite sandwich beams with different kinds of GFRP ribs in flatwise and edgewise positions. The analytical results were agreed well with test results.
  • Buckling of functionally graded graphene reinforced conical shells under
           external pressure in thermal environment
    • Abstract: Publication date: Available online 18 August 2018Source: Composites Part B: EngineeringAuthor(s): Y. KianiAbstractIn the present research, buckling analysis of composite laminated conical shells reinforced with graphene sheets is investigated. Graphene sheets as reinforcements are distributed in each lamina. Volume fraction of graphene in each layer may be different which results in a piecewise functionally graded conical shell. First order shear deformation shell theory, Donnell kinematic assumptions and von Kármán type of geometrical non-linearity are used to establish the governing equations of the conical shell and the associated boundary conditions. The pre-buckling forces of the shell are obtained employing a membrane analysis. The linear stability equations are developed using the adjacent equilibrium criterion. These equations are discreted by means of the generalised differential quadratures across the shell length and Fourier expansion through the circumferential direction. An eigenvalue problem is obtained which yields the critical buckling pressure of the conical shell in thermal environment and the circumferential mode number at the onset of buckling. Comparison studies are provided for graphene reinforced and conventional composite laminated cylindrical shells and also isotropic conical shells with and without thermal environment. Afterwards parametric studies are given for buckling of functionally graded graphene reinforced composite laminated conical shells in thermal environment with different boundary conditions. It is shown that, temperature elevation decreases the critical buckling pressures of the conical shell significantly. Also buckling pressure of the shell may be enhanced through a piecewise functionally graded distribution of volume fraction of reinforcements.
  • Surface functionalization of boron nitride platelets via a catalytic
           oxidation/silanization process and thermomechanical properties of boron
           nitride-epoxy composites
    • Abstract: Publication date: Available online 17 August 2018Source: Composites Part B: EngineeringAuthor(s): Jae-Ha Lee, Hyunho Shin, Kyong Yop RheeAbstractSurfaces of hexagonal boron nitride (BN) platelets (with an average platelet diameter of 1 μm) were oxidized in sulfuric acid solution under the presence of a sodium nitrate catalyst, followed by silanization in aqueous ethanol solution. Based on Fourier-transform infrared spectroscopy, catalytic oxidation of BN surfaces in this way resulted in a very successful degree of silanization thereafter compared with other non-catalytic surface-oxidation processes reported in the literature. After silanization, both the width and thickness of the catalytically oxidized BN platelets notably increased, suggesting silanization of not only the edge but also the basal planes. When the epoxy matrix was reinforced with the surface-silanized BN platelets, prepared composites demonstrated notably improved thermal and mechanical properties compared with those of raw BN-epoxy composites. Such improvement of thermal and mechanical properties is ascribed to successful surface silanization of BN platelets, yielding enhanced interfacial bonding and dispersion in the epoxy matrix.
  • Damage sensing, mechanical and interfacial properties of resins suitable
           for new CFRP rope for elevator applications
    • Abstract: Publication date: Available online 17 August 2018Source: Composites Part B: EngineeringAuthor(s): Dong-Jun Kwon, Jong-Hyun Kim, Sung-Min Park, Il-Jun Kwon, K. Lawrence DeVries, Joung-Man ParkAbstractThe evaluation of damage sensing for flexural, interfacial and fatigue conditions was studied for carbon fiber reinforces plastic (CFRP) rope, with 4 different formulations of epoxy resin. Thermal analysis and tensile tests were used to investigate the thermal and mechanical properties for different epoxy formulations. Using these experimental results along with the empirical equation between tensile strength, glass transition temperature, Tg, and enthalpy, ΔH, optimum conditions for the epoxy formulations were found. Eddy current and static contact angle measurements were made to evaluate the wettability of epoxy into the carbon fibers with the different epoxy types. Flexural strength, fatigue strength and inter-laminar shear strength (ILSS) were evaluated for manufactured CFRP rope via pultrusion process. Changed ratio of electrical resistance (ER) of CFRP rope were measure during flexural testing, for signs of micro-cracking leading up to final fracture. The signal of CFRP rope were measured by changes in electrical resistance (ER) to predict the fracture failure. From the results of these studies it was concluded that an acid anhydride-based epoxy was the optimal epoxy formulation for manufacture of CFRP rope.
  • An exact three dimensional solution for bending of thick rectangular FGM
    • Abstract: Publication date: Available online 16 August 2018Source: Composites Part B: EngineeringAuthor(s): Zahra Vafakhah, Bahram Navayi NeyaAbstractThis study uses the displacement potential function, DPF, to present an exact solution for bending of functionally graded, FGM, thick plates. The plates are simply-supported rectangular, isotropic, and nonhomogeneous, with exponential variation of Young's modulus along their thickness Using the DPF, the governing equations are simplified to second and fourth order partial differential equations solved by using the separation of variables method and applying exact boundary conditions. The solution is applicable to any plate with no restriction on its thickness as well as to all FGM plates. The results are compared with other existing analytical and numerical results for thin, moderately thick, and thick plate. Comparisons show excellent agreement making the method applicable and reliable for various kinds of material properties, thickness ratios and loading conditions without any simplifying assumptions such as for strain or stress distribution in plate thickness. Various inhomogeneity, thicknesses, and aspect ratios are also investigated with respect to plate responses with results showing that increase in inhomogeneity, and decrease of aspect ratio and FGM plate thickness result in decrease in the dimensionless transverse displacement of the plate. Moreover, the effects of increasing inhomogeneity on transverse displacement are more significant for thicker plates and higher aspect ratios.
  • Dynamic impact response of aluminum honeycombs filled with Expanded
           Polypropylene foam
    • Abstract: Publication date: Available online 16 August 2018Source: Composites Part B: EngineeringAuthor(s): Yanqing Zhang, Qiang Liu, Zhaoheng He, Zhijian Zong, Jianguang FangAbstractThe paper investigated the dynamic impact response and characteristics of aluminum honeycomb filled with EPP foam (Expanded polypropylene) experimentally and numerically. It was found that the initial peak strength and mean strength of the filled honeycomb were improved significantly attributable to the interaction effect between the aluminum honeycomb and the foam, but the specific energy absorption (SEA) decreased. For the filled specimens with the same foam density, the initial peak strength, mean strength and SEA increased with the increase in impact velocity. Compared with the characteristics in the static compression test, the initial peak strength in the dynamic impact test increased, whereas the mean strength and SEA decreased. The study showed that EPP foam filling was effective to improve the impact characteristics of the bare aluminum honeycomb. Numerical simulation for the dynamic impact of filled honeycombs was also explored. It accurately reproduced the deformation process and addressed the interaction between the wall and EPP foam. By comparison of the properties in different filling types, it showed the single-cell filling was a good choice to improve the load resistance while using the least filling material.
  • The geometrical advantages of helical carbon nanotubes for
           high-performance multifunctional polymeric nanocomposites
    • Abstract: Publication date: Available online 16 August 2018Source: Composites Part B: EngineeringAuthor(s): Ravikumar Vijayan, Ali Ghazinezami, Sean R. Taklimi, Moheimin Khan, Davood AskariAbstractPolymer Matrix Composites (PMCs) with their low densities exhibit remarkable material properties, making them as an excellent choice for high-performance structural applications. However, the polymer matrix used to bond the fibres are very weak and exhibit poor mechanical properties. The focus of this study was to take advantage of the unique helical (i.e., coil-like) geometries of Carbon Nanotubes (CNTs) to improve the properties of polymer matrix, more effectively and at very low concentrations (e.g., less than 0.2% by weight to reduce the nanomaterials' cost). One of the unique characteristics of the helical CNTs is their 3-dimensional helical geometry that can physically intertwine/entangle/interlock with traditional microfiber reinforcements and be mechanically interlocked within the solidified resin system, when they are used as reinforcements in polymeric composites. Nanocomposite samples were fabricated using CNTs with different geometrical configurations (i.e., straight and helical) and loading percentages and their properties (e.g., mechanical, thermal, and electrical) were evaluated according to the ASTM standards. Based on the results, the optimum weight percentage of the CNTs reinforcements that exhibit maximum properties improvements for the matrix system were identified, considering their geometrical configuration. The main objective here was to demonstrate/prove that helical structures of CNTs can perform better than straight CNTs, because of their 3-D helical interlocking mechanism. The 2nd objective of this work was to demonstrate/proof that inclusion of CNTs with various geometries in polymeric resins can improve their electrical and thermal conductivities, as well, even at low concentrations.
  • A facile process to manufacture high performance copper layer on ceramic
           material via biomimetic modification and electroless plating
    • Abstract: Publication date: Available online 14 August 2018Source: Composites Part B: EngineeringAuthor(s): Yan Wang, You-he Xu, Zhi-yuan Cao, Chuan Yan, Kang Wang, Jin-ju Chen, Chuan Yan, Zhe-sheng FengAbstractA convenient and eco-friendly approach to fabricate high-quality copper layer on ceramic viasurface modification combined with electroless plating is introduced in thispaper. Through the surface modification of polydopamine, alumina ceramic substrate is capable ofadsorbing silver ions, which could create an activating layer to catalyze the subsequent electrolesscopper plating (ECP) at low temperature. The finding that modificationcould obviously enhance the adhesion betweensubstrates and copper layers are evaluated by water contact angle measurement, XPS, FT-IR, SEM, EDS andadhesion tests. Moreover, after30 min of ECP, the resulting deposited copper layer presents an excellent performance in adhesion (highest level in ASTM D3359) andconduction (up to 4.2×107S⋅m−1, nearly 70% of bulk copper). This technology might provide a potential way to realize surface metallization on ceramicsubstrates applied in electronic circuits and devices.
  • Fabrication of polymer composite films with carbon composite nanofibers
           doped MWNTs-OH for multilevel memory device application
    • Abstract: Publication date: Available online 13 August 2018Source: Composites Part B: EngineeringAuthor(s): Yuanyuan Liu, Jinghua Yin, Xiaoxu Liu, Xiaofeng Zhao, Minghua Chen, Jialong Li, He Zhao, Congcong Zhu, Bo SuAbstractNovel carbon composite nanofibers with hierarchical microstructure were synthesized using electro-spinning and carbonization (SC) techniques, and were combined into polyimide matrix based on in-situ polymerization method. The resulted polyimide composites exhibit multilevel resistive switching behavior (MRSB) for memory storage applications, with a favorable ON/OFF current ratio and a high retention time at an operating voltage less than 3 V. A hierarchical microstructure can be observed by SEM, TEM and SAXS tests, which was formed with different sizes between the hydroxyl multi-walled carbon nanotubes (MWNTs-OH), carbon nanofibers and PI matrix, influencing on the MRSB of the composite films. A physical model based on the molecular orbit energy level was utilized to investigate how the microstructures acting as charge transmission layers affect the MRSB. This result provides a new strategy for further improving the high density storage of polymer multilevel switching memory storage device.
  • High selective production of 5-hydroxymethylfurfural from fructose by
           sulfonic acid functionalized SBA-15 catalyst
    • Abstract: Publication date: Available online 13 August 2018Source: Composites Part B: EngineeringAuthor(s): Lei Wang, Libo Zhang, Hongyi Li, Yubo Ma, Ronghui ZhangAbstractA mesoporous SBA-15 supported sulfonic acid catalyst (SBA-15-SO3H) was successfully prepared and used for the selective conversion of fructose to 5-hydroxymethylfurfural (HMF). Up to 96% of HMF selectivity with 100% fructose conversion was obtained under mild conditions (120 °C, 60 min, DMSO as solvent). Solvent effect, reaction time, reaction temperature and fructose-to-catalysts mass ratio have been investigated. The SBA-15-SO3H solid acid catalyst can be separated from the reaction mixture after reaction and reused by simple centrifugalization, and 100% fructose conversion with 95% HMF yield could be retained. Further, reaction activation energy of 56.4 kJ/mol has been fitted with kinetic analysis, which means that the dehydration of fructose into HMF is relative easier over SBA-15-SO3H catalyst in this work. Besides, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM) measurements reveal that the –SO3H grafting on the SBA-15 surface have no obvious influence on its mesoporous structure even after five catalytic cycles, and acid site measurements demonstrate that there was no significant loss of acid site concentration, indicating high catalytic stability. This fruit give a useful reference to chemical engineering and materials.
  • Bending strength of CFRP laminated adhesive joints fabricated by
           vacuum-assisted resin transfer molding
    • Abstract: Publication date: Available online 13 August 2018Source: Composites Part B: EngineeringAuthor(s): Mahmoud R. Abusrea, Seung-Wook Han, Kazuo Arakawa, Nak-Sam ChoiAbstractThe laminated joints used in this work were adhesive joints constructed using two dry carbon fiber halves. Some improvements were introduced to the joints to enhance their bending strength performance: stitching of the two halves together by fiber bundles and inserting extra carbon fiber covers in the joint connection. We studied three adhesive joints: a conventional basic and two improved laminated joints. All joint specimens were fabricated using a vacuum-assisted resin transfer molding (VARTM) process. The joints were evaluated with a bending test, and were compared to the bending strength of a jointless carbon fiber reinforced plastic (CFRP) laminate. Two acoustic emission (AE) sensors were placed on the specimen to monitor the fracture progresses during the test. The improved laminated joints, stitched and multiple-cover overlapped joints, showed enhanced bending strength and joint efficiency. The improvement depended significantly on the number of carbon fiber layers. The maximum increase was 24% for the stitched laminated joint of 5 layers and 58% for the multiple-overlapped joint of 6 layers, respectively. Such high joint efficiency was due to the effect of the carbon fiber reinforcement on the joints, by which many carbon fibers supported the strength in advance of reaching the maximum load point, as confirmed by AE measurement analysis.
  • Numerically-aided 3D printed random isotropic porous materials approaching
           the Hashin-Shtrikman bounds
    • Abstract: Publication date: Available online 13 August 2018Source: Composites Part B: EngineeringAuthor(s): O. Zerhouni, M.G. Tarantino, K. DanasAbstractThe present study introduces a methodology that allows to combine 3D printing, experimental testing, numerical and analytical modeling to create random closed-cell porous materials with statistically controlled and isotropic overall elastic properties that are extremely close to the relevant Hashin-Shtrikman bounds. In this first study, we focus our experimental and 3D printing efforts to isotropic random microstructures consisting of single-sized (i.e. monodisperse) spherical voids embedded in a homogeneous solid matrix. The 3D printed specimens are realized by use of the random sequential adsorption method. A detailed FE numerical study allows to define a cubic representative volume element (RVE) by combined periodic and kinematically uniform (i.e. average strain or affine) boundary conditions. The resulting cubic RVE is subsequently assembled to form a standard dog-bone uniaxial tension specimen, which is 3D printed by use of a photopolymeric resin material. The specimens are then tested at relatively small strains by a proper multi-step relaxation procedure to obtain the effective elastic properties of the porous specimens.
  • Preparation and properties of modified porous starch/carbon black/natural
           rubber composites
    • Abstract: Publication date: Available online 13 August 2018Source: Composites Part B: EngineeringAuthor(s): Xueyu Du, Yucang Zhang, Xuemei Pan, Fanrong Meng, Jianhua You, Zhifeng WangAbstractStarch is considered as a cost-effective, abundant, renewable and environmental-friendly filler for rubber reinforcement via proper modification. In the present study, porous starch (PS) was modified by esterification with dodecenyl succinic anhydride (DDSA) for preparation of DDSA-modified porous starch (DDSA-PS). The suitable esterification conditions (e.g., temperature, time and dosage of DDSA) were discussed by single-factor experiments as 40 °C, 8 h, and 8 wt % (based on porous starch dry weight), respectively. Later on, a series of DDSA-PS/carbon black (CB)/natural rubber (NR) composites were prepared from the mixture of carbon black and DDSA-PS/NR compound that was pre-processed by co-coagulation of DDSA-PS and rubber latex. When the total filler dosage is constant as 60 parts per hundred rubber (phr), various properties of DDSA-PS/CB/NR composites were investigated by varying the composition ratio of DDSA-PS/CB. The results showed that when the ratio of DDSA-PS/CB was increased, the Payne effect of rubber compounds was attenuated to a large extent as well as the reduction of mechanical properties and wear resistance of vulcanized rubbers. Notably, the rolling resistance and hysteretic property were improved, reflected as the reduction of heat built-up, by incorporation of modified porous starch into the final NR composites. Therefore, DDSA-PS could be served as a promising filler for rubber industry partially instead of carbon black.
  • Novel TiB2-reinforced 316L stainless steel nanocomposites with excellent
           room- and high-temperature yield strength developed by selective laser
    • Abstract: Publication date: Available online 25 July 2018Source: Composites Part B: EngineeringAuthor(s): Bandar AlMangour, Young-Kyun Kim, Dariusz Grzesiak, Kee-Ahn LeeSelective laser melting (SLM) is an emerging additive manufacturing process to fabricate multifunctional parts by locally melting and consolidating powders in a layer-by-layer manner. Its flexibility enables the development of new alloys and metal matrix composites with unique, fine microstructures and complex-shaped components that are all difficult to realize with traditional manufacturing processes. This study investigates how TiB2 nanoparticle reinforcements affect the microstructure and high-temperature deformation behavior of a 316 L stainless steel matrix. In SLM-processed pure stainless steel, fully directional columnar grains were observed, whereas TiB2 nanoparticles added to the steel matrix significantly reduced sizes of the molten pools and grains and disrupted the directional structures. A chemical analysis revealed no compositional difference between the boundary and interior of the molten pool areas of the SLM-processed TiB2/316 L nanocomposites, suggesting that elements did not segregate macroscopically. However, for higher TiB2 contents, alloying elements microsegregated at the boundaries of cellular structures due to the particle accumulation structure mechanism. Transmission electron microscopy confirmed the existence of mostly cube-like TiB2 nanoparticles both at the boundaries and in the interiors of the cellular structures. The nanocomposites exhibited high compressive yield strength and ductility at room and high temperatures, except at 600 °C, where embrittlement was observed. Observing the microstructure and flow stress of nanocomposites deformed at 700 and 800 °C shed light on the dynamic recovery and dynamic recrystallization phenomena. However, several conventional strengthening effects could not predict the entire yield strength increase. Thus, a novel microsegregation strengthening mechanism was presented to explain the effect of TiB2 on the refined microstructure, and the novel microsegregation phenomenon and the enhanced mechanical properties were correlated. Hence, the SLM process shows high potential for fabricating new materials with outstanding properties.Graphical abstractImage 1
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