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Composites Part B : Engineering
Journal Prestige (SJR): 2.039
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1359-8368
Published by Elsevier Homepage  [3157 journals]
  • Molecular dynamics and micromechanics study of hygroelastic behavior in
           graphene oxide-epoxy nanocomposites
    • Abstract: Publication date: Available online 19 January 2019Source: Composites Part B: EngineeringAuthor(s): Seunghwa Yang, Sunyong Kwon, Man Young Lee, Maenghyo Cho The hygroelasticity of oxygen-functionalized graphene (GO)-epoxy nanocomposites is studied. Two different transversely isotropic nanocomposite molecular models are constructed: with uniformly distributed and interface-concentrated water molecules, respectively. The stress-strain curves and coefficients of moisture expansion (CMEs) are determined according to moisture content. The degradation of the GO/epoxy interface due to the infiltrated moisture is characterized by interfacial decohesion tests. The micromechanics model is used to derive new closed-form solutions for the effective elastic stiffness and CME of multi-phase composites with interfacial imperfections. Regardless of the moisture distribution, the overall hygroelastic behavior of nanocomposites clearly degrades upon moisture absorption.
  • Hybrid composite mats composed of amorphous carbon, zinc oxide nanorods
           and nickel zinc ferrite for tunable electromagnetic interference shielding
    • Abstract: Publication date: Available online 18 January 2019Source: Composites Part B: EngineeringAuthor(s): Shivam Gupta, Ching Chang, Chih-Huang Lai, Nyan-Hwa Tai With the rapid growth of electronics and telecommunication industries, electromagnetic pollution is a serious concern to be addressed because it not only affects the sensitivity and performance of the devices but also affects human's health. Here, we report lightweight hybrid composite mats, having porosity around 40%, composed of amorphous carbon, zinc oxide nanorods and nickel zinc ferrite for excellent electromagnetic interference (EMI) shielding in the X-band (8.2–12.4 GHz). The vibrating sample magnetometer measurement confirmed that the saturation magnetization value (Ms) of the composite materials enhances with the weight percentage of zinc oxide nanorods-nickel zinc ferrite (ZNF) powder, which leads to enhanced magnetic loss of the electromagnetic waves. With the thickness of 1.0 mm, the total EMI shielding effectiveness of the amorphous carbon composite was measured to be 25.70 dB which was further enhanced to 53 dB by the incorporation of the ZNF powder. Such high increment is attributed to the enhanced magnetic properties, interfacial polarization and dielectric properties of the composite. The synergistic combination of the materials results in the high reflection coefficient and absorption coefficient of the composites which were measured to be ∼0.916 and ∼0.083, respectively. Thus, the composites can shield up to 99.999% power of the electromagnetic waves which is shared by the 8.394% reflection and 91.605% absorption. Moreover, the magnetic, electrical and EMI shielding properties of the composites can be tuned by controlling the amount of ZNF powder in composites. Hence, the composite mats can be suitable for applications in defense and telecommunication.Graphical abstractImage 1
  • Prediction of the ultimate strength of quasi-isotropic TP-based laminates
           structures from tensile and compressive fracture toughness at high
    • Abstract: Publication date: Available online 18 January 2019Source: Composites Part B: EngineeringAuthor(s): B. Vieille, J.-D. Pujols Gonzalez, C. Bouvet This paper is intended to test the capacity of a simple model based on fracture mechanics concepts to predict the ultimate strength of notched hybrid carbon and glass fibers woven-ply reinforced PolyEther Ether Ketone (PEEK) thermoplastic (TP) quasi-isotropic (QI) laminates under different temperature conditions. In such materials, translaminar failure is the primary failure mode driven by the breakage of 0° and 45° oriented fibers in tension as well as the formation of kink-band in compression. Single-Edge-Notched Bending (SENB), Open-Hole-Tensile (OHT) and Open-Hole-Compression (OHC) specimens have been conducted at room temperature (RT) and at a temperature higher than the glass transition temperature (Tg). The Critical Damage Growth model derived from the Average Stress Criterion and Linear Elastic Fracture Mechanics (LEFM) have been applied to open-hole specimens to determine the critical damage zone from which the fracture toughness in tension (0° and 45° fibers breakage) KIctension and in compression (kink-band formation) KIccomp. are estimated. In Single Edge Notched Bending (SENB) specimens experience simultaneous tension/compression. From the estimation of KIctension and KIccomp., the ultimate strength of SENB specimens can be predicted. LEFM equations combined with the critical fracture toughness in tension give relatively accurate results, suggesting that failure is driven by fibers bundles breakage in tension.
  • Power generation by PVDF-TrFE/graphene nanocomposite films
    • Abstract: Publication date: Available online 16 January 2019Source: Composites Part B: EngineeringAuthor(s): Liangke Wu, Min Jing, Yaolu Liu, Huiming Ning, Xuyang Liu, Shifeng Liu, Liyang Lin, Ning Hu, Liangbing Liu Poly(vinylidene difluoride)(PVDF) and its copolymers are promising materials to fabricate self-powered devices, while their relatively low power generation capability limits their applications. In this work, graphene was added into poly(vinylidene-trifluoroethylene)(PVDF-TrFE) to prepare excellent piezoelectric composite films by a solution-casting method. The PVDF-TrFE/graphene containing 0.15 wt% graphene generated a calibrated open circuit of 12.43 V, which is 104% higher than that without graphene. Similarly, the harvested power density was increased by 302% (AC circuit) and 359% (DC circuit), respectively. The XRD spectra indicate that the PVDF-TrFE/graphene with an extremely low content of graphene did not work well on the phase formation in the initial crystallization. The crystallinity degree of the untreated films was about 40%. After stretching, the crystallinity degree increased to above 60%, especially for the films containing 0.15 wt% graphene (67%). Hence, stretching was the main factor to increase the crystallinity degree. This study also confirmed that the heat treatment could further improve the crystallinity of the stretched films to some extent.
  • Multilayer cotton fabric bio-composites based on PLA and PHB copolymer for
           industrial load carrying applications
    • Abstract: Publication date: Available online 15 January 2019Source: Composites Part B: EngineeringAuthor(s): Daniele Battegazzore, Tobias Abt, Maria Lluisa Maspoch, Alberto Frache The thermo-mechanical and impact behavior of bio-based polymers reinforced with a multilayer cotton fabric were determined and assessed for the potential use in building, furniture or automotive applications. The measured properties were compared to other composites with similar natural fabric content or to international standard requirements. Flexural properties of PLA composites fully satisfied the requirements for heavy duty load-bearing boards in humid condition (EN 312 standard), while the PHB copolymer composites still satisfied the conditions for load-bearing boards. The HDT evaluation through the dynamic mechanical thermal analysis revealed the great increase (+53 °C) in the temperature for PHB composites that reached 123 °C, potentially extending their application fields to automotive applications. For this focus, the Charpy impact strengths were also investigated. One of the highest values reported in the literature (54.5 kJ/m2) was reached with PHB, superior to what is commercially used for the interior part of the cars. Furthermore, an epoxy functional additive was employed and was found to reduce the void content and increase the flexural properties and the impact strength.
  • A semi-analytical model for predicting nonlinear tensile behaviour of
           corrugated flexible composite skin
    • Abstract: Publication date: Available online 14 January 2019Source: Composites Part B: EngineeringAuthor(s): Jiang-Bo Bai, Di Chen, Jun-Jiang Xiong, Chen-Hao Dong This paper seeks to present a semi-analytical model for predicting the nonlinear tensile properties of corrugated flexible composite skin (FCS) within large deformation range based on iterative integration procedure. The FCS is constructed with two thin-walled curved fibre-reinforced-plastics (FRP) composite shells with a biaxially symmetrical lenticular cross-section, which can be stretched largely along the corrugated direction through pure elastic deformation. Analytical formulations for tensile stiffness of the FCS are derived based on the unit virtual load method, and geometrical equations are established to describe tensile deformation of the FCS. By means of linear elastic and strain energy theory, new geometry and tensile force increment of extended FCS are calculated at a given small increment of tensile displacement. In order to obtain the tensile behaviour of the FCS within large deformation range, semi-analytical model is presented by using the iterative calculation, and then is verified from experiments. Finally, the effect of the geometry on tensile behaviour of the FCS is analyzed numerically.
  • Dynamic mechanical behavior and pedestrian safety characteristics of
           toughened laminated windshield
    • Abstract: Publication date: Available online 14 January 2019Source: Composites Part B: EngineeringAuthor(s): Yunqi Li, Danping Xiong, Lubing Wang, Bill Feng, Jun Xu The windshield is one of the important components of a vehicle for pedestrian protection. Thin chemically toughened glass (TG) is regarded as a promising substitute for soda–lime glass in traditional soda–lime laminated glass (SLG). The mechanical behavior of TG and toughened laminated glass (TLG) is experimentally studied. Finite element models based on experiment results are established and validated. The pedestrian protection characteristics of the TLG windshield are numerically investigated and compared with its counterpart, the SLG windshield. A significant decrease in head injury criteria in the TLG windshield compared with the SLG windshield is observed with the significant weight reduction of the TLG windshield. Finally, parametric studies on the effect of impact speed, location, and angle are conducted. Results show the reasonable pedestrian protection capability of the TLG windshield, and they provide useful design tools and practical evaluation guidance for safe and light laminated windshields.Graphical abstractImage 1
  • Vibrational behavior of doubly curved smart sandwich shells with FG-CNTRC
           face sheets and FG porous core
    • Abstract: Publication date: Available online 12 January 2019Source: Composites Part B: EngineeringAuthor(s): A.R. Setoodeh, M. Shojaee, P. Malekzadeh As a first endeavor, the free flexural vibration behavior of doubly curved complete and incomplete sandwich shells with functionally graded (FG) porous core, FG carbon nanotube reinforced composite (FG-CNTRC) face sheets and integrated piezoelectric layers is investigated. The variable radii shells with the three most common types of geometries, i.e., elliptical, cycloid and parabolic, are considered. The system equations are derived based on the general higher-order shear deformation theory and Maxwell's equation. The generalized differential quadrature (GDQ) method is employed to discretize the governing partial differential equations subjected to different boundary conditions. The accuracy and reliability of the approach are verified by comparing the results with the existing solutions in open literature. The effects of porosity parameter and porosity distribution through the thickness direction, carbon nanotube (CNT) volume fraction, different boundary conditions and various shell geometrical parameters on the flexural vibrational behavior of the smart sandwich shell structures are investigated and useful results are presented.
  • The mechanical properties of monodisperse foam scaffolds
    • Abstract: Publication date: Available online 10 January 2019Source: Composites Part B: EngineeringAuthor(s): Jen-Nan Yang, Li-Syuan Liang, Keng-hui Lin, Wen-Yea Jang Tissue engineering scaffolds provide mechanical supports and microenvironment for cells to grow in the third dimensionality (3D). Inspired by the recent advance to fabricate monodisperse foam scaffold by self-assembly of monodisperse liquid foam created by the microfluidic method, we investigated the mechanical properties of an open-cell solid foam with pores packed in the face-centered cubic (FCC) structure. We first characterized the microstructural geometry of solid foam with different porosities made by the microfluidic technique. We then developed both analytical and finite element method (FEM) models based on the measured geometric features. We computed mechanical parameters such as the elastic modulus, Poisson's ratio, and the shear modulus. Finally, we performed mechanical measurements of FCC solid foam fabricated by a 3D printer. All experimental, analytical, and numerical results show good agreement, which validate the FEM models.
  • Influence of material uncertainties on vibration and bending behaviour of
           skewed sandwich FGM plates
    • Abstract: Publication date: Available online 10 January 2019Source: Composites Part B: EngineeringAuthor(s): Sanjay Singh Tomar, Mohammad Talha Present study aims to investigate the Influence of material uncertainties on vibration and bending behaviour of skewed sandwich FGM plates. Reddy's higher order shear deformation theory has been employed to model the displacement field. Variational approach has been used to derive the governing differential equations. Effect of material uncertainties in the formulation have been incorporated using first order perturbation technique(FOPT). An efficient stochastic finite element formulation (SFEM) have been used for the calculation of first and second order statics of natural frequency and transverse deflection. Validation of the results have been performed with the help of available literature and separately developed Monte Carlo formulation (MCS) algorithm. A large number of examples have been solved to quantify the effect of uncertainties on the vibration and bending characteristics of functionally graded skew sandwich plates.
  • Tooling materials compatible with carbon fibre composites in a microwave
    • Abstract: Publication date: Available online 9 January 2019Source: Composites Part B: EngineeringAuthor(s): Betime Nuhiji, Timothy Swait, Matthew Bower, James E. Green, Richard J. Day, Richard J. Scaife Although metals are the most commonly used tooling materials to cure composites, they do not provide optimal results in a microwave environment. Following a selection process based on the properties of the materials, an alternative tooling material in carbon fibre reinforced plastic (CFRP) was successfully utilised to cure CFRP panels in laboratory and industrial microwaves. The conductive carbon fibres in the tool facilitated the fast heat transfer across the part. Other tooling materials including a glass fibre cyanate ester prepreg and tooling board were trialled, although the latter exhibited damage during cure. These advantages demonstrate that the CFRP tool is a compatible material that can be used when microwave curing composites.
  • A stress-driven local-nonlocal mixture model for Timoshenko nano-beams
    • Abstract: Publication date: Available online 8 January 2019Source: Composites Part B: EngineeringAuthor(s): Raffaele Barretta, Andrea Caporale, S. Ali Faghidian, Raimondo Luciano, Francesco Marotti de Sciarra, Carlo Maria Medaglia A well-posed stress-driven mixture is proposed for Timoshenko nano-beams. The model is a convex combination of local and nonlocal phases and circumvents some problems of ill-posedness emerged in strain-driven Eringen-like formulations for structures of nanotechnological interest. The nonlocal part of the mixture is the integral convolution between stress field and a bi-exponential averaging kernel function characterized by a scale parameter. The stress-driven mixture is equivalent to a differential problem equipped with constitutive boundary conditions involving bending and shear fields. Closed-form solutions of Timoshenko nano-beams for selected boundary and loading conditions are established by an effective analytical strategy. The numerical results exhibit a stiffening behavior in terms of scale parameter.
  • Effect of shrinkage reducing admixture on the new-to-old concrete
    • Abstract: Publication date: Available online 22 November 2018Source: Composites Part B: EngineeringAuthor(s): Renyuan Qin, Huali Hao, Theodoros Rousakis, Denvid Lau New-to-old concrete interfaces can be widely seen in repairing or strengthening concrete structures, such as the concrete jacketing and concrete overlay or repair mortar (high performance fiber reinforced one included etc.) or self-consolidated concrete or self-consolidated mortar. One major difference between new and old concrete is that the shrinkage of new concrete is much higher than that of old concrete during its hardening process. Such difference in volume change results in the incompatibility between old concrete structure and new concrete (as strengthening and repair material). Moreover, prior research studies in this area indicate that such incompatibility between new and old concrete can result in the development of stress concentration at the interface, leading to cracks and premature failure of the repair overlay. The cracks provide access for free water carrying chloride ions or carbon dioxide, which further reduce the durability of new-to-old concrete system. The usage of shrinkage reducing admixture (SRA) in new concrete design can reduce the shrinkage of new concrete by reducing the surface tension of water. Moreover, it is reported that the SRA can reduce the water diffusivity of concrete to achieve an enhanced durability. To study the effect of SRA on the interface integrity of new-to-old concrete system, the experimental study was firstly conducted for investigating the interfacial fracture toughness of new-to-old concrete system. The results showed that the interface fracture toughness of new-to-old concrete system increased by adopting SRA in the new concrete mixing design. Moreover, when the samples were exposed to moisture condition, the decreasing rate of interface fracture toughness was lower when SRA was adopted in mixing design, which indicated that the new-to-old system is more durable in moisture condition with SRA. To explore the water transition behavior at interfacial area of new-to-old concrete system, molecular dynamics simulation was performed. From an atomistic perspective, molecular dynamics simulations revealed that the use of SRA can reduce the water diffusion coefficient at pores at new-to-old interface, so that a more durable performance was achieved when the system was under moisture attack. The finding provides the piece of insight information on the role of SRA on the interfacial integrity and durability of new-to-old concrete system and may cover strengthening jackets and repair mortars.Graphical abstractImage 1
  • Failure mechanism of bonded joints with similar and dissimilar material
    • Abstract: Publication date: Available online 3 November 2018Source: Composites Part B: EngineeringAuthor(s): Seyyed Mohammad Hasheminia, Beom Chul Park, Heoung-Jae Chun, Jong-Chan Park, Hong Suk Chang Adhesive joints with dissimilar materials have gained substantial attention recently due to their lighter specific weight compared to the joints with similar metallic components. In particular, dissimilar material joints with a structure such as composite materials combined with light-weight metals have been widely used in the automobile industries to overcome the issue of fuel efficiency and weight reduction. Therefore, accurate analysis and study about the mechanical behavior of dissimilar materials joints are fundamentally required. In this study, the experiments and finite elements analysis were performed on single lap-shear bonded joints with metal-composite, similar composites and dissimilar composites components to investigate the factors that affect the joint failure load.
  • Aluminum-sulfur composites for Li-S batteries with high-rate performance
    • Abstract: Publication date: Available online 25 September 2018Source: Composites Part B: EngineeringAuthor(s): Sophia P. Zhou, Yanqiu Lu, Shouyu Shen, Shao-Jian Zhang, Xiao-Dong Zhou, Jun-Tao Li, Lin Huang, Shi-Gang Sun Over the past few years, lithium sulfur (Li-S) batteries have attracted attention as an enabling technology because of their high energy density. The limitations to commercialize Li-S batteries originate from the intrinsic properties of sulfur: its poor electronic conductivity and the polysulfide shuttle. The aim of this research is to address these challenges by developing an additive for Li-S batteries. Al-powders prepared from soda-cans were mixed with S to form a composite with a mass loading of S up to 90 wt%. The electrochemical performance shows that the Al-S composite in Li-S cells exhibits a reasonable retention after 200 cycles and a remarkable ability to stabilize quickly (
  • Gamma irradiated poly (methyl methacrylate)-reduced graphene oxide
           composite thin films for multifunctional applications
    • Abstract: Publication date: Available online 8 January 2019Source: Composites Part B: EngineeringAuthor(s): J. Ramana Ramya, K. Thanigai Arul, P. Sathiamurthi, E.A.K. Nivethaa, S. Baskar, S. Amudha, B. Mohana, K. Elayaraja, Sarath Chandra Veerla, K. Asokan, S. Narayana Kalkura Poly (methyl methacrylate) (PMMA)-Reduced Graphene Oxide (rGO) (PrGO) composite films were fabricated by solvent evaporation technique and exposed to gamma radiation at different dosages viz. 25 kGy, 50 kGy and 100 kGy. The XRD analysis revealed the phases of PMMA and rGO and further confirmed the semi-crystalline nature of PMMA. The irradiation also decreased the peak intensities of the functional groups of PMMA and rGO. At 50 kGy irradiation, lamellar structures were formed on the surface of the films (50 kGy) due to the thermal fluctuations whereas, at higher dosage (100 kGy), pores were formed. The surface roughness and contact angle were enhanced on 50 kGy sample. The drug impregnated PrGO50 and PrGO100 samples showed sustained and burst release of drug respectively and in addition exhibited a better zone of inhibition against E. coli bacteria. All the samples were hemocompatible in nature. Fibroblast proliferation was enhanced with no cytotoxic effect on 50 kGy samples. Hence, the gamma irradiated samples could be an excellent candidate for biosensing and biomedical applications.
  • Consistent application of periodic boundary conditions in implicit and
           explicit finite element simulations of damage in composites
    • Abstract: Publication date: 1 July 2019Source: Composites Part B: Engineering, Volume 168Author(s): D. Garoz, F.A. Gilabert, R.D.B. Sevenois, S.W.F. Spronk, W. Van Paepegem This paper presents an implementation-dedicated analysis of Periodic Boundary Conditions (PBCs) for Finite Element (FE) models incorporating highly non-linear effects due to plasticity and damage. This research addresses fiber-reinforced composite materials modeled at micros-scale level using a Representative Volume Element (RVE), where its overall mechanical response is obtained via homogenization techniques. For the sake of clearness, a unidirectional ply with randomly distributed fibers RVE model is assumed. PBCs are implemented for implicit and explicit FE solvers, where conformal and non-conformal meshes can be used. The influence of applying PBCs in the reliability of the mechanical response under tension and shear loading is assessed. Furthermore, the Poisson effect and the consistency of damage and fiber debonding propagation through the periodic boundaries are reported as well as their impact on the homogenized results. Likewise, numerical aspects like computational performance and accuracy are evaluated comparing implicit- versus explicit-based solutions.
  • Long-term durability of thermoset composites in seawater environment
    • Abstract: Publication date: 1 July 2019Source: Composites Part B: Engineering, Volume 168Author(s): Abdel-Hamid Ismail Mourad, Amir Hussain Idrisi, Maria Christina Wrage, Beckry Mohamed Abdel-Magid The long-term durability of E-glass/epoxy and E-glass/polyurethane composites in seawater environment were investigated. Samples were conditioned for ninety months (7.5 years) in seawater at room temperature and at an elevated temperature of 65 °C. Changes in mechanical properties are reported and discussed. At room temperature, the tensile strength of the glass/epoxy composite decreased at a very low rate to 94% of its original strength after 7.5 years of immersion in seawater. At an elevated temperature of 65 °C, the strength decreased rapidly to 53% of its original value after five years, then decreased by only 1% between five and seven and a half years. The strength of the E-glass/polyurethane composite started to decline immediately and also reached bottom after five years of immersion where the strength dropped by 34% at room temperature and by 63% at 65 °C. No significant change was observed in the tensile modulus of both composites. The strain-at-failure of both composites increased gradually with water absorption, then dropped to about 50% of its original value after ninety months. After extended exposure to seawater, both composites exhibited brittle failure; and results show that the elevated temperature accelerated the degradation in the matrix and at the fiber/matrix interface. However, it is noted that at room temperature the E-glass/epoxy retained 94% of its strength and the E-glass/polyurethane retained nearly 63% of its strength after 7.5 years of immersion in seawater.
  • Thermal-mechanical coupling buckling analysis of porous functionally
           graded sandwich beams based on physical neutral plane
    • Abstract: Publication date: 1 July 2019Source: Composites Part B: Engineering, Volume 168Author(s): Yijie Liu, Shengkai Su, Huaiwei Huang, Yingjing Liang Porosity of functionally graded materials (FGMs) is usually aroused by fabrication defects. It had been proven that the porosity has a significant influence on the static responses of their structures, but the effects of porosity on buckling behaviors are still worth investigating. To reveal these effects, the thermal-mechanical coupling buckling issue of a clamped-clamped porous FGM sandwich beam is investigated in this paper by employing the high-order sinusoidal shear deformation theory. The modified Voigt mixture rule is used to approximate the temperature-dependent material properties of porous FGMs. The physical neutral plane of FGM sandwich beams is taken into account to reflect the actual condition of the structures and simplify the calculation. The thermal environments are considered as uniform, linear and nonlinear temperature rises, and both the temperature-independent and temperature-dependent material properties are discussed in order to justify the importance of the thermal-mechanical coupling effect. An iterative algorithm is used to solve the thermal-mechanical coupling critical buckling temperature. The present theoretical results are verified by comparing with the literature and ABAQUS results, and the effects of porosity, the physical neutral plane, gradient index, material temperature dependence, sandwich structural parameters are discussed. Results show that for buckling issue excluding the pre-buckling deformation effect, considering either the physical neutral plane or the geometrical middle plane of FGM beams would produce alike critical buckling temperatures. With the rise of porosity, the critical temperature increases greatly, which is quite different from the changing rule observed in the buckling issue of inplane-loaded porous FGM plates in literature. The beam with a smaller face-to-core ratio is more sensitive to the change in porosity. Moreover, to improve the thermal buckling load of FGM beams, ceramic constituents with the lower thermal expansion coefficient would be preferred.
  • Contactless high-speed eddy current inspection of unidirectional carbon
           fiber reinforced polymer
    • Abstract: Publication date: 1 July 2019Source: Composites Part B: Engineering, Volume 168Author(s): Miguel A. Machado, Kim-Niklas Antin, Luís S. Rosado, Pedro Vilaça, Telmo G. Santos This paper presents the development and the results of a customized eddy current (EC) non-destructive testing (NDT) system for highly demanding online inspection conditions. Several planar eddy current array probes were designed, numerically simulated and experimentally compared for the inspection of low conductivity unidirectional carbon fibre reinforced polymer (CFRP) ropes. The inspections were performed using a dedicated scanner device at 4 m/s with 3 mm probe lift-off where defects under 1 mm were detected with an excellent SNR. Different defect morphologies and sizes, such as broken fibres and lateral cuts, were successful detected and compared to conventional probes.
  • Influence of fiber length and its distribution in three phase
           poly(propylene) composites
    • Abstract: Publication date: 1 July 2019Source: Composites Part B: Engineering, Volume 168Author(s): Dong Gi Seong, Chul Kang, Seong Yeol Pak, Chai Hwan Kim, Young Seok Song We explored how the fiber lengh affects physical properties of three phase polymer composites. The composites including glass fibers, graphites and poly(propylene) were produced via injection molding. The fiber length and its distribution were analyzed before and after molding. Two different fiber lenghs (i.e., 2 mm and 10 mm) were adopted in this study. The morphological analysis of the samples was carried out to evaluate the fiber orientation depending on the fiber length. The thermal, mechanical, and viscoelastic behaviors of the composites were analyzed experimentally. The finding revealed that the longer fiber reinforced composites showed higher viscoelastic properties, Young's modulus, and melting temperature but showed less uniform distribution of fibers. In addition, numerical simulation was conducted to help understand the experimental results.
  • A comprehensive study of basalt fiber reinforced magnesium phosphate
           cement incorporating ultrafine fly ash
    • Abstract: Publication date: 1 July 2019Source: Composites Part B: Engineering, Volume 168Author(s): Muhammad Riaz Ahmad, Bing Chen, Jiang Yu This study investigated the influence of ultrafine fly ash (FA) on the mechanical properties, elevated temperature resistance and water stability of basalt fiber reinforced magnesium phosphate cement, and synergy mechanism was examined with the help of X-ray diffraction (XRD), thermogravimetric analysis (TGA), mercury intrusion porosimeter (MIP) and scanning electron microscopy energy dispersive spectroscopy (SEM/SEM-EDS) analysis techniques. Experimental results showed that incorporation of FA improved the mechanical properties, temperature resistance and water stability of MPC composites. TGA results exhibited that the mass loss of MPC composites was gradually reduced by increasing the percentage of FA. MIP analysis showed that cumulative pore volume, volume percentage of large pores and mean pore diameter of were decreased with the addition of FA. XRD and SEM-EDS analysis of MPC composites revealed the formation of secondary reaction products, that could be possibly responsible for the superior properties of FA/MPC composites. Importantly, the results of all characterization techniques corroborated with the mechanical results of MPC composites.
  • Effect of short carbon fiber on thermal, mechanical and tribological
           behavior of phenolic-based brake friction materials
    • Abstract: Publication date: 1 July 2019Source: Composites Part B: Engineering, Volume 168Author(s): Farhad Ahmadijokani, Akbar Shojaei, Mohammad Arjmand, Yasaman Alaei, Ning Yan The phenolic-based brake friction composites containing 0, 1, 2 and 4 vol% carbon fiber were fabricated in this study. Thermogravimetric analysis (TGA) revealed the adverse impact of carbon fiber on the thermal stability of the composites under air atmosphere. Differential scanning calorimetry (DSC) of the uncured samples indicated the positive impact of carbon fiber on the crosslink density of the phenolic resin. Viscoelastic results drawn from the dynamic-mechanical analysis (DMA) suggested that inclusion of carbon fiber increased the storage modulus and decreased the damping factor of the frictional composites. The tribological behavior of the specimens was assessed with a chase type friction tester. Both the friction coefficient and specific wear rate decreased with enhancing carbon fiber content. Furthermore, carbon fiber deteriorated the fade behavior of the developed composites. The TGA, DSC and DMA results were used to justify and interpret the observed tribological behavior.
  • Stress transfer through the interphase in curved-fiber pullout tests of
    • Abstract: Publication date: Available online 4 January 2019Source: Composites Part B: EngineeringAuthor(s): P.R. Budarapu, S. Kumar, B. Gangadhara Prusty, M. Paggi The properties of nanoscale interphase significantly influence the mechanics of load transfer and hence the macroscopic behavior of fiber-reinforced composites. Herein, we present a theoretical framework to study the mechanics of stress transfer through both homogeneous and inhomogeneous interphases in a curved-fiber pull-out test and analyse the stress field in the three-phase composite system based on the shear-lag theory. Explicit expressions are derived for the normal and shear stresses in the fiber, interphase and matrix. The results from the analytical model are validated with those obtained from a finite element analysis. Furthermore, influence of radially modulus graded interphase, according to linear and power laws, on the pull-out performance is also investigated. Graded interphases are observed to reduce the interfacial shear stresses by up to 40% as compared to the homogeneous interphases. The stress transfer in three-phase curved-fiber pullout test considering interfacial debonding and sliding has also been studied. Finally, models are simplified for straight-fiber pullout case considering both homogeneous and graded interphases. The study can serve as a framework to investigate the pull-out characteristics of a curved fiber in nanocomposites.
  • Synergetic effect of graphene nanoplatelet, carbon fiber and coupling
           agent addition on the tribological, mechanical and thermal properties of
           polyamide 6,6 composites
    • Abstract: Publication date: Available online 3 January 2019Source: Composites Part B: EngineeringAuthor(s): Ecem Karatas, Okan Gul, Nevin Gamze Karsli, Taner Yilmaz Polyamide 6,6 (PA6,6) is one of the commonly used engineering polymers and it is used for various applications. Moreover, tribological and mechanical performance of PA6,6 can be improved with the addition of fibers or particulates. However, properties of reinforced PA6,6 matrix composites are affected by many factors. Interfacial adhesion between the reinforcement and matrix material is one of these factors and there should be good interfacial adhesion to obtain good ultimate properties. In this study, it was aimed to improve tribological and mechanical properties of carbon fiber reinforced PA6,6 composites by means of improving the fiber-matrix interaction by using graphene nanoplatelet (GNP) and 1,4-phenylene-bis-oxazoline (PBO). Adhesive wear test, tensile test, dynamic mechanical, differential scanning calorimetry and scanning electron microscopy analyses were performed. Consequently, all the test results manifested that CF_0.5GNP_PBO coded composites exhibited improved tribological and mechanical properties among the all composites.
  • Nonlocal strain gradient exact solutions for functionally graded inflected
    • Abstract: Publication date: Available online 2 January 2019Source: Composites Part B: EngineeringAuthor(s): A. Apuzzo, R. Barretta, S.A. Faghidian, R. Luciano, F. Marotti de Sciarra The size-dependent bending behavior of nano-beams is investigated by the modified nonlocal strain gradient elasticity theory. According to this model, the bending moment is expressed by integral convolutions of elastic flexural curvature and of its derivative with a bi-exponential averaging kernel. It has been recently proven that such a relation is equivalent to a differential equation, involving bending moment and flexural curvature fields, equipped with natural higher-order boundary conditions of constitutive type. The associated elastostatic problem of a Bernoulli-Euler functionally graded nanobeam is formulated and solved for simple statical schemes of technical interest. An effective analytical approach is presented and exploited to establish exact expressions of nonlocal strain gradient transverse displacements of doubly clamped, cantilever, clamped-pinned and pinned-pinned nano-beams, detecting thus also new benchmarks for numerical analyses. Comparisons with results of literature, corresponding to selected higher-order boundary conditions are provided and discussed. The considered nonlocal strain gradient model can be advantageously adopted to characterize scale phenomena in nano-engineering problems.
  • Distributed modular temperature-strain sensor based on optical fiber
           embedded in laminated composites
    • Abstract: Publication date: Available online 20 December 2018Source: Composites Part B: EngineeringAuthor(s): Pingyu Zhu, Xiaobo Xie, Xiaopeng Sun, Marcelo A. Soto A smart structure based on carbon fiber reinforced polymer (CFRP) embedding optical fibers is proposed for distributed sensing in structural health monitoring. The proposed CFRP package provides mechanical protection to the optical fiber, enables temperature-strain discrimination, and also facilitates the sensor's installation to secure reliable measurements. Experimental results verify a linear strain sensor response with temperature compensation, agreeing well with the response of strain gauges and the expected theoretical behavior. The smart structure can be used by gluing it on the surface of the monitored structure or by embedding it as one of the layers used during manufacturing big composite structures.
  • Creep performance of CNT polymer nanocomposites -An emphasis on
           viscoelastic interphase and CNT agglomeration
    • Abstract: Publication date: Available online 19 December 2018Source: Composites Part B: EngineeringAuthor(s): Mohammad Kazem Hassanzadeh-Aghdam, Mohammad Javad Mahmoodi, Reza Ansari The present work is aimed at presenting a multi-stage hierarchical micromechanical model to investigate creep response of polymer nanocomposites containing randomly dispersed carbon nanotubes (CNTs). Two frequently real situations-encountered fundamental aspects affecting the polymer nanocomposite mechanical behavior including the CNT/polymer interphase region and CNT agglomeration are taken into account. It is assumed that the CNT to be a transversely isotropic material and the polymer matrix obeys a viscoelastic constitutive law. The multi-stage procedure homogenizes the nanocomposite by exploiting a unit cell-based micromechanical model coupled with Eshelby method. Generally, an excellent agreement is found between the results of the current model and available experiment. The outcomes clearly prove that for a more realistic prediction in the case of creep performance of CNT-polymer nanocomposites, considering the (i) random dispersion and (ii) transversely isotropic behavior of CNTs as well as (iii) viscoelastic interphase region is essential. Moreover, when CNTs are not well-dispersed into the polymer nanocomposites, the three significant factors together with the CNTs agglomerated state must be precisely incorporated in the analysis to achieve a more accurate estimation of the creep response. It is shown that the CNT agglomeration dramatically influences and degrades the creep resistance of the CNT-polymer nanocomposites. Also, the effects of CNT volume fraction and interphase characteristics on the nanocomposites creep behavior are extensively examined.Graphical abstractImage 1
  • Polydimethylsiloxane nanocomposite filled with 3D carbon nanosheet
           frameworks for tensile and compressive strain sensors
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Part B: EngineeringAuthor(s): Jinzhang Liu, Zehui Liu, Ming Li, Yi Zhao, Guangcun Shan, Mingjun Hu, Dezhi Zheng Elastomeric matrix filled with carbon nanotubes or graphene has been focused for making resistive-type strain sensors. Here, we report the low-cost synthesis of 3D carbon nanosheet frameworks by exploiting the chemical reaction between magnesium powder and carbon disulfide vapor, and prepared piezoresistive nanocomposites of as-prepared carbon nanomaterials and polydimethylsiloxane elastomer for tensile and compressive strain sensors with different device configurations. The optimal carbon content in PDMS for achieving high sensitivity is obtained. The tensile strain sensor shows fast response and high gauge factor in the order of 102. The compressive strain sensor that is elaborated designed as in-plane and miniature concept also shows striking response to external loads.
  • Mechanical properties of steel fiber-reinforced UHPC mixtures exposed to
           elevated temperature: Effects of exposure duration and fiber content
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Part B: EngineeringAuthor(s): Shamsad Ahmad, Mehboob Rasul, Saheed Kolawole Adekunle, Salah U. Al-Dulaijan, Mohammed Maslehuddin, Syed Imran Ali In the present study, ultra-high performance concrete (UHPC) mixtures reinforced with varying dosage of steel fibers were considered for studying the effects of exposure duration and fiber content on mechanical properties of the mixtures subjected to a sustained pre-spalling elevated temperature of 300 °C for different durations. Test results showed an increase in compressive strength and modulus of toughness even after exposing to elevated temperature for 5 h. However, modulus of elasticity and flexural strength decreased significantly with increase in exposure duration. The experimental data were statistically analyzed using analysis of variance (ANOVA) method to examine the effects of fiber content and exposure duration on the mechanical properties. Empirical equations were obtained with excellent degrees of fit correlating the mechanical properties of UHPC mixtures with fiber content and exposure duration.
  • BFRP reinforcing hierarchical stiffened SMC protective structure
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Part B: EngineeringAuthor(s): Zheng Zhao, Bei Zhang, Fengnian Jin, Jiannan Zhou, Hailong Chen, Hualin Fan To improve the anti-blast ability of sheet molding compound (SMC) protective structure, basalt fiber reinforced polymers (BFRPs) are applied to strengthen SMC and improve its stiffness and strength. To simultaneously guarantee the overall and local rigidities, the panel adopts hierarchical orthogrid-stiffened structure. Explosion experiments were carried out to reveal the blast resistance of the BFRP reinforced SMC door. With much lighter mass, the BFRP-SMC protective door exhibits excellent anti-balst ability and would be an ideal substitute for metallic or concrete protective doors. Equivalent method based on identical volume and mode superposition was adopted to build dynamic theory of blast-loaded hierarchical stiffened panels. Equivalent static load method was adopted to predict the maximum displacement of the blast-loaded panel. These two methods are reliable and provide simple ways to design hierarchical stiffened composite protective structures.
  • The design of novel neutron shielding (Gd+B4C)/6061Al composites and its
           properties after hot rolling
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Part B: EngineeringAuthor(s): L.T. Jiang, Z.G. Xu, Y.K. Fei, Q. Zhang, J. Qiao, G.H. Wu In this paper, a novel approach to evaluate the neutron shielding performance of multiphase neutron absorber reinforced aluminum matrix composites was proposed through the establishment of a direct relationship between equivalent B areal density (EBAD) of the composite and its thermal neutron shielding coefficient. It was found when the EBAD of the composite was 0.1105 g/cm2, the thermal neutron shielding coefficient will achieve 99%. Based on this proposed approach, (1% Gd+15% B4C)/6061Al composite plates were successfully fabricated using vacuum hot pressing method followed hot rolling. The results showed that when the EBAD of the composite was 0.1871 g/cm2, the thermal neutron shielding coefficient was above 99.9%, which was consistent with the theoretical calculation. The 5 mm-thick composite plate also had a good shielding effect on the Am-Be neutron source. Meanwhile the composite possessed a 380 MPa tensile strength as well as an elongation of 5% after hot rolling. In all, the (Gd + B4C)/6061Al composite designed in this paper showed better comprehensive performance compared with the literature's. The work of this paper has a great guiding significance for the design and preparation of neutron absorbing composites with high thermal neutron shielding performance as well as high strength and plasticity.Graphical abstractImage 1
  • A novel design and synthesis of ruthenium sulfide decorated activated
           graphite nanocomposite for the electrochemical determination of
           antipsychotic drug chlorpromazine
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Part B: EngineeringAuthor(s): Subbiramaniyan Kubendhiran, Rajalakshmi Sakthivel, Shen-Ming Chen, Rajeshkumar Anbazhagan, Hsieh-Chih Tsai A novel electrochemical sensor based on ruthenium sulfide nanoparticles decorated activated graphite sheets (RuS2/AG) was designed and fabricated for the determination of antipsychotic drug chlorpromazine hydrochloride (CPZ). Activated graphite sheets (AG) were prepared by non-explosive, non-hazardous and simple chemical activation technique. Then, the AG sheets were used for the synthesis of RuS2/AG nanocomposite by single step hydrothermal synthesis method. The synthesized materials were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), Raman spectrometer, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The synergistic effect of the RuS2/AG nanocomposite was applied for the determination of CPZ by cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. Fascinatingly, the RuS2/AG nanocomposite exhibited the excellent electrocatalytic activity and detects the CPZ at very lowest oxidation potential about 0.60 V vs Ag/AgCl in pH-7 PB solution. Moreover, the lowest LOD 8 nM and wider linear ranges from 0.05 to 79.75 and 79.75–1249 μM was obtained towards the CPZ determination. Besides, the proposed sensor shows the good selectivity, satisfactory repeatability, reproducibility and stability. Furthermore, the real time application was evaluated in pharmaceutical tablets and human urine samples.Graphical abstractImage 1
  • CFRP barely visible impact damage inspection based on an ultrasound wave
           distortion indicator
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Part B: EngineeringAuthor(s): Xiaofei Zhang, Xuan Wu, Yunze He, Shuming Yang, Sheng Chen, Shigang Zhang, Deqiang Zhou The impact damage of carbon-fiber-reinforced polymers (CFRPs) must be considered important in order to avoid catastrophic accidents. Low-velocity impact commonly results in barely visible impact damages (BVIDs) in a CFRP component, and is impossible to be detected by visual inspection or machine vision. To rapidly and effectively detect BVIDs in CFRPs, this work proposes a damage inspection method based on an ultrasound wave distortion indicator. The indicator reveals ultrasound higher harmonics, subharmonics, and self-modulation caused by local damage in CFRPs. The experimental system was built after the proposed non-destructive testing (NDT) methodology was introduced. An intact CFRP plate specimen, and specimens with BVIDs and visible impact damage (VID) were tested using the proposed method. The relationship between impact energies and the ultrasound wave distortion indicator was built. The proposed method could provide an effective inspection means for assessing the impact damage of CFRP materials.
  • Recyclability/malleability of crack healable polymer composites by
           response surface methodology
    • Abstract: Publication date: Available online 18 December 2018Source: Composites Part B: EngineeringAuthor(s): Pengfei Zhang, Moulero Akobi, Ahmed Khattab The production of polymeric materials contributes remarkably to the accelerating growth of greenhouse gases (GHG) in the atmosphere. The use of recycled material replacing natural resources yields to the decrease of environmental burden and reduction of processing energy. Thermosets composites are among the top list of material selections for many engineering applications. The environmental sustainability of thermosets recycling gains more attention than ever. In this study, recyclable polymer composites based on self-healing effect were fabricated through polymerization-induced phase separation (PIPS) because of the advantages of polymer blend technology in industrial applications. The thermosets composites were recycled after storage for 20 months. The relationship between processing variables and material properties was investigated by using responsive surface methodology (RSM) models. The processing variables include thermal compression molding temperature, loading pressure, and compaction time. The mechanical properties of recycled composite samples were tested by static uniaxial compression and three-point bending. According to the RSM analysis, the recyclability up to 85% was achieved. Moreover, the recycling process has the potential to be repeated multiple times.Graphical abstractImage 1
  • An analytical study of the plasticity of sandwich honeycomb panels
           subjected to low-velocity impact
    • Abstract: Publication date: Available online 17 December 2018Source: Composites Part B: EngineeringAuthor(s): Mengqian Sun, Diane Wowk, Christopher Mechefske, Il Yong Kim A new analytical modelling method for the study of low-velocity impact response in honeycomb sandwich panels with metallic face-sheets is proposed by using Hamilton's principle. A modified Lagrange's function for this model is then proposed by extending the application of Hamilton's principle from elastic bodies to face-sheets with plasticity. The internal physical mechanism in the system is proved to be reasonable by comparing the energy converting history with published data. This study advances the understanding of the role of face-sheet plasticity in low-velocity impact response of honeycomb sandwich panels by having the ability to incorporate either the energy absorption from elastic deformation or the energy dissipation from plastic deformation of the face-sheet depending on the severity of the damage state in the dented region. The predicted maximum deflection and impact force history are compared with published experimental and finite element results, and lower and upper bounds of the maximum dent depth are obtained.
  • Classification of damages in composite images using Zernike moments and
           support vector machines
    • Abstract: Publication date: Available online 17 December 2018Source: Composites Part B: EngineeringAuthor(s): A.R. Jac Fredo, R.S. Abilash, Femi Robert, A. Mythili, C. Suresh Kumar In this work, the strength of the composite material is tested and the damages are classified using supervised method. The image is obtained from the front and rear sides of the composite material after applying 5 mm, 6 mm and 7 mm impingement. Initially, the images are filtered using anisotropic diffusion filter. Global and local damages in the structures are segmented using Fuzzy C-Means (FCM) clustering method. Geometrical features and Zernike Moments (ZM) are calculated from the delineated regions. The performance of the features is tested using Support Vector Machine classifier. Results show that the FCM with three and four cluster centres is able to segment the global and local damages respectively. The global damages due to different impinges are classified better compared to the local damages. The global damages in the rear side are able to classify better compared to the front side in both geometrical and ZM features. In the case of local damages, the rear side is able to classify better in 5 mm–6 mm and front side in 6 mm–7 mm. It is concluded that the features obtained from the ZM gives better accuracy in both global and local damages compared to the geometrical features. The image based analysis carried out on this work is able to classify the impairment in composite materials; this framework can be used in the industrial applications for the quantification of damages.
  • Analysing impact properties of CNT filled bamboo/glass hybrid
           nanocomposites through drop-weight impact testing, UWPI and
           compression-after-impact behaviour
    • Abstract: Publication date: Available online 17 December 2018Source: Composites Part B: EngineeringAuthor(s): Ariff Farhan Mohd Nor, Mohamed Thariq Hameed Sultan, Mohammad Jawaid, Ahmad Mustafa Rayney Azmi, Ain Umaira Md Shah The addition of carbon nanotubes (CNTs) in natural fibre based hybrid composites as filler to enhanced low velocity impact (LVI) and compression after impact (CAI) properties of composites are not explored by researchers in literature. In this study, we examined the effect of using multi-walled carbon nanotube material (MWCNT) as nanofillers in LVI followed by ultrasonic wave propagation imaging (UWPI) to visualize the impacted damage and CAI properties of bamboo/glass fibre hybrid composites. Hybrid composites containing 0.5% weight fractions of CNTs were compared with the control hybrid composites. The experimental results revealed that adding CNTs into the hybrid composites show less energy absorption, improved peak force, and increased deflection at maximums of 9.21%, 36.23% and 26.06% respectively in terms of LVI properties. Furthermore, smaller damage size was detected by non-destructive approach for CNTs/hybrid composites as compared to the controls. A maximum of 23.67% increment on CAI strength obtained by addition of CNTs into hybrid composites. We concluded that addition of CNTs into bamboo/glass hybrid composites improved impact and after-impact properties.
  • A new computationally efficient finite element formulation for nanoplates
           using second-order strain gradient Kirchhoff's plate theory
    • Abstract: Publication date: Available online 16 December 2018Source: Composites Part B: EngineeringAuthor(s): Bishweshwar Babu, B.P. Patel The strain gradient nonlocal theory is important to include the size effects of nanostructures in classical continuum theory with the corresponding development of computationally efficient numerical tool such as finite elements for the analysis of such structures with different boundary conditions. However, there is no literature on the finite element formulation of second-order strain gradient elastic plates. The weak form of the governing equation of motion of the Kirchhoff nanoplate using second-order positive/negative strain gradient nonlocal theories requires C2 continuity of transverse displacement. In this paper, a new computationally efficient nonconforming finite element formulation for the modelling of nanoplates using second-order positive/negative strain gradient nonlocal theories is presented. The performance of the developed finite element is compared with conforming finite element for rectangular isotropic Kirchhoff nanoplates with different boundary conditions. Analytical solution for static bending, free vibration, and buckling under biaxial in-plane compressive loading are also obtained for rectangular all edges simply supported isotropic Kirchhoff nanoplate for the comparison purpose. The nonconforming element is found to be computationally more efficient than the conforming element with better accuracy and convergence rate. The negative strain gradient model predicts results matching with the experimental results available in the literature.
  • Behaviour of pultruded GFRP truss system connected using through-bolt with
           mechanical insert
    • Abstract: Publication date: Available online 16 December 2018Source: Composites Part B: EngineeringAuthor(s): R.M. Hizam, Allan C. Manalo, Warna Karunasena, Yu Bai This paper presents the experimental and analytical studies of double-chorded composite truss system connected using stainless steel through-bolts with mechanical inserts. The composite trusses were assembled using rectangular hollow sections of pultruded glass fibre reinforced polymer (GFRP) where adhesively bonded mechanical inserts were introduced at the vicinity of the joining areas. The trusses were tested under 4-point bending (Load Case 1) and 3-point bending (Load Case 2). From this experimental program, the load-vertical deflection behaviour of the truss, internal forces distribution in the members and joint behaviour were investigated. The pultruded GFRP truss under Load Case 1 was capable of resisting the maximum load capacity of the testing equipment at 450 kN with the lowest factor of safety of 1.10 was attained by the external diagonal members. High axial compression forces experienced by the external diagonal members has exceeded the American pre-standard theoretical joint bearing capacity by 2%, and this was reflected by the minor bearing damage observed on the joints of these members. Meanwhile, the truss under Load Case 2 failed at 160 kN with the continuous top chords ruptured in flexural bending manner. The satisfactory comparisons between the Strand 7 truss model and experimental results demonstrated the validity of the adopted simplified numerical model. Additionally, the theoretical strength limits of pultruded GFRP truss members in tension, compression and flexural according to American pre-standard are in close agreement with the experimental results.
  • Toughening of high performance tetrafunctional epoxy with poly(allyl
           amine) grafted graphene oxide
    • Abstract: Publication date: Available online 16 December 2018Source: Composites Part B: EngineeringAuthor(s): Megha Sahu, Ashok M. Raichur The mechanical and thermal properties of epoxy composites were improved by using poly (allyl amine) (PAA) grafted graphene oxide (GO) as a toughening agent. The GO was first converted to GO-COOH where all the hydroxyl groups on the basal plane were converted to COOH containing groups. GO-COOH was reacted with PAA to yield GO-g-PAA. The effect of PAA grafted GO nanosheets as fillers on mechanical and thermal properties of aerospace grade epoxy was studied. Epoxy nanocomposites containing graphene oxide (GO) and GO-g-PAA nanosheets were fabricated by incorporating 0.35 to 1.4 wt% of filler. GO-g-PAA modified epoxy nanocomposites showed excellent improvement in flexural, compression and fracture properties compared to neat epoxy and GO modified epoxy. Fracture toughness increased from 0.94 MPa m to 1/2 for neat epoxy to 1.75 MPa m-1/2 (87%) for epoxy nanocomposites modified with 0.7 wt% of GO-g-PAA nanosheets. The temperature for 5% weight loss showed drastic improvement of 24 °C for epoxy nanocomposites modified with 0.7 wt% of GO-g-PAA nanosheets. The examination of fractured surfaces of modified epoxy nanocomposites showed better interaction of GO-g-PAA nanosheets with epoxy compared to GO nanosheets.Graphical abstractImage 1
  • Dynamic moduli and creep damping analysis of short carbon fiber reinforced
           polymer hybrid nanocomposite containing silica nanoparticle-on the
           nanoparticle size and volume fraction dependent aggregation
    • Abstract: Publication date: Available online 15 December 2018Source: Composites Part B: EngineeringAuthor(s): M. Vakilifard, M.J. Mahmoodi A hierarchical micromechanical procedure in conjunction with the elastic-viscoelastic correspondence principle is presented to estimate the dynamic moduli and creep damping capacity of short carbon fiber (CF) reinforced polymer hybrid nanocomposite (HNC) containing silica nanoparticle (SNP). At First, an analytical expression is derived to extract the damping properties in the frequency domain associated with a power law creep-time model. Then, a third phase known as interphase whose properties vary gradually, is taken into account to model the SNP/polymer interactions. The polymer matrix and the interphase obey a viscoelastic constitutive law. The CF random orientation is involved in the analysis as well. The effects of various parameters, including the SNP content, aggregation state and size; the CF content; the interphase properties; and the loading frequency (LF) on the HNC elastic modulus, creep compliance, storage modulus, loss modulus, and hysteresis loop are examined. As a novel idea, the SNP aggregation state is considered to be dependent on the SNP volume fraction (SNPVF). The SNP size effect is speculated by a newly presented intuition-based idea validated by the molecular dynamics simulation. Acceptable agreements in comparison with experiments prove the accuracy of the proposed model in the case that the intensity of the SNP aggregation is dependent on the SNPVF. It is found that a threshold for the SNPVF value can be reported to improve the HNC effective properties that beyond it, they tend to degenerate. It is also revealed that the SNP aggregation effect on the loss modulus diminishes as the LF increases in the manner that no change occurs in the LFs beyond 1e7 Hz. Additionally, the HNC overall properties are greatly affected by the NP diameters less than 20 nm.Graphical abstractImage 1
  • Microstructures and piezoelectric performance of eco-friendly composite
           films based on nanocellulose and barium titanate nanoparticle
    • Abstract: Publication date: Available online 15 December 2018Source: Composites Part B: EngineeringAuthor(s): Hyeong Yeol Choi, Young Gyu Jeong Eco-friendly nanocellulose-based composite films including different barium titanate (BaTiO3) nanoparticle contents were fabricated by an efficient aqueous suspension casting and following electric poling. The microstructures, dielectric/electrical property, and piezoelectric performance of the nanocellulose composite films were investigated as a function of the BaTiO3 content. The electron microscopic images demonstrated that the BaTiO3 nanoparticles were uniformly dispersed in the nanocellulose-based composite films. The X-ray diffraction results confirmed the presence of piezoelectric tetragonal BaTiO3 nanoparticles in the nanocellulose matrix with cellulose II phase. The dielectric constant and loss tangent of the composite films were found to increase and decrease with increasing the BaTiO3 content, respectively, which is favorable to achieve high piezoelectric outputs. On the other hand, the piezoelectric performance of the composite films increased with the BaTiO3 content up to 40 wt% and it decreased for the composites with 50–60 wt% BaTiO3, which results from the trade-off effect between the piezoelectric performance and the mechanical stiffness of BaTiO3 nanoparticle. Accordingly, the nanocellulose composite film with 40 wt% BaTiO3 was found to attain maximum piezoelectric outputs of voltage of ∼2.86 V, current of ∼262.4 nA, and electric power of ∼378.2 nW under a relatively low compressional stress of 5 kPa, which was high enough to charge microcapacitors after rectification.Graphical abstractImage 1
  • Stability and vibration analysis of CNT-Reinforced functionally graded
           laminated composite cylindrical shell panels using semi-analytical
    • Abstract: Publication date: Available online 15 December 2018Source: Composites Part B: EngineeringAuthor(s): Sumeet Chakraborty, Tanish Dey, Rajesh Kumar The present paper examined the buckling, postbuckling and vibration characteristics of pre-buckled and post-buckled laminated CNT reinforced composite (CNTRC) cylindrical shell panel made up of single walled carbon nanotubes (SWCNTs) and isotropic matrix. The effective material properties of CNTRC panel are computed using extended rule-of mixture (ROM) method. Higher order shear deformation theory (HSDT) with von Kármán type of nonlinearity is adopted to model the CNTRC cylindrical shell panel. Four different boundary conditions are considered. Besides uniform loading, different types of non-uniform in-plane load distribution such as triangular, trapezoidal, parabolic and partial edge loadings are considered. The internal stress distribution within the shell panel due to applied non-uniform loadings is evaluated by prebuckling analysis. Subsequently, via Hamilton's principle the governing partial differential equations of CNTRC laminated cylindrical shell panel are derived. Employing Galerkin's method and by neglecting the inertia terms the partial differential equations are reduced to a set of non-linear algebraic equation for the static problem. However, for dynamic problem the partial differential equations are converted to a set of ordinary differential equations. Beside parametric study the obtained numerical results from the present semi-analytical study illustrates the effects of CNT volume fraction, CNT dispersion profile, non-uniform load distribution and boundary conditions on the stability and vibration characteristics of CNTRC cylindrical panel.
  • Mitigating the electromagnetic radiation by coupling use of waste
           cathode-ray tube glass and graphene oxide on cement composites
    • Abstract: Publication date: Available online 15 December 2018Source: Composites Part B: EngineeringAuthor(s): Wu-Jian Long, Yu-cun Gu, Hongyan Ma, Hao-dao Li, Feng Xing With technological development, the rapid growing numbers of electronic devices generate severe electromagnetic interference (EMI) and radiation to human environment. In this study, the coupling effect of graphene oxide (GO) addition (up to 0.10 wt.% of cement) and waste cathode-ray tube (CRT) glass replacement for fine aggregates (30 and 60 wt.%) in cement-based composites on mitigating EMI was studied. The electric permittivity obtained using a decoupling method was applied for evaluating the EMI shielding capacity of cement-based composites, while direct current (DC) electrical resistance measurement is conducted using four-probe method. The DC electrical resistivity of specimens increases insignificantly with increasing in GO content, but remarkably with increasing CRT glass content from 30 to 60 wt.%. The 60 wt.% replacement of waste CRT glass with 0.1 wt.% GO addition increases the relative permittivity by about 50% and 200% when the frequency is in the ranges of 104–5 × 106 Hz and 101–103 Hz, respectively. It is concluded that a significant increase in the permittivity can be obtained owing to the synergetic interaction between waste CRT glass and GO. The improvement in the EMI shielding ability of cement-based composites not only enables the applications of these composites in mitigating electromagnetic pollution, but also promotes large-volume recycling of toxic waste CRT glass.Graphical abstractImage 1
  • Preparation and property evaluation of glass/ramie fibers reinforced epoxy
           hybrid composites
    • Abstract: Publication date: Available online 14 December 2018Source: Composites Part B: EngineeringAuthor(s): R. Giridharan Ramie fiber in combination with glass has proved to be excellent for making cost effective composite materials. They are prepared by hand layup method using E-glass and ramie fibers with. The resin used in the preparation of composites was epoxy. Fiber reinforced composites were hybridised at two weight percentages (20% and 30%). Samples prepared were tested to evaluate its properties, such as tensile strength, flexural strength, impact strength, and scanning electron microscope (SEM). Scanning electron microscope analysis revealed the morphological features. HFREC (Hybrid fiber reinforced epoxy composite) exhibited better mechanical properties than the individual samples.
  • BST-P(VDF-CTFE) nanocomposite films with high dielectric constant, low
           dielectric loss, and high energy-storage density
    • Abstract: Publication date: Available online 14 December 2018Source: Composites Part B: EngineeringAuthor(s): Xu Lu, Lin Zhang, Yang Tong, Z.Y. Cheng Free-standing, flexible, and transparent ceramic-polymer nanocomposite films with a uniform thickness of about 5 μm were fabricated using a simple spin-coating process, in which the polymer solution with a high concentration was used. Ba0.5Sr0.5TiO3 (BST) nanoparticles and P(VDF-CTFE) 91/9 mol.% (VC91) copolymer were used as ceramic filler and polymer matrix, respectively. Microstructures, dielectric properties, and energy-storage performances of the BST-VC91 nanocomposite films have been investigated. With increasing volume fraction of BST, the dielectric constant increases, while the dielectric loss decreases. A dielectric constant of about 38.4 at 100 Hz associated with a dielectric loss of only about 0.02 was obtained in the nanocomposite film with 40 vol% of BST. It is experimentally found that the temperature dependences and the frequency dispersions of dielectric properties were strongly influenced by the volume fraction of BST, especially at high temperatures. Good temperature stability and small frequency dispersion of dielectric constant can be obtained in the BST-VC91 nanocomposite films with 40 vol% and 50 vol% of BST, which are also associated with a low dielectric loss. It is concluded that the motion of the polymer chains is the micro-origin of the relaxation process observed at high temperatures. With increasing volume fraction of BST, the dielectric breakdown strength decreases, while the maximal polarization and remnant polarization increase. The maximal charge-energy density and discharge-energy density of about 21.7 J/cm3 and 7.5 J/cm3 are obtained in the BST-VC91 nanocomposite film with 30 vol% BST under 2500 kV/cm, which are more than 2 times larger than those observed in pure VC91 film under the same electric field.
  • Theoretical deflection analysis of multi-walled carbon nanotube reinforced
           sandwich panel and experimental verification
    • Abstract: Publication date: Available online 14 December 2018Source: Composites Part B: EngineeringAuthor(s): Kulmani Mehar, Subrata Kumar Panda In this article, the influence of the multi-walled carbon nanotube reinforcement on the stiffness of sandwich curved panel is examined theoretically via deflection analysis and compared with own experimental data for the verification of accuracy. The nanotube-reinforced sandwich structural panel model is derived theoretically using the higher-order polynomial functions and displacement finite element steps adopted for the numerical solution purpose. The structural stiffness values are measured from the deflection resistance of the theoretical structural model by computing the structural equilibrium equation with the help of an own customized MATLAB code. Firstly, the numerical solution accuracy and the corresponding reliability of the present solutions are cross-checked through the element sensitivity including the comparison test. Further, the multi-walled carbon nanotube reinforced sandwich plate is fabricated for the required experimentation including the mechanical as well as the material characterization. Finally, the validity of theoretically predicted deflection data of sandwich structure demonstrated by comparing with the own experimental results. In addition, the effect of various design parameters on the stiffness behavior of the own fabricated sandwich construction is computed using the proposed theoretical model and discussed in detail.
  • Development and implementation of a multi-scale model for matrix
           micro-cracking prediction in composite structures subjected to low
           velocity impact
    • Abstract: Publication date: Available online 14 December 2018Source: Composites Part B: EngineeringAuthor(s): Thomas Berton, Farzin Najafi, Chandra Veer Singh In this paper, a novel multi-scale damage model has been developed to predict the progression of matrix micro-cracking in a prototype car bumper under low-velocity impact. The methodology is based on FE micro-damage modelling to calibrate the parameters of a Synergistic Damage Mechanics model considering multi-axial loading, combined with a matrix micro-crack multiplication model. Python scripting was used to model a series of micro-mechanical FE models to determine the damage parameters, which were then used to simulate damage evolution at the structural scale, using a VUMAT subroutine. Following validation, the effects of the impactor's initial velocity, stacking sequence, rate-dependency and bumper's cross sectional profile have been evaluated for different material systems. The patterns of damage progression show that the damage model can accurately predict the progression of matrix micro-cracking, paving the way for the utilization of accurate multi-scale analysis tools in composite structures.
  • Self-assembled nanostructures of 3D hierarchical faceted-iron oxide
           containing vertical carbon nanotubes on reduced graphene oxide hybrids for
           enhanced electromagnetic interface shielding
    • Abstract: Publication date: Available online 14 December 2018Source: Composites Part B: EngineeringAuthor(s): Rajesh Kumar, Andrei V. Alaferdov, Rajesh K. Singh, Ashwani K. Singh, Jyoti Shah, Ravinder K. Kotnala, Kedar Singh, Yoshiyuki Suda, Stanislav A. Moshkalev The self-assembled three dimensional (3D) hybrids nanostructure containing uniform growth of vertical carbon nanotubes (VCNTs) with faceted iron oxide nanoparticles (f-Fe3O4 NPs) on the surfaces of reduced graphene oxide nanosheets (rGO NSs) is achieved using microwave assisted approach. The formation of hierarchical 3D f-Fe3O4-VCNTs@rGO hybrids, using microwave method is a rapid, simple, and inexpensive synthetic route. First, the VCNTs grow with help of Fe NPs, and after oxidizing of Fe NPs in form of f-Fe3O4 NPs, the growth has terminated resulting in formation of small size (
  • Free vibrations of functionally graded porous rectangular plate with
           uniform elastic boundary conditions
    • Abstract: Publication date: Available online 13 December 2018Source: Composites Part B: EngineeringAuthor(s): Jing Zhao, Qingshan Wang, Xiaowei Deng, Kwangnam Choe, Rui Zhong, Cijun Shuai In this paper, the free vibrations of functionally graded porous (FGP) rectangular plate with uniform elastic boundary conditions is investigated by means of an improved Fourier series method (IFSM). 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 was expressed as the simple cosine. The size of the pore in a rectangular plate is determined by the porosity coefficients. Using the first-order shear deformation theory(FSDT), the energy expression of FGP rectangular plate is created. In order to obtain the admissible function of displacement for functionally graded porous rectangular plate, the IFSM is employed. Then, the Rayleigh-Ritz method is used to solve coefficients in the Fourier series which determine natural frequencies and modal shapes. Convergence and comparative research are performed to prove the convergence, reliability and accuracy of the current method. On this foundation, some new results covering the influence of the geometrical parameters subject to classical and elastic boundary condition are presented, and the parametric studies are also investigated in detail, which can provide a reference for future research by other researchers.
  • The evaluation of the interfacial and flame retardant properties of glass
    • Abstract: Publication date: Available online 13 December 2018Source: Composites Part B: EngineeringAuthor(s): Jong-Hyun Kim, Dong-Jun Kwon, Pyeong-Su Shin, Yeong-Min Baek, Ha-Seung Park, K. Lawrence DeVries, Joung-Man Park Ammonium dihydrogen phosphate (ADP) as a glass fiber (GF) coating is useful as a flame retardant for glass fiber reinforced composites (GFRC). Three different ADP weight fraction coatings on GF resulted in distinctly different behavior. Single fiber tensile tests were conducted and statistically evaluated by Weibull distribution, for the three different ADP coatings. The tensile strength of neat GF and ADP coated GFs was not significantly affected by the ADP weight fraction. GFRC was manufactured using ADP coated GF mat reinforcement in unsaturated polyester (UP). The flame retardant test was used to access and compare the flame retardant property for the different composite specimens. The GFRC with the 20 wt% ADP coating exhibited the best flame retardant property. Interfacial/wettability properties were determined using static contact angle measurements. The static contact angle increased with increasing ADP weight fraction. Interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) were measure using the short beam and microdroplet pull-out tests respectively. Both ILLS and interfacial adhesion decreased somewhat in the ADP coated GF, while the flame retardant property markedly improved in GFRC, for ADP coated GF mat.
  • Improvement of the dynamic instability of shallow hybrid composite
           cylindrical shells under impulse loads using shape memory alloy wires
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): Ghazaleh Soltanieh, Mohammad Z. Kabir, M. Shariyat In the present paper, the prevention of a probable instability after a sudden change in deformation of thin shallow cylindrical composite panels under impulse loads is pursued using embedded super-elastic SMA wires. A novel and practical framework is proposed to analyze these panels according to the precisely determined super-elastic function of the shape memory alloys. The suggested phase transformation algorithm can deal with the existing deficiencies in the modeling of the super-elastic behaviors. The governing equations of motion are obtained based on a matrix form of the energy equilibrium, using Sanders’ shell theory, and including the in-plane and rotary inertia effects. The resulting nonlinear finite element formulation is programmed in FORTRAN language to solve the time-dependent equations by the Newmark-beta numerical time-integration approach. The Budiansky-Roth criterion is used to determine the stability thresholds of the structures by detecting the abrupt and unexpected deformations under the suddenly imposed transverse concentrated load. Effects of imposing loads with different time durations, types, and characteristics, various amounts of the pre-tension, different viscous damping and volume fractions of the SMA are examined in order to determine the dynamic instability strength of the hybrid composite cylindrical shells and the resulting deformations in a fully non-linear solution. The large magnitudes of the pre-tension loads can change the instability performance of the structures under even small loads. In this study, the viscous damping of the host composite panels is ignored in comparison to the energy absorption due to the hysteresis loops of the stress-strain transformation diagrams of the SMA wires.
  • Effects of tension rates and filler size on tensile properties of
           polypropylene/graphene nano-platelets composites
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): Ji-Zhao Liang The influence of tension rates and filler size on the tensile properties of polypropylene (PP) composites separately reinforced with graphene nano-platelets (GNPs) were investigated at room temperature within a tension rate range from 20 to 300 mm/min using a universal materials tester. The results showed that the Young's modulus, the tensile yield strength and the tensile fracture strength of these three PP composite systems increased obviously when tension rate was lower than 100 mm/min, and then increased slightly with increasing tension rate. The tensile elongation at break of these three composite systems decreased obviously when tension rate was lower than 100 mm/min, and then decreased slightly with increasing tension rate. The morphology of the tensile specimens of the composite was observed after tensile tests. Finally, the reinforcement mechanisms of the composites under different tension rates were discussed.Graphical abstractImage 1
  • Effects of thermal cycling on physical and tensile properties of injection
           moulded kenaf/carbon nanotubes/polypropylene hybrid composites
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): Zakaria Razak, Abu Bakar Sulong, Norhamidi Muhamad, Che Hassan Che Haron, Mohd Khairol Fadzly Md Radzi, Nur Farhani Ismail, Dulina Tholibon, Izdihar Tharazi Polymer as well as polymer composites are inclined to premature due to effect on mechanical and physical properties during service time. In this paper, the effect of thermal cycling (−30 to 80 °C) on the physical and tensile properties of Polypropylene (PP), Kenaf/PP, Kenaf/PP/CNTs and Kenaf/CNTs/MAPP/PP hybrid composites for the injection moulded car battery tray was investigated. Although this study had found no physical changes on the samples in terms of colour or cracking, the samples, however, had experienced warpage and dimensional changes. The dimension of samples containing CNT had increased by 20%, while the PP and PP/Kenaf samples had decreased by 3.5% and 87%, respectively. Although the process of thermal cycling was found to have rapidly decreased the hardness of Pure PP and Kenaf/PP composites, it had, however, gradually increased the hardness of composites with CNT fillers. The tensile strength, Young's modulus and elongation of the composites had also been examined in this research. Furthermore, according to the fractographic investigations using scanning electron microscope, it is perceived that the fracture morphology of the samples is strongly influensed by thermal cycling.
  • Na2OB2O3 CaOAl2O3 SiO2+glass+systems&rft.title=Composites+Part+B+:+Engineering&rft.issn=1359-8368&">Radiation shielding features using MCNPX code and mechanical properties of
           the PbONa2OB2O3 CaOAl2O3 SiO2 glass systems
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): Shams A.M. Issa, Yasser B. Saddeek, M.I. Sayyed, H.O. Tekin, Ozge Kilicoglu The novel glasses with compositions PbONa2B4O7 CaOAl2O3SiO2 glasses are prepared by the melt quenching technique. The radiation shielding and mechanical properties of the prepared glasses are presented and discussed in details. The mass attenuation coefficient (μ/ρ) which is the basic parameter in the evaluation of the radiation interaction with shielding materials was calculated according to MCNPX code, and the results were compared with those obtained by XCOM program. The simulation results match most of the XCOM data very well. Additionally, the results revealed that both (μ/ρ) and the effective atomic number (Zeff) of the prepared glasses increase with increasing lead monoxide from 0 to 50 mol. %. Also, the difference of HVL values of the prepared glass samples and that for the pure lead decrease when the concentration of lead monoxide increases. It is found that the removal cross-sections, ΣR values for the prepared glasses lie within the range 0.1006–0.1215 cm−1.
  • Efficient generator of random fiber distribution with diverse volume
           fractions by random fiber removal
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): Shin-Mu Park, Jae Hyuk Lim, Myeong Ryun Seong, Dong-Woo Sohn In this paper, we propose a simple and efficient generator of random fiber distribution with diverse fiber volume fractions (Vf) for unidirectional composites by a random fiber removal technique. From the representative volume element (RVE) consisting of 100 fibers that have a maximum Vf of about 65% in this work, also termed the master model, we randomly eliminate fibers to match the predefined Vf ranging from 60%, 55%, 45%, 35%, 25%, 15%, and 5%, which are lower than that of the master model. Accordingly, 100 RVE samples for each Vf can be constructed in a straightforward manner.To demonstrate the performance of the proposed algorithm, its fiber locations are verified in terms of statistical spatial metrics, such as the nearest neighbor orientation, Ripley's K function, and pair distribution function. Furthermore, the elastic properties and the anisotropic ratios of the generated RVEs are investigated and compared to those of other random fiber generation algorithms.Graphical abstractImage 1
  • An experimental and numerical investigation on low-velocity impact damage
           and compression-after-impact behavior of composite laminates
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): Hongliang Tuo, Zhixian Lu, Xiaoping Ma, Chao Zhang, Shuwen Chen This study investigated the damage and failure mechanism of composite laminates under low-velocity impact and compression-after-impact (CAI) loading conditions by numerical and experimental methods. Ultrasonic C-scan, DIC and SEM methods were combined to give a new and deep insight of damage evolution and failure mechanisms in composite laminates. A novel three-dimensional damage model based on continuum damage mechanics was developed to investigate the impact and CAI behavior with consideration of both interlaminar delamination damage and intralaminar damage. The maximum-strain failure criterion and an improved three-dimensional Puck criterion, which was physically-based, were employed to capture the initiation of fiber and matrix damage respectively and a bi-linear damage constitutive relation was used for characterization of damage evolution. The interlaminar delamination damage was simulated by the interfacial cohesive behavior. Good correlation between numerical and experimental results demonstrated the effectiveness and rationality of the proposed numerical model. The effects of impact energy level and multiple impacts were discussed.
  • Failure mechanisms of cross-ply carbon fiber reinforced polymer laminates
           under longitudinal compression with experimental and computational
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): Qingping Sun, Guowei Zhou, Haiding Guo, Zhaoxu Meng, Zhangxing Chen, Haolong Liu, Hongtae Kang, Xuming Su This study investigates the failure mechanisms of cross-ply laminates subjected to longitudinal compressive loading. A sequence of failure initiation and propagation process is observed based on optical microscopy images of failed specimens. Specifically, the failure process in the cross-ply laminates involves a combination of four failure mechanisms: fiber kinking, delamination, matrix cracking, and fiber/matrix splitting. We find that the kink-bands in the middle 0° plies of the cross-ply laminates most often show a wedge shape and the angle of matrix cracks in the 90° plies is slightly larger than that of pure 90° plies. The reason has been attributed to the constraining effects by the adjacent plies. The next focus of this study is to propose hybrid micro-macro models to more systematically study the failure mechanisms of the cross-ply laminates. We show that these models accurately predict the combined failure modes of the cross-ply laminates and enable us to closely investigate the interactions of different failure mechanisms. More importantly, the hybrid models achieve great computational efficiency compared to full-scale microstructural models. The combined experimental and computational analyses presented here provide a new level of understanding of the kink-band morphology and damage mechanisms in the cross-ply laminates.
  • Novel treatment methods for improving fatigue behavior of laminated glass
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): Ajitanshu Vedrtnam The use of laminated glasses (LG) is increasing day-by-day in the fatigue prone structures. In the present work, the pre- and post-breakage behavior of LG was improved for the fatigue loading via five novel thermo-chemical treatment methods. The fatigue life of LG samples was evaluated using the standard bending cyclic fatigue test. The prime goal of the treatment methods was to bring the surfaces of LG samples in the compressive state without causing melting or bubbling of interlayer having a melting temperature lesser than 150 °C. A comparison of treatment methods based on cyclic fatigue strength (CFS) of LG was reported. Further, a theoretical explanation for improved fatigue life was presented. The life of LG samples was increased by more than 40% by one of the treatment methods. The finite element (FE) model was developed to calculate the deformations and stresses for the corresponding number of cycles at which LG samples were fractured. Further, the FE model was extending to consider the residual stresses profile due to different treatments before modeling the effect of cyclic fatigue loading. The strain-life and stress-life relations were established using experimental and modeling results. The crack propagation and fracture of LGs were explained using previously established models and correlated with the effect of treatment. The statistical analysis was conducted for ensuring the validity of the results.
  • A model of heterogeneous thermoviscoplastic material preserving uniform
           normal strains under combined compression, tension (or compression) and
           shearing. Instability and homogenization results
    • Abstract: Publication date: Available online 12 December 2018Source: Composites Part B: EngineeringAuthor(s): George Chatzigeorgiou, Nicolas Charalambakis In this paper, we present the special solution of the two-dimensional problem of a continuously graded composite made of thermovisco-rigid plastic materials under combined biaxial quasistatic compression and tension (or compression) and shear, that preserves prescribed uniform normal strains. The related reference initial-boundary value problem is fully defined and the corresponding solution is analyzed and computed numerically. In the context of a linearized instability analysis, critical conditions, as the critical shear banding angle, in terms of the loading level and material heterogeneities, are presented. In the context of non-linear instability, these results are examined and explained. Additionally, in the same context of non-linear analysis, the destabilizing mechanism, the onset of instability and the critical time for prescribed lower and upper bounds of equivalent strain-rate and upper bound of equivalent strain are defined and related to the lateral normal stress. The limitations of linearized analysis results are also revealed. Moreover, a semi-analytical homogenization scheme for a periodically-graded plate is presented. The related results are used for the derivation of a homogenized problem of a multilayered composite with continuously graded interlayers.
  • Radiation stability and thermal behaviour of modified UF resin using
           biorenewable raw material-furfuryl alcohol
    • Abstract: Publication date: Available online 10 December 2018Source: Composites Part B: EngineeringAuthor(s): Suzana Samaržija-Jovanović, Vojislav Jovanović, Branka Petković, Slaviša Jovanović, Gordana Marković, Slavica Porobić, Milena Marinović-Cincović The thermal stability of organic-inorganic nano-composites prepared by a two-stage polymerization of urea-formaldehyde resin (UF) with furfuryl alcohol (FA) and TiO2 before and after irradiation has been researched. The two resins of urea-formaldehyde–TiO2 composites, named: UF/TiO2 and UF/TiO2/FA, were synthesized. The thermal stability of obtained materials was studied by non-isothermal thermo-gravimetric analysis (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA). UF hybrid composites have been irradiated (50 kGy) and after that their radiation stability was evaluated on the basis of thermal behavior. The free formaldehyde (HCOH) percentage in all prepared samples was determined. The minimum percentage values of free formaldehyde (0.04% and 0.03%) for UF/TiO2 and UF/TiO2/FA, respectively, after irradiation dose of 50 kGy are detected. The shift of temperature values for selected mass losses (T10%) to a high temperature indicates the increase in thermal stability of samples based on UF resin modified with FA.
  • Impact of Al2O3, TiO2, ZnO and BaTiO3 on the microwave absorption
           properties of exfoliated graphite/epoxy composites at X-band frequencies
    • Abstract: Publication date: Available online 10 December 2018Source: Composites Part B: EngineeringAuthor(s): Sandeep Kumar Singh, M.J. Akhtar, Kamal K. Kar Bi-filler composites composed of exfoliated graphite (EG) and any one of Al2O3, BaTiO3, ZnO and TiO2 metallic oxides are fabricated in epoxy matrix to improve microwave absorption properties exclusively in X band. These composites are characterized for their morphology and compositional studies using SEM, Raman spectroscopy and X-rays photoelectron spectroscopy. The strong reflection loss values of −43 dB (99.995% absorption), −25.7 dB (99.731% absorption), −33.9 dB (99.959% absorption) and −46.0 (99.997% absorption) with wide effective bandwidths are successfully achieved by the EG/epoxy composites containing 40 wt% Al2O3, 30 wt% BaTiO3, 30 wt% TiO2 and 20 wt% ZnO when the thicknesses are 1.8, 1.6, 1.4 and 1.8 mm, respectively. These absorption performances are attributed to the perfect matching conditions, multiple internal reflections, interface polarizations and defect polarizations. The incorporation of metallic oxides demonstrated improved adhesion and reinforcement efficiency factors, as well as uplifted the values of flexural strength and thermal conductivity of EG/epoxy composites. These properties justifies the potential future of metallic oxide/EG/epoxy composite in microwave absorption applications.Graphical abstractImage 1
  • Structure-property relationship of PLA-Opuntia Ficus Indica
    • Abstract: Publication date: Available online 10 December 2018Source: Composites Part B: EngineeringAuthor(s): Roberto Scaffaro, Andrea Maio, Emmanuel Fortunato Gulino, Bartolomeo Megna In this work, a lignocellulosic flour was achieved by grinding the cladodes of Opuntia Ficus Indica and then added to a poly-lactic acid (PLA) in order to prepare biocomposites by melt processing. The influence of filler content and size on the morphological, rheological, and mechanical properties of the green composites was assessed. Moreover, solvent-aided filler extraction enabled to evaluate the homogeneity of filler dispersion, as well as the effect of processing on the geometrical features of the fillers. The experimental data obtained by tensile tests proved to be remarkably higher than those predicted by Halpin–Tsai model, presumably due to the capability of the polymer to enter the empty channels of the fillers, thus dramatically increasing the interphasic region.
  • A novel isogeometric beam element based on mixed form of refined zigzag
           theory for thick sandwich and multilayered composite beams
    • Abstract: Publication date: Available online 10 December 2018Source: Composites Part B: EngineeringAuthor(s): Adnan Kefal, Kazim Ahmet Hasim, Mehmet Yildiz This study presents a highly accurate, computationally efficient, and novel isogeometric beam element, named as IG-RZT(m), whose formulation is derived by using the kinematic assumptions and “a priori” transverse-shear stress continuity conditions of mixed form of the refined zigzag theory, known as RZT(m). Both the displacement field and geometry of the beam is approximated by using non-rational B-spline (NURBS) basis functions and the IG-RZT(m) element accommodates only four degrees-of-freedom at each control point. Since the present formulation incorporates isogeometric analysis into the RZT(m) theory, it provides various advantages for displacement and stress analysis of thin/thick composite beams such as high-order continuity representation and simple mesh refinement. Furthermore, the utilization of RZT(m) theory within the current beam formulation enables the calculation of nonlinear transverse-shear stress variations through the thickness of highly anisotropic beams without any post-processing. Various numerical analysis are performed to validate the accuracy of the IG-RZT(m) element and its wide range of applicability including beams with a resin-rich damage zone. Comparisons with analytic solutions and high-fidelity finite element models demonstrate the superior accuracy and practical applicability of the present formulation, especially making the IG-RZT(m) element as an attractive candidate for modelling delamination initiation and propagation in composite structures.
  • Compressive properties of zinc syntactic foams at elevated temperatures
    • Abstract: Publication date: Available online 8 December 2018Source: Composites Part B: EngineeringAuthor(s): Emanoil Linul, Daniel Lell, Nima Movahedi, Cosmin Codrean, Thomas Fiedler This paper investigates the effect of temperature on the microstructure, failure mechanism and compressive mechanical properties of newly developed ZA27 syntactic foams. Two different types of filler particles are considered, i.e. expanded perlite (P) and expanded glass (G). Metallic syntactic foam (MSF) has been produced via a counter-gravity infiltration process of packed particle beds, followed by controlled thermal exposure. Quasi-static compressive tests were carried out on cylindrical samples at five different in-situ testing temperatures between 25 °C and 350 °C. At all considered temperatures, P-MSF exhibits superior mechanical properties compared to G-MSF. The mechanical properties of both foam types decrease significantly with increasing testing temperature. For comparison, solid ZA27 samples were compressed at the same testing temperatures. Due to microstructural changes, a significant strength degradation of solid ZA27 was observed starting at 100 °C. Comparison of results indicates that the temperature-dependent mechanical properties of P-MSF and G-MSF are strongly controlled by the matrix material. However, the addition of particles decreased the relative reduction of plateau stress and volumetric energy absorption of ZA27 MSF at elevated temperatures.
  • Enhanced simple beam theory for characterising mode-I fracture resistance
           via a double cantilever beam test
    • Abstract: Publication date: Available online 7 December 2018Source: Composites Part B: EngineeringAuthor(s): Leo Škec, Giulio Alfano, Gordan Jelenić We study a double-cantilever beam (DCB), in which either the crack-mouth opening displacement or the end rotations are prescribed, in the linear-elastic-fracture-mechanics (LEFM) limit of an infinitely stiff and brittle interface. We present a novel, yet extremely simple, derivation of the closed-form solution of this problem when the arms are modelled with Timoshenko beam theory. We remove the assumption that the cross sections of the DCB arms are assumed not to rotate (i.e. that they are clamped) at the crack tip, which is made in so-called ‘simple beam theory’ (SBT). Therefore, with our ‘enhanced simple beam theory’ (ESBT), in front of the crack tip, cross sections are allowed to rotate, although the beam axis stays undeformed. Thus, we can determine the crack-tip rotation caused by the deformation of the beam in front of the crack tip also in the LEFM limit. As a result, most of the inaccuracies of the SBT are eliminated, without the need for a crack-length correction, used in the ‘corrected beam theory’ (CBT). In this way, we can derive a very accurate data reduction formula for the critical energy release rate, Gc, which does not require the measurement of the crack length, unlike CBT. In our numerical results we show that, compared to the most effective data reduction methods currently available (including CBT), our formula is either as accurate or more accurate for the case of brittle delamination of thick composite plates, in which shear deformability can play a significant role.
  • Automated generation of carbon nanotube morphology in cement composite via
           data-driven approaches
    • Abstract: Publication date: Available online 7 December 2018Source: Composites Part B: EngineeringAuthor(s): Hyeong Min Park, S.M. Park, Seung-Mok Lee, In-Jin Shon, Haemin Jeon, B.J. Yang Electrified cement composite has attracted considerable attention in major scientific and engineering fields due to its excellent functional characteristics. With increasing interest in this functional material, the need for an advanced theoretical approach has also increased significantly. In the present study, a data-driven model based on hierarchical micromechanics and particle swarm optimization is proposed to estimate the morphological characteristic of conductive nanofiller of cement composites. Experimental data needed for the simulation are acquired by fabricating cement specimens with various contents of multi-walled carbon nanotube (MWCNT), carbon fiber, and water-to-cement ratios, and measuring their electrical resistivity, porosity, and aspect ratio by relevant experimental and computational techniques. Based on the proposed framework, a series of numerical simulations including the experimental comparisons of the electrified cement composite are carried out to clarify the potential of the present model. The number of model parameters is reduced to the curviness of MWCNT, which is the most influential model parameter, and the process of collecting and simplifying the pattern is included.
  • Interfacial structure and bonding mechanism of
           AZ31/carbon-fiber-reinforced plastic composites fabricated by thermal
           laser joining
    • Abstract: Publication date: Available online 6 December 2018Source: Composites Part B: EngineeringAuthor(s): Barton Mensah Arkhurst, Jae Bok Seol, Youn Seoung Lee, Mok-Young Lee, Jeoung Han Kim Multi-material joining is attracting attention in automotive industry due to the potential for lighter weight vehicles, fuel savings, and reduced emissions. The aim of present work is to understand the bonding mechanisms between metal and plastic/composites joints and improve the multi-material joint strength. In this work, the effect of thermal oxidation of Mg alloy sheets on the strengths of Mg–CFRP (carbon-fiber-reinforced plastic) lap joints prepared using laser-assisted metal and plastic joining technique was investigated. Characterization techniques including scanning electron microscopy, transmission electron microscopy, micro-computed tomography, x-ray photoelectron spectroscopy (XPS), and atom probe tomography (APT) were used to study the underlying mechanisms of the effect of thermal oxidation. The formation of bubbles, mechanical interlocking and chemical reactions at the joint interface were the three key factors that influenced the strength of joints. Thermal oxidation increased joint strength significantly through suppression of bubble formation, CFRP decomposition and the setting up of mechanical interlocking effects at the joint interface. Moreover, MgCO3, MgO1+x, and Mg(OH)2 phases were detected by XPS analysis at the joints prepared with thermally oxidized Mg alloy sheets. The presence of the high O/Mg ratio phases was also confirmed by the APT analysis. The formation of these phases confirmed the chemical reactions between the MgO and CFRP matrix at the nanometer level and is considered to contribute to the increase of the joint strength.Graphical abstractImage 1
  • Thermal stability and heat release effect of flame retarded PA66 prepared
           by end-pieces capping technology
    • Abstract: Publication date: Available online 5 December 2018Source: Composites Part B: EngineeringAuthor(s): WenYan Lyu, XiuMin Chen, YouBing Li, Shuang Ca, YiMing Ha In order to improve the flame retardancy of PA66, bis-N-benzoguanamine-phenylphos-phamide (MCPO) was grafted to PA66 main chains by end-pieces capping technology. The thermal properties and heat release effect of flame retardant PA66 (FR PA66) composites were investigated by thermogravimetry, differential scanning calorimetry, and cone calorimetry test analyses. In the presence of 8 wt% MCPO in PA66 composites, the initial decomposition temperature (T5) and peak decomposition temperature (Tmax) of PA66 composites were 47 °C and 34 °C higher than that of pristine PA66, respectively. Compared to the traditional flame retardant PA66 composites, the heat release rate, total heat release, total smoke production, and CO release rate significantly reduced by 31.3%, 36.3%, 16.9%, and 14.7% by introducing P containing benzoguanamine derivative, respectively. Moreover, the vertical flame spread test illustrated that the melt dripping of PA66 stopped for higher precursor concentrations in the composites carbonized char, and the limiting oxygen index (LOI) value of PA66 composites reached 29% as evidenced by the LOI test.Graphical abstractImage 1
  • Interfacial reaction induced efficient load transfer in few-layer graphene
           reinforced Al matrix composites for high-performance conductor
    • Abstract: Publication date: Available online 5 December 2018Source: Composites Part B: EngineeringAuthor(s): Weiwei Zhou, Pavlina Mikulova, Yuchi Fan, Keiko Kikuchi, Naoyuki Nomura, Akira Kawasaki Fabricating high-strength Al matrix composites without sacrificing their electrical conductivity is a critical issue in the design of Al-based conductors. Here, we demonstrate for the first time, an example of improving the interfacial load transfer and strength of few-layer graphene (FLG)/Al composites by an appropriate interfacial reaction. Monocrystalline Al4C3 nanorods that tightly conjoined the FLG platelets with the Al matrix were produced by manipulating the sintering temperature. As revealed by transmission electron microscopy and by a shear lag model that provides a quantitative estimate of the strengthening, the Al4C3 nanorods ensured an efficient load transfer at the FLG-Al interface, thereby giving rise to a considerable enhancement of strength in the composite. Moreover, the electrical conductivity is almost as high as that of pure Al, which could be a significant step toward the preparation of high-performance Al-based conductors.Graphical abstractImage 1
  • Effect of starch reduced graphene oxide on thermal and mechanical
           properties of phenol formaldehyde resin nanocomposites
    • Abstract: Publication date: Available online 5 December 2018Source: Composites Part B: EngineeringAuthor(s): P.K. Sandhya, M.S. Sreekala, Moothetty Padmanabhan, K. Jesitha, Sabu Thomas Phenol formaldehyde (PF) resins are one of the oldest synthesized and very widely used resins. Their properties can be improved with the incorporation nano-fillers even with lower loadings. Graphene materials have attracted significant attention in recent years owing to its exceptional thermal, mechanical and electrical properties. Herein, we report a very simple and effective way to reduce graphene oxide (GO) by using highly abundant potato starch instead of conventionally used toxic and hazardous reducing agents like hydrazine. The reduced GO (RGO) is then effectively incorporated into PF resin by optimizing various processing parameters. The reinforcing effect of RGO sheets on the PF matrix was investigated by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The effect of RGO on thermal properties of the polymer nanocomposites was studied using Thermogravimetric Analysis (TGA). The mechanical properties of PF/RGO composites were studied by tensile and Izod impact tests. The fracture mechanism of the composites was investigated by Scanning Electron Microscopy. Theoretical prediction of the mechanical properties of the nanocomposites using Halpin-Tsai models gave sufficient information regarding the orientation of graphene sheets in PF matrix.Graphical abstractScheme illustrating formation of PF/RGO nanocomposites.Image 1
  • Reinforcement size dependence of mechanical properties and strengthening
           mechanisms in diamond reinforced titanium metal matrix composites
    • Abstract: Publication date: Available online 4 December 2018Source: Composites Part B: EngineeringAuthor(s): Farhad Saba, Faming Zhang, Suli Liu, Tengfei Liu Diamond particulates reinforced titanium matrix composites (TiMMCs) were fabricated by spark plasma sintering technique at different reinforcement sizes of 5, 100, 200 nm and 3 μm. The dependence of reinforcement size on the mechanical and tribological properties in the TiMMCs was studied, paying particular attention to the nanoscale effects. The enhancement in strength of the composites was elucidated on the basis of strengthening mechanisms characterized by load transfer, thermal mismatch, grain size, and Orowan strengthening. The strengthening mechanisms were quantitatively analyzed and evaluated as a function of particle size. The results revealed that the presence of 5 nm diamond particles enhance strength by interacting with dislocations, while simultaneously retarding grain growth. Although the micro-composite has a little higher strength than the nanodiamonds reinforced composite, the latter has a combination of high strength and high ductility as wells excellent tribological properties.
  • Stiffness and strength evaluation of a novel FRP sandwich panel for bridge
    • Abstract: Publication date: Available online 4 December 2018Source: Composites Part B: EngineeringAuthor(s): Maciej Kulpa, Tomasz Siwowski The objective of the research described in the paper was the structural development of a FRP composite bridge deck intended for manufacturing and application in road bridges in Poland, mainly for redecking the deteriorated bridge slabs. The appropriate shape of the sandwich bridge deck panel, its overall structure, constituent materials and the associated cost-effective manufacturing technology were determined following a comprehensive analysis of the similar solutions recently developed worldwide. In the first stage three different small-scale deck panel prototypes were designed and fabricated, assuming the various core configuration of the sandwich structure. Based on manufacturing tests and initial static tests the feasibility and stiffness of all prototypes were assessed to select the optimal deck solution in terms of material, structure and technology. In the second stage of the research a full-size 2.0 × 5.0 m bridge deck panel was designed taking into account the bridge loading according to Eurocode 1. The full-size bridge deck prototype was subjected to a series of static load tests simulating the relevant load. The tests confirmed the appropriate stiffness and load carrying capacity of the novel FRP bridge deck panel, quite similar to performance characteristics of other FRP bridge decks implemented worldwide. However, the necessary technological and research works on the novel sandwich bridge deck panel in order to increase its safety level were also outlined.
  • Flammability and mechanical properties of composites fabricated with
           CaCO3-filled pine flakes and Phenol Formaldehyde resin
    • Abstract: Publication date: Available online 4 December 2018Source: Composites Part B: EngineeringAuthor(s): Yubo Tao, Peng Li, Liping Cai, Sheldon Q. Shi Flammability of wood composites has always been of a concern. To investigate whether CaCO3 particles are efficient fire-retardant fillers for wood composites, wood composites were prepared with Phenol Formaldehyde (PF) resin and pine flakes that were deposited with CaCO3 by the treatments of Na2CO3 and CaCl2. The flammable performance, Limiting Oxygen Index (LOI), simultaneous Thermogravimetric Analysis and Differential Scanning Calorimetry (TGA–DSC), mechanical properties, and water resistance of wood-flake composites deposited with CaCO3 were evaluated. Furthermore, the Scanning Electron Microscopy (SEM) was used to observe the surface morphology of the treated wood flakes, showing that CaCO3 microparticle crystals grew onto the wood flake surfaces. The increase of reactant concentrations from 0.5 M to 1.0 M resulted in an increase in LOI and improvements of the flame-retardant performance of the composites. The TGA–DTG examination showed that the decomposition peak of the treated wood flakes shifted to a lower temperature range. The TGA also demonstrated that the treatment contributed to the accumulation of char layer, which benefited the flame retardancy of the composites. The growth of energy consumed during the sample pyrolysis could be attributed to the insulation of CaCO3 and thicker char layers. After the treatment with reactants (concentration of 0.5 M), although the internal bonding (IB) slightly decreased by 8.3%, the modulus of elasticity (MOE) and the modulus of rupture (MOR) of the composites significantly increased by 182.9% and 63.5%, respectively.
  • Biosynthesized Co-doped TiO2 nanoparticles based anode for lithium-ion
           battery application and investigating the influence of dopant
           concentrations on its performance
    • Abstract: Publication date: Available online 3 December 2018Source: Composites Part B: EngineeringAuthor(s): Anil A. Kashale, Akash S. Rasal, Gokul P. Kamble, Vijay H. Ingole, Pravin K. Dwivedi, Swapnil J. Rajoba, Lata D. Jadhav, Yong-Chien Ling, Jia-Yaw Chang, Anil V. Ghule TiO2 is a good alternative anode material for lithium-ion battery application because of its incomparable high structural stability and safety during the charge/discharge cycles. However, the low intrinsic conductivity of TiO2 has been a limiting factor affecting its cycling and rate capability performance. Here in this work, we present Co-doped TiO2 nanoparticles based anode with good reversibility, cycling stability and rate capability performance for its envisaged application in lithium-ion battery. The Co-doped TiO2 nanoparticles with different Co concentrations (3%, 5%, and 7%) are synthesized using simple and economic biomediated green approach, wherein TiCl4 and Co precursors are allowed to react in Bengal gram bean extract containing biomolecules which act as natural capping agents to control the size of nanoparticles. Among the pure TiO2 and different Co-doped TiO2 samples, the 7% Co-doped TiO2 anode show the highest capacity of 167 mAh g−1 (88.3%) after 100 cycles at the 0.5C current density. The Co-doped TiO2 shows higher and stable coulombic efficiency up to 100 GCD cycles indicating good reversibility. Based on the results, it is expected that the Co-doped TiO2 nanoparticles might be contributing to the enhanced electronic conductivity providing an efficient pathway for fast electron transfer.Graphical abstractImage 1
  • Numerical study on three-point bending behavior of honeycomb sandwich with
           ceramic tile
    • Abstract: Publication date: Available online 1 December 2018Source: Composites Part B: EngineeringAuthor(s): Zhonggang Wang, Zhendong Li, Wei Xiong Honeycomb sandwich structures have been extensively investigated in the past decades. A kind of innovative honeycomb sandwich with ceramic face sheet (ceramic sandwich), was investigated here for its bending behavior by using finite-element model implemented in Abaqus/Explicit code. In our studies, a series numerical simulation of three-point bending were carried out for the ceramic sandwich and conventional aluminum honeycomb sandwich. The numerical model was validated by experiments. As confirmed that the ceramic tile largely enhances the stiffness of the structure, which contributes a lot to the promotion of the bending resistance capacity. Parametric studies were performed to further investigate the effects brought from the ceramic tile and honeycomb core in terms of changing the thickness of ceramic tile, the thickness of honeycomb wall, the length of honeycomb cells. It was found that the bending performance heavily relay on the geometric configuration of the present sandwich panel. In addition, the ceramic sandwich with reinforced honeycomb core also shows better mechanical behavior in the simulation. All these achievements provide more likelihood of designing composited high-performance sandwich.
  • Double scaling and master curve to predict Kts for elliptically notched
           orthotropic plates from Kts in circularly notched isotropic plates
    • Abstract: Publication date: Available online 30 November 2018Source: Composites Part B: EngineeringAuthor(s): Nando Troyani, Milagros Sánchez The key role played by the so-called stress concentration factors (symbolically usually referred to as Kts) while performing either analysis or design in both mechanical engineering and structural engineering is a well-proven fact; hence, the corresponding accuracy and ease of determination in their estimation have critical implications related to engineering matters. In a previous work, we showed that starting with the Kts for rectangular isotropic plates with circular holes the Kts for rectangular orthotropic plates with elliptic holes can be easily and accurately predicted, using a double scaling procedure (a geometric scaling and a material scaling) together with a basic Kt curve employed as a master curve. In the present work we investigate, in an engineering heuristic manner, whether the stated double scaling procedure exhibits a more general structure so that it can accurately be applied to different plate stress raiser geometries. Specifically, we examine if starting with the known Kts for rectangular isotropic plates with circular notches, used as a master curve, the Kts for orthotropic plates with elliptic notches can be easily and accurately predicted as well. Using a simple hand calculator, we show that the resulting proposed set of predicting mathematical expressions makes virtually unnecessary the use of complex numerical programs (FEM based for example) to determine the corresponding Kts, producing at the same time accurate results with a maximum average recorded error of 2.59%. Additionally, given that a Kt predictive procedure for holed plates was presented in our previous work, and for notched plates in this work, we found necessary first to examine the hypothesis that suggests using Kts from holed plates as good approximations for Kts for notched ones and vice versa. We found this hypothesis not to be valid for either isotropic or orthotropic plates. In the course of this work it was found, rather significantly, that the well-known double square root material contribution to Kts is valid for both holed plates as well as notched ones.
  • Study on mechanical properties of ternary blended concrete containing two
           different sizes of nano-SiO2
    • Abstract: Publication date: Available online 29 November 2018Source: Composites Part B: EngineeringAuthor(s): Amin Nazerigivi, Alireza Najigivi The aim of this study was to investigate the influences of combination of the two different SiO2 nanoparticles (15 nm and 80 nm) on compressive, flexural and tensile strength of ternary blended concrete. SiO2 nanoparticles with two different sizes of 15 and 80 nm have been used as a partial cement replacement by 0.5, 1.0, 1.5 and 2.0 wt.% in 16 different proportions of mixture followed by curing in lime solution for 7, 28 and 90 days. The results indicate that in all curing ages in lime solution specimens with 2.0% of 15 nm plus 1.5% of 80 nm cement replacement achieved higher mechanical properties. The continuous cement paste with the lowest delicate zones might be due to the fact of quick formation of C–S–H gel in the existence of ultra-high dynamic nanosized SiO2 in both average particle sizes together with their high filler effect. It was concluded that the use of novel ternary blended concrete provides significant improvement in the all mechanical properties of concrete. In other words, increasing in the strength could be due to this fact that the nucleus of strengthening gel might merely reach to the critical volume of nucleation.
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Heriot-Watt University
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