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Composite Structures
Journal Prestige (SJR): 1.905
Citation Impact (citeScore): 5
Number of Followers: 277  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0263-8223
Published by Elsevier Homepage  [3163 journals]
  • Finite element analysis for the biomechanical effect of tibial insert
           materials in total knee arthroplasty
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Kyoung-Tak Kang, Juhyun Son, Sae Kwang Kwon, Oh-Ryong Kwon, Joon-Hee Park, Yong-Gon Koh
      Instability and wear are the most common causes of failure of total knee arthroplasty (TKA). The purpose of this study is to evaluate the biomechanical effects on knee joints of different tibial insert materials: UHMWPE, PEEK and CFR-PEEK. The forces exerted on soft tissues were evaluated under a deep knee bend condition in posterior-stabilized (PS) and cruciate-retaining (CR) TKA. The efficacy of quadriceps muscle force in flexion, in both TKA, was reduced when the tibial insert material was changed to PEEK and CFR-PEEK. There was no difference in the collateral ligament force in PS TKA. However, the medial collateral ligament force was greater with PEEK and CFR-PEEK than UHMWPE in CR TKA. The posterior cruciate ligament force was lower with PEEK and CFR-PEEK than UHMWPE. Our results showed that PEEK and CFR-PEEK can be alternative materials to existing UHMWPE, but it should be careful to adapt them in CR TKA.

      PubDate: 2018-06-21T10:10:19Z
       
  • Investigation of mechanical behavior of weld seams of composite envelopes
           in airship structures
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Taibai Shi, Wujun Chen, Chengjun Gao, Jianhui Hu, Bing Zhao, Xueming Wang, Xique Wang, Guofu Lu
      With the favorable space retaining advantage, airship structures provide a cost-effective approach for the high altitude payload platform. While composite envelopes, the key material for an airship capsule, were extensively studied, the mechanical behavior of weld seams remained unclear. As weld seams may be the authentic controlling factor for the mechanical performance of airship structures, a comprehensive study on its mechanical behavior is necessary. An in-depth investigation revealing the tensile properties of weld seam was carried out in this study. Three types of weld seam specimens were designed and manufactured. To illustrate the microstructure of the weld seams, an electron scanning microscope apparatus was employed conducting observation. Systematic tensile tests were performed on envelopes, weld tapes and weld seams. It was found that the failure occurred at the heated zone rim. Furthermore, noncontact measurement was utilized obtaining the global strain field, based on which elastic constants were calculated. Eventually, a numerical model was proposed to simulate the tensile behavior of the weld seam.

      PubDate: 2018-06-18T09:57:32Z
       
  • Topology optimization for the design of perfect mode-converting
           anisotropic elastic metamaterials
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Xiongwei Yang, Yoon Young Kim
      This work is concerned with the topology optimization of anisotropic elastic metamaterials exhibiting perfect mode conversion, a newly discovered phenomenon that an incident longitudinal (transverse) mode is solely and maximally converted to a transmitted transverse (longitudinal) mode. The wave phenomenon occurs at a series of interference frequencies due to elaborate multimodal interferences, known as the perfect transmodal Fabry-Perot interferences. Because the metamaterial must satisfy unique anisotropic relations among its effective stiffness, design of its unit cell is difficult without a systematic strategy. Here, we propose a topology optimization method based on the effective material properties to design such artificial composites. The homogenization method is employed to evaluate the effective material properties and the anisotropy requirements are treated as a special form of constraints. Because there is no natural mass constraint, we propose to maximize the effective longitudinal-transverse coupling stiffness for stable convergence. The sensitivity analysis is performed analytically within the finite element framework to update the design variables. The validity and effectiveness of the developed method are verified by considering different lattice types and interference cases. Considering the wide potential applications of anisotropic metamaterials in industrial applications, the developed numerical method can be an important and critically useful design tool.

      PubDate: 2018-06-18T09:57:32Z
       
  • Postbuckling analysis of functionally graded nanoplates based on nonlocal
           theory and isogeometric analysis
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Son Thai, Huu-Tai Thai, Thuc P. Vo, Seunghye Lee
      This study aims to investigate the postbuckling response of functionally graded (FG) nanoplates by using the nonlocal elasticity theory of Eringen to capture the size effect. In addition, Reddy’s third-order shear deformation theory is adopted to describe the kinematic relations, while von Kámán’s assumptions are used to account for the geometrical nonlinearity. In order to calculate the effective material properties, the Mori-Tanaka scheme is adopted. Governing equations are derived based on the principle of virtual work. Isogeometric analysis (IGA) is employed as a discretization tool, which is able to satisfy the C 1 -continuity demand efficiently. The Newton-Raphson iterative technique with imperfections is employed to trace the postbuckling paths. Various numerical studies are carried out to examine the influences of gradient index, nonlocal effect, ratio of compressive loads, boundary condition, thickness ratio and aspect ratio on the postbuckling behaviour of FG nanoplates.

      PubDate: 2018-06-18T09:57:32Z
       
  • Flexural behavior of large-size RC beams strengthened with side near
           surface mounted (SNSM) CFRP strips
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Zewen Zhu, Eryu Zhu
      Taking the reinforcement of monorail guide-way as the background, the effectiveness of SNSM carbon fiber reinforced polymer (CFRP) strengthening technique applied for the large-size reinforced concrete (RC) beams was evaluated. First, considering the effect of curing condition, the single shear pull-out tests of NSM CFRP were carried out to determine proper curing temperature and time. Second, considering the influence of CFRP spacing, prestress level of CFRP and longitudinal reinforcement ratio, the flexural experiments of strengthened beam with SNSM CFRP technique were carried out by four-point loading method. The results showed that the bond behavior between CFRP and concrete represented a negative quadratic curve with curing temperature and a positive arc-tangent curve with curing time. The flexural capacity of strengthened beams was obvious higher than the un-strengthened beam, which were increasing with the improvement of prestress level and the reduction of CFRP spacing. However, the improvement of flexural capacity of strengthened beam with prestressed CFRP was not obvious with the increase of prestress level, and the longitudinal reinforcement ratio had a negative impact on the flexural capacity. Finally, considering above-mentioned factors, a predicted model of flexural capacity and mid-span deflection for the beam strengthened with SNSM CFRP was developed and validated.

      PubDate: 2018-06-18T09:57:32Z
       
  • Thermo-mechanical behaviour of smart composite beam under quasi-static
           loading
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Reza Alebrahim, G. Sharifishourabi, S. Sharifi, Mahdi Alebrahim, Haifeng Zhang, Y. Yahya, Amran. Ayob
      Experimental and numerical studies on a hybrid composite smart beam under quasi-static loading were carried out. The composite beam is consisted of two layers; carbon fibre/epoxy and SMA wire/epoxy layer. Carbon fibres as well as SMA wires were embedded in the host epoxy unidirectionally. SMA wires were programmed before being embedded in the composite beam. All thermo-mechanical properties associated with SMA wires were experimentally determined. A constant flexural load was initially applied to the middle of a simply-supported beam and temperature of the beam was then increased. The beam was heated using a thermal-chamber. During the heating process the deflection of the beam at midpoint was measured and the behaviour of the hybrid beam under incremental load was investigated. It was observed that, the presence of embedded SMA wires in the beam can effectively reduce deflection. Furthermore, using high volume fraction of fibres can cause buckling in the opposite direction of lateral force. Experimental results were compared against FE method and a perfect fit was obtained.

      PubDate: 2018-06-18T09:57:32Z
       
  • Experimental investigation on the mechanical properties of a bond-type
           anchor for carbon fiber reinforced polymer tendons
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Kuihua Mei, Shengjiang Sun, Bo Li, Yamin Sun, Guoqing Jin
      Carbon fiber reinforced polymer (CFRP) has gained popularity in civil engineering applications due to its high tensile strength, light weight, corrosion resistance, and fatigue resistance. However, the anchorage of CFRP tendons has been a challenge due to the relative low transverse shear strength of CFRP. To study the mechanical properties of bond-type anchor for CFRP tendons, straight-type, inner-cone-type, and composite-type anchors were developed in this study. The bond-slip behavior of CFRP tendons inside anchors and multiaxial stresses of the steel sleeve were experimentally tested. The effects of anchor type and length on the anchorage performance of CFRP tendons were studied with the focus on the anchoring mechanism. Test results demonstrate that the composite-type anchor exhibits the most reliable load-transfer mode and can eliminate the notch effect occurred in the inner-cone-type anchor. The peak bond stress initially occurs at the loading end of the anchor and gradually moves to the free end of the anchor as the load increases. This is related to the gradual failure of chemical adhesive between the CFRP tendon and the colloid. Besides, bond-slip relationship of CFRP tendon inside anchor is nonlinear. The slippages of CFRP tendons are initially small but increase quickly with increasing load. When approaching failure, the slippages increased significantly. In addition, the slippage of the anchor with scattered-end tendon is smaller than that with non-scattered-end tendon, indicating that the anchor with scattered-end tendon has superior bonding property.

      PubDate: 2018-06-18T09:57:32Z
       
  • Numerical prediction of mechanical properties of rubber composites
           reinforced by aramid fiber under large deformation
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Jianhong Gao, Xiaoxiang Yang, LiHong Huang
      Recently, rubber composites reinforced by short aramid fiber have been widely used in tires and have attracted considerable attention because of their excellent characteristics. In this study, uniaxial tests and scanning electron microscope experiments were performed to obtain the mechanical response and to study the microscopic structure of the composites, respectively. A finite element numerical model is proposed to predict the mechanical properties of rubber composites reinforced by short aramid fiber based on experimental observation. Using the random sequential adsorption algorithm, fibers were generated with embedded element technique; this makes finite element modeling more convenient and enables the analysis of two key issues: the large aspect ratio of the aramid fiber and large deformation of the rubber. The close agreement between the experimental results and numerical results verifies the reliability of the proposed finite element model for aramid-fiber-reinforced rubber.

      PubDate: 2018-06-18T09:57:32Z
       
  • Fundamental frequency of a composite anisogrid lattice cylindrical panel
           with clamped edges
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): A.V. Lopatin, E.V. Morozov, A.V. Shatov
      A derivation and validation of an analytical formula for the calculation of the fundamental frequency of a composite anisogrid lattice cylindrical panel with clamped edges is presented in this paper. Free vibration analysis is performed based on the continuous model of a lattice structure using the equations of engineering theory of orthotropic cylindrical shells. The problem was solved using the Galerkin method in which the displacements of the panel were approximated by the clamped-clamped beam functions. The analytical formula derived from this solution was employed to study the effects of the structural parameters of composite lattice panels on their fundamental frequencies. The results of these parametric analyses were successfully verified by comparisons with the finite-element solutions. It is shown that the analytical model that only takes into account the inertia of the transverse motion of the panel in the direction normal to its surface provides a reasonable estimate of the value of fundamental frequency. It is also demonstrated how the formula works in the calculations delivering the required fundamental frequency when designing the composite lattice panels.

      PubDate: 2018-06-18T09:57:32Z
       
  • A quasi-3D refined theory for functionally graded single-layered and
           sandwich plates with porosities
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Ashraf M. Zenkour
      The bending responses of porous functionally graded (FG) single-layered and sandwich thick rectangular plates are investigated according to a quasi-3D shear deformation theory. Both the effect of shear strain and normal deformation are included in the present theory and so it does not need any shear correction factor. The equilibrium equations according to the porous FG single-layered and sandwich plates are derived. The solution of the problem is derived by using Navier’s technique. Numerical results have been reported, and compared with those available in the open literature for non-porous single-layered and sandwich plates. Effects of the exponent graded and porosity factors are investigated.

      PubDate: 2018-06-18T09:57:32Z
       
  • Formulation of a consistent pressure-dependent damage model with fracture
           energy as input
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Azam Arefi, Frans P. van der Meer, Mohammad Reza Forouzan, Mohammad Silani
      Micromechanical simulation of composite material failure requires a pressure-dependent failure model for the polymeric matrix. Available pressure-dependent damage formulations assume a certain shape of the stress-strain law under uniaxial loading. However, upon close inspection none of the available formulations is able to reproduce the assumed shape. This implies that input values for the fracture energy cannot be recovered exactly. In this paper, a new methodology for developing consistent pressure-dependent damage models for polymeric materials is presented. Using this method the predefined shape of the stress-strain relation of an element with localized deformation under uniaxial tension can be exactly reproduced which enables further to recover the exact amount of energy dissipation consistent with the input toughness. The methodology is demonstrated for two different softening laws, namely linear and exponential softening. These models are applied to the damage analysis of unidirectional continuous fiber-reinforced composites. The formulation is validated by simulation of a test for Mode-I fracture energy characterization and comparing the load-displacement response with that obtained with cohesive elements.

      PubDate: 2018-06-18T09:57:32Z
       
  • Relevant factors in the design of composite ballistic helmets
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Marta Palomar, Estívaliz Lozano-Mínguez, Marcos Rodríguez-Millán, María Henar Miguélez, Eugenio Giner
      In this paper, the design methodology of composite ballistic helmets has been enhanced considering biomechanical requirements by means of finite element analysis. Modern combat helmets lead to a new type of non-penetrating injury, the Behind Helmet Blunt Trauma (BHBT), generated by the deformation of the inner face of the helmet, the so-called backface deformation (BFD). Current standard testing methodologies use BFD as the main measure in ballistic testing. Nonetheless, this work discusses the relationship between this mechanical parameter and the head trauma (BHBT) by studying different head injury criteria. A numerical model consisting of a helmet and a human head is developed and validated with experimental data from literature. The consequences of non-penetrating high-speed ballistic impacts upon the human head protected by an aramid combat helmet are analysed, concluding that the existing testing methodologies fail to predict many types of head injuries. The influence of other parameters like bullet velocity or head dimensions is analysed. Usually, a single-sized helmet shell is manufactured and the different sizes are adjusted by varying the foam pad thickness. However, one of the conclusions of this work is that pad thickness is critical to avoid BHBT and must be considered in the design process.

      PubDate: 2018-06-18T09:57:32Z
       
  • Topology optimization for continuous and discrete orientation design of
           functionally graded fiber-reinforced composite structures
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Jaewook Lee, Dongjin Kim, Tsuyoshi Nomura, Ercan M. Dede, Jeonghoon Yoo
      This paper presents a topology optimization method for the sequential design of material layout and fiber orientation in functionally graded fiber-reinforced composite structures. Specifically, the proposed method can find the optimal structural layout of matrix and fiber materials together with optimal discrete fiber orientations. In this method, an orientation design variable in the Cartesian coordinate system is employed with a conventional density design variable. The orientation design variable controls not only the fiber orientation, but also fiber volume fraction. The fiber volume fraction control can be used to relax the orientation design problem and simultaneously design a functionally graded structural layout of fiber material. To avoid intermediate fiber orientations and achieve discrete fiber orientation design, a penalization scheme is applied to the orientation design variable. For solving the optimization problem which involves multiple design variables such as the density variable, fiber orientation variable, and target discrete orientation set, a three-step sequential optimization procedure is proposed. In this procedure, the result for each step provides the isotropic design, continuous fiber orientation design, and functionally graded discrete orientation design, respectively. To validate the effectiveness of the proposed approach, numerical examples for structural compliance minimization and compliant mechanism design are provided.

      PubDate: 2018-06-18T09:57:32Z
       
  • Meso-scale progressive damage modeling and life prediction of 3D braided
           composites under fatigue tension loading
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Chao Zhang, J.L. Curiel-Sosa, Tinh Quoc Bui
      3D braided composites have broad potential applications in the high-tech industries because of their superior mechanical properties. Fatigue is an essential design factor for their use in those engineering applications. The fatigue damage accumulation during cyclic loading should be involved in the numerical models in order to predict the fatigue life accurately. In this paper, a unit-cell based finite element model in conjunction with continuum damage mechanics (CDM) is developed for simulating the fatigue damage evolution process and predicting the fatigue life of 3D braided composites under fatigue tension loading. This meso-scale fatigue modeling, including stress analysis, failure criteria and material property degradation scheme, is implemented via a user-material subroutine UMAT based on ABAQUS/Standard platform with FORTRAN code. The fatigue damage initiation and propagation processes of 3D braided composites with typical braiding angles on the unit-cell model as a function of number of cycles are presented in detail. The fatigue life of 3D braided composites is predicted from the computed S-N curve and the stiffness degradation process is also investigated. The obtained numerical results indicate that the present model can provide a suitable reference to the numerical study of the fatigue issues in other textile composites.

      PubDate: 2018-06-18T09:57:32Z
       
  • New higher order Haar wavelet method: Application to FGM structures
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): J. Majak, M. Pohlak, K. Karjust, M. Eerme, J. Kurnitski, B.S. Shvartsman
      A new higher order Haar wavelet method (HOHWM) has been developed for solving differential and integro-differential equations. Generalized approach has been proposed for wavelet expansion allowing improvement of the accuracy and the rate of convergence of the solution. The sample problem considered shows, that applying the approach proposed allows to improve the order of convergence of the HWM from two to four and to reduce the absolute error by several orders of magnitude (depending on mesh). Furthermore, in the case of sample problem considered, the computational and implementation complexities are kept in the same range with widely used HWM.

      PubDate: 2018-06-18T09:57:32Z
       
  • Interlaminar failure behavior of GLARE laminates under double beam
           five-point-bending load
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Yanyan Lin, Cheng Liu, Huaguan Li, Kai Jin, Jie Tao
      GLARE laminates were prepared in this work to characterize their interlaminar shear failure behavior by Double Beam Shear (DBS) method. The effect of span-to-thickness ratio (L/h ratio) and lay-up configuration on the interlaminar failure feature of the laminates was investigated respectively. The results indicated that the failure mode in DBS method was single interlaminar shear delamination due to the existence of pure shear stress points. Furthermore, the apparent interlaminar shear strength (ILSS) values measured by DBS method were higher than those of Short-beam Shear (SBS) method, which were closer to the true value. However, the two methods did not show exclusiveness.

      PubDate: 2018-06-18T09:57:32Z
       
  • Free vibration analysis for composite laminated doubly-curved shells of
           revolution by a semi analytical method
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Haichao Li, Fuzhen Pang, Xueren Wang, Yuan Du, Hailong Chen
      In this paper, a unified Jacobi-Ritz method is present to analyze the free vibration of composite laminated doubly-curved shells of revolution with general boundary conditions. The composite laminated doubly-curved shells of revolution are divided into their segments in the axial direction, and the theoretical model for vibration analysis is formulated by applying first-order shear deformation theory. The Jacobi polynomials along the axial direction and the standard Fourier series along the circumferential direction make up the displacement functions of shell segments. The boundary conditions at the ends of the composite laminated doubly-curved shells of revolution and the continuity conditions at two adjacent segments were enforced by penalty method. The results including frequency parameter and mode shapes of composite laminated doubly-curved shells of revolution are easy obtained by Ritz method. The major advantage of presented solutions for solving the vibration characteristics of composite laminated doubly-curved shells of revolution is no need to change the mathematical model or the displacement functions. The accuracy and reliability of the proposed method are verified by the results of literature and finite element method (FEM), and various numerical examples are presented for free vibration analysis of composite laminated doubly-curved shells of revolution.

      PubDate: 2018-06-18T09:57:32Z
       
  • Investigation on delamination and flexural properties in drilling of
           carbon nanotube/polymer composites
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Hossein Heidary, Navid Zarif Karimi, Giangiacomo Minak
      The drilling of composite laminates is difficult to control and often leads to delamination that significantly affects the strength of the structure. Of the mechanical properties of composite materials affected by drilling-induced damage, flexural strength has received very little attention. In the present paper, experiments were conducted to analyze the thrust force, delamination factor and residual flexural strength in the drilling of woven E-glass fiber-epoxy composites reinforced with functionalized multi-walled carbon nanotubes. The process parameters considered for the experiments are the feed rate, spindle speed, drill diameter, and the weight percentage of carbon nanotubes present in nanocomposite laminates. Drilling experiments were conducted based on Taguchi design of experiment and three-point bending tests were then done to assess the residual flexural strength of drilled specimens. Analysis of variance and Taguchi S/N ratio analysis were performed to investigate the influence of input parameters on each individual drilling characteristics. In addition, the orthogonal array with grey relational analysis was employed to simultaneously optimize the multiple performance characteristics of the drilling process. According to the results, the feed rate is the factor which has the greatest influence on the thrust force and delamination factor, followed by spindle speed. Residual flexural strength, however, is mostly influenced by nano content, followed by feed rate.

      PubDate: 2018-06-18T09:57:32Z
       
  • A novel composite multi-layer piezoelectric energy harvester
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Qingqing Lu, Liwu Liu, Fabrizio Scarpa, Jinsong Leng, Yanju Liu
      A typical linear piezoelectric energy harvester (PEH) is represented by a unimorph or bimorph cantilever beam. To improve the efficiency of linear PEHs, classical strategies involve the increase of the beam length, tapering or adding additional cantilever beams to the free end. In this work we discuss the design of novel type of composite linear multi-layer piezoelectric energy harvester (MPEH). MPEHs here consist of carbon fibre laminates used as conducting layers, and glass fibre laminas as insulating components. We develop first a electromechanical model of the MPEH with parallel connection of PZT layers based on Euler-Bernoulli beam theory. The voltage and beam motion equations are obtained for harmonic excitations at arbitrary frequencies, and the coupling effect can be obtained from the response of the system. A direct comparison between MPEH and PEH configurations is performed both from the simulation (analytical and numerical) and experimental point of views. The experiments agree well with the model developed, and show that a MPEH configuration with the same flexural stiffness of a PEH can generate up to 1.98–2.5 times higher voltage output than a typical piezoelectric energy harvester with the same load resistance.

      PubDate: 2018-06-18T09:57:32Z
       
  • Introducing composite lattice core sandwich structure as an alternative
           proposal for engine hood
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Sha Yin, Haoyu Chen, Yaobo Wu, Yibing Li, Jun Xu
      Pedestrian protection capability is critical for lightweight design of automotive engine hood. Here, a novel and lightweight composite sandwich hood including two fiber reinforced composite panels and a lattice core was proposed and the corresponding pedestrian protection performance was evaluated via Head Injury Criterion (HIC). The novel double-curvature composite sandwich hood with a pyramidal lattice core was designed based on a commercialized product with a weight reduction by 25%, and fabricated using interlocking approach. A homogenized constitutive model was developed for the pyramidal lattice core and utilized in the following headform-to-hood impact simulations with LS-DYNA. The stiffer sandwich hood revealed better pedestrian safety performance compared with the corresponding baseline hood without lattice core where secondary collision happened. Also, effects of geometrical variables, material selection and core types were discussed. The variation of panel thickness played a more important role in the average HIC values compared with that of core geometries. Among various material selections, hoods designed with carbon fiber reinforced composite (CFRC) panels and a flax fiber reinforced composite (FFRC) lattice core achieved the minimum head injury. Additionally, lattice core outperformed traditional honeycomb and foam in sandwich hood design. The present study demonstrates the feasibility of employing lattice materials in lightweight design of hood and other car body coverage.

      PubDate: 2018-06-18T09:57:32Z
       
  • Effect of inclination angle on hooked end steel fiber pullout behavior in
           ultra-high performance concrete
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Y.Y.Y Cao, Q.L. Yu
      The bond relationship between the concrete matrix and steel fiber is a significant factor that affects the performance of ultra-high performance fiber reinforced concrete (UHPFRC). In the present research, pullout performances of hooked end fibers embedded in ultra-high performance concrete matrix under various inclination angles are systematically investigated, with special attention on fiber dimension and embedded length. Pullout load-slip curves are obtained and experimental observations including complete fiber pull-out, fiber rupture and matrix failure are analyzed in detail. The effects of the pullout angle are then studied quantitatively by parameter calculations and mechanism analysis. A new analytical model for evaluating the snubbing and spalling effects of the hooked end steel fiber is proposed and validated. It is shown that the influences of the inclination angle on the peak pullout load vary with different fiber types, embedded lengths and fiber diameters, which are also associated with the occurrences of the fiber rupture and the matrix failure. In addition, optical microscope and scanning electron microscopy observations at mesoscale are performed to further analyze the effects of orientation angle.

      PubDate: 2018-06-18T09:57:32Z
       
  • Confinement path-dependent analytical model for FRP-confined concrete and
           concrete-filled steel tube subjected to axial compression
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Peng Chen, Yuyin Wang, Changyong Liu
      In composite component, confined concrete is widely used in civil engineering due to its excellent performance, such as high compressive strength and good plasticity. In this study, an actively-confined concrete model is developed using current published models and test data, the stress-strain behavior of concrete in active confinement and fiber-reinforced polymer confinement are compared, then the influence of loading path on concrete is quantified. An analytical model is developed to predict the mechanical behavior of confined concrete columns, and validated using previously published test results. The analytical model is found to provide satisfactory predictions in short concrete columns confined by FRP or steel tubes.

      PubDate: 2018-06-18T09:57:32Z
       
  • Cyclic flexural behavior of hybrid SMA/steel fiber reinforced concrete
           analyzed by optical and acoustic techniques
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Muhammad M. Sherif, Evelina M. Khakimova, Jonathon Tanks, Osman E. Ozbulut
      Superelastic shape memory alloys (SMAs) are smart materials that can recover 6–8% elastic strains due to their phase transformation. SMAs also possess unique characteristics such as good energy dissipation, excellent re-centering capabilities and corrosion resistance. Recent studies have incorporated the use of superelastic SMA fibers in cementitious composites to achieve re-centering and crack-closing capabilities. Consequently, it is important to investigate the performance of fiber reinforced concrete (FRC) members under cyclic loading. This study investigates the use of hybrid steel/SMA fibers as reinforcement in concrete members subjected to cyclic flexural loading. Digital image correlation (DIC) was used to monitor the full field displacements and strains of the concrete beam specimens. Fiber density and statistical spatial point pattern functions were used to assess the fiber distribution. Two acoustic emission sensors were attached to each side of the concrete specimens to characterize crack development. A correlation between the crack width propagation and cumulative energy captured by the acoustic emission sensors was established. Results showed that the hybrid specimen with equal fiber volume ratios for steel and SMA fibers exhibit a lower mid-span deflection and smaller crack width.

      PubDate: 2018-06-18T09:57:32Z
       
  • 3D explicit finite element analysis of tensile failure behavior in
           adhesive-bonded composite single-lap joints
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Jinxin Ye, Ying Yan, Jie Li, Yang Hong, Ziyang Tian
      The tensile failure behavior in adhesive-bonded composite single-lap joints with different overlap lengths is investigated through experiments and various three-dimensional (3D) explicit finite element methods (FEMs). Different failure modes are observed in different overlap lengths. Three parameterized finite element models are developed to discuss the accuracy and applicability of the 3D explicit FEMs based on different modeling strategies and improved failure criteria. All criteria are programmed with the explicit user subroutines employing element deletion to avoid convergence problems caused by element distortion. The load-displacement curves predicted by these models are consistent with the experimental results, while the prediction of failure morphology depends on model types. The models neglecting interface elements cannot simulate the delamination when cohesive zone models (CZMs) are adopted to predict adhesive failure. The influence of CZMs on delamination is analyzed comprehensively to address this problem. Analysis of stress distribution in an overlap of a length of 10 mm indicates that the peak stress of the adhesive layer occurs on the overlap ends along the axial direction, coinciding with implicit results.

      PubDate: 2018-06-18T09:57:32Z
       
  • On the static strength of aluminium and carbon fibre aircraft lap joint
           repairs
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Siddharth Pitta, Victor de la Mora Carles, Francesc Roure, Daniel Crespo, Jose I. Rojas
      The behaviour of various aircraft lap joint repair configurations is investigated experimentally and numerically under static loading. The lap joints consist of aluminium alloy (AA) 2024-T3 substrates repaired with twin single-sided AA 2024-T3 or Carbon Fibre Reinforced Epoxy (CFRE) doublers. Pure riveted, pure bonded and hybrid (riveted and bonded) joints of metal–metal and metal–composite configurations are investigated. From experimental results, joints with adhesive bond showed nearly 5 times higher average strength than pure riveted joints, while hybrid joints performed better than riveted and bonded joints because of higher stiffness. On the other hand, hybrid metal–metal joint has 70% higher average strength compared to hybrid metal–composite joint. Rivet-shear has caused failure of riveted joints, and adhesive failure is observed in pure bonded joints. Hybrid joints with metal doublers have failed initially due to adhesive failure and later rivet shear. Interestingly, net-section failure is observed in composite doublers with breakage of doublers due to the presence of holes in the doublers. Experimental results are complimented with numerical analysis using commercial finite element code ABAQUS. Load–displacement curves obtained from the numerical results are in good agreement with experiments with a marginal error of 2%. In addition to load–displacement curves, a detailed stress analysis is performed numerically on metal–metal and metal-composite joints under riveted, bonded and hybrid configurations to study stress distribution on substrate and doublers. Numerical analysis showed hybrid and bonded joints have lower stresses in substrate and doublers compared to the riveted joints. Bonded joints have smoother load transfer due to the adhesive spread over a larger area. And finally, Stress Intensity Factors (SIFs) are performed numerically for unreinforced and reinforced metal substrate with crack length of 1, 5 and 10 mm with metal and composite doublers under riveted and bonded configuration. For crack of 10 mm, 35% reduction in SIFs is observed for reinforced substrate with bonded metal or composite doublers compared to unreinforced cracked substrate.

      PubDate: 2018-06-18T09:57:32Z
       
  • Elastoplastic CDM model based on Puck’s theory for the prediction of
           mechanical behavior of Fiber Reinforced Polymer (FRP) composites
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): I. Ud Din, P. Hao, G. Franz, S. Panier
      In this paper, the plane stress version of the Puck’s failure theory is used as an indicator of the intra-laminar meso-damage initiation. The thermodynamically consistent damage evolution law is defined to accumulate the damage leading to the subsequent stiffness degradation coupled with the isotropic hardening plasticity. The model is formulated in incremental form keeping in view the implementation by following the plasticity theory which is later used in the Return Mapping Algorithm (RMA). In the implicit scheme based on the Newton-Raphson approach, the consistent tangent operator is derived for the current model. The developed model has been implemented in ABAQUS/Standard via UMAT subroutine in a strain-driven problem where strain tensor is provided as an independent argument into the solution scheme. The non-linear mechanical behavior and ultimate failure of Carbon Fiber Reinforced Polymers (CFRPs) laminates are predicted for the small strain time-independent boundary value problem. The results are compared with the experimental results collected from the previously published literature which exhibit better correspondence.

      PubDate: 2018-06-18T09:57:32Z
       
  • Effect of resin matrix on the strength of an AZ31 Mg alloy-CFRP joint made
           by the hot metal pressing technique
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Barton Mensah Arkhurst, Mokyoung Lee, Jeoung Han Kim
      This study investigated the effect of two types of carbon fiber reinforced plastics (CFRPs) with different matrices, on the strength of a metal alloy–plastic composite joint made by the hot metal pressing (HMP) technique. One set of experiments was carried out with a PAN-type CFRP with a thermoplastic polyurethane (TPU) matrix, and the other with a PAN-type CFRP with a polyamide 6 (PA6) matrix. Both matrices were joined with either as-received or annealed AZ31 Mg-alloy sheets processed at different annealing durations to produce oxide layers on the alloy sheets. Due to the complete suppression of CFRP-resin decomposition at its joint interface, the CFRP with a PA6 matrix exhibited superior joint strength as compared to the TPU-matrix CFRP, which showed partial suppression of the CFRP-resin decomposition and bubble formation, with complete suppression characterized by microcracking at its joint interface. A reaction between C and MgO was observed at the joint interface for the TPU-CFRP but not for the PA6-CFRP. The melting/decomposition temperature of the matrix materials and the influence of the oxide layer on the conduction of heat between the materials were the key determinants of the AZ Mg alloy-CFRP joint strength.

      PubDate: 2018-06-18T09:57:32Z
       
  • Eccentric low-velocity impact on fiber-metal laminates under in-plane
           loading using unified zigzag theory
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Mehran Ghalami-Choobar, Gholamhossein Liaghat, Mojtaba Sadighi, Hamed Ahmadi
      This paper investigates the eccentric low-velocity impact of Fiber metal laminates (FMLs) subjected to spherical projectile using a unified Zig-Zag plate theory. The presented zig-zag plate theory enforces transverse shear stress continuity through the thickness and can be reduced to conventional plate theories using appropriate shape function. The governing equations and suitable boundary conditions are obtained using the principle of minimum total potenital energy. Runge-Kutta method is employed to solve initial value problem resulted by the method of Ritz. The present model is validated by comparison and good agreement between its results and those of reports in open literature. Influence of various specifications of impact phenomenon such as laminate thickness, projectile radius, projectile velocity, in-plane load and eccentricity parameter is examined on deflection and contact force time history. The obtained results indicate that continuity of transverse shear stress is required to achieve accurate contact force even for moderately thin FMLs.

      PubDate: 2018-06-18T09:57:32Z
       
  • FRCM/internal transverse shear reinforcement interaction in shear
           strengthened RC beams
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): Tadesse G. Wakjira, Usama Ebead
      This paper presents a study on the efficacy of a shear strengthening technique utilizing fabric reinforced cementitious matrix (FRCM) systems for beams with and without internal transverse shear reinforcement (ITSR) within the critical shear span (CSS). The paper focuses on the FRCM/ITSR interaction, experimentally and analytically. Three different FRCM fabric types were used; namely, glass, carbon and polyparaphenylene benzobisoxazole (PBO). The test matrix consisted of fourteen medium-scale RC beams prepared and tested to fail in shear. The test results indicated a clear influence of the ITSR within the CSS on the gain in the ultimate load carrying capacity (Pu ) of the beams. The FRCM strengthening system has enhanced the shear strength of the beams. With regard to the FRCM fabric type, carbon FRCM was the most effective of all in terms of the gain in Pu of the strengthened beams. Moreover, the beams strengthened with continuous strengthening configuration intuitively performed better than those strengthened with discontinuous configuration. A simplified compression field theory (SCFT) model was used for predicting the ultimate load carrying capacity of the beams. This model features two important contributions; namely, considering the effect of FRCM strengthening and accounting for the critical shear span to depth ratio.

      PubDate: 2018-06-18T09:57:32Z
       
  • Bloch wave filtering in tetrachiral materials via mechanical tuning
    • Abstract: Publication date: 1 October 2018
      Source:Composite Structures, Volume 201
      Author(s): F. Vadalà, A. Bacigalupo, M. Lepidi, L. Gambarotta
      The periodic cellular topology characterizing the microscale structure of a heterogeneous material may allow the finest functional customization of its acoustic dispersion properties. The paper addresses the free propagation of elastic waves in micro-structured cellular materials. Focus is on the alternative formulations suited to describe the wave propagation in the material, according to the classic canons of solid or structural mechanics. Adopting the centrosymmetric tetrachiral microstructure as prototypical periodic cell, the frequency dispersion spectrum resulting from a synthetic lagrangian beam-lattice formulation is compared with its counterpart derived from different continuous models (high-fidelity first-order heterogeneous and equivalent homogenized micropolar continuum). Asymptotic perturbation-based approximations and numerical spectral solutions are cross-validated. Adopting the low-frequency band gaps of the material band structures as functional targets, parametric analyses are carried out to highlight the descriptive limits of the synthetic models and to explore the enlarged parameter space described by high-fidelity models. The final tuning of the mechanical properties of the cellular microstructure is employed to successfully verify the wave filtering functionality of the tetrachiral material.

      PubDate: 2018-06-18T09:57:32Z
       
  • Mechanical behavior of carbon fibers polyphenylene sulfide composites
           exposed to radiant heat flux and constant compressive force
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Y. Carpier, B. Vieille, M.A. Maaroufi, A. Coppalle, F. Barbe
      The thermo-mechanical behavior of carbon/PPS laminates under a constant compressive stress and radiant heat flux has been studied in the case of a quasi-isotropic layup. Though lots of studies focus on the time-to-failure, the present work is aimed at investigating the influence of thermal and mechanisms phenomena on the fire behavior of composite structures. The mechanical response is studied at different scales. From the total macroscopic strain standpoint, the response is divided into three stages, referred to as transient, stationary and failure stages. During these stages, different thermal and mechanical mechanisms compete and prevail depending on the applied compressive stress: thermal and thermo-chemical expansion, decomposition, changes in the mechanical properties, etc. With the measurement of macroscopic thermal strains, the mechanical strain is calculated, enabling the calculation of a macroscopic damage factor describing only the mechanical phenomena. Other quantitative indicators are also used to study the competition between thermally- and mechanically-induced mechanisms: maximal expansion, strain rate, etc. It is shown that under a low compressive force, the thermal expansion is a strain-driven mechanism. Failure is studied at the meso scale. The formation and development of porosities associated with the transition liquid-gas (due to the PPS matrix decomposition) leads to micro-buckling in matrix-rich areas and ultimately, to the formation and propagation in the transverse direction of plastic kink bands. Post-failure observations show that this macroscopic kinking propagates specifically according to the decomposition state of the material.

      PubDate: 2018-05-28T08:28:27Z
       
  • Development a refined numerical model for evaluating the matrix cracking
           and induced delamination formation in cross-ply composite laminates
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Hamidreza Madadi, Amin Farrokhabadi
      In this study, at first the dominant micro scale failure modes including fiber–matrix debonding and matrix cracking are studied in 2D RVEs extracted from the layer 90° in different cross-ply laminates. To model the debonding and matrix cracking formation in RVEs, cohesive zone model (CZM) and Extended finite element method (XFEM) are applied. Then to investigate induced delamination formation originates from the tips of matrix cracking as a secondary damage mode, the cohesive surfaces are embedded at the interfaces of different plies in considered lay-ups. Generally, a parametric study is done on different cross-ply laminates with various thickness of layer 90° to obtain the in-situ strength due to matrix cracking and induced delamination by a numerical tool for the first time. The verification of results with the available analytical models shows an acceptable agreement. Then, by considering the long unit cells, the sequences of different damage modes formation are investigated numerically and some physical phenomena including the formation of new matrix cracking in the random locations between the previous cracks, matrix cracking saturation, symmetric and staggered pattern of matrix cracking formation and the axial stress redistribution due to each damage formation are represented in different [0/90n]s and [90n/0]s for the first time.

      PubDate: 2018-05-28T08:28:27Z
       
  • Modelling and testing of fibre metal laminates and their constituent
           materials in fire
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): K. Grigoriou, A.P. Mouritz
      A modelling and experimental study is presented into the deterioration to the load-bearing performance of fibre metal laminates (FML) when exposed to fire, and compared to the constituent materials (monolithic metal and composite). A thermal-mechanical model is presented to calculate the temperature, softening and failure stress of load-bearing FMLs in fire. Experimental fire-under-load tests are performed on an FML consisting of thin bonded sheets of aluminium (AA2024) and glass fibre-polymer (GRP) composite, and its load-bearing performance in fire is compared to its consistent materials (monolithic aluminium and GRP composite) of the same thickness. The softening rate of the FML is generally faster than the monolithic aluminium or GRP plates, and its load-bearing capacity is inferior or similar to its constituent materials depending on the applied stress and radiant heat flux of the fire. The load-bearing performance of the FML is reduced by softening of both the metal and GRP layers as well as interfacial debonding between the layers. The model is capable of calculating with reasonable accuracy the reductions of the tensile and buckling failure stresses of the load-bearing FML in fire.

      PubDate: 2018-05-28T08:28:27Z
       
  • Inclined FRP U-jackets for enhancing structural performance of FRP-plated
           RC beams suffering from IC debonding
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): B. Fu, X.T. Tang, L.J. Li, F. Liu, G. Lin
      Intermediate crack debonding (i.e., IC debonding) commonly controls the failure of FRP-plated RC beams. Such IC debonding often occurs with the maximum strain of the FRP soffit plate being far lower than its rupture strain, thus leading to a low utilization of the high strength of expensive FRP material. It is of increasing interest of the research and engineering community to explore an effective anchorage for enhancing the structural performance of FRP-plated RC beams suffering from IC debonding. Inclined FRP U-jacketing is among the easiest and most effective options for this purpose. This paper presents an experimental study to systematically investigate the effect of inclined FRP U-jacketing on the structural performance of FRP-plated RC beams suffering from IC debonding. Eight full-scale RC beams were tested with the width, height and inclination of the U-jacket as the experimental variables. Findings from the present tests show that inclined FRP U-jacketing could successfully lead to concrete crushing failure from IC debonding in the control specimen without anchorage, and significant increase in the load and mid-span deflection of up to 55.8% and 229% over these of the control specimen.

      PubDate: 2018-05-28T08:28:27Z
       
  • Impact response of low-density foam impinging onto viscoelastic bar: A
           theoretical analysis
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Hu Liu, Jialing Yang, Hua Liu
      The Taylor-Hopkinson test is widely used in predicting the dynamic strength of materials. For low-density foam materials, the output bar in the Taylor-Hopkinson test is often made from much weaker materials like polymethylmethacrylate (PMMA) to reduce the wave impedance mismatch between the foam sample and the output bar. These low impedance materials exhibit viscoelastic properties and may affect the dynamic stress prediction of foam samples. In this paper, the shock wave theory for the foam sample in conjunction with the viscoelastic wave propagation in the output bar is employed to illustrate the influence of the viscoelastic output bar on the dynamic response of foam samples in the Taylor-Hopkinson impact. The theoretical model presented in this paper can be degenerated into previous elastic target bar model and rigid target bar model. Finite element simulations are further performed to verify the proposed theory. The influence of material parameters on the final deformation of the foam sample, impact duration and residual velocity of the foam sample are investigated. The results in this paper not only help in understanding the effect of the viscoelastic bar on the dynamic response of foam samples, but also set up guidelines to perform the Taylor-Hopkinson test more precisely.

      PubDate: 2018-05-28T08:28:27Z
       
  • Effect of the large cells on the fatigue properties of closed-cell
           aluminum alloy foam
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Yang Hu, Qin-Zhi Fang, Bao-Lin Sha, Modi Zhao
      The effect of the large cells on the fatigue properties of closed-cell aluminum alloy foam is studied experimentally and numerically. To do this, a parameter termed as characteristic diameter (Dch ) is introduced. 44 dog-bone type specimens are tested with MTS fatigue test machine. In addition, the fatigue performances are numerically simulated by using foam models generated with a program given in this paper. In both cases, large scatter in fatigue life is observed. After classifying the foams into different groups based on their Dch , the fatigue life results of foams within the same Dch range show smaller diversity. It indicates that Dch is an effective parameter which can be used to classify the fatigue performance of foam materials. For foams with same relative density, foams with higher Dch are inclined to have shorter fatigue lives, even though the cell size distributions of foams are different. It is concluded that the fatigue life of foam is dominated by the large cells rather than the cell size distribution. By observing the fatigue life contour obtained from numerical simulation, the dangerous regions in the cell structure are found near the cell walls of larger cells and on the outer surfaces of foam.

      PubDate: 2018-05-28T08:28:27Z
       
  • Design model of concrete for circular columns confined with AFRP
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Paulo Silva Lobo, Pedro Faustino, Mariana Jesus, Rui Marreiros
      The advantages of confining reinforced concrete are well-known, making it possible to increase both strength and ductility of structural elements. On this matter, the application of fibre reinforced polymer sheets has been a subject of increasing interest. Various constitutive models of confined concrete have been proposed, the majority of which calibrated with results of experimental tests using mainly carbon fibre composites. In this paper, a design-oriented model is proposed for the prediction of the axial response of confined concrete columns, calibrated exclusively with the results of tests using aramid fibre reinforced polymers. The proposed model parameters were determined based on experimental tests reported in the published literature. The new model is compared with a design-oriented model calibrated with different fibre based composites and with an analysis-oriented model. This assessment was carried out using existing experimental results as well as two specimens confined with aramid fibre composites tested by the authors. The results of the proposed model correlate well with the experimental results, being generally more accurate than the other two models considered.

      PubDate: 2018-05-28T08:28:27Z
       
  • Numerical and analytical investigation of tensile behavior of
           non-laminated and laminated CFRP straps
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Haifeng Fan, Anastasios P. Vassilopoulos, Thomas Keller
      The tensile behavior of non-laminated and laminated CFRP straps composed of up to 100 layers was numerically and analytically investigated. The failure mode in non-laminated straps changed at 20–30 layers from brittle and sudden rupture of the outermost layer to progressive rupture starting from the innermost layer, due to the different non-uniform strain distributions across the layers. Non-laminated straps showed a significantly higher load-bearing efficiency for layer numbers higher than 20 and exhibited lower sensitivity to tape anisotropy and friction at the strap/pin interface than laminated straps. An empirical model was established to estimate the ultimate load of non-laminated straps with up to 100 layers and an analytical model was derived to predict the load-bearing efficiency of laminated straps, taking into account the strap anisotropy and friction at the strap/pin interfaces.

      PubDate: 2018-05-28T08:28:27Z
       
  • Analytical layerwise stress and deformation analysis of laminated
           composite plates with arbitrary shapes of interfacial imperfections and
           discontinuous lateral deflections
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): M.M. Alipour, M. Shariyat
      In the present article, a double power series analytical layerwise model is proposed for analysis of multilayer orthotropic plates with arbitrary shapes of interfacial bond defects. In contrast to the previous models, the discontinuity in the lateral deflections of the successive layers is also considered. The adhesive bonding layers are modeled by elastic elements with normal and shear stiffness coefficients; so that, the continuity conditions of the transverse shear and normal stresses are met at the layer interfaces. It is the first time that an analytical solution rather than the data-dependent finite element method is proposed for stress and displacement analysis of multilayer rectangular plates with arbitrary shapes of interfacial bond damages, including the discontinuity in the transverse displacements of the successive layers. Results of the transverse displacement and stresses are then refined according to the 3D theory of elasticity. Results reveal that even small violations in the bonding between layers, may increase the resulting stresses, lateral deflections, and the differences between lateral deflections of the successive layers to more than twice, thrice, and five times, respectively. Moreover, in contrast to the growth of the in-plane stresses, redistribution of the transverse shear stress is governed by the equilibrium rather than the constitutive-law-based conditions.

      PubDate: 2018-05-28T08:28:27Z
       
  • Seismic behavior of beam-column joints strengthened with ultra-high
           performance fiber reinforced concrete
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Muhammad Irfan Khan, Mohammed Ali Al-Osta, Shamsad Ahmad, Muhammad Kalimur Rahman
      This paper presents a study on evaluation of seismic performance of shear-deficient beam column joints (BCJs) strengthened by ultra-high performance fiber reinforced concrete (UHPFRC). Normal concrete BCJs having deficiencies in resisting the seismic action were cast, strengthened with a thin layer of UHPFRC, and tested under seismic loading. Two different methods were used for strengthening the normal concrete BCJ specimens consisted of: i) sandblasting the normal concrete substrate surface of BCJs and in-situ casting of a 30 mm thick UHPFRC jacket and ii) bonding 30 mm thick prefabricated UHPFRC plates to seismically deficient BCJ using epoxy resins and special fillers. The performance of UHPFRC jacketing in strengthening the seismically deficient BCJs was experimentally evaluated under reverse cyclic loading using displacement control approach keeping column axial load constant at 150 kN. The analysis of test results showed that the first method of strengthening was highly effective in terms of shear capacity, deformation capacity, stiffness characteristics and energy dissipation capacity, as compared to the second method.

      PubDate: 2018-05-28T08:28:27Z
       
  • Enhanced filler-tube wall interaction in liquid nanofoam-filled
           thin-walled tubes
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Mingzhe Li, Junfeng Li, Saeed Barbat, Ridha Baccouche, Weiyi Lu
      Interfacial bonding is essential to the mechanical properties of foam-filled tubes, but the imperfection in the solid–solid interfacial bonding limits the filler-tube wall interaction, leading to reduced performance. Here, we have employed liquid nanofoam (LN) as a novel filling material in thin-walled tubes, creating a liquid–solid “interfacial bonding”. The crushing behavior of LN-filled tube (LNFT) has been characterized by quasi-static compression and dynamic impact tests. Results show that the strengthening coefficient of the LNFTs was 3.8, much higher than that of best solid foam-filled tubes. The improved reinforcement effect indicates that the filler-tube wall interaction is much enhanced at the liquid–solid interface, which demonstrates the “perfect bonding” between LN and the tube wall. These findings provide new concepts in designing novel composite materials and structures.

      PubDate: 2018-05-28T08:28:27Z
       
  • Using textile reinforced mortar modified with carbon nano tubes to improve
           flexural performance of RC beams
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Mohammad R. Irshidat, Ammar Al-Shannaq
      Textile reinforced mortar (TRM) represents one of the alternatives to substitute the fiber reinforced polymer (FRP) composites to strengthening reinforced concrete structures. This paper investigates the influence of using carbon nano tubes (CNTs) to enhance the flexural performance of reinforced concrete (RC) beams strengthen with TRM. Twenty-six RC beams were prepared, strengthened using either TRM or nano-modified TRM, and tested under four-point bending. The investigated parameters include the modification of cement mortar with CNTs, number of TRM layers, type of cementitious binder materials, and type of textile materials. Experimental results showed that the CNTs addition improved the compressive and flexural strengths of the cementitious binder materials used in this study. Using cementitious binder with CNTs caused marginal enhancement in the flexural capacity but significant enhancement in the initial stiffness of beams strengthen with single layer of TRM. The enhancement in the flexural capacity of the strengthen beams due to CNTs addition affected by the type of cement matrix, whereas the enhancement in the stiffness of the strengthen beams was affected by the type of the textile material. Using multi-layer TRM with CNTs caused debonding of the TRM layers.

      PubDate: 2018-05-28T08:28:27Z
       
  • Strain rate effect on the dynamic tensile behaviour of flax fibre
           reinforced polymer
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Wenjie Wang, Xuejie Zhang, Nawawi Chouw, Zhongxian Li, Yanchao Shi
      Flax fibre reinforced polymer (FFRP) has been heavily studied in terms of static properties. To study its dynamic behaviour, experimental work also needs to be carried out. This study presents the tensile properties of flax fibre reinforced polymer (FFRP) composite under static and dynamic loadings. Experiments and Weibull distribution analysis were performed to investigate the strain rate effect on the dynamic properties of FFRP composites. In total, 45 specimens were considered. Dynamic tensile tests were performed by using a high-speed servo-hydraulic testing machine with a strain rate ranging from 0.764 s−1 to 135.68 s−1. Empirical formulas of dynamic increase factor (DIF) were derived at various strain rates. Weibull distribution analysis was applied to quantify the variability of tensile strength at different strain rates. Failure process and failure modes of FFRP were discussed via analysing high-speed camera recording. The results show that the tensile strength, failure strain, DIF and energy absorption of FFRP increased with the strain rate when it was higher than 79.12 s−1.

      PubDate: 2018-05-28T08:28:27Z
       
  • Modeling of natural fiber reinforced composites under hygrothermal ageing
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Fang Tian, Zheng Zhong, Yihui Pan
      In this paper, we focus on the mechanical performance of fibers naturally derived from plants as reinforcement of a composite structure. A nonlinear constitutive model for the whole hygrothermal ageing process of natural fiber reinforced composites is established. This theoretical model accounts for large elastic and inelastic deformation, diffusion of water molecules and hydrolysis reaction. Based on the non-equilibrium thermodynamic framework, the Helmholtz free energy functions and the corresponding dissipation laws are established. The effects of matrix cracking, fiber-matrix interfacial debonding and change in the microstructure of natural fibers are all considered in this theoretical model. And the competition between the loss and the recovery of mechanical properties of natural fibers is investigated. Moreover, this theoretical model is applied to analyze the elastic response of natural fiber reinforced composites and the influence of ageing temperature is discussed. The obtained theoretical results are compared with corresponding experimental data and it is shown that the present theoretical model is capable of describing the evolution of elastic moduli of composite samples and their temperature dependence during the whole hygrothermal ageing process.

      PubDate: 2018-05-28T08:28:27Z
       
  • Stochastic reconstruction and microstructure modeling of SMC chopped fiber
           composites
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Yi Li, Zhangxing Chen, Lingxuan Su, Wei Chen, Xuejun Jin, Hongyi Xu
      To establish an integrated Processing-Microstructure-Property workflow for the prediction of material behaviors, this paper presents a new stochastic pseudo-3D microstructure reconstruction method for Sheet Molding Compounds (SMC) chopped fiber composites. The proposed method captures the bi-level microstructural features of SMC composites. At the higher level, a Voronoi diagram-based algorithm is developed to reconstruct the unique substructure features of SMC fiber tows. The geometry of Voronoi cells is adjusted by a Simulated Annealing (SA) algorithm to match the geometrical statistics of the real fiber tows. At the lower level, the algorithm assigns fiber orientation to each Voronoi cell (which represents a fiber tow). The fiber orientation angles are recovered from a statistical fiber orientation tensor. The proposed method is employed to establish a multi-layer pseudo-3D SMC Representative Volume Element (RVE) model for Finite Element Analysis (FEA) of SMC microstructure. This model enables the prediction of mechanical properties based on the material processing information (e.g. fiber orientation tensor obtained from compression molding simulation), and the microstructure information obtained from microscopic imaging for an SMC composite. The predicted properties are successfully validated by experimental tensile tests.

      PubDate: 2018-05-28T08:28:27Z
       
  • Broadband locally resonant metamaterial sandwich plate for improved noise
           insulation in the coincidence region
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Zibo Liu, Romain Rumpler, Leping Feng
      A new design for locally resonant metamaterial sandwich plates is proposed in this paper for noise insulation engineering applications. A systematic method to tune the resonance frequency of local resonators is developed in order to overcome the coincidence phenomenon. This method, based on an impedance approach, additionally explains the ability to overcome the antiresonance associated with these local resonators. The influence of the radiated sound from these local resonators is further investigated with finite element (FE) models, particularly in connection with the sound transmission loss (STL) of the resulting metamaterial sandwich plates. The new sandwich design proposed emerges from these analyses, encapsulating the resonators inside the core material. In addition to overcoming the coincidence effect and limiting the noise radiation by the resonators, the proposed design allows to improve the mass ratio of the metamaterial sandwich structure. This, in turn, enables to broaden the working frequency band independently of the material adopted for the resonator. The proposed metamaterial sandwich plate thus combines improved acoustic insulation properties, while maintaining the lightweight nature of the sandwich plate and its good static properties.

      PubDate: 2018-05-28T08:28:27Z
       
  • Finite element analysis of pre-stretch effects on ballistic impact
           performance of woven fabrics
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Guodong Guo
      Pre-stretch effects on ballistic impact performance of woven fabrics that made of Kevlar KM2 is investigated with finite element simulation. Individual yarns of the fabrics are modeled with truss elements incorporated with equivalent material properties of real fiber yarns. Before the projectile is issued, a fabric panel that has a rectangular configuration is pre-stretched by directly applying displacement boundary conditions. This two-step loading condition is realized through results transferring capability offered by the commercial software ABAQUS. Simulation results reveal that pre-stretch can significantly influence the fabric’s ballistic response such as ballistic limit, energy absorption and wave propagation. The fabric with higher pre-stretch absorbs more energy, however fails earlier than the fabric with lower pre-stretch. Parametric studies show that with the increase of pre-stretch, the deformation contour evolves from a pyramid shape that is conventionally observed in non-pre-stretched fabrics into a conical shape.

      PubDate: 2018-05-28T08:28:27Z
       
  • Edge effects in adhesively bonded composite joints integrated with
           piezoelectric patches
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): S.A. Yousefsani, M. Tahani
      Analytical electromechanical solutions to the interfacial stresses in the adhesively bonded composite joints integrated with piezoelectric actuator are presented in this paper within the framework of full layerwise theory. Two lap joints with and without interfacial void are studied, and the edge effects near the end-points of the bondline as well as around the void are investigated. Sets of fully coupled governing equations of equilibrium are derived using the principle of minimum total potential energy and are simultaneously solved using the state space approach. It was observed that the edge effects results in significant interfacial stress concentrations around the void edges that may cause propagation of microcracks and debonding.

      PubDate: 2018-05-28T08:28:27Z
       
  • Progressive failure analysis of laminates in the framework of 6-field
           non-linear shell theory
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): A. Sabik
      The paper presents the model of progressive failure analysis of laminates incorporated into the 6-field non-linear shell theory with non-symmetrical strain measures of Cosserat type. Such a theory is specially recommended in the analysis of shells with intersections due to its specific kinematics including the so-called drilling rotation. As a consequence of asymmetry of strain measures, modified laminates failure criteria must be used in the prediction of the failure initiation. The model is implemented into the noncommercial numerical code of finite element method. Several examples are examined and the obtained solutions are compared with analytical, numerical and experimental results.

      PubDate: 2018-05-28T08:28:27Z
       
  • Multifidelity multiscale modeling of nanocomposites for microstructure and
           macroscale analysis
    • Abstract: Publication date: 15 September 2018
      Source:Composite Structures, Volume 200
      Author(s): Ashwin Rai, Aditi Chattopadhyay
      A high-fidelity multiscale modeling framework that integrates information from atomistic simulations pertaining to polymer chain sliding and bond dissociation is utilized to study damage evolution and failure in carbon nanotube (CNT)-reinforced nanocomposites. The nanocomposite constituents (microfiber, polymer, and CNTs) are explicitly modeled at the microscale using representative unit cells (RUCs). The modeled constituents are subsequently employed in a multiscale framework to describe damage initiation and propagation in these systems under transverse loading. Two CNT architectures, randomly dispersed and radially grown, are investigated. Damage initiation sites and damage evolution trends are studied, with results indicating that the presence of CNTs causes a unique stress state at the sub-microscale. This can lead to accelerated damage progression, which can be mitigated by architectural reconfiguration of the CNTs. Additionally, the Schapery potential theory is extended to develop an orthotropic nonlinear damage model that captures global behavior of the nanocomposite RUCs in a computationally efficient manner, and can be utilized as a numerical surrogate for structural scale nanocomposite analysis.

      PubDate: 2018-05-28T08:28:27Z
       
 
 
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