Journal Cover Composite Structures
  [SJR: 2.408]   [H-I: 92]   [277 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0263-8223
   Published by Elsevier Homepage  [3177 journals]
  • Dynamic constitutive response of novel auxetic Kevlar®/epoxy
           composites
    • Authors: Md Fazlay Rabbi; Vijaya Chalivendra; Yong Kim
      Pages: 1 - 13
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Md Fazlay Rabbi, Vijaya Chalivendra, Yong Kim
      A comprehensive experimental investigation was performed to study the dynamic compressive constitutive response of novel auxetic Kevlar®/epoxy laminated composites. Strain rate response was investigated using the split Hopkinson pressure bar (SHPB) test setup. Laminated composites were fabricated using the vacuum infusion process. Short Nylon fibers were flocked between the laminates with different flock densities and flock length. For obtaining dynamic force equilibrium in SHPB experiments, a copper pulse shaper was used to increase the rising time of incident pulse. To have a comparison, woven Kevlar®/epoxy composites were also characterized at similar strain rates. In addition, quasi-static tests were also performed on both woven and auxetic laminated composites for completeness of the study. For quasi-static loading conditions, auxetic composites showed higher peak strain and lower peak stress compared to woven composites. For non-flocked composites, both auxetic and woven composites showed rate dependency. Woven composites provided 353% increase in peak stress when the strain rate increased from 1200 s−1 (low) to 3300 s−1 (high). However, in the same conditions, auxetic composites showed only 155% increase in peak stress. For different flocking conditions, woven composites showed rate dependency for all strain rates, but auxetic composites demonstrated rate dependency only from low to medium strain rates. Both auxetic and woven composites experienced shear failure under quasi-static compression, where auxetic composites failed at higher shear angle of 37°, but woven composites had a failure angle of 30°. For impact loads, under no flocking condition, woven composites did undergo severe edge failure at all strain rates, but auxetic composites showed a sign of edge failure only at high strain rates. With the flocking condition, auxetic composites had through thickness shear failure and woven composites experienced splitting and fibrillation of Kevlar® fibers.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.056
      Issue No: Vol. 195 (2018)
       
  • Overlap length for confinement of carbon and glass FRP-jacketed concrete
           columns
    • Authors: Marina L. Moretti; Eftichios Arvanitopoulos
      Pages: 14 - 25
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Marina L. Moretti, Eftichios Arvanitopoulos
      This paper presents the experimental results of a study on the occurrence of debonding along the overlap length of fiber reinforced polymer (FRP) confined concrete prior to rupture of the FRP jacket. Plain concrete cylinders, twenty-six with 152 mm diameter and 305 mm height, and four with 100 mm diameter and 200 mm height, with cylinder compressive concrete strength 19 MPa, were wrapped with carbon- and glass-FRP jackets and tested under monotonic axial compression. Different overlap configurations and different FRP application methods were investigated. The parameters found to most significantly affect the bond resistance along the overlap zone are the type of the FRP material and the curing age of the resin when dry lay-up application is used.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.038
      Issue No: Vol. 195 (2018)
       
  • Investigation on fatigue performance of T800 composites structural
           component
    • Authors: Yidong Zhang; Li Zhang; Licheng Guo; Yubo Feng; Gang Liu; Xinyang Sun
      Pages: 26 - 35
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Yidong Zhang, Li Zhang, Licheng Guo, Yubo Feng, Gang Liu, Xinyang Sun
      This paper presents a practical method for investigating fatigue performance of the typical structural component of carbon fiber reinforced plastic. Servo-hydraulic fatigue test machine is properly refitted to conduct the fatigue test under load controlled method. Distribution location of strain gauges is determined by finite element method (FEM). Strain values on surface are recorded with the increase of the fatigue cycle number. In the process of fatigue testing, the cracks are observed under the optical microscope. The experiment results show that failure modes of the structural component are mainly characterized by delamination which occurred in the thickness transition area. Strain will redistribute with the cracks propagating. And the suddenly decreased strain values will return to a stable level. Moreover, the application of Digital Image Correlation (DIC) technique for fatigue testing of structural component is discussed.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.023
      Issue No: Vol. 195 (2018)
       
  • Structure dependent properties of carbon nanomaterials enabled fiber
           sensors for in situ monitoring of composites
    • Authors: Guantao Wang; Yong Wang; Peipei Zhang; Yujiang Zhai; Yun Luo; Liuhe Li; Sida Luo
      Pages: 36 - 44
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Guantao Wang, Yong Wang, Peipei Zhang, Yujiang Zhai, Yun Luo, Liuhe Li, Sida Luo
      Carbon nanomaterials enabled fibers have been witnessed as a promising technology for in situ structural health monitoring of polymeric composites. Self-sensing composites were enabled with varied integration strategies, including carbon nanotube (CNT) coated fibers (CNTF), reduced graphene oxide (RGO) coated fibers (RGOF) and carbon fibers (CF). Piezoresistive response of varied sensors was disclosed and showed that gauge sensitivity of RGOF is the highest with a clear two-stage performance from linear to non-linear, while CNTF consistently shows well-organized signal before final fracture. Resin infiltration theory was raised to explain the observed structure–property relationship. For CNTF, resin molecules are permeable to its porous network and form integrated CNT/resin nanocomposites. Comparatively, RGO with large lateral dimension and surface conformability forms the noninvasive network from resin penetration. Based on results analysis and mechanism study, CNTF is more suitable for status recognition and long-term purposes; RGOF is more feasible for early warning of structural damages.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.052
      Issue No: Vol. 195 (2018)
       
  • Dynamic compressive response of additively manufactured AlSi10Mg alloy
           hierarchical honeycomb structures
    • Authors: Yuwu Zhang; Tao Liu; Huan Ren; Ian Maskery; Ian Ashcroft
      Pages: 45 - 59
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Yuwu Zhang, Tao Liu, Huan Ren, Ian Maskery, Ian Ashcroft
      Periodic honeycombs have been used for their high strength, low weight and multifunctionality. The quasi-static and dynamic compressive responses of three types of additively manufactured AlSi10Mg honeycomb structures, specifically a single-scale honeycomb and two hierarchical honeycombs with two and three levels of hierarchy, respectively, have been investigated using experimental measurement and finite element (FE) simulations. The validated FE simulation has been employed to investigate the effects of relative density of the honeycombs and the key experimental parameters. The following failure modes of the three types of honeycombs have been observed both under quasi-static and dynamic compression: (1) the single-scale honeycomb experienced a transition of failure mechanism from local plastic buckling of walls to local damage of the parent material without buckling with the increase of the relative density of the honeycomb; (2) the hierarchical honeycombs all failed with parent material damage without buckling at different relative densities. For both quasi-static and dynamic compression, the hierarchical honeycombs offer higher peak nominal wall stresses compared to the single-scale honeycomb at low relative density of ρ ¯ = 0.19 ; the difference is diminished as relative density increases, i.e. the three types of honeycombs can achieve similar peak wall stresses when ρ ¯ ⩾ 0.26 . Numerical results have suggested the hierarchical honeycombs can offer better energy absorption capacity than the single-scale honeycomb. The two-scale and three-scale hierarchical honeycombs achieved similar peak nominal wall stresses for both quasi-static and dynamic compression, which may suggest that the structural performance under out-of-plane compression is not sensitive to the hierarchical architecture. This work indicates that the structural advantage of hierarchical honeycombs can be utilised to develop high performance lightweight structural components.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.021
      Issue No: Vol. 195 (2018)
       
  • Physically non-linear analysis of beam models using Carrera Unified
           Formulation
    • Authors: M.R.T. Arruda; L.M.S Castro; A.J.M. Ferreira; D. Martins; J.R. Correia
      Pages: 60 - 73
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): M.R.T. Arruda, L.M.S Castro, A.J.M. Ferreira, D. Martins, J.R. Correia
      This paper presents and discusses the numerical performance of a set of physically non-linear models applied together with Carrera’s Unified Formulation (CUF) for the analysis of beams. The main objective of this work is to assess the numerical efficiency of CUF when non-linear material analysis is applied to 1D elements using the equivalent single layer (ESL) formulation. To model material behaviour this work considers three different alternative approaches: (i) the classical isotropic plasticity with no hardening, (ii) the Mazars isotropic concrete damage model, and (iii) the composite orthotropic Hashin damage model. To validate the models proposed, the numerical solutions are compared both with analytical results and experimental data. The results obtained show that it is possible to provide accurate results with CUF when physically non-linear analysis is performed, even when considering approximations involving a small number of degrees of freedom.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.03.107
      Issue No: Vol. 195 (2018)
       
  • X-ray computed tomography characterization of manufacturing induced
           defects in a glass/polyester pultruded profile
    • Authors: Ismet Baran; Ilya Straumit; Oksana Shishkina; Stepan V. Lomov
      Pages: 74 - 82
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Ismet Baran, Ilya Straumit, Oksana Shishkina, Stepan V. Lomov
      Critical assessment of the internal geometry after manufacturing of fiber reinforced polymer composites is essential for developing more reliable and robust production. In the present work, manufacturing induced defects such as fiber misalignment and porosity in a glass/polyester pultruded composite profile are evaluated. The internal geometry of the composite is characterized by X-ray micro-computed tomography (micro-CT) and analyzed using the VoxTex software which allows validated and detailed characterization of the internal geometry. Resin rich areas are observed in between the glass rovings at which the unidirectional fibers are misaligned with respect to the desired pulling direction. Results show that the misalignment in in-plane fiber orientation is more severe (30–40°) than the out-plane fiber orientation (10–20°). Two different types of porosities are quantified: the first one is discontinuous and located inside the resin rich areas; the second one is more severe and continuously located between the glass rovings. The area of the total continuous porosity is estimated approximately as 0.212–0.246 mm2 per unit length in the pulling direction. The fiber misalignments and resin rich areas cause 15–20% reduction in the studied part stiffness in the longitudinal direction.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.030
      Issue No: Vol. 195 (2018)
       
  • Beam on elastic foundation analysis of sandwich SCB specimen for debond
           fracture characterization
    • Authors: Keishiro Yoshida; Takahira Aoki
      Pages: 83 - 92
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Keishiro Yoshida, Takahira Aoki
      Sandwich single cantilever beam (SCB) test has attracted attention as one of the best candidates for evaluating the debond fracture toughness between face sheet and core in sandwich panels under mode I type loading. To theoretically analyze the sandwich double cantilever beam specimen, a beam on Vlasov foundation model has been proposed. In this study, the Vlasov foundation model is applied to the analysis of SCB specimen. Then, the experimental data reduction method of sandwich SCB test is examined based on the semi-analytical solution obtained by the Vlasov foundation model. The validity of the Vlasov foundation model for the analysis of sandwich SCB specimen is confirmed by comparing it with finite element analysis. The influences of the material properties and the thicknesses of face sheet and core on the data reduction method are clarified.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.032
      Issue No: Vol. 195 (2018)
       
  • An anisotropic non-linear material model for glass fibre reinforced
           plastics
    • Authors: J. Jansson; T. Gustafsson; K. Salomonsson; J. Olofsson; J. Johansson; P. Appelsved; M. Palm
      Pages: 93 - 98
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): J. Jansson, T. Gustafsson, K. Salomonsson, J. Olofsson, J. Johansson, P. Appelsved, M. Palm
      This paper aims to present a methodology to predict the anisotropic and non-linear behaviour of glass fibre reinforced plastics using finite element methods. A material model is implemented in order to remedy the need of multiple material definitions, and to control the local plastic behaviour as a function of the fibre orientation. Injection moulding simulations traditionally provide second order orientation tensors, which are considered together with a homogenization scheme to compute local material properties. However, in the present study, fourth order tensors are used in combination with traditional methods to provide more accurate material properties. The elastic and plastic response of the material model is optimized to fit experimental test data, until simulations and experiments overlap. The proposed material model can support design engineers in making more informed decisions, allowing them to create smarter products without the need of excessive safety factors, leading to reduced component weight and environmental impact.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.044
      Issue No: Vol. 195 (2018)
       
  • The unit cell method in predictions of thermal expansion properties of
           textile reinforced composites
    • Authors: Jian-Jun Gou; Chun-Lin Gong; Liang-Xian Gu; Shuguang Li; Wen-Quan Tao
      Pages: 99 - 117
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Jian-Jun Gou, Chun-Lin Gong, Liang-Xian Gu, Shuguang Li, Wen-Quan Tao
      Thermal expansion properties of textile reinforced composites with certain structure symmetries can be efficiently calculated by a size-limited unit cell. In this paper, a general approach is developed for the establishment of such a unit cell model. For the derivation of unit cell boundary conditions, three rules are summarized according to the displacement fields in translational, reflectional and 180° rotational symmetric structures under a uniform temperature change loading. The application scope of present unit cell method is clarified from the thermal and mechanical point of views. Three typical composites, i.e., unidirectional fiber reinforced composite, plain woven composite and multi-harness (4HS, 5HS, 6HS, 7HS and 8HS) satin woven composites are then studied, and four, three and two size-reducing unit cells are formulated, respectively. The thermal expansion behaviors of each composite are analyzed, and the effective thermal expansion coefficients are predicted. The influence of structure symmetries on the deformation pattern of unit cell models is clarified. The numerical models are validated by the identical results obtained from unit cells of different sizes and also by the results available in literatures. The approach developed in this paper can be applied to thermal expansion studies of any other composites with relevant structure symmetries.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.045
      Issue No: Vol. 195 (2018)
       
  • Effects of tablet waviness on the mechanical response of architected
           multilayered materials: Modeling and experiment
    • Authors: Sina Askarinejad; Habibeh Ashouri Choshali; Christina Flavin; Nima Rahbar
      Pages: 118 - 125
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Sina Askarinejad, Habibeh Ashouri Choshali, Christina Flavin, Nima Rahbar
      The excellent mechanical properties that biological materials possess are greatly influenced by the geometrical properties of their small scale constituents. Nacre, also known as Mother of Pearl, is an organic-inorganic composite material that makes up the inner layer of seashells. Nacre is observed for its impressive combination of stiffness, strength, and toughness which can be attributed to its waviness and the layering pattern of the brick and mortar structure of ceramic and protein that allows nacre to exhibit great mechanical energy and dissipate it over a large volume. In this study, the effect of this waviness on a model architected multilayered material system is analyzed numerically and experimentally in order to understand its effects on the stiffness, strength, and toughness of nacre. 3-D printed composites with auxetic and nacreous structure were created and tested in tensile boundary conditions. Finite element analysis was used to study the stress distribution and mechanical response of these composites. Results from the finite element models and the mechanical tests results show that increasing the tablet’s waviness increases the stiffness, however, there is an optimum value of tablet waviness for the highest strength and tensile toughness. Increasing waviness level can improve the elastic modulus by about 23%, strength by about 65% and toughness by about 42%. Using the proposed modeling approach, more detailed studies can be done on the toughening mechanisms of composite multilayered materials. These results can be used as a guide to design super-tough composites with multilayered structures.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.047
      Issue No: Vol. 195 (2018)
       
  • Mechanical characterization and damage mechanism of a new flax-Kevlar
           hybrid/epoxy composite
    • Authors: Clément Audibert; Anne-Sophie Andreani; Éric Lainé; Jean-Claude Grandidier
      Pages: 126 - 135
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Clément Audibert, Anne-Sophie Andreani, Éric Lainé, Jean-Claude Grandidier
      A new composite, made with a woven constituted by Kevlar fibers and flax fibers in an epoxy resin is tested. Tensile and three-point bending tests are performed to identify mechanical properties and damage mechanisms. Compressive properties are identified by an inverse method using numerical simulation of the bending test. In addition, failure mechanisms are established by macroscopic and microscopic observations. The composite exhibits a strong non-linear anisotropic behavior. This non-linearity comes from the plastic strain of Kevlar fibers and flax fibers pull out, whereas the damaged modulus depends on the flax fibers damage. The hybrid composite has the same compression weakness as Kevlar composite, with compression properties that are lower than the tensile properties. Hybrid composite has an intermediate mechanical property between flax composite and aramid composite.

      PubDate: 2018-04-23T08:54:30Z
      DOI: 10.1016/j.compstruct.2018.04.061
      Issue No: Vol. 195 (2018)
       
  • Numerical studies on composite meta-material structure for mid to low
           frequency elastic wave mitigation
    • Authors: H.Y.Y. Shi; T.E. Tay; H.P. Lee
      Pages: 136 - 146
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): H.Y.Y. Shi, T.E. Tay, H.P. Lee
      In the past decade, meta-materials have drawn increasing attention from researchers due to their unique properties, including wave attenuation with potential applications in acoustic engineering. A number of meta-material designs have been proposed for wave attenuation at different frequencies. In this work, a new configuration of chiral honeycomb composites is proposed for the attenuation of mid to low frequency elastic waves in structural applications. The dispersion characteristics of the proposed structure were investigated numerically. The results show that the proposed structure is able to create multiple bandgaps at mid frequency range. Interestingly, two extra bandgaps induced by local resonance effect can be created with slight reduction of the chiral angle of the structural unit cell, and one bandgap is located in the low frequency range. The wave attenuation performance of the proposed composite structure was also simulated using sound transmission loss finite element analysis, demonstrating its potential in real applications.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.049
      Issue No: Vol. 195 (2018)
       
  • Dynamic equations for solid isotropic radially functionally graded
           circular cylinders
    • Authors: Hossein Abadikhah; Peter D. Folkow
      Pages: 147 - 157
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Hossein Abadikhah, Peter D. Folkow
      A hierarchy of dynamic equations for solid isotropic functionally graded circular cylinders is derived based on the three dimensional elastodynamic theory. The material parameters are assumed to vary in the radial direction. Using Fourier expansions in the circumferential direction and power series expansions in the radial direction, equations of motion are obtained for longitudinal, torsional, flexural and higher order motion to arbitrary Fourier and power orders. Numerical examples for eigenfrequencies and plots on mode shapes and stress distributions curves are presented for simply supported cylinders for different material distributions. The results illustrate that the present approach renders benchmark solutions provided higher order truncations are used, and act as engineering cylinder equations using low order truncation.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.03.087
      Issue No: Vol. 195 (2018)
       
  • A review on optimization of composite structures Part I: Laminated
           composites
    • Authors: S. Nikbakt; S. Kamarian; M. Shakeri
      Pages: 158 - 185
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): S. Nikbakt, S. Kamarian, M. Shakeri
      Composite, sandwich and functionally graded materials are frequently utilized for different applications. Thus, numerous optimization studies have been conducted on structures made up of these materials to improve their mechanical or thermal behavior such as buckling resistance, stiffness and strength along with reducing weight, cost and stress under various types of loadings. This work which is the first part of two sequential review papers attempts to review most of the studies carried out from 2000 on optimizing composite structures by representing a classification based on the type of structures. Important parameters of these optimization approaches namely objective functions, design variables, constraints and the applied algorithms are highlighted. The influential factors including boundary conditions, orientation of curved fibers, piezo electric patches, Shape Memory Alloy (SMA) fibers and stiffeners as well as the effect of design variables on the determined objectives are also noticed. Moreover, the examined outperformance of developed algorithms in case of accuracy and pace over their common counterparts is mentioned. The second part will be allocated to the publications on optimization of sandwich and functionally graded structures.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.03.063
      Issue No: Vol. 195 (2018)
       
  • Probabilistic defect analysis of fiber reinforced composites using kriging
           and support vector machine based surrogates
    • Authors: Paul Davidson; Anthony M. Waas
      Pages: 186 - 198
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Paul Davidson, Anthony M. Waas
      In this study a framework for analyzing defects and their effect on the performance of composites, using wavy fiber composites as a test case, is presented. The focus is on predicting the composite strength and failure mode in the presence of through thickness waviness. The framework utilizes surrogate models, derived from a high fidelity validated Finite Element analysis, to perform Monte Carlo simulations. The final analysis product that is developed is versatile enough to solve the forward and inverse problem, while considering partial or uncertain data as input.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.03.007
      Issue No: Vol. 195 (2018)
       
  • Impact energy absorption of bio-inspired tubular sections with structural
           hierarchy
    • Authors: H.H. Tsang; S. Raza
      Pages: 199 - 210
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): H.H. Tsang, S. Raza
      Structural hierarchy in nature can be mimicked in order to develop novel composites and structures with desirable properties. In this study, hierarchy is introduced at multiple length scales into tubular sections that can be utilised as energy absorbing systems in various industries. The proposed hierarchical tubular section is inspired by the micro- to nano-architecture of biological materials, such as tendon and muscle, which can be mimicked by packing smaller tubes into a tube of a higher hierarchical level. The process can be repeated for creating tubular sections of higher orders of structural hierarchy, regardless of size or choice of materials. Numerical experiment has revealed that the impact energy absorption capability can be improved significantly when hierarchy is introduced and greater enhancement is achieved for higher-order hierarchical sections. A parametric study has been undertaken, and with the use of dimensionless parameters, the robustness and the generality of the phenomenon are demonstrated.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.057
      Issue No: Vol. 195 (2018)
       
  • Experimental and numerical investigation of loading speed effect on the
           bearing strength of glass/epoxy composite joints
    • Authors: F. Nazari; M. Safarabadi
      Pages: 211 - 218
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): F. Nazari, M. Safarabadi
      Polymer-matrix composites have a variety of uses in industry. However, their failure behavior is not well characterized yet. Specially, the bearing response of mechanical composite joints is very complex and needs further study. One of the important parameters influencing the bearing strength is loading speed that has not been investigated thoroughly and lacks sufficient data. In this research, effect of loading speed on bearing strength has been investigated empirically on glass-epoxy composites. Samples have been tested in different loading speeds in batches of five. The finite element model has been developed for this experiment in Abaqus. Considering that there is no specific amount to show the mechanical behavior of joint, using statistical analysis is essential. Empirical results based on ASTM D 5961 Standard have been fitted to Weibull distribution. The effect of loading rate on the probability of failure and survival have been analyzed. The results demonstrate that by increasing the loading rate, survival reliability and bearing strength increases, absorbed energy increased to a specific loading rate, then decreases and also the sigma of statistical charts is increases. In comparison between experimental results and finite element result, by increasing the loading speed the error of FE result will increase.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.064
      Issue No: Vol. 195 (2018)
       
  • Micro-composite films constrained by irregularly bilateral walls: A
           size-dependent post-buckling analysis
    • Authors: Pengcheng Jiao; Amir H. Alavi; Wassim Borchani; Nizar Lajnef
      Pages: 219 - 231
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Pengcheng Jiao, Amir H. Alavi, Wassim Borchani, Nizar Lajnef
      Post-buckling analysis of micro-composite films (MCF) has been extensively investigated in recent years. However, the literature of composite elements at micro/nanoscale has been mainly focused on buckling response without lateral confinements. This paper takes one step forward to theoretical studying of static and dynamic post-buckling response of MCF constrained by irregularly bilateral walls using the modified couple stress theory. A discretization algorithm is developed to convert the irregular constraints into normalized gap vectors. An energy method is presented to solve the proposed model by minimizing the total energy with respect to the gap vectors. Numerical simulations are carried out to validate the theoretical model. Satisfactory agreements are obtained between the theoretical and FE results. The proposed theoretical model is used to study the effect of the material length factor ς on the buckling mode transition force P and highest achievable buckling mode of the irregularly constrained micro-films. The presented model can be used to predict and tune the post-buckling response of the axially loaded MCF subjected to irregularly bilateral constraints.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.046
      Issue No: Vol. 195 (2018)
       
  • Bi-material microstructural design of chiral auxetic metamaterials using
           topology optimization
    • Authors: Huikai Zhang; Yangjun Luo; Zhan Kang
      Pages: 232 - 248
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Huikai Zhang, Yangjun Luo, Zhan Kang
      This paper presents a new bi-material microstructural design method for chiral auxetic metamaterials. Based on the independent point-wise density interpolation (iPDI) and a bi-material model, optimal design problem of periodic unit cells is formulated using nodal density variables. The design objective is to minimize the Poisson’s ratio while satisfying the specified volume constraints of the hard and soft materials, and the effective elastic properties of the bi-material microstructure are computed by the asymptotic homogenization method under periodic boundary conditions. This topology optimization problem is solved with a gradient-based mathematical programming algorithm on the basis of the sensitivity analysis. Several numerical examples, regarding design of anisotropic, orthogonal anisotropic and isotropic bi-material microstructures of chiral auxetic metamaterials, are given to demonstrate the effectiveness of the method. It is shown that the proposed bi-material design optimization method can be used to improve the performance of chiral auxetic metamaterials through enlarging the design space.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.058
      Issue No: Vol. 195 (2018)
       
  • Theoretical solutions of 2–2 multi-layered cement-based piezoelectric
           composite under impact load
    • Authors: Taotao Zhang; Yangchao Liao; Wende Liu
      Pages: 249 - 264
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Taotao Zhang, Yangchao Liao, Wende Liu
      An analysis model of the dynamic properties of 2–2 multi-layered cement-based piezoelectric composite under impact load and its definite problems are investigated based on the theory of piezo-elasticity in this paper. The theoretical solutions are obtained according to the Duhamel integral and variable separation method. After analyzing the physical meaning and the convergence of the theoretical solutions, the numerical simulations of the composite are presented by utilizing the various loads including the transient step, the transient haversine wave and the transient isosceles triangle loads. The theoretical solutions are compared with the numerical simulations, as well as reported results. Excellent agreements among these results are found. In addition, the influences of the number of layers of the composite and the piezoelectric parameters on the response of dynamic properties are discussed. The work could benefit the design and preparation of the 2–2 multi-layered cement-based piezoelectric composite in engineering practice.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.059
      Issue No: Vol. 195 (2018)
       
  • Probabilistic multiscale modeling of 3D randomly oriented and aligned wavy
           CNT nanocomposites and RVE size determination
    • Authors: Fei-Yan Zhu; Sungwoo Jeong; Hyoung Jun Lim; Gun Jin Yun
      Pages: 265 - 275
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Fei-Yan Zhu, Sungwoo Jeong, Hyoung Jun Lim, Gun Jin Yun
      This paper presents a probabilistic multiscale approach to model the random spatial distribution of local elastic properties arising from the heterogeneous waviness and orientation of CNT fillers within a 3D microscale continuum representative volume element (RVE) of a CNT-reinforced polymer matrix. The proposed direction-sensitive 3D Karhunen-Loève expansion (KLE) provides the basis to simulate stochastic variations in the CNT orientations rather than assuming a perfect alignment. Computational homogenization analyses are carried out to investigate the effects of the statistical parameters of random CNT waviness on the microscale continuum RVE size. The proposed probabilistic multiscale modelling framework allows to consider the uncertainty associated with the use of CNT nanocomposites for various applications.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.060
      Issue No: Vol. 195 (2018)
       
  • Synergy in shear response of ultra-high-performance
           hybrid-fiber-reinforced concrete at high strain rates
    • Authors: Tri Thuong Ngo; Dong Joo Kim
      Pages: 276 - 287
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Tri Thuong Ngo, Dong Joo Kim
      Synergistic effects on shear resistance of ultra-high-performance hybrid-fiber-reinforced concrete (UHP-HFRCs) at high strain rates was investigated using a new shear test setup. Two UHP-HFRCs: L05S10 (containing 0.5 vol-% long and 1.0 vol-% short fiber) or L10S05; and, two ultra-high-performance mono-fiber-reinforced concretes (UHP-MFRCs): L15S00 (containing 1.5 vol-% long fiber) or L00S15, were tested. The L05S10 generated high synergy in shear resistance whereas the L10S05 did little. Synergies were significant for shear strength, shear peak toughness, but not for shear strain capacity. Moreover, the L00S15 produced the highest rate-sensitivity although the shear response of both UHP-MFRCs and UHP-HFRCs was generally sensitive to the applied strain rates. The experimental shear strengths were well-matched with the theoretical calculations.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.075
      Issue No: Vol. 195 (2018)
       
  • Effect of polymer-grafted carbon nanofibers and nanotubes on the
           interlaminar shear strength and flexural strength of carbon fiber/epoxy
           multiscale composites
    • Authors: Huichao Yao; Guodong Zhou; Weitao Wang; Mao Peng
      Pages: 288 - 296
      Abstract: Publication date: 1 July 2018
      Source:Composite Structures, Volume 195
      Author(s): Huichao Yao, Guodong Zhou, Weitao Wang, Mao Peng
      Multiwalled carbon nanotubes (MWNTs) and vapor-grown carbon nanofibers (VGCNFs) were grafted with poly(styrene-co-maleic anhydride) (SMA) and poly(glycidyl methacrylate) (PGMA) by free radical polymerization, and used as the secondary reinforcing agent for multiscale carbon fiber (CF) reinforced epoxy composites. The polymer-grafted VGCNFs and MWNTs were simply suspended in ethanol and spray-coated onto the surface of CF fabrics to fabricate the multiscale composites. The structures of the polymer-grafted VGCNFs/MWNTs were characterized and their effect on the mechanical properties of multiple composites was compared. Interestingly, polymer-grafted VGCNFs with much larger diameters and lower grafting ratios are more effective than polymer-grafted MWNTs for the reinforcement; and SMA-grafted VGCNFs are more effective than PGMA-grafted VGCNFs. Addition of only 0.4 wt% (on the basis of CF fabrics) of SMA-grafted VGCNFs increases interlaminar shear strength (ILSS) by ∼73% and flexural strength by ∼21%. The increase of ILSS exceeds those of previously reported functionalized nanotubes/nanofibers, graphene oxide or organoclay nanoplatelets as the secondary reinforcement. The high straightness and large aspect ratio of SMA-grafted VGCNFs and the strong interaction with the matrix play the key roles in the reinforcement. This new and simple method simplifies the fabrication of high-performance multiscale composites for broad applications in the future.

      PubDate: 2018-05-01T09:15:06Z
      DOI: 10.1016/j.compstruct.2018.04.082
      Issue No: Vol. 195 (2018)
       
  • Vibration analysis for coupled composite laminated axis-symmetric
           doubly-curved revolution shell structures by unified Jacobi-Ritz method
    • Authors: Kwangnam Choe; Jinyuan Tang; Cijun shui; Ailun Wang; Qingshan Wang
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Kwangnam Choe, Qingshan Wang, Jinyuan Tang, Cijun shui
      In this paper, a unified Jacobi-Ritz method is presented and implemented to study the free vibration analysis of coupled composite laminated axis-symmetric doubly-curved revolution shell structures with general boundary conditions in the framework of the first-order shear deformation theory. The substructure of coupled structures mainly contains the laminated elliptical, hyperbolical, paraboloidal and cylindrical shells. In the theoretical analysis model, the multi-segment partitioning strategy is adopted. The displacement functions of each shell segment are uniformly expanded in the form of a double mixed series in which Jacobi polynomials are along the meridional direction and the standard Fourier series is along the circumferential direction, regardless of the shell components and the boundary conditions. The vibration results including frequency parameters and mode shapes of coupled composite laminated axis-symmetric doubly-curved revolution shell structures are easily obtained by means of the Ritz method. The major advantages of the present solutions for coupled structure are to eliminate the need of changing the displacement or the equations of motion and to improve the efficiency of modeling. The accuracy and reliability of the proposed method are verified with the FEM and literature results, and various numerical examples are presented for the free vibration of the various coupled structures of composite laminated axis-symmetric shell, and these results can be used as reference data.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.04.035
      Issue No: Vol. 194 (2018)
       
  • Modular assembly of water-retaining walls using GFRP hollow profiles:
           Components and connection performance
    • Authors: Wahid Ferdous; Yu Bai; Ahmed D. Almutairi; Sindu Satasivam; Juri Jeske
      Pages: 1 - 11
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Wahid Ferdous, Yu Bai, Ahmed D. Almutairi, Sindu Satasivam, Juri Jeske
      This study proposes and examines a new structural retaining wall system using pultruded glass fibre reinforced polymer (GFRP) composites. The flexural behaviour of the two section types (double-H-planks and round-piles) are investigated at various spans under four-point bending. The effects of shear span-to-depth (a/d) ratio and sectional geometry on the structural capacity, stiffness and failure mode are studied. The effectiveness of the mechanical interlocking system between double-H-plank and round-pile for a continuous assembly is evaluated. Results suggest that the a/d ratio plays an important role in determining failure modes and ultimate capacities of double-H-plank and round-pile specimens. Additionally, a low a/d ratio or a larger depth incurs premature local crushing rather than flexural or shear failure. The mechanical interlocking system used to connect components together was found to be reliable as it effectively transfers bending loads from the double-H-plank to adjacent connected components even when the connection rotation is greater than 12°. Finally, FE modelling showed a good agreement with the experimental failure modes and satisfactorily estimated the failure loads and structural stiffness.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.074
      Issue No: Vol. 194 (2018)
       
  • Probabilistic bolt load distribution analysis of composite single-lap
           multi-bolt joints considering random bolt-hole clearances and tightening
           torques
    • Authors: Fengrui Liu; Meijuan Shan; Libin Zhao; Jianyu Zhang
      Pages: 12 - 20
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Fengrui Liu, Meijuan Shan, Libin Zhao, Jianyu Zhang
      This paper presents a stochastic bolt load distribution analysis method of composite single-lap multi-bolt joints by using an improved three-stage spring-based method and Monte Carlo simulation. In the proposed method, the random properties of tightening torque, bolt-hole clearance, lamina properties and geometric parameters were involved. The allowable manufacturing tolerance band of parameters and clearance fit were considered, and a combining distribution function consisting of binomial distribution and normal distribution function was adopted for modeling the random tightening torque relaxation. To validate the proposed method, a set of composite single-lap three-bolt joints were designed and tested to achieve the stochastic bolt load distribution of the joint. Good agreements between the numerical and experimental stochastic bolt load distribution validated the proposed method. Furthermore, the probabilistic bolt load distributions of the three-bolt joints in four tightening torque conditions, including finger-tight, wrench torque, standard tightening torque and relaxation tightening torque, were investigated. It is found that tightening torque conditions and bolt-hole clearances have significant influences on the variation of the bolt load distribution, while the effects of other random parameters on the variation of the bolt load distribution are slight.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.100
      Issue No: Vol. 194 (2018)
       
  • Effect of polyamide-6,6 (PA 66) nonwoven veils on the mechanical
           performance of carbon fiber/epoxy composites
    • Authors: Bertan Beylergil; Metin Tanoğlu; Engin Aktaş
      Pages: 21 - 35
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Bertan Beylergil, Metin Tanoğlu, Engin Aktaş
      In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.097
      Issue No: Vol. 194 (2018)
       
  • Crashworthiness design of novel hierarchical hexagonal columns
    • Authors: Xiang Xu; Yong Zhang; Jin Wang; Feng Jiang; Chun H. Wang
      Pages: 36 - 48
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Xiang Xu, Yong Zhang, Jin Wang, Feng Jiang, Chun H. Wang
      Self-similar hierarchical structures are widely observed in nature, and have been credited with superior mechanical properties. In this paper, a novel self-similar hierarchical hexagonal columns (HHC) is proposed to improve structural crashworthiness performance. The self-similar hierarchical hexagonal columns are constructed by iteratively adding sub-hexagons at the corners of primary hexagon. To investigate the crashworthiness of HHC, the nonlinear finite element model is first developed and validated against experimental data obtained from 1st order HHC. Numerical investigations of 1st and 2nd order hierarchical hexagonal columns with different hierarchical levels are performed to compare with 0th order HHC, the results show that 1st and 2nd order hierarchical hexagonal columns improve the energy absorption and crush force efficiency by governing the material distribution, especially, 2nd order HHC exhibits significant advantage for energy absorption. In addition, parametric designs of 2nd order HHC are carried out to explore crashworthiness effect on hierarchical size ratio, cell wall thickness and impact velocity. The significant effects on both specific energy absorption (SEA) and the peak crushing force (PCF) are observed. The findings of this study offer a new route of designing novel crashworthiness structure with highly energy absorption capacity.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.099
      Issue No: Vol. 194 (2018)
       
  • Vibration analysis of functionally graded carbon nanotube reinforced
           composites (FG-CNTRC) circular, annular and sector plates
    • Authors: Rui Zhong; Qingshan Wang; Jinyuan Tang; Cijun Shuai; Bin Qin
      Pages: 49 - 67
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Rui Zhong, Qingshan Wang, Jinyuan Tang, Cijun Shuai, Bin Qin
      The intent of this paper is to firstly perform the vibration analysis of the functionally graded carbon nanotube reinforced composites (FG-CNTRC) circular, annular and sector plates with arbitrary boundary conditions by means of the semi-analytical method which is proposed by the author’s team. In the material model, the distribution of the carbon nanotubes is uniform or functionally graded along with the thickness direction of structures and four types of the CNTs distribution are studied in this paper. The refined rule of mixtures approach containing the efficiency parameters is adopted to determine the properties of the composite media. The admissible displacement functions of the FG-CNTRC circular, annular and sector plates are uniformly expanded as the modified Fourier series which embodies a standard cosine Fourier series and several auxiliary functions which are introduced to eliminate the limit of the boundary conditions. On this foundation, the first-order shear deformation elasticity theory is employed to construct the energy expression of the FG-CNTRC circular, annular and sector plates. Then the Ritz-variational energy method is used to decide the natural frequencies and the associated mode shapes. To examine the convergence, accuracy, stability and efficiency of the computational model, the comprehensive studies are conducted. Based on that, some crucial parametric studies covering the influence of the geometrical parameters, CNTs distributions, volume fraction of CNTs and boundary conditions are also investigated in detail.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.104
      Issue No: Vol. 194 (2018)
       
  • Influence of low and high temperature on mixed adhesive joints under
           quasi-static and impact conditions
    • Authors: J.J.M. Machado; E.A.S. Marques; Lucas F.M. da Silva
      Pages: 68 - 79
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): J.J.M. Machado, E.A.S. Marques, Lucas F.M. da Silva
      The increasing use of composite structures in the automotive industry is due to strict regulations regarding fuel efficiency and safety standards. The main advantage of the use of adhesives is the possibility of joining dissimilar materials, particularly composites. The technique studied was the mixed adhesive joints, as two or more adhesives can be used in a single lap joint combining the properties of those adhesives to attain mechanical performance superior to that obtained using those adhesives individually. The main goal was to assess if a previously validated combination of mixed adhesives in a composite joint, tested under quasi-static and impact conditions, offers the same advantage over the use of a single adhesive when subjected to low (−30 °C) and high (80 °C) temperatures. The influence of temperature on the behaviour of the composite joints was assessed in quasi-static and impact conditions allowing to infer the effect on each adhesive. Another important aspect of the use of this type of technique is to avoid the early delamination of the composite substrates. This method was found to improve the performance under quasi-static and impact conditions although its behaviour under the wide range of temperature tested was found to vary significantly.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.093
      Issue No: Vol. 194 (2018)
       
  • Study of mechanical behavior of BNNT-reinforced aluminum composites using
           molecular dynamics simulations
    • Authors: Ziyu Cong; Seungjun Lee
      Pages: 80 - 86
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Ziyu Cong, Seungjun Lee
      Fabrication of metallic matrix boron nitride nanotubes (BNNT) composites have remained challenging due to their high reactivity of metals at elevated processing temperatures. Recently, however, the successful fabrication of BNNT-metal composites has been reported using a plasma technique. Since carbon nanotubes (CNT), which are a structural analogy of BNNTs, easily react with aluminum to form aluminum carbides at the interface, serving as mechanically weak points, BNNTs can be a good alternative for the reinforcing component of metal-matrix composites (MMC). In this study, we conducted several molecular dynamics (MD) simulations to investigate the mechanical behaviors of BNNT-Al composites under tensile loading. The simulations provided quantitative information on the mechanical properties of the BNNT composite, revealing the effect of various BNNT diameters and volume fractions. The contributions of the BNNT and Al component to the total improvement of mechanical properties were quantified through a component analysis. The analysis revealed that the effect of the volume fraction of BNNTs is more significant than that of the size. In addition, the quantified relation between the volume fraction of BNNTs and the enhancement in elasticity can be effectively used for the engineering design of BNNT-Al MMCs.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.103
      Issue No: Vol. 194 (2018)
       
  • Crash responses under multiple impacts and residual properties of CFRP and
           aluminum tubes
    • Authors: Qiang Liu; Hao Shen; Yinghan Wu; Zhencong Xia; Jianguang Fang; Qing Li
      Pages: 87 - 103
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Qiang Liu, Hao Shen, Yinghan Wu, Zhencong Xia, Jianguang Fang, Qing Li
      This study aimed to explore the impact responses and residual properties of thin-walled carbon fiber reinforced plastics (CFRP) tubes and aluminum (Al) tubes subjected to multiple axial impacts. Five repeated impacts with the same impact energy were first conducted to evaluate the effect of repeated impact number, and then the crushing tests were performed to explore the post-impact residual behavior. Regardless of number of repeated impacts, the progressive end crushing modes for the CFRP tubes and stable progressive folding mode for aluminum tubes were identified under repeated dynamic impacts. The CFRP tubes exhibited the highest specific energy absorption (SEA) under the 1st impact, then the similar SEA values in the other four subsequent impacts; whereas the SEA of aluminum tubes fluctuated with the repeated impact numbers which were related to formation of different folds. The quasi-static crushing tests revealed that the residual SEAs of the CFRP tubes and aluminum tubes were not much influenced by the impact number, only within a difference of 5% under the 5 repetitive impacts conducted. It was demonstrated that the CFRP tubes had much better performance in energy absorption capability in comparison with the aluminum tubes in terms of repeated impacts and residual crushing tests.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.04.001
      Issue No: Vol. 194 (2018)
       
  • Effect of internal surface damage on vibration behavior of a composite
           pipe conveying fluid
    • Authors: Wasiu A. Oke; Yehia A. Khulief
      Pages: 104 - 118
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Wasiu A. Oke, Yehia A. Khulief
      Composite pipes have become a viable alternative to metallic pipes in several applications. Flow-accelerated erosion and internal surface attack often result in thickness thinning that may compromise the structural integrity of the pipe and lead to its failure. In this paper, we investigate how the internal surface damage is reflected on the vibration behavior of a composite pipe conveying fluid. The defected pipe-fluid system is modeled using the extended Hamilton’s approach and discretized using the wavelet-based finite element method. The modal characteristics of the pipe vibrations have been obtained by solving the generalized eigenvalue problem. The developed model was validated and some benchmark solutions are presented to highlight the effects of the internal wall-thinning on the vibrational behavior of composite pipes conveying fluid. The obtained results facilitate the future research by revealing the potential of using the vibration signature as a basis for detection of erosion-induced internal defects in pipelines.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.098
      Issue No: Vol. 194 (2018)
       
  • Design of filament-wound composite structures with arch-shaped cross
           sections considering fiber tension simulation
    • Authors: Lei Zu; Hui Xu; Bing Zhang; Debao Li; Bin Zi
      Pages: 119 - 125
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Lei Zu, Hui Xu, Bing Zhang, Debao Li, Bin Zi
      The binding effect of fiber materials due to the winding tension during the filament winding process of arch-shaped cross sections was successfully evaluated using the Finite Element Method (FEM). The use of FEM was validated by comparing results obtained with the results from the numerical analysis of a classic cylindrical mandrel winding model. In this study, four methods were combined in the commercial finite element code ANSYS to predict the change trend of the residual stress of the layer and explore the relationship between the winding layer thickness and the winding relaxation effect. These methods include the element birth and death option, which was used to simulate the step-by-step winding process, the thermal parameter method, which produced the equivalent filament winding tension, contact analysis, which was used to carry out the transmission of radial pressure and deformation, and the restart method, which was used to simulate the procuring process. Compared with the mathematical algorithm and test of variable thickness, the results of FEM were in the range of allowable error. Therefore, these results provide a useful reference in designing the filament wound composite structures with considerably high fiber tensions.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.04.018
      Issue No: Vol. 194 (2018)
       
  • Impacts of configurations on the strength of FRP anchors
    • Authors: Wei Sun; Haifeng Liu; Yajun Wang; Tao He
      Pages: 126 - 135
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Wei Sun, Haifeng Liu, Yajun Wang, Tao He
      The usage of FRP anchors to prevent FRP strips from premature debonding failure is gaining acceptance in strengthening applications of concrete members. FRP anchors can fully develop the strength of FRP strips when they are properly designed. However, existing equations do not well include the comprehensive impact of the spike embedment depth, the bend ratio, the strength ratio of FRP anchor to FRP strip and the dowel angle on the anchor strength. Based on 64 tests failed in anchor rupture, this study proposes a comprehensive equation to determine the anchor strength. Comparisons between equation based predictions and 12 experimental results indicate the advantage of the proposed equation against existing equations. Then, the study propose a feasible technique, i.e. the bidirectional FRP patch, to improve the efficiency of current FRP anchors. Compared with equation based predictions for those FRP anchors without FRP patches, experimental results obtained from 20 specimens with FRP patches indicate significant increases on the anchor strength. This observation favors the usage of FRP patches to improve the efficiency of FRP anchors.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.04.020
      Issue No: Vol. 194 (2018)
       
  • Analysis of low velocity impacts on sandwich composite plates using cubic
           spline layerwise theory and semi empirical contact law
    • Authors: C.S. Rekatsinas; D.K. Siorikis; A.P. Christoforou; N.A. Chrysochoidis; D.A. Saravanos
      Pages: 158 - 169
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): C.S. Rekatsinas, D.K. Siorikis, A.P. Christoforou, N.A. Chrysochoidis, D.A. Saravanos
      The theoretical and numerical framework for the simulation of impacts on thick sandwich composite plates is presented. It encompasses three new elements: 1) A three-dimensional layerwise theory, which approximates the in-plane and transverse displacements through the thickness using third-order Hermite spline polynomials that captures the high inhomogeneity of all interlaminar stresses present in the thick sandwich laminate. 2) The integration of the layerwise theory into a time domain plate spectral finite element with nodes collocated to Gauss-Lobatto-Legendre integration points, which provides a consistent semi-diagonal mass matrix and high-order spatial approximation in the plane of the structure, thus enabling high spatial convergence and fast explicit time integration of impact events. 3) A semi-empirical contact law that is derived from analytical expressions and validated with indentation experiments and numerical results, to provide the coupling between the impactor and target structure. Numerical simulations of the transient impact response obtained by the present method are correlated with 3D continuum finite element impact models and experimental results to quantify accuracy and computational speed. It is demonstrated, that the simulation of impacted sandwich composite plates requires integration of all three previous elements to obtain accurate and fast results.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.081
      Issue No: Vol. 194 (2018)
       
  • Effective piezoelectric coefficients of cement-based 2–2 type
           piezoelectric composites based on a multiscale homogenization model
    • Authors: Chuanqing Fu; Zhi Wang; Xianyu Jin; Xingyi Zhu; Jun Zhu
      Pages: 170 - 177
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Chuanqing Fu, Zhi Wang, Xianyu Jin, Xingyi Zhu, Jun Zhu
      The effective piezoelectric properties of the cement-based 2–2 type piezoelectric composites have been investigated both experimentally and theoretically. The two-scale asymptotic expansion method is employed to develop a homogenized model for the effective properties calculation. The validity of the theoretical solution is confirmed through the comparison with the experimental results. The influence of the volume fraction of the piezoelectric phase on the effective piezoelectric coefficients is then examined. It is found that higher volume fraction will induce obvious increment of the magnitude of the effective piezoelectric strain coefficients d 31 Eff , d 32 Eff , and d 33 Eff , however, the hydrostatic piezoelectric strain coefficient d h Eff will reach a maximum value at a lower volume fraction.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.055
      Issue No: Vol. 194 (2018)
       
  • Manufacturing and compressive response of ultra-lightweight CFRP cores
    • Authors: Pablo Vitale; Gaston Francucci; Helmut Rapp; Ariel Stocchi
      Pages: 188 - 198
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Pablo Vitale, Gaston Francucci, Helmut Rapp, Ariel Stocchi
      Three-dimensional carbon fiber reinforced polymer (CFRP) cores are high performance ultra-lightweight materials that can reduce the structural mass of vehicles used in the transportation and aerospace industry, increasing capabilities and performance, and reducing fuel consumption. In this work, three different carbon fiber cores are obtained using an interlocking method from flat composite laminates with different geometries. The density of the cores is maintained less than 48 kg m−3. Sandwich panels are manufactured using these cores and carbon fiber reinforced epoxy skins. Compressive properties of the sandwich panels are evaluated and the failure modes are studied. Experimental results are compared to those predicted by analytical modeling and finite element method analysis (FEM).

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.065
      Issue No: Vol. 194 (2018)
       
  • An experimental study on the radar absorbing characteristics of folded
           core structures
    • Authors: Zhijin Wang; Chen Zhou; Valentin Khaliulin; Alexey Shabalov
      Pages: 199 - 207
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Zhijin Wang, Chen Zhou, Valentin Khaliulin, Alexey Shabalov
      Folded core sandwich structures are promising multifunctional structures for both load bearing and radar absorbing capability. This paper presents an experimental study on the radar absorbing characteristics of folded core structures. The influences of various factors on the folded core radar cross section (RCS) are investigated. The experiments were carried out in an anechoic chamber. Comparisons are made between folded core samples and an aluminium flat panel. The results show that the folded core height has significant effects on the radar absorbing performance of V-pattern folded core, while core material only leads to a slight difference. The RCS of V-pattern folded core is lower than that of the flat panel, while the RCS of M-pattern folded core is of the same order of magnitude as that of the flat panel with a much wider range.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.106
      Issue No: Vol. 194 (2018)
       
  • Experimental investigation of the quasi-static axial crushing behavior of
           filament-wound CFRP and aluminum/CFRP hybrid tubes
    • Authors: Guangyong Sun; Zhen Wang; Jiaying Hong; Kai Song; Qing Li
      Pages: 208 - 225
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Guangyong Sun, Zhen Wang, Jiaying Hong, Kai Song, Qing Li
      This study aims to investigate the effects of winding angles (25°, 50°, 75°, 90°; the 0° winding angle is along the axial direction of the tube) and thicknesses (3-ply, 6-ply, 9-ply) on crashworthiness characteristics of carbon fiber reinforced plastics (CFRP) tube and aluminum/CFRP hybrid tube molded by the filament winding technique through quasi-static crushing tests. The interaction between the outer CFRP tube and inner aluminum tube in a hybrid configuration was explored by comparing the sum of energy absorption of individual components with the hybrid form. It was found that both winding angle and wall thickness had significant influence on failure modes and crushing characteristics of both CFRP and hybrid tubes. With the same laminate thickness, increasing the winding angle decreased the specific energy absorption (SEA), energy absorption (EA) and peak crushing force (PCF) of pure CFRP and hybrid tubes. With the same winding angle of CFRP tube, increasing the thickness of CFRP tube increased the SEA, EA and PCF of both the CFRP and hybrid tubes. The SEA of 9-ply CFRP tube with winding angle of 25° and 9-ply CFRP/aluminum hybrid tube with winding angle of 25° were the highest of all the CFRP and hybrid tubes (48.74 J/g and 79.05 J/g), respectively. Moreover, EA of the hybrid tube exceeded the sum of that of the individual components thanks to the positive interaction between these components; making the hybrid tubes better crashworthiness than individual components.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.02.005
      Issue No: Vol. 194 (2018)
       
  • Influence of stochastic variations in manufacturing defects on the
           mechanical performance of textile composites
    • Authors: Xiao-Yi Zhou; P.D. Gosling
      Pages: 226 - 239
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Xiao-Yi Zhou, P.D. Gosling
      This paper presents a methodology to evaluate the effects of microscopic manufacturing defects, namely fibre misalignment, waviness and volume fraction, on the mechanical performance. Influences of these defects on the effective elastic properties of composites are quantified by a dual homogenization method. For estimating stochastic characteristics of the properties induced by the variations in these defects, a probabilistic extension of the dual homogenization method is developed and numerically implemented through a perturbation-based stochastic finite element method. It is further incorporated in a multiscale finite element based reliability method to measure the influences of these manufacturing defects on structural performance in terms of reliability. The effectiveness of the proposed method in capturing defects is illustrated initially by investigating the effective elastic properties of a unidirectional fibre composite based yarn and then a plain woven textile composite. The capability of the proposed method in quantifying the variations in these defects is further demonstrated through statistical analysis of the effective elastic properties and a woven textile composite and structural reliability analysis of a textile composite laminate. This paper represents a significant advancement in the probabilistic prediction of the behaviour of woven and non-woven composites.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.04.003
      Issue No: Vol. 194 (2018)
       
  • Effects of surface laser treatment on direct co-bonding strength of CFRP
           laminates
    • Authors: C. Leone; S. Genna
      Pages: 240 - 251
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): C. Leone, S. Genna
      Laser surface treatment is a promising technique to increase the adhesive strength of carbon fibres reinforced plastics joints. In this technique, the laser beam is adopted to remove the outer matrix layer up to the expose the underlying reinforcement. This study deals on the effect of laser treatment on the joint strength of CFRP laminate obtained by direct co-bonding. To this aim, laser treatments at different process conditions were performed on autoclave cured CFRP, adopting a pulsed Yb:YAG fiber laser. The obtained surfaces were characterized by microscopy. Single lap joints were obtained by infusion techniques by superposition of fresh laminates and laser treated laminates without any kind of adhesive. Untreated and sandpaper treated samples were adopted as reference specimens. After joints consolidation, mechanical tests were carried out; apparent shear strength was measured and post mortem analysis was performed. The results show that laser treatments allow the doubling of the apparent shear strength.
      Graphical abstract image

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.096
      Issue No: Vol. 194 (2018)
       
  • Behavior of steel fiber-reinforced concrete-filled FRP tube columns:
           Experimental results and a finite element model
    • Authors: Aliakbar Gholampour; Togay Ozbakkaloglu
      Pages: 252 - 262
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Aliakbar Gholampour, Togay Ozbakkaloglu
      This paper presents the results of an experimental study together with the first finite element (FE) model for the compressive behavior of fiber-reinforced polymer (FRP)-confined steel fiber-reinforced concrete (SFRC). 73 existing experimental test results of FRP-confined and actively confined SFRC specimens tested under axial compression were initially assembled. Additional axial compression tests were conducted on 16 actively confined SFRC specimens to address the gaps in the existing test database to compile a reliable database for the FE modeling of FRP-confined SFRCs. The analysis of experimental test results revealed that the compressive behavior of FRP-confined SFRCs is influenced by the steel fiber volume fraction and aspect ratio. New expressions were developed for the hoop rupture strain of the FRP jacket, axial strain-lateral strain relationship of FRP-confined and actively confined SFRC, and relationship between the confining pressure and the compressive strength of actively confined SFRC by considering the influences of the volume fraction and aspect ratio of internal steel fibers. A recently developed concrete damage-plasticity model, which was shown to be the most accurate currently available model for confined plain concrete, was adopted for the prediction of the compressive behavior of FRP-confined SFRC. The failure surface and flow rule of the model were modified based on the results from actively and FRP-confined SFRC. The results show that model predictions of the axial stress-axial strain, lateral strain-axial strain, axial stress-volumetric strain, plastic volumetric strain-axial plastic strain, and plastic dilation angle-axial plastic strain relationships are in good agreement with the experimental results of FRP-confined SFRC. The new model provides improved accuracy over the best performing existing models of FRP-confined plain concrete in predicting the behavior of FRP-confined SFRC.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.094
      Issue No: Vol. 194 (2018)
       
  • Flexural performance of a hybrid GFRP-concrete bridge deck with composite
           T-shaped perforated rib connectors
    • Authors: Yize Zuo; Ayman Mosallam; Haohui Xin; Yuqing Liu; Jun He
      Pages: 263 - 278
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Yize Zuo, Ayman Mosallam, Haohui Xin, Yuqing Liu, Jun He
      In this study, the flexural performance of an innovative hybrid GFRP-concrete deck is evaluated. The proposed hybrid composite deck consists of a pultruded GFRP plate with T-shaped perforated ribs for resisting tensile stresses, while concrete with reinforcements is placed at the compressive side of the deck. In order to better understand the flexural performance of proposed hybrid decks under sagging moment, a total of six full-scale hybrid deck models were experimentally investigated. Five test parameters were considered, namely: (i) hole spacing, (ii) presence of bent-up rebars, (iii) quality of GFRP composites surface treatment, (iv) deck depth, and (v) type of reinforcements. Experimental results identified three different typical failure modes, namely: diagonal and longitudinal shear, as well as flexure. Furthermore, it was found that the inclusion of bent-up rebars, sand bonded to GFRP plates surfaces, and increasing deck thickness enhance the ultimate strength of the proposed hybrid deck. It was also concluded that the hole spacing and the reinforcement type have negligible influence on ultimate capacity of the proposed deck. Moreover, finite element models considering the laminate damage based on Hashin’s theory were built and load transfer and failure mechanisms of GFRP perforated ribs were discussed. The validity of the proposed analytical method, with respect to failure mode and ultimate strength for the hybrid deck, was confirmed through the close correlation between analytical and experimental results.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.105
      Issue No: Vol. 194 (2018)
       
  • Static and fatigue analysis of bolted/bonded joints modified with CNTs in
           CFRP composites under hot, cold and room temperatures
    • Authors: U.A. Khashaba
      Pages: 279 - 291
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): U.A. Khashaba
      The present study evaluated for the first time, the tensile and fatigue properties of bolted/bonded scarf adhesive joints (SAJs) in carbon fiber reinforced polymer (CFRP) composites at room temperature of +25 °C, +50 °C and −70 °C. The adhesive layer of the SAJs was modified with multi-walled carbon nanotubes (CNTs) and the results are compared with respect to neat adhesive and adhesive thickness. A new simple approach was developed to measure bolt-hole elongation, which successfully differentiates between bearing failure and interfacial shear failure modes and loads. Results from tensile tests showed that the bolted/bonded SAJs can perform well at −70 °C with maximum loss in strength of 9.6% and stiffness improvement of 30%. Incorporation of CNTs into the adhesive layer improved fatigue lives, at +25 °C, by about 72.1%–97.8% compared with that of neat-adhesives. Interfacial shear failure, cohesive failure and CNTs pull-out are the dominated failure modes in the SAJs, whereas bearing, shear-out, longitudinal splitting and bolt fracture are observed for the bolted joints. Considerable attention was given to analyze the scatter in the tensile strength and fatigue life results.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.04.008
      Issue No: Vol. 194 (2018)
       
  • Multiscale microstructural characterization of particulate-reinforced
           composite with non-destructive X-ray micro- and nanotomography
    • Authors: J. Nafar Dastgerdi; A. Miettinen; J. Parkkonen; H. Remes
      Pages: 292 - 301
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): J. Nafar Dastgerdi, A. Miettinen, J. Parkkonen, H. Remes
      Methods based on X-ray tomography are developed to study the relevant statistical quantities describing the microstructural inhomogeneity of particulate reinforced composites. The developed methods are applied in estimating microstructural inhomogeneity parameters of composites containing metallic glass particles in metal matrix, extruded in varying pressure loads. This study indicates that the critical characteristics with regard to the effect of particle clustering are cluster size and shape, local volume fraction of particles in the cluster and the distance between clusters. The results demonstrate that the spatial distribution of reinforcement is very uneven and the amount of particle clustering varies with amount of reinforcement. Moreover, X-ray nanotomography was used to investigate the structure of individual clusters and the results suggest that high extrusion load may cause break-up of individual particle clusters so that their shape changes from solid and spherical to broken and ellipsoidal.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.04.022
      Issue No: Vol. 194 (2018)
       
  • Multiscale modeling of polymer systems comprising nanotube-like inclusions
           by considering interfacial debonding under plastic deformations
    • Authors: S.M.R. Paran; G. Naderi; M.H.R. Ghoreishy; C. Dubois
      Pages: 302 - 315
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): S.M.R. Paran, G. Naderi, M.H.R. Ghoreishy, C. Dubois
      The mechanical properties of polymer nanocomposites are severely governed by the situation of the interphase region. Yet, a few was known about interfacial adhesion/debonding in the vicinity of polymer-nanofiller interface. The inadequateness of our information on such region takes its origin in the assumptions involved in theoretical models describing interfacial debonding. Particularly, zero interphase region, constant modulus, and elastic deformation assumptions make predictions unreliable when experimental mechanical characteristics are meticulously analyzed. In this work, multiscale modeling approach was implemented in prediction of plastic deformation of stress-strain of a typical thermoplastic polymer filled with nanotube-like inclusions. In contrast to the above-mentioned assumptions that take a naïve look at the interphase region, a finite element code was developed here to assist in interfacial debonding evaluation by considering a variable modulus for non-zero layer between polymer and nanotube-like filler phases under plastic deformation. Experimental plots of stress-strain on typical nanocomposites prepared varying the amount and surface chemistry of the nanofiller were used for approval of the model outcome. The use of finite element method in such a complex systems improved significantly the predictability of theories by making possible monitoring the effect of thickness of interphase on debonding behavior.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.059
      Issue No: Vol. 194 (2018)
       
  • Numerical analysis and experimental observation of ultrasonic wave
           propagation in CFRP with curved fibers
    • Authors: Takeshi Ashizawa; Yoshihiro Mizutani; Nobuyuki Toyama; Akira Todoroki; Yoshiro Suzuki
      Pages: 316 - 327
      Abstract: Publication date: 15 June 2018
      Source:Composite Structures, Volume 194
      Author(s): Takeshi Ashizawa, Yoshihiro Mizutani, Nobuyuki Toyama, Akira Todoroki, Yoshiro Suzuki
      The relationship between the propagation directions of ultrasonic wave and the direction of the principal axis of anisotropy in uni-directional CFRP with straight fiber is well known. However, the behavior of ultrasonic wave in CFRP with curved fibers is not clarified in details. In this paper, numerical analyses using the finite difference method were conducted to visualize the behavior of ultrasonic waves in CFRP with concentrically curved fibers. Numerical simulation results showed the energy of quasi-longitudinal ultrasonic wave curved along the fiber direction. In order to confirm the analytical result, CFRP specimen with curved fibers were prepared by utilizing 3D-printer and the behavior of ultrasonic propagation was observed by using Laser ultrasonic system. The observed results confirmed the analytical results that the ultrasonic wave curved along carbon fibers.

      PubDate: 2018-04-15T09:22:00Z
      DOI: 10.1016/j.compstruct.2018.03.089
      Issue No: Vol. 194 (2018)
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.81.68.240
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-