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  • Open Access

    ARTICLE

    Analytical Models for Sliding Interfaces Associated with Fibre Fractures or Matrix Cracks

    L. N. McCartney1

    CMC-Computers, Materials & Continua, Vol.35, No.3, pp. 183-227, 2013, DOI:10.3970/cmc.2013.035.183

    Abstract Analytical stress transfer models are described that enable estimates to be made of the stress and displacement fields that are associated with fibre fractures or matrix cracks in unidirectional fibre reinforced composites. The models represent a clear improvement on popular shear-lag based methodologies. The model takes account of thermal residual stresses, and is based on simplifying assumptions that the axial stress in the fibre is independent of the radial coordinate, and similarly for the matrix. A representation for both the stress and displacement fields is derived that satisfies exactly the equilibrium equations, the required interface… More >

  • Open Access

    ARTICLE

    Investigation of Progressive Damage and Fracture in Laminated Composites Using the Smeared Crack Approach

    Christian Heinrich1, Anthony M. Waas2

    CMC-Computers, Materials & Continua, Vol.35, No.2, pp. 155-181, 2013, DOI:10.3970/cmc.2013.035.155

    Abstract The smeared crack approach (SCA) is revisited to describe post-peak softening in laminated composite materials. First, predictions of the SCA are compared against linear elastic fracture mechanics (LEFM) based predictions for the debonding of an adhesively bonded double cantilever beam. A sensitivity analysis is performed to establish the influence of element size and cohesive strength on the load-deflection response. The SCA is further validated by studying the in-plane fracture of a laminated composite in a single edge bend test configuration. In doing so, issues related to mesh size and their effects (or non-effects) are discussed More >

  • Open Access

    ARTICLE

    On Multiscale Modeling Using the Generalized Method of Cells: Preserving Energy Dissipation across Disparate Length Scales

    E. J. Pineda1, B. A. Bednarcyk1, A. M. Waas2, S. M. Arnold1

    CMC-Computers, Materials & Continua, Vol.35, No.2, pp. 119-154, 2013, DOI:10.3970/cmc.2013.035.119

    Abstract A mesh objective crack band model was implemented within the generalized method of cells micromechanics theory. This model was linked to a macroscale finite element model to predict post-peak strain softening in composite materials. Although a mesh objective theory was implemented at the microscale, it does not preclude pathological mesh dependence at the macroscale. To ensure mesh objectivity at both scales, the energy density and the energy release rate must be preserved identically across the two scales. This requires a consistent characteristic length or localization limiter. The effects of scaling (or not scaling) the dimensions More >

  • Open Access

    ARTICLE

    Prediction of Delamination Onset and Critical Force in Carbon/Epoxy Panels Impacted by Ice Spheres

    Jennifer D. Rhymer1, Hyonny Kim1

    CMC-Computers, Materials & Continua, Vol.35, No.2, pp. 87-117, 2013, DOI:10.3970/cmc.2013.035.087

    Abstract Polymer matrix composite structures are exposed to a variety of impact threats including hail ice. Internal delamination damage created by these impacts can exist in a form that is visually undetectable. This paper establishes an analysis methodology for predicting the onset of delamination damage in toughened carbon/epoxy composite laminates when impacted by high velocity ice spheres (hailstones). Experiments and analytical work focused on ice sphere impact onto composite panels have determined the failure threshold energy as a function of varying ice diameter and panel thickness, and have established the ability to predict the onset of More >

  • Open Access

    ARTICLE

    Finite Element Analysis of Delamination inWoven Composites under Quasi-Static Indentation

    M. C. Song1, B.V. Sankar1, G. Subhash1, C. F. Yen2

    CMC-Computers, Materials & Continua, Vol.35, No.1, pp. 67-85, 2013, DOI:10.3970/cmc.2013.035.067

    Abstract Delamination initiation and propagation in plain woven laminates and 3D orthogonal woven composites during short beam shear (SBS) test were analyzed using finite element (FE) analyses. Two kinds of 3D woven composites, containing single z-yarns and double z-yarns, were considered. The FE models were guided by experimental observations from SBS tests for the same material systems. A series of mechanisms including creation and evolution of matrix cracks and delaminations were modeled discretely. The force-displacement curves obtained from the FE simulations were compared with those from experiments. Further parametric studies were conducted to investigate the effects More >

  • Open Access

    ARTICLE

    Influence of Scale Specific Features on the Progressive Damage of Woven Ceramic Matrix Composites (CMCs)

    K. C. Liu1, S. M. Arnold2

    CMC-Computers, Materials & Continua, Vol.35, No.1, pp. 35-65, 2013, DOI:10.3970/cmc.2013.035.035

    Abstract It is well known that failure of a material is a locally driven event. In the case of ceramic matrix composites (CMCs), significant variations in the microstructure of the composite exist and their significance on both deformation and life response need to be assessed. Examples of these variations include changes in the fiber tow shape, tow shifting/nesting and voids within and between tows. In the present work, the influence of many of these scale specific architectural features of woven ceramic composite are examined stochastically at both the macroscale (woven repeating unit cell (RUC)) and structural More >

  • Open Access

    ARTICLE

    A Novel Approach to Modeling of Interfacial Fiber/Matrix Cyclic Debonding

    Paria Naghipour1, Evan J. Pineda2, Steven M. Arnold2

    CMC-Computers, Materials & Continua, Vol.35, No.1, pp. 17-33, 2013, DOI:10.3970/cmc.2013.035.017

    Abstract The micromechanics theory, generalized method of cells (GMC), was employed to simulate the debonding of fiber/matrix interfaces, within a repeating unit cell subjected to global, cyclic loading, utilizing a cyclic crack growth law. Cycle dependent, interfacial debonding was implemented as a new module to the available GMC formulation. The degradation of interfacial stresses with applied load cycles was achieved via progressive evolution of the interfacial compliance A periodic repeating unit cell, representing the fiber/matrix architecture of a composite, was subjected to combined normal and shear loadings, and degradation of the global transverse stress in successive More >

  • Open Access

    ARTICLE

    The Effect of Tow Gaps on Compression after Impact Strength of Robotically Laminated Structures

    A. T. Rhead1, T. J. Dodwell1, R. Butler1,2

    CMC-Computers, Materials & Continua, Vol.35, No.1, pp. 1-16, 2013, DOI:10.3970/cmc.2013.035.001

    Abstract When (robotic) Automated Fibre Placement (AFP) is used to manufacture aerospace components with complex three dimensional geometries, gaps between fibre tows can occur. This paper explores the interaction under compressive load of these tow gaps with impact damage. Two coupons with different distributions of tow-gaps were impacted. Results indicated that the area of delamination is smaller for an impact directly over a tow gap where the tow gap is situated close to the non-impact face. Subsequent Compression After Impact (CAI) testing demonstrated that both the formation of sublaminate buckles and subsequent growth of delaminations is More >

  • Open Access

    EDITORIAL

    Preface

    A.M. Waas

    CMC-Computers, Materials & Continua, Vol.34, No.3, 2013, DOI:empty

    Abstract Fiber reinforced composites (FRCs) are fast becoming the material of choice in a wide range of applications where lightweight and high performance are critical. The deformation response, damage onset and failure of pre-preg based FRCs, textile FRCs and nanocomposites (where filler is reinforced with particles of dimensions in the nanometer scale) are now contemporary fields of research and there is wide variety of experimental, analytical and computational advances that have recently emerged. In this special issue of the CMC journal, leading experts in the mechanics of composites have contributed 14 papers devoted to addressing the… More >

  • Open Access

    ARTICLE

    Influence of Stress Singularities on Scaling of Fracture of Metal-Composite Hybrid Structures

    Jia-Liang Le1, Bing Xue1

    CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 251-264, 2013, DOI:10.3970/cmc.2013.034.251

    Abstract It has been recently shown that the nominal structural strength of metal-composite structures depends on the structure size, and such dependence is strongly influenced by the stress singularities. Nevertheless, previous studies only focused on structures that exhibit very strong stress singularities, which are close to the crack-like stress singularity. In the actual engineering designs, due to the mismatch of material properties and complex structural geometries, many metalcomposite structures may contain stress singularities that are much weaker than the crack-like stress singularity. This paper presents a numerical study on the size dependence of scaling of fracture… More >

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