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 delamination using cohesive elements in… More >

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 of z-yarns and interlaminar fracture… More >

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 scale (idealized using multiple RUCs).… More >

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 cycles was monitored. The obtained… More >

A. T. Rhead¹, T. J. Dodwell¹, R. Butler^1,2

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 inhibited by the presence of… More >

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 deformation response, damage onset and… More >

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 of metal-composite hybrid structures for… More >

Chandra Veer Singh^1,*

CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 227-249, 2013, DOI:10.3970/cmc.2013.034.227

Abstract A non-linear damage model is developed for the prediction of stiffness degradation in composite laminates due to transverse matrix cracking. The model follows the framework of a recently developed synergistic damage mechanics (SDM) approach which combines the strengths of micro-damage mechanics and continuum damage mechanics (CDM) through the so-called constraint parameters. A common limitation of the current CDM and SDM models has been the tendency to over-predict stiffness changes at high crack densities due to linearity inherent in their stiffness-damage relationships. The present paper extends this SDM approach by including higher order damage terms in the characterization of ply cracking… More >

A. Ataş¹, C. Soutis²

CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 199-226, 2013, DOI:10.3970/cmc.2013.034.199

Abstract A strength prediction method is presented for double-lap single fastener bolted joints of cross-ply carbon fibre reinforced plastic (CFRP) composite laminates using cohesive zone elements (CZEs). Three-dimensional finite element models were developed and CZEs were inserted into subcritical damage planes identified from X-ray radiographs. The method makes a compromise between the experimental correlation factors (dependant on lay-up, stacking sequence and joint geometry) and three material properties (fracture energy, interlaminar strength and nonlinear shear stress-strain response). Strength of the joints was determined from the predicted load-displacement curves considering sub-laminate and plylevel scaling effects. The predictions are in a reasonable agreement with… More >

V. Filonova¹, Y. Liu¹, M. Bailakanavar¹, J. Fish¹, Z. Yuan²

CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 177-198, 2013, DOI:10.3970/cmc.2013.034.177

Abstract A corotational formulation for reduced order homogenization is presented. While in principle the proposed method is valid for problems with arbitrary large strains, it is computational advantageous over the classical direct computational homogenization method for large rotations but moderate unit cell distortions. We validate the method for several large deformation problems including: (i) hat-section composite beam with two-dimensional chopped tow composite architecture, (ii) polyethylene microstructure consisting of 'hard' and 'soft' domains (segments), and (iii) fiber framework called fiberform either embedded or not in an amorphous matrix. More >