A damage model for knitted fabric composites

A progressive damage model is presented for the prediction of the overall n on-linear tensile behaviour of knitted fabric composites. The model is an e xtension of a recently developed inclusion method for textile composites, t aking into account the major damage modes of knitted fabric composites simu ltaneously. Matrix non-linearities, playing an important role in the behavi our of knitted fabric composites, are implemented using the secant stiffnes s method. Whereas, non-linearities can be attributed to different sources, depending upon the resin toughness, only some limited yielding was currentl y investigated. Yam/matrix debonding, predominantly responsible for the kne e behaviour of knitted fabric composites, is investigated using a simple in terfacial failure criterion. A selective degradation scheme based upon a fi nite set of interfacial damage state variables is employed in the reduction of the inclusion stiffness. Finally, a Hoffman criterion is used for yam f ailure. The model was used to simulate the tensile behaviour of knitted fab ric E-glass/epoxy composites, showing the ability to predict the material r esponse with reasonable accuracy in the region before ultimate failure. (C) 2001 Published by Elsevier Science Ltd.