On the modelling of interfacial transition behaviour in composite materials

Here, the development of two types of models for describing the transition behaviours of interfacial regions such as interlayers in laminated composites has been presented. The first model is defined based on physical considerations, using a spatial function continuously varying/describing the graded properties of the interlayer, for example, in the case of epoxy laminates, it depends on resin enrichment and fibre specific distribution. The second kind of model is proposed using interface laws defined on material surfaces (with no thickness). These laws, obtained by asymptotic analysis, are equivalent to the evolutive behaviour model primarily developed for the interlayer. Depending on the flexible or rigid nature of the interlayer, two types of interface laws have been suggested. Finally, these models are employed in a numerical analysis for studying the stress concentration due to free-edge effects in a multilayered symmetric cross-ply (0 degrees /90 degrees )s laminate having different kinds of interlayers. The present results are compared with those of classical/ideal perfect interface model to show the significance of the proposed models, incorporating the influence of the interlayer transition behaviour on the free-edge effect evaluation. (C) 2001 Elsevier Science B.V. All rights reserved.