Modelling effect of layer shift on properties of woven fabric composites

Abstract

The effect of layer shift on the mechanical behaviour of woven fabric laminates has been examined using finite element analysis. Simplified two-dimensional generalised plain strain models have been developed for laminates in which the neighbouring layers are in phase (no layer shift), out of phase, or 'staggered' with respect to each other. Values for moduli and energy release rates associated with matrix crack formation are presented both for woven fabric laminates, as functions of layer shift and laminate thickness, and for a nominally equivalent crossply (non-woven) laminate. It is shown that at the same level of applied mechanical strain, the values of energy release rate for crack formation are similar for crossply and woven laminates in which the cracking occurs away from the crimp region, provided that there is no significant bending. When crack formation is adjacent to the crimp region, the associated energy release rates are higher.