Synergism between layer cracking and delaminations in multidirectional laminates of carbon-fibre-reinforced epoxy.

Abstract

Photographs of different crack modes are shown giving insight into the damage behaviour of composites fabricated of T300/914C plies of 0.125 mm thickness. An increase in the damage tolerance was observed for laminates stacked by quasi-unidirectional(+-2)angle plies. For cross-ply laminates under tension fatigue loading, test results, supplied for the spacings of layer cracks, are used to generate formulae for the residual layer stiffnesses. As an extension to the common energy relaese rate (ERR) concept an ERR tensor is established. The first invariant of this tensor and its mean values describe the energy release rate and its partitioning into different crack modes, respectively. From the complete set of invariants a first estimation of crack condition for the delamination growth is proposed which includes the effect of fibre orientation.