A criterion for predicting delamination growth in composite laminates

To develop a simplified and physically sound delamination-failure criterion, this paper reports a joint experimental and numerical study in which out-of-plane quasi-static indentations with different indentation forces were applied to the centre of fully clamped rectangular carbon fibre-reinforced polymer (CFRP) laminates. The results show that two basic micro-delamination growth modes, which are separately dominated by opening and sliding microcracks, can be distinguished according to the fracture morphologies of the delaminations along the 0° fibre direction. Both are driven by the out-of-plane shear stress σ13, and the corresponding delamination failure threshold is the out-of-plane shear strength S13. Based on these results, a concise Hashin-type delamination-propagation criterion containing only a single stress component and single strength parameter is proposed, which, by incorporating it into the finite element model, the delamination growth along the fibre directions of multidirectional CFRP laminates can be precisely predicted; the prediction error is less than 10 %.