Delamination growth directionality and the subsequent migration processes - The key to damage tolerant design

Delamination has been recognised as one of the most challenging hurdles in using laminated composites, and has been the focus of considerable research over the last three decades. The research reported in this paper investigated the influence of ply interface on the delamination propagation processes. Experimental evidence is presented which illustrates that delamination does not grow in a self-similar manner. Instead, delaminations were shown to propagate preferentially in the direction of one ply at the delaminating interface; which ply was dictated by the orientation of the principal delaminating stress at the ply interface. In conjunction with the experimental studies, an initial methodology for modelling delamination directionality is presented. The results of this study have considerable implications for tailoring stacking sequences to promote delamination migration and thus enhance damage tolerance.