The onset of delamination at stress-free edges in angle-ply laminates — analysis of two criteria

Abstract Prediction of delamination onset in ±θ s angle-ply carbon-fiber/epoxy-resin laminates is proposed by means of two approaches. Both are based on a preliminary analysis of the boundary effects. In the first, more classical, case, an ‘average stress’ criterion retaining only the interface shear component of the stress field is used. Layer-thickness influence is taken into account to estimate the averaging length. The second case takes advantage of the stress concentrations caused by singularities to put to work an incremental Griffith-like criterion. Initiation is considered to be a locally unstable process. It requires us to account for the existence of surface flaws to explain the influence of layer thickness on the critical delamination stress.