An improved Puck’s failure theory for fibre-reinforced composite laminates including the in situ strength effect

Fibre-reinforced composites are being used more and more widely in many fields. However, the theoretical prediction of the failure of these composites is still a challenging task. In this paper, the physically-based failure theory developed by Puck and co-workers is combined with the fracture mechanics based in situ strength theory developed by Wang and Karihaloo. The latter considers the influence of both the thickness of the lamina itself and the ply angles of its neighbouring laminae. This combined failure theory also incorporates a new final failure mode. It is able to predict accurately the initial failure stress, thus overcoming one of the weaknesses of Puck’s theory which significantly underestimates this stress. Also, it explains why the number of non-fatal failure modes predicted by Puck’s theory is different from those observed in experiments under certain loads. Finally, it is able to overcome the problem of discontinuities in the failure envelope under some load combinations predicted by Puck’s original theory.