An experimental investigation of delamination buckling and postbuckling of composite laminates

The mechanics and mechanisms of delamination buckling and postbuckling of composites have been studied. Compression tests were carried out on HYE-3574 OH graphite/epoxy composites with built-in delaminations in order to evaluate the critical load and the actual postbuckling load-carrying capacity. The variation in structural configurations, such as ply stacking sequence and the location and the length of the delamination, were considered. It is observed that, in general, composite laminates can retain their load-bearing capacity by carrying higher loads after buckling. For particular cases, the ultimate load is found to be as high as three times the critical load. The delamination buckling mode is found to be closely related to the location and the length of the delamination. Excellent agreement is observed between the experimental values of critical load and those predicted by the previously developed new higher-order theory. Good comparisons are also presented for the initial postbuckling behavior.