Impact damage with compressive preload and post-impact compression of carbon composite plates

This paper examines the effect on laminated composites of in-plane compression followed by impact damage, and the coupling between the two, on compression-after-impact (CAI) performance. It is found that preload can actually raise the CAI strength if the load approaches the initial buckling value, since the plate loses stiffness and the impact-induced force is reduced and so is the consequent damage. However, as the preload approaches the CAI strength the induced delamination can propagate catastrophically during the impact, but at a preload value below the CAI strength. The coupling between impact and preload is simulated using the equations of motion, and the same dynamic solver is then used to capture the snap-through when a plate is loaded beyond its initial buckling load. A special 'dynamic relaxation' routine is shown to be robust and reliable when handling these 'snap-through' problems which can be formidable challenges to conventional static incremental loading. (C) 1999 Elsevier Science Ltd. All rights reserved.