Impact on Buckled Composite Panels

Aircraft structures are vulnerable to impacting projectiles like runway debris, birds or hail. With the increased application of composite materials in aircrafts, improving the high velocity impact (HVI) response of reinforced polymers has been a topic of research for the last decades. Only a limited number of authors investigated the effect of the stress state in the target structure on the impact response and observed that preloads can significantly amplify the extent of damage. Current design practice for composite aircraft skin structures is to allow local buckling at limit load under compression. The HVI response of buckled skin plates is therefore highly relevant and studied in this paper. The methodology includes a test campaign with the DLR gas gun firing projectiles on flat buckled plates and numerical finite element simulations with the commercial code Abaqus using intra- and inter-ply damage models. Impact on buckled plates was modelled using a coupled implicit-explicit simulation procedure. From the experimental and numerical results an influence of compressive preloads and the different buckling patterns on the impact damage was observed. The numerical model was validated and shown to be able to capture the interaction between static preloads and impact loads.