Pin Reinforcement of Delaminated Sandwich Beams Under Axial Compression

The present study is concerned with translaminar reinforcements in a sandwich beam for preventing buckling of the delaminated face sheet under edge-wise axial compression. Sandwich beams consisting of graphite/epoxy face sheets and an aramid honeycomb core were reinforced in the thickness direction using two techniques: Z-pinning using graphite/epoxy pins and a novel “C-pinning technique” developed by the authors. To evaluate the effect of reinforcement type and reinforcement spacing on the ultimate compressive strength of delaminated beams, compression tests were performed. Critical buckling loads and post-buckling behavior of sandwich beams under axial compression were evaluated by finite element analysis to provide insight into the effectiveness of translaminar reinforcement. Pin reinforcement has been shown to significantly improve the ultimate compressive load of a delaminated sandwich beam.