Low‐velocity impact damage in graphite‐fiber reinforced epoxy laminates

Abstract An experimental investigation was conducted to identify the failure mechanism and to understand damage propagation in compression‐loaded composite structures. The tests were conducted on several laminates of different ply orientation with thicknesses that ranged from 0.56 to 0.79 cm. The panels were damaged by 1.27‐cm‐diameter aluminum spheres propelled normal to the specimen surface at velocities ranging from 30 m/s to 140 m/s. Results indicate that there is significant internal laminate damage due to low‐velocity impact with no surface damage. The internal damage consists of delamination and intraply cracking. Three damage propagation modes were identified as causing specimen failure; delamination, axial load‐lateral deformation coupling, and local shear failure.