Low-velocity impact damage in graphite-epoxy laminates subjected to tensile initial stresses

L OW-VELOCITY impact tests in the velocity range of 10-40 m/s were conducted with graphite-epoxy laminated beams as targets. In some of the tests the beams were subjected to tensile initial stresses. The delamination area was measured by ultrasonic C-scanning. The damage was characterized by the reduction in tensile strength and by the delamination area. It was found that tensile initial stresses reduce the threshold impact velocity for damage, but beyond certain impact velocity they may help in containing delamination.