An experimental study on the low velocity impact resistance of fibre metal laminates under successive impacts with reduced energies

The response of Glare 3 and Glare 5 to repeated impacts and dropped tools was experimentally investigated using drop weight equipment. Two repetition sequences were tested. The first sequence consisted of successive impacts with the same impact energy, but lower than the first impact. In the second sequence the rebound energy of one impact was taken as the impact energy for the subsequent impact. This sequence represents the drop weight impact. The damage was evaluated using visual inspection and ultrasonic C-scan. Three categories of impact damage were observed: visible deformation without internal or external damage, visible internal damage (C-scan) without external damage, and visible internal and external damages. The “threshold energy” defined as the magnitude of maximum impact energy in successive impacts that caused no further damage after the first impact. For the successive impacts with energy between the threshold energy and the first impact, repeated impacts were observed to cause damage propagation. Successive impacts with impact energy less than the threshold did not reveal any effect on the structural integrity. The dropped tool sequence revealed that the rebound energies do not have a considerable effect; the force–time and force–displacement curves for Glare laminates did not change with successive rebound impacts. Therefore, it can be concluded that damage propagation due to rebound energies is negligible.