The high velocity impact response of composite and FML-reinforced sandwich structures

The high velocity impact response of a range of novel aluminium foam sandwich structures has been investigated using a nitrogen gas gun. Tests were undertaken on sandwich structures based on plain composite and fibre-metal laminate (FML) skins. Impact testing was conducted using a 10 mm diameter projectile at energies up to that required to achieve complete perforation of the target. High velocity impact tests on the sandwich structures resulted in a number of different failure modes. Delamination and longitudinal splitting of the composite skins were observed in the unidirectional glass fibre/polypropylene-based systems. In contrast, the woven glass fibre/polypropylene-based sandwich structures exhibited smaller amounts of delamination after high velocity impact testing. In addition, the aluminium foam in both systems exhibited a localised indentation failure followed by progressive collapse at higher impact energies. The ballistic limit of all of the sandwich structures was predicted using a simple analytical model. It has been shown that the predictions of the model are in good agreement with the experimental data. Finally, it has been shown that these novel systems offer excellent energy absorbing characteristics under high velocity impact loading conditions.