Impact response of polyurethane and polystyrene sandwich panels

Sandwich panels with aluminum faces and polyurethane or polystyrene core were tested in impact on an Instron Ceast 9340 impact tower at speeds from 0.77 to 4.5 m/s. The faces were made from Al 6082-T6 sheet with a thickness of 1.5 mm and the thickness of the polyurethane panel (Necuron 100 core of density 100 kg/m3) and of the polystyrene panel (commercial extruded polystyrene core of density 30 kg/m3) were 15 mm, respectively 22 mm. Specimens of 140x140 mm were impacted with a mass of 13.15 kg and the variations of the impact force were monitored during the initial impact at a data acquisition frequency of 200 kHz. The important events took place in less than 15 ms. Particularities of the impact response of the sandwich panels were observed and discussed. The influence of the speed of impact was analyzed for both types of panels. The force variation during impact has a different evolution as influenced by the core behavior. There are noticed differences in the size and shape of the produced penetration of the skins after low-velocity impact.