The impact response of environmental-friendly sandwich structures

The low-velocity impact response of sandwich structures based on fully-recyclable skin and core materials has been investigated. Particular attention has been focused on structures based on self-reinforced polypropylene skins combined with a polypropylene honeycomb core. Two types of skin designs were considered, the first being based on a single 'as-supplied' monolithic self-reinforced polypropylene laminate and the second being manufactured from thin self-reinforced polypropylene sheets bonded together using a hot-melt polypropylene film. For comparative purposes, a limited number of tests have also been carried out on a more conventional GFRP/aluminium honeycomb sandwich structure. Drop-weight impact test have shown that all-polypropylene honeycomb sandwich structures absorb significant energy through plastic deformation in the composite skins as well as plastic buckling in the honeycomb core. It has also been shown that the design of the self-reinforced polypropylene skin has a significant effect on the energy-absorbing characteristics of the sandwich structure, with the performance of systems based on multiple layer skins greatly exceeding that observed following tests on a monolithic design. Tests on plain laminates also yielded similar conclusions, with multilayer systems offering much higher perforation resistances than their plain counterparts. Finally, it has been demonstrated that when the impact data are normalised by their respective areal densities, the all-polypropylene composites significantly out-perform GFRP/aluminium honeycomb sandwich structures