Enhancement of low velocity impact damage resistance of sandwich plates

Two different interlayer materials are used, a stiff and incompressible polyurethane (PUR), and a compliant and compressible elastomeric foam (EF), together with the same face sheet and core materials. Response of the three different sandwich plate configurations of constant overall thickness is analyzed under uniformly applied load to a span of a continuous plate, and under forces imparted by two shapes of rigid indenters in a low velocity impact. The results show that the PUR interlayer reduces both overall and local deflections of the face sheet, and also the local compression of the foam core and the residual stresses left after unloading. The EF interlayer offers a much better protection against compression of the foam core, while magnifying both overall and local deflections. Both interlayers substantially reduce the strain energy release rates of interfacial cracks driven by residual stresses generated by foam core compression.