Adiabatic shear failure of a syntactic polymeric foam

The recent tragedy of the Columbia shuttle has drawn much attention to the potential damage that may result from high velocity impact of foam on structural components. For obvious reasons, the emphasis was put on the structure rather than on the foam itself. We performed impact tests of polyurethane foam cylinders on various metallic plates, using small lightweight (m≈1.4 gr) cylinders launched at velocities in the range of 235-280 m/s. In addition to the resulting structural damage, we observed a peculiar and previously unreported failure mode for this kind of foam, which bears a high similarity to adiabatic shear failure. In this paper, we describe and discuss the essential results of the study with emphasis on the new failure mechanism for dynamically loaded polymeric foam.