Analysis of rigid polyurethane foam as a shock mitigator

Abstract

In problems of impact, the compressive-stress wave generated at the surface of contact can be quite severe. In certain instances, it may be necessary to mitigate the peak stress. Many materials, e.g., rigid polyurethane foam, exhibit elastic, nearly perfectly plastic stress-strain relations. Stresses greater than the yield stress cannot be transmitted until compaction occurs.

The purpose of this paper is to investigate the mitigation of shock and absorption of energy under impact-loading conditions through the use of crushable materials. Experimental data are presented on the mitigated impacts of a short steel projectile on a long aluminum rod. A theoretical analysis is formulated and the results are compared with the experimental results. Mitigators of varying cross-sectional area, as well as mitigators of constant cross-sectional area, are included. The dynamic properties of the rigid polyurethane foam were obtained both experimentally and from the literature, and used as input for the theoretical analysis.