Expanded Polystyrene Re-Expansion Analysis Following Impact Compression.

摘要

Post-accident aviator helmet analysis involves a visual inspection of damage to the energy absorbing liner. U.S. Army aviator helmets use expanded bead polystyrene (EPS) of various densities for the energy attenuating liner (EAL) material. This material is known to rebound after compression, and the rebound properties must be understood in order to estimate the actual EAL compression sustained in an impact. This report describes the method and results of compression and rebound tests on the four polystyrene densities, illustrating the results in the form of regression curves. A high degree of linear correlation was found between initial compression and the final thickness ratio of the EPS material. Rebound was essentially complete 24 hours after compression. The results will be used also when examining post-accident helmet damage to help determine helmet impact forces experienced in survivable helicopter accidents.