Design and optimization of layered composite foam liners and shell material for protective helmets

n this study, different configurations of layered composite foam liners for a protective helmet were prepared by arranging layers of EPS foams with different densities in a series configuration. The performance of the layered "composite foams" in terms of peak force/accelerations and time duration in linear impact were compared with single layer homogenous EPS foam. Linear impact tests were performed for two different initial energies of 40 and 66 J. Results demonstrate that in a liner with a density gradient through the thickness, positioning the higher density close to the head can reduce the peak accelerations transferred to the head. In addition, in his paper, the effect of using different materials as a helmet shell on the performance of a helmet in linear impact has been studied. For this purpose high energy absorbing composites such as Curv® and silk/HDPE have been benchmarked against conventional shell materials such as polycarbonate. Results demonstrated the superior performance of silk/HDPE composite compared to the other materials for more localized loads.