Effects of the Mechanical Properties of the Shell and Liner on the Shock Absorption of Helmets

A combination of the characteristics of the shell and liner of a helmet, that makes it possible to improve the shock absorption capacity was investigated by constructing the finite element model of the helmet modeling both the bottoming of the liner and the fracture of the shell. The material model of the shell was defined as an elasto-plastic material, taking into account brittle fracture. The liner was modeled as a non-linear visco-elastic material, expressing both energy absorption by buckling of the cell foam, and the extreme increase of the stiffness caused by bottoming. The results of the parametric study, where the foaming ratio of the liner and the shell-thickness were varied, indicated that there is an optimum combination where the shell part fails without the liner bottoming, improving the shock absorption ability of a helmet.