Blast-wave impact-mitigation capability of polyurea when used as helmet suspension-pad material

Traumatic brain injury (TBI) is generally considered as a signature injury of the current military conflicts, with costly and life-altering long-term effects. Hence, there is an urgent need to combat this problem by both gaining a better understanding of the mechanisms responsible for the blast-induced TBI and by designing/developing more effective head protection systems. In the present work, the blast-wave impact-mitigation ability of polyurea when used as a helmet suspension-pad material is investigated computationally. Towards that end, a combined Eulerian/Lagrangian fluid/solid transient non-linear dynamics computational analysis is carried out at two levels of blast peak overpressure: (a) one level corresponding to the unprotected-lung- injury-threshold; and (b) the other level associated with the corresponding 50% lethal dose (LD50), i.e. with a 50% probability for lung-injury induced death. To assess the blast-wave impact-mitigation ability of polyurea, the temporal evolution of the axial stress and the particle (axial) velocity at different locations within the intra-cranial cavity are analyzed. The results are compared with their counterparts obtained in the case of a conventional foam suspension-pad material. This comparison showed that, the use of polyurea suspension pads is associated with a substantially greater reduction in the peak loading experienced by the brain relative to that observed in the case of the conventional foam. The observed differences in the blast-wave mitigation capability of the conventional foam and polyurea are next rationalized in terms of the differences in their microstructure and in their mechanical response when subjected to blast loading.