Effect of Helmet Pads on the Load Transfer to Head Under Blast Loadings

Recent wars have highlighted the need to better protect dismounted soldiers against emerging blast and ballistic threats. Current helmets are designed to meet ballistic performance criterion. Therefore, ballistic performance of helmets has received a lot of attention in the literature. However, blast load transfer/mitigation has not been well understood for the helmet/foam pads. The pads between the helmet and head can not only absorb energy, but also produce more comfort to the head. The gap between the helmet and head due to the pads helps prevent or delay the contact between helmet shell and the head. However, the gap between the helmet shell and the head can produce underwash effect, where the pressure can be magnified under blast loading. In this paper, we report a numerical study to investigate the effects of foam pads on the load transmitted to the head under blast loading. The ALE module in the commercial code, LS-DYNA was used to model the interactions between fluid (air) and the structure (helmet/head assembly). The ConWep function was used to apply blast loading to the air surrounding the helmet/head. Since we mainly focus on the load transfer to the head, four major components of the head were modeled: skin, bone, cerebrospinal fluid (CSF) and brain. The foam pads in fielded helmets are made of a soft and a hard layer. We used a single layer with the averaged property to model both of those layers for computational simplicity. Sliding contact was defined between the foam pads and the helmet. A parametric study was carried out to understand the effects of material parameters and thickness of the foam pads.