Internship_CSM_XSTRMLAB_Sandor_Habets_2024

Title: Influence of repetitive impact loading on nested cylinder polymer structures for protective helmet liners

Abstract:
This research is part of the PANTHER program, an interdisciplinary research hub funded by the of Naval Research, dedicated to advancing the understanding, detection, and prevention of traumatic brain injuries (TBIs). As part of the PANTHER initiative, Team Wendy, a U.S. manufacturer of head protection systems (typically for military), is exploring potential designs for the next-generation combat helmets. The focus here is on the helmet’s interior, also known as the helmet liner. One candidate helmet liner design consists of nested cylinders that absorb energy by buckling sequentially. After a previous study investigated the necessary dimensions, eight elastomer materials have been selected for potential use as the nested cylinders within the combat helmet liner. Four grades of Elastollan (1174D, 1164D, 1154D, and 1195A) and Texin-245, which all have Thermoplastic Polyurethane as the underlying chemical, are selected for their toughness, tear propagation resistance, damping characteristics, and other properties. In addition, three Santoprene grades (201-87, 101-73, 201-64), produced from Thermoplastic Vulcanizate, are chosen for their ability to return to their original shape after enduring considerable compressive strains. The performance of these eight distinct materials is assessed by analyzing their protective capabilities when exposed to repetitive impact fatigue in the intermediate strain-rate regime. In addition to varying the number of impacts, the samples have been heated or cooled to mimic exposure in desert and arctic climates. The results show that Elastollan 1174D and 1164D are unsuitable due to their inability to strain and absorb impacts. All Santoprene samples are considered too sensitive to fatigue to be suitable as a helmet liner. Texin-245 shows the most promising results as it can sustain energy absorption values even after fatiguing at all temperatures. It is recommended that additional experiments are conducted with Texin-245, Elastollan 1195A, and Elastollan 1154D to determine which material is most suitable for helmet liner design.