Auxetic metamaterial optimisation for head impact mitigation in American football

American football has a comparatively high rate of sports-related concussions, despite mitigating strategies including the use of protective helmets. The traditional energy absorbing component, elastomeric foam pads, have limited scope for leveraging any further protection. Alternative structures and materials that exhibit novel deformation mechanics have been proposed as a route to increased energy absorption capacity. This study investigated a metamaterial based on the Miura Ori folding pattern. Eighty-one potential structural variations were conceptualised and evaluated via the Taguchi method. Twenty-seven geometries were then additively manufactured using commercially available thermoplastic polyurethane, before being impacted at multiple velocities. Experimental data were then extrapolated to predict the impact behaviour across all 81 variants. An optimised geometry was then proposed, which reduced linear accelerations across the test conditions and performed favourably when compared to current, elastomeric foam solutions. This work provides a promising foundation for future investigation.

Automated summary

This study explored a metamaterial based on the Miura Ori folding pattern as an alternative structure for increased energy absorption in American football helmets, showing promising results in reducing linear accelerations compared to traditional elastomeric foam solutions. The use of novel deformation mechanics and the Taguchi method in evaluating 81 potential structural variations could pave the way for future research and development in protective sports equipment design.