Ballistic response of composite helmets engineered with cellular metamaterials

This study investigates the integration of cellular metamaterials into combat helmet systems under ballistic loading, with a focus on realistic helmet geometries and both direct and oblique impact conditions. As global conflict zones increasingly demand lightweight and high-performance protective gear for enhanced mobility and survivability, auxetic structures, particularly the double arrowhead (DAH) topology, demonstrated substantial improvements in head protection, reducing injury metrics such as peak linear acceleration and head injury criterion (HIC) by over 50% compared to non-auxetic designs. Cellular helmet pad systems, explored here for the first time, achieved comparable or superior impact mitigation while halving system weight. Detailed damage evolution analysis revealed that DAH structures exhibited more gradual and confined failure compared to re-entrant designs, further supporting their superior performance. These results offer valuable insights into the mechanics of impact resistance and set a new benchmark for the design of lightweight, high-performance protective equipment. • Cellular metamaterials integrated into full helmet and pad system designs. • Three metastructures studied: hexagonal, re-entrant, and double arrowhead. • Double arrowhead design yields up to 65% lower head acceleration under impact. • Pad systems halve weight and outperform liners in direct impact protection. • Damage maps show that double arrowhead structures delay and confine failure more effectively.