Multifunctional performance of 3D-printed helmet liners under impact and blast loadings

To address the growing demand for lightweight and multifunctional protection against combined blunt and blast loadings, the study designed, fabricated, and experimentally evaluated novel foam-filled helmet liner structures. Two types of liner architectures, including lattice and honeycomb, were manufactured using EPU 45 elastomer through 3D printing. Energy absorption performance was assessed through uniaxial compression tests, while impact mitigation capabilities were evaluated using low-velocity impact tests (4 m/s and 5 m/s) with a Hybrid III dummy head. Shock wave attenuation was examined using a shock tube under incident overpressures of 100 kPa and 200 kPa. The results demonstrated that honeycomb structures exhibit higher energy absorption and HIC₁₅ with a heavier weight, whereas the single-type lattice offered lower energy absorption and HIC₁₅ with reduced weight. In contrast, hybrid graded lattices achieved an optimal balanced performance, combining efficient energy absorption, reduced HIC₁₅, and a relatively lower weight. Furthermore, all foam-filled lattices achieved over 90 % shock wave attenuation efficiency. The foam-filled Kagome–Voronoi and Kelvin–Voronoi graded lattices demonstrated superior overall performance in energy absorption, impact mitigation, and shock wave attenuation within the constrained clearance between helmet and head, offering a robust theoretical and experimental foundation for the development of next-generation lightweight, high-performance helmet liners.