Experimental study on the design and modeling of honeycomb structures for impact force attenuation in hip protectors

Hip protectors are essential for mitigating hip fractures, particularly among elderly individuals at risk of falls. This study investigates the impact force attenuation of 3D-printed honeycomb structures in hip protectors, focusing on cell wall thickness, relative density, and orientation. The design integrates an EVA foam outer layer with a thermoplastic polyurethane (TPU) honeycomb core fabricated using fused-deposition modeling (FDM). Horizontal and vertical orientations were tested at relative densities of 12%, 20%, and 28%, with wall thicknesses of 0.4, 0.6, and 0.8 mm. Compression and impact tests showed that vertical structures offer superior impact reduction at equal relative densities. Higher densities enhanced energy absorption, while wall thickness had minimal effects within elastic and plateau regions. Notably, a vertical structure with 12% density matched a horizontal one with 28%, demonstrating effective force attenuation with reduced material and weight. These findings provide design guidance for developing lightweight, high-performance hip protectors based on 3D-printed honeycomb architectures.