Experimental and numerical investigations of bio-inspired hollow re-entrant auxetic metamaterials manufactured using laser powder bed fusion

Auxetics have been extensively studied due to their excellent mechanical properties. Researchers strive to apply them in load-bearing and energy absorption fields. However, their application has been limited by relatively low stiffness and low specific energy absorption (SEA). In this work, a bamboo-inspired 3D hollow re-entrant auxetics (HRA) and solid re-entrant auxetics (SRA) were designed, fabricated, and studied to enhance the stiffness and SEA of auxetics. First, the HRA and SRA were fabricated using additive manufacturing, and computed tomography was employed to verify their printing quality. Subsequently, the mechanical response of the HRA and SRA was analyzed through experiments and numerical methods. The results showed that, under the same relative density and key geometric parameters, the maximum improvements of SEA and stiffness for HRA compared to SRA are 147 % and 297.4 %, respectively. This methodology establishes a novel framework for advancing auxetics, with applications in civil engineering, aerospace, crash protection, etc.