Dual-stage energy-absorbing corrugated-reinforced re-entrant honeycomb with enhanced stiffness

This study presents a novel bio-inspired corrugated-reinforced re-entrant honeycomb (CRH) with a unique externally attached reinforcement topology, designed to overcome the stiffness and energy absorption limitations of conventional auxetic honeycombs. Unlike previous internally reinforced or nested designs, the CRH incorporates independent wavy reinforcements along its outer boundary, leading to a previously unreported dual-stage plateau behavior under compression. Quasi-static compression tests and finite element simulations reveal that this behavior is initiated by contact between the corrugated reinforcements and inner inclined struts, followed by interaction with the horizontal ligaments. Compared to traditional re-entrant honeycombs, the CRH demonstrates approximately 10-fold higher initial stiffness, 3-fold greater plateau stress, and 2.375-fold improvement in specific energy absorption. To enable efficient large-scale analysis, a novel 3D equivalent Cauchy model (3D-ECM) is developed and validated for rapid prediction of effective elastic properties. Theoretical models based on unit cell collapse mechanisms accurately predict the dual-plateau stresses. Parametric studies identify an optimal design with a re-entrant angle of 65°, strut spacing ratio of 1.5, and strut thickness ratio of 1.0, offering superior stiffness, energy absorption, and preserved auxeticity. The CRH represents a significant advance in auxetic metamaterial design, providing a lightweight and highly efficient energy-absorbing structure for impact-resistant applications.