Geometrically negative Poisson's ratio via laser additive manufacturing: Synergistic energy absorption through multi-scale cooperative deformation

Abstract

This study proposes an innovative negative Poisson's ratio honeycomb metamaterial characterized by a tailored geometric topology, fabricated by laser powder bed fusion (LPBF). By integrating the topological benefits of re-entrant hexagonal honeycomb structures in conjunction with star-shaped lattices, a composite structure was developed that incorporates multi-scale synergistic deformation mechanisms. The LPBF-optimized 316L stainless steel specimens demonstrated high dimensional accuracy. Quasi-static compression and dynamic impact tests demonstrated that the synergistic interaction between plastic hinge propagation within the honeycomb units and branch buckling in the star-shaped units significantly enhances energy absorption efficiency. Notably, under quasi-static loading conditions, the proposed structure exhibits a substantial enhancement in specific energy absorption compared to conventional star-shaped lattices. Finite-element analysis (FEA), corroborated by the digital image correlation technique, provided a detailed characterization of the deformation modes throughout the linear elastic stage, plateau yield region, and densification process. Furthermore, it was observed that internal voids generated during the melting and cooling of the powder contributed to strain-rate softening behavior under dynamic impact loading. This research establishes a robust workflow that integrates “topology optimization–LPBF manufacturing–experimental validation–FEA simulation,” laying a theoretical groundwork for lightweight protective structures applicable in aerospace and biomedical implants. Future endeavors may extend this methodology to encompass functionally graded material design and applications involving multi-physics field coupling.