Auxetic metamaterials with double re-entrant configuration

Abstract

The load-bearing and deformation behaviors of structures and materials play a decisive role in their applicability. While re-entrant auxetic structures—a classic type of mechanical metamaterials—exhibit impressive mechanical properties, their functionality has traditionally been constrained by a single stress plateau under compression, limiting their multifunctional applications. In this study, we present an auxetic metamaterial with a double re-entrant configuration (DREC), engineered to achieve dual stress plateaus while preserving auxeticity, setting it apart through its simplicity and self-similarity. This metamaterial shows distinct two-phase behavior under quasi-static compressive loading, delineated as phase I and phase II. By leveraging stacking and symmetry programming of the DREC, we construct multi-cellular variants that possess additional phases, unlocking multi-step deformation characteristics driven by the formation and transformation of new configurations and showing a significant improvement in specific energy absorption over the conventional re-entrant configuration. Theoretical models, based on Euler beam and plastic hinge theories, have been developed that effectively capture the mechanical behavior of the DREC metamaterials. This work opens new avenues for engineering applications that demand adaptable and high-performance mechanical responses.