High-performance 3D auxetic metamaterials enabled by multiple auxetic mechanisms

Abstract

The negative Poisson's ratio (NPR) effect can modify the deformation path and thus enhance the mechanical performance of metamaterials, which have been widely used in biomedical, aerospace, and vibration damping applications. However, designing 3D auxetic structures with NPR over a large strain range remains challenging. This study proposes a novel combined-auxetic-mechanism design method that integrates three distinct auxetic mechanisms — rotational polygonal, chirality, and re-entrant. This approach enables the effective maintenance of the NPR effect across a large strain range (0–0.8), while simultaneously enhancing mechanical properties such as load-bearing capacity, energy absorption, and fracture resistance. The innovative design allows for these mechanisms to be applied both individually or in combination, resulting in four distinct configurations of combined-auxetic-mechanism structures (CAMSs). The mechanical performances and underlying mechanisms of 3D-printed CAMSs using superelastic thermoplastic polyurethane (TPU) and plastic photopolymer were experimentally and numerically investigated. In addition, a new theoretical model capable of predicting their effective elastic modulus was developed based on energy conservation principles and verified by finite element analysis (FEA) and experiments. The experimental and simulation results demonstrate that the CAMSs containing the rotational polygonal, chirality, and re-entrant auxetic mechanisms could exhibit the NPR effect in a large compression strain range of 0–0.8, high load-bearing capacity, large energy absorption, and advantages in mitigating the effects of viscosity and reducing the risk of fracture. This research provides valuable insights for overcoming existing limitations and advancing the multifunctionality of 3D auxetic structures.