Impact resisting mechanism of tension–torsion coupling metamaterials

Tension–torsion coupling (TTC) metamaterials are man-made architectures that exhibit unexpected rotational deformation when subjected to unidirectional loads. Since their discovery, numerous studies have been conducted to investigate the static properties of TTC metamaterials resulting from this twisting effect. However, research on their dynamic properties, particularly in terms of impact resistance, has been limited with little understanding of the underlying mechanisms. In this study, we performed simulations at different length scales to quantitatively analyze the energy flow during impact and gained insights into the mechanisms of energy damping and impact resistance. Our simulations demonstrate that the twisting effect of cellular materials generally leads to reduced stiffness, which is advantageous for improving impact mitigation. Furthermore, we discovered that the unique chiral characteristics of TTC metamaterials enable a greater amount of strain energy to be stored during impact, and this portion of energy will be ultimately dissipated through after-impact vibrations. Additionally, we found that energy dissipation via friction between lateral struts or ligaments, although less significant, is enhanced by the TTC effect. The current study provides a preliminary analysis of energy flow and sheds light on the mechanisms underlying the energy damping and impact resistance of TTC metamaterials. These findings not only contribute to a better understanding of the dynamic properties of TTC metamaterials but also have practical implications for the advanced design of impact resistance structures.