Low-Frequency Band Gaps in S-Shaped Strut Chiral Mechanical Metamaterials

Periodic chiral lattices possess unusual physical and mechanical properties for elastic wave control and attenuation. Here, an S-shaped strut chiral mechanical metamaterial (SSCM) with compression-torsion coupling (CTC) effect designed by mirror symmetry is proposed. Based on finite element (FE) theory and Bloch’s theorem, a kinetic model of chiral metamaterials is developed to analyze the band structure, band gap formation mechanism and transmissibility response. The results show that the proposed metamaterial generates an omnidirectional band gap with a width of 519 from 182 to 701 Hz. In the band gap edge vibration modes, it can be observed that the energy localization effect caused by the CTC effect prevents further propagation of the elastic wave. In addition, the tuning of geometric parameters can effectively adjust the bandgap frequency position and bandwidth. Finally, a vibration experimental setup was established, and the vibration attenuation and numerical analysis was experimentally verified. This study opens up a potential way to manipulate elastic waves in the low-frequency range.