Chiral trabeated metabeam for low-frequency multimode wave mitigation via dual-bandgap mechanism

An elastic wave in a physical beam naturally possesses many wave modes, such as flexural, longitudinal, and torsional. Therefore, suppression of all possible vibration modes has been rarely achieved in beam-shaped periodic systems, especially at low frequencies. Here we present a low-frequency complete bandgap mechanism by overlapping the flexural bandgap with the longitudinal-torsional bandgap. To strengthen the general framework, we enforce an extra degree of freedom (rotational and torsional-spring) on the spring-mass system for the flexural and coupled (longitudinal-torsional) modes. The low rotational stiffness provides a low flexural bandgap, whereas the torsional stiffness yields a coupled-mode bandgap. To meet these prerequisites in physical modeling, a chiral trabeated metabeam is conceived, which allows all wave modes to be suppressed by a complete bandgap. Apart from single-mode mitigation, our work provides a route to implementing a low-frequency complete bandgap in a periodic fashion, potentially enabling the use of chirality in elastic structures. Engineering the mechanical response of metamaterials allows control of mechanical modes, with potential application to vibrational isolation. Here, a general framework for achieving a complete band-gap by combining orthogonal flexural and longitudinal-torsional band-gaps is demonstrated analytically and experimentally.

Automated summary

This article presents a mechanism for achieving a low-frequency complete bandgap by overlapping the flexural bandgap with the longitudinal-torsional bandgap. A chiral trabeated metabeam is constructed in the physical model to suppress all wave modes. This work provides a route to implementing a low-frequency complete bandgap in a periodic fashion, with potential applications in elastic structures.