Buckling-regulated bandgaps of soft metamaterials with chiral hierarchical microstructure

Abstract

In traditional phononic metamaterials, elastic wave bandgaps are usually tuned by introducing periodic rigid inclusions in a soft matrix, but they are difficult to adapt to the changes of external mechanical environments. In this paper, inspired by the strategies of biological materials to achieve specific functions, we propose a kind of soft metamaterials with chiral and hierarchical structures. Their elastic wave bandgaps can be easily regulated in a larger space of frequency by means of the postbuckling-induced evolution of microstructures under loading. The postbuckling behavior of chiral hierarchical structures is investigated through finite element simulations and compared with those of symmetric hierarchical structures. The stress–strain curves, the phase diagram of uniaxial critical compressive strength, and the tunable elastic wave bandgaps of the proposed metamaterials are analyzed.