Periodic co-continuous acoustic metamaterials with overlapping locally resonant and Bragg band gaps

This Letter reports a group of triply periodic co-continuous acoustic metamaterials exhibiting simultaneous wave filtering capability and enhanced mechanical properties. We numerically demonstrate the existence of complete band gaps in these acoustic metamaterials, which is attributed to the coupling effects of local resonances and Bragg scattering. Intrinsically, the coupling effects are governed by the topological arrangements of the co-continuous structures and mechanical properties of constituent phases. We further show that the frequency tunability of the complete band gaps can be achieved by tailoring the geometrical arrangements and volume fraction distribution of the co-continuous acoustic metamaterials. This work provides a clue to the design of mechanically robust acoustic metamaterials to absorb acoustic and elastic waves under harsh environments.