Bridging-Coupling Band Gaps in Nonlinear Acoustic Metamaterials

Nonlinear acoustic metamaterials (NAMs) provide possibilities for exploiting the latest technologies for wave manipulations. Recently, the desired ultralow- and ultrabroadband wave suppressions have been achieved by chaotic bands in NAMs [Nat. Commun. 8, 1288 (2017)]. This work describes a remote interaction mechanism in NAMs: bridging coupling of nonlinear locally resonant band gaps. Theoretical studies on a triatomic model containing two nonlinearly coupled resonances clarify the principle of bridging band gaps. Bridging band gaps greatly change the nonlinear effective mass density and generate chaotic bands between nonlinear local resonances. The bandwidth and the efficiency of the wave reduction in chaotic bands can be effectively manipulated by modulating the frequency distance between the bridging pair. NAM beams are created to experimentally demonstrate this mechanism by including the bifurcations of periodic solutions. Our study extends the knowledge of NAMs, and more nonlinear effects are anticipated based on this mechanism.