Periodic composite structures like acoustic metamaterials (AMMs) and phononic crystals (PCs) are able to forbid the propagation of sound and elastic waves for some specific frequency ranges, leading to the emergence of so-called band gaps. So far, the optimization to attain sought band gaps, has been performed on passive PCs and AMMs. Hence, the band gap properties cannot be changed anymore after the production process of the materials. This problem can be overcome thanks to the use of active materials. In this work, both material and geometric non-linearities are exploited to actively tune the frequency ranges of the band gaps of an AMM characterized by a three-dimensional periodicity. Specifically, a piezoelectric hyperelastic composite, obtained by embedding piezo-nanoparticles in a soft polymer matrix, is adopted to assess the effect of nonlinearities on the behavior of sculptured micro-structures, taking also advantage of instability-induced pattern transformation and piezoelectricity on the active tuning of the band gaps.

Keywords: acoustic metamaterials, hyperelasticity, multi-physics, piezoelectricity, buckling