Full paper – A hybrid elastic metamaterial with tunable bending stiffness

Achieving vibration and/or wave attenuation with locally resonant metamaterials has attracted a great deal of attention due to their frequency dependent negative effective mass density. Moreover, adaptive phononic crystals with shunted piezoelectric patches have also demonstrated a tunable wave attenuation mechanism by controlling electric circuits to achieve a negative effective stiffness. In this paper, we propose an adaptive hybrid metamaterial that possesses both a negative mass density as well as an extremely tunable stiffness by properly utilizing both the mechanical and electric elements. The tunable wave manipulation abilities are investigated and revealed in terms of both the effective negative mass density and/or bending stiffness of the hybrid metamaterial. The programmed flexural wave manipulations and broadband negative refraction are then illustrated through three-dimensional (3D) multi-physical numerical simulations in hybrid metamaterials. Our numerical results demonstrate that the flexural wave propagation can essentially be switched between “ON/OFF” states by connecting different shunting circuits.