Continuum Flexural Metamaterial for Broadband Low-Frequency Band Gap

Despite enormous efforts being invested in the elastic wave's band gap, achieving a broadband low-frequency band gap is still a great challenge. Previous attempts to realize a broadband low-frequency band gap have focused on specific cases, such as linkage connections, the piezoelectric effect, or elastic foundations, which cannot be extended to other meaningful advances. Herein, we propose a way to achieve a broadband low-frequency band gap without any specific conditions, but with only the continuum metamaterial itself. Our proposed idea consists of a hollow cylindrical configuration and a bow-tie-shaped part, which can be easily extended to any other vibrational systems. To explain the idea, the extended massspring system is analytically investigated, and the idea is explained in detail based on the mass, inertia, bending, and shear-stiffness values. The proposed idea is supported by various numerical simulations. In addition, experimental realization of the broadband low-frequency band gap is carried out. It is expected that the proposed idea could be utilized to realize various vibration systems, such as a low-frequency cavity, vibration shielding, or filtering devices, which can extend vibration physics at the low-frequency regime.