Study on multi-bandgaps and elastic wave suppression characteristics of sawtooth-shaped acoustic metamaterials

Acoustic metamaterials can achieve elastic wave absorption and vibration isolation across a wider frequency range through artificially designed units, compared with traditional vibration isolation materials. Two novel sawtooth-shaped acoustic metamaterials are proposed, and called cross-core sawtooth acoustic metamaterial (CSAM) and ring-core sawtooth acoustic metamaterial (RSAM). These metamaterials effectively generate multiple bandgaps at low (0–250 Hz), mid (250–2000 Hz), and high (2000–3300 Hz) frequency ranges. Finite element method (FEM) is used to analyze their bandgap characteristics and transmission loss. Bandgap rates of CSAM and RSAM in various frequency bands are defined and analyzed to better study their bandgap characteristics. The dissipation effect of elastic wave is analyzed through the frequency response. Vibration modes of the two metamaterials when the bandgap is open and closed are analyzed, revealing the potential mechanism. That is, the dissipation of elastic wave propagation energy is achieved through torsion and deformation of the central scatterer, coupled with mutual interaction of multiple vibrational modes. Finally, the propagation characteristics of waves are analyzed using equifrequency lines, propagation directions, and group velocities. The proposed acoustic metamaterials exhibit exceptional bandgap performance across low, mid, and high frequencies, providing a viable solution for vibration control under complex operational conditions.