Low-frequency broadband acoustic modulation mechanism of composite pentamode metamaterials

In this paper, an acoustic bandgap (ABG) manipulation method for pentamode metamaterials is proposed, by which a composite pentamode metamaterial with the low-frequency broadband can be obtained. Combined with the spring-mass model, the generation and regulation mechanism of the low-frequency ABG is analyzed, and the approximate relationship between the ABG and the structural parameters is obtained. The effects of the narrow diameter ratio (n) and the soft material height ratio (r, s) on the first ABG are calculated by using the finite element method. The simulation results are in good agreement with the theoretical predictions. Through the ABG modulation method, a low-frequency ultra-wideband PM structure in the range of 43.91 similar to 299.26 Hz can be obtained without changing the structural parameters. The proposed mechanism provides theoretical guidance for PMs to widen the low-frequency bandgap and modulate the ABG frequency range.