Design and analysis of pneumatic composite phononic crystal

Tuning band gaps in soft phononic crystal by air pressure-induced deformation is a feasible method to manipulate elastic waves. In this paper, we design a pneumatic composite phononic crystal that incorporates a labyrinthine structure into the Helmholtz-type phononic crystal. By calculating the band gaps of the representative volume element (RVE) arranged in a two-dimensional triangular lattice, we find that this design effectively extends the transmission path of sound waves, achieving band gaps in the vicinity of the lower frequency range. We apply pressure to the scatterer's pneumatic actuator to adjust its volume through the deformation of soft material, altering the air filling rate and enabling reversible adjustment of the frequency and width of band gaps. Nonlinear finite element simulations investigate the effects of different pressure levels on the band gaps. Furthermore, we explore bandgaps tuning in one-dimensional phononic crystals and the impact of various types of point defects on the transmission characteristics of phononic crystals. Results show that the pneumatic phononic crystal exhibits rich band gaps under air pressure loading, in which a low-frequency band gap exists, and is capable of reversible continuous tuning. This study provides valuable for manipulating elastic waves in periodic structures and designing soft acoustic devices.