Design of a defect containing bi-material nested structure phononic crystal with adjustable band gap

In this work, a bi-material nested square phononic crystal structure containing defects with adjustable band gap is proposed. Defects are achieved by opening different numbers of square holes at different locations at the unit cell interior. Based on Bloch’s theorem, the propagation wave behavior of the bi-material nested structure with defects is discussed using the finite element method (FEM). The effects of the number of square holes, the location of defects, the shape of nested lattice and the density of filled metal materials on the band gap distribution are studied. In order to verify the existence of band gap, low amplitude elastic wave propagation experiment is made by 3D printing technology. The results show that non-overlapping band gaps appear in the bi-material nested structure with defects within 1000 Hz by changing the defect position and the number of square holes, and the switching control effect of frequency 500–1000 Hz band gaps is realized. The effect of filler metal density on the band gap is discussed on the basis of I-type phononic crystal structure, which provides design support for the application requirements of different working conditions. When the surface area of filled metal material is 52 % of the total surface area, circular nested phononic crystal band gap modulation works best. The experimental and simulation results are consistent to verify the existence of band gap. These findings can provide new ideas for the design of vibration damping metamaterials.