Vibration isolation and energy directional propagation in three-dimensional hollow sphere arrays

Multifunctional design of hollow structures is the hot topic in the lightweight structure design. In this paper, based on the excellent mechanical properties of hollow sphere arrays (HSAs), the wave dispersion in squarely stacked hollow sphere arrays is investigated. Instead of using binders, the spheres are closely packed together. First, the existence of absolute band gaps and correctness of numerical simulation for wave dispersion in HSAs are verified by the experiment. Then, the absolute band gap evolution in aluminum HSAs with respect to dimensionless geometric parameter is discussed. The two- and three-dimensional wave directional propagation in HSAs are realized by introducing defect spheres, and corresponding transmission spectrum is given to demonstrate the availability of directional propagating along specified paths. The results show that wide low-frequency absolute band gaps exist in the HSA, and excellent directional wave propagation along two- and three-dimensional preset complex paths is obtained through introducing designed defect spheres. The results obtained in this paper provide a simple but flexible and effective way for elastic wave propagation modulation, both in terms of vibration isolation and complex directional wave propagation. It also shows prospective application in the acoustic-mechanical multifunctional design of HSAs.