Investigation Of Acoustical Properties Of Two-dimensional Porous Materials

In recent years, due to their particular properties, the prospective application of porous materials has attracted more and more attention. How to accurately describe the dynamics properties of porous materials has become one of the hot topics. Compared to the abundant fruits on the deformation, fracture and damage of the porous materials, the relation between the wave propagation characteristic and the micro-topology of the materials has not been established. In this dissertation, the influence of the geometrical factor (pore shape, porosity, lattice arrangement) and the physical factor (bulk and pore material) on the x-y mode waves in the porous materials has been discussed. Firstly, assuming the bulk material is Aluminum and the pore is vacuum, the comparative studies about the waves in the porous materials with square, circular or triangular pores and different porosity and lattice structures are carried out. Then, assuming the pore medium is Hg, and the bulk materials are taken to be Al, Au, Pb, Steel and Pe, respectively, the influence of the acoustic mismatch between the pore and bulk medium on the wave dispersion in porous materials with square lattice is investigated. The following conclusions are obtained:1 Under the condition that the pore is vacuum, along with the variation of the porosity and misarranged rate, band gaps are easiest to form in the porous materials with triangular pores, and no band gaps would form in the materials with square pores;2 Under the condition that the porosity is the same, the width of the band gaps is increased with the misarranged rate for porous materials with triangular pores, but decreased for materials with circular pores; under the condition that the misarranged rate is certain, the width of the band gaps is increased with the porosity for the porous materials with triangular or circular materials;3 The band gaps are easy to form in the systems with large acoustic mismatch. The centre frequency of the band gaps is related to the velocities of the transverse waves. The faster the transverse waves are, the higher the centre frequency is.