Study On The Characteristics Of Phononic Crystal's Bandgaps

The phononic crystal is a kind of media with bandgap characteristics, and it has drawn high attention of different nations'research institutions and scholars for its high potential in the application of shock absorption and noise control.The formation of the bandgap of locally resonant phononic crystals has great theoretical value. The arrangement of the scatters has very little influence on the characteristics of the phononic crystals'bandgaps. Because of the inner negative reflection mechanism, the lattice constant is one or two orders smaller than the wavelength of the wave which lies in the bandgaps. Thus, this kind of phononic crystals has many advantages in the application of shock absorption and noise control in low frequency.This thesis mainly studied the characteristics of metal sphere/silicone rubber/epoxy resin locally resonant three dimensional phononic crystals. The theoretical regularities are proved in experiments, and some good experimental results are also achieved.Regularities of the influence of the parameters such as component materials and lattice structures on the bandgap characteristics are studied theoretically. The study indicates that, while using the same matrix material, the frequency range of the first bandgap will be lower but broader if the density of the vibrating spheres is higher, and it will be lower and narrower if the Lamécoefficient of the coating material is smaller.The result of systematically theoretical calculations indicates that, while fixing the filling fraction, the physical parameters of the scatters'component materials will be the decisive factors of the bandgaps'characteristics, and the arrangement of the scatters in three dimensions will have little influence on the first bandgap.It is found that the lower edge of the bandgap depends on the structure and the component materials of the scatters. Using the same scatters, the upper edge depends on the filling fraction and the bandgap becomes narrower while reducing the filling fraction and broader while increasing the filling fraction.Regularities of the influence of the materials of the coating layer and of the vibrating spheres on the characteristics of the bandgaps of three components locally resonant three dimensional phononic crystals are also proved in sonic experiments. The experimental result indicates that highly effective sound insulation will be achieved if the sound powers the scatters directly. It is also found that, the lower the Lamécoefficient of the coating material is, the lower the resonant...