Sound radiation and transmission characteristics of finite composite panels

Laminated composite and sandwich composite panels are used widely in aircraft and space structures. Corrugated panels or bead-stiffened panels are used in building structures and automobiles. In these applications, the sound transmission through such panels is an important factor in their design. Their sound radiation characteristics are also important. These panels have been analyzed earlier mostly by assuming them to be of infinite size. But in real applications, only finite panels were used. The finite size of a panel affects its sound radiation below the critical frequency and consequently it also affects the resonant sound transmission through the panel. In the present work, such panels are analyzed considering their finite size. The analysis presented in this thesis is restricted to laminated composite panels, which have no coupling between bending and twisting. Corrugated panels with corrugations in only one direction were analyzed in this work. Sandwich composite panels, which have a symmetric configuration, were analyzed as well. Statistical Energy Analysis (SEA) was used for this purpose. The dispersion relations for laminated composite, sandwich composite and corrugated panels were studied. The phenomenon known as ‘critical frequency band’ was explained. Wavenumber diagrams were plotted for various frequencies. The mode count was obtained for the panels. A frequency averaged radiation efficiency was obtained from first principles. These results were used to calculate various SEA parameters. The transmission loss of the panels was predicted by using SEA and it is compared with the experimental results obtained by other researchers. The parametric analysis and optimization of a sandwich composite panel was carried out here. The analysis in this thesis is useful in the design of panels used for various engineering applications.