Sound transmission through finite laminated composite panels using statistical energy analysis

Abstract

Laminated composite panels are widely used in aerospace structures and other applications where weight reduction of the structure is desired without compromising the strength. They can be made up of a number of layers of unidirectional laminas. Sound radiation and sound transmission properties of these panels are different than those for isotropic panels. This is because of the variation of the material properties along the direction of bending wave propagation. During this work, analysis of those finite laminated composite panels which exhibit uncoupling of bending/twisting phenomenon is done. A bending wave number diagram is drawn to study the variation of bending wave number with respect to the angle of bending wave propagation for a given frequency. Instead of a single critical frequency as in the case of an isotropic panel, a band of critical frequencies is observed. In this band of critical frequencies, coincidence occurs only at a certain angle of bending wave propagation for a particular frequency. Frequency average radiation efficiency of such a panel is predicted by considering the variation of wave number along different directions of bending wave propagation. Modal density is predicted from the bending wave number diagram. Transmission loss of the panel is predicted using the statistical energy method.