A fully coupled finite element-boundary element vibro-acoustic analysis for laminated composite structures with enclosed acoustic cavities

Abstract

A major contribution of aircraft cabin noise is due to the vibrating airframe structure in which the use of lightweight composite materials is quite common. Due to the strong influence of such vibrating structures on the enclosing fluid, such as air, and vice-versa, a fully coupled analysis involving both the systems is necessary in many cases. Hence the present work details a fully coupled vibro-acoustic analysis of such type of flexible cavity subjected to the external mechanical excitation based on a coupled finite element (FE) and boundary element (BE) approach. The structural mode shapes and eigen frequencies are computed using the FE free vibration analysis of in-vacuo structures, which are subsequently coupled through the mobility equation with the acoustic part modeled with the BE method. The developed approach is also well compared with the fully coupled FE approach but the advantage derived here is that it is sufficient to model each domain independently thus reducing the problem dimension. The discussed method ensures full coupling between the two systems considering the cavity acoustic back pressure and also enables a fully coupled analysis of a double-walled structure attached to an acoustic cavity which resembles a true aircraft cabin.