Structural–acoustic optimization of sandwich cylindrical shells for minimum interior sound transmission

This paper presents an optimization study of cylindrical sandwich shells to minimize the transmitted sound into the interior induced by the exterior acoustic excitations. The boundary elements and finite elements are, respectively, used to model the interior and exterior acoustics and the vibration of the shell. The design parameters of the optimization are the reinforcement angles of the orthotropic composite materials of the skins and core. The sensitivity analysis of the objective function with respect to the design variables is computed by the adjoint-variable technique. The optimizations of the shell at a single frequency and in a band of frequencies are investigated. From the promising optimization results it is seen that the reinforcement angles in the composite sandwich layers are effective structural design parameters to minimize the sound transmission into the interior without giving up the structural rigidity, particularly at low frequencies where the structural damping is not effective.