Thickness Optimization for Multilayered Structures Located on the Coupling Surface Between a Structure and an Acoustic Cavity

This paper describes a new design method for optimizing the thickness distribution of a multilayered structure located on the coupling surface between a structure and an acoustic cavity. The design method is based on the concept of a topology optimization method incorporating a transfer matrix for the multilayered structure that includes a poroelastic media layer. The one-dimensional transfer matrix adopted here is an approximate representation addressing vibro-acoustic effects inherent in a multilayered structure over a range of low frequencies, and balances calculation times and desired accuracy. In this study, the problem of minimizing the acoustic pressure within the cavity over the prescribed frequency range is formulated under the constraint of the total weight of the design domain. The thickness of the poroelastic media layer at each nodal point is chosen as the design variables. Numerical results show that acoustic response is significantly reduced by an optimal thickness distribution having a total weight equal to or less than that of the initial thickness.