Nonlinear Vibro-Acoustic Analysis of Composite Sandwich Plates with Skin–Core Debondings

Abstract

A numerical model was developed for nonlinear vibro-acoustic analysis of a skin–core debonded sandwich plate immersed in an infinite fluid and subjected to time-varying loads. The structural model of the plate was formulated using a modified variational principle in conjunction with a multilevel partitioning procedure. The nonlinear contact constraints on the detached interfaces of the plate were imposed by using the Nitsche’s method. This led to a stable contact solution that does not depend on the penalty parameter as strongly as in the traditional penalty approach. A time-domain Burton–Miller boundary integral formulation was employed to couple with the structural model of the plate to determine the acoustic field, which avoids spurious instabilities in long-time simulations. Comparisons of the present results were made with solutions obtained from finite element analyses. The results show that both the structural and acoustic responses of a sandwich plate can be significantly affected by the presence of a debonding. For a debonded sandwich plate under harmonic excitation forces, the vibration and acoustic responses of the plate consist of not only the fundamental excitation frequencies, but also subharmonic and superharmonic components and combination harmonics of the excitation frequencies. The effect of the debonding size on the nonlinear vibration and acoustic-radiation responses of sandwich plates was investigated.