Numerical hybrid TMM-modal finite element method prediction of the vibroacoustic of sandwich panels with add-on damping

This paper discusses the numerical modeling of the vibroacoustic response of sandwich-composite panels with add-on damping, under a diffuse acoustic field (DAF) excitation. A modal synthesis approach is used for the calculation of the structural response and the Rayleigh’s integral is used for the acoustic response. Since the panel has a viscoelastic core, a methodology is presented to handle efficiently the modeling of the frequency depended properties of the viscoelastic layer. A hybrid TMM-modal FEM method is used to predict the acoustic response at high frequency, using the equivalent damping of panel which are calculated from strain energies. Next, a parameters study on the effect of the viscoelastic layer location is presented. In particular, three locations are compared: within the Honeycomb core, within the skins and added to the skin with a constraining layer. The effects of the excitation type on the vibration and acoustic response are also discussed. Key words: Sandwich NIDA, Modal FEM method, TMM method, viscoelastic damping, acoustic response, equivalent properties.