An efficient tool for predicting the structural acoustic and vibration response of sandwich plates in light or heavy fluid

The vibroacoustics of a plate covered by a free or a constrained viscoelast ic layer is analyzed in this article. A variational model, solved by the Ra yleigh-Ritz method, is proposed for the case of a rectangular, baffled, sim ply supported multilayered plate immersed either in a light fluid or in a h eavy fluid. In order to simplify the theoretical formulation, approximate a ssumptions are made regarding the calculation of the strain energy of the p late. These assumptions are inspired from Ungar's work on viscoelastically damped beam. They allow the equation of motion of the plate to be expressed in terms of one unknown displacement while most of the classical variation al models use at least five unknown displacements, Hence, the size of the m ass matrix and of the stiffness matrix are reduced and the computing time i s decreased. The radiation of sound from the plate is rigorously calculated with the method of Sandman and Nelisse which makes high frequencies attain able without convergence problems, Theoretical validations of the proposed model are made using a well-known multilayered plate model. In addition, ve ry precise experiment set up allows the measurement of the vibration respon se of two sandwich plates that reveal the precision of the proposed model a nd present the type of damping achievable with commercially available visco elastic material. (C) 1998 Elsevier Science Ltd. All rights reserved.