Modeling the Vibro-Acoustical Behavior of Composite Multi-layered Systems

Composite multi-layered systems are of particular interest in the automotive industry since the design of the various components in an efficient sound package requires a good predictive model. The state of the art in this matter shows that the medium and high frequency ranges are well mastered in terms of predictive tools based on infinite models. But this is not the case for the lower frequency range.

The paper will start with a discussion of the medium and high frequency range where, for example, the Transfer Matrix Method (TMM) is an efficient framework to predict the acoustical properties of multi-layer materials. Emphasis will be put on correlation data obtained with a variety of multi-layer systems.

In the low frequency range the use of infinite models leads to significant discrepancies. In the present paper the authors propose a finite “hybrid type” formulation which combines the advantages of both single layer and multi-layer approaches of stratified composite structures. From a structural point of view, the description includes the effect of bending, membrane and shear waves by means of the displacement field. The generality of the composite is extended to include anisotropic properties. The Rayleigh-Ritz method is used to derive the equations of motion. One of the features of this method is that the size of the system involved in the calculation does not increase with the number of layers. The vibro-acoustical behavior can then be deduced to give the main acoustical properties of the multi-layer material. The efficiency and the application of the proposed modeling method will be illustrated.