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In the car design process, damping treatments have to be optimized as part of the sound package in order to reduce vibrations and sound generation of the car body panels. The simulation technique presented determines the effects of multi-layer damping treatments and represents them in terms of equivalent single-layer material characteristics. The procedure allows the temperature-and frequency-dependent characteristics of all individual materials to be taken into account as well as effects caused by panel curvature or panel stiffeners. The resulting data can be applied subsequently in overall car-body FEM-simulations, thus accounting for all damping effects without complicating the model.

Multi-layer insulation systems are widely used in many industrial sectors (particularly in automotive and aeronautic industries). They have a complex dynamic behavior due to the use of different materials like visco-elastic, poro-elastic and acoustic layers. The interface conditions between these materials play also a significant role in the global behavior. The paper concentrates on modeling poro-elastic layers using a 3-D finite element (FE) approach. A Biot model is selected for that purpose. A mixed displacement formulation is used. This can easily be coupled with other FE sub-models related to elastic thin shell layers or acoustic layers. Applications related to the prediction of the surface impedance of multi-layer configurations are presented.