Prediction of the six parameters of an equivalent fluid model for thermocompressed glass wools and melamine foam

The thermo-compression manufacturing process of sound absorbing materials modifies greatly their micro-geometry, and in particular the fiber orientation and alignment. The parameters that characterize such materials in equivalent fluid models vary therefore according to the compression rate. Here the Johnson-Champoux-Allard-Lafarge (JCAL) model is used with six parameters: porosity, resistivity, tortuosity, characteristic lengths and static thermal permeability. Instead of measuring all the parameters at different compression rates, a compression model is presented to predict all the parameters after compression from the initial parameters. The model also addresses the effect of fiber orientation. Finally the formulas proposed for each parameter are validated on two commonly used materials in the automotive industry, a glass wool and a melamine foam, at high compression rates.