Journal of Sound and Vibration vol:333 issue:24 pages:6560-6571
The aspects related to the frequency dependence of the elastic properties of porous materials have been largely neglected in the past for several reasons. For acoustic excitation of porous materials, the material behaviour can be quite well represented by models where the properties of the solid frame have little influence. Only recently has the importance of the dynamic moduli of the frame come into focus. This is related to a growing interest in the material behaviour due to structural excitation.
Two aspects stand out in connection with the elastic-dynamic behaviour. The first is related to methods for the characterisation of the dynamic moduli of porous materials. The second is a perceived lack of numerical methods able to model the complex material behaviour under structural excitation, in particular at higher frequencies. In the current paper, experimental data from a panel under
structural excitation, coated with a porous material, is used in correlation with numerical predictions, involving a frequency-dependent material model for the stiffness properties of the porous material.
The results suggest that the frequency dependence is of importance for a correct prediction of the response of trim installations. The change in material behaviour due to the frequency-dependent properties is illustrated in terms of the propagation of the slow wave and the shear wave in the porous material.