Inverse characterization of the damping performance of porous materials

Abstract

Porous materials are traditionally used in industry for their sound absorption and insulation properties. Over the past decade, more attention has been given to their elastic and damping properties. There is a particular interest in the automotive industry to replace heavy layers (consisting of constrained viscoelastic rubber layers) with felts or foams evidencing high damping capabilities. Hence, characterizing efficiently the viscoelastic properties of porous materials is crucial for purposes of quality control and for further improvements in product development and fabrication. The goal of this work is to propose an experimental-numerical method for inverse characterization of the frequency dependent properties of porous materials. The proposed inverse approach is based on a fractional derivative model whose parameters are identified to minimize the difference between the simulated and the measured dynamic response of a porous layer bonded to an elastic structure. Vibration tests are carried out on simply supported panels with a free layer of porous material. The corresponding finite element simulations consider only the viscoelasticity of the porous skeleton and neglect the influence of the fluid phase. The proposed methodology is tested on two different porous materials: an open-cell melamine foam and a closed-cell polyurethane. The results of the inverse characterization are compared to the viscoelastic properties identified by dynamical mechanical analysis.