Contribution à la caractérisation mécanique de matériaux poro-visco-élastiques en vibro-acoustique

Abstract

This work presents two experimental methods for the characterization of elastic and damping properties of acoustic porous materials in dynamic regime. Young's or shear moduli and structural damping coefficients of polymer foams or fibrous materials are estimated in practical conditions, i.e. in bending or shear vibrations for temperature and frequency ranges existing in buildings construction or in the transport industries. The Biot-Johnson-Champoux-Allard theory is used to describe the poro-visco-elastic behaviour of these materials, modeled as biphasic systems constituted of a solid phase and a fluid one, the air, coupled in time and space. The first method derive from the Oberst's beam one: a transverse displacement is imposed at the center of a free-free beam. A hierarchical finite element calculus and a non-linear inversion algorithm are used to estimate the material unknown parameters and to determine their evolutions in frequency and temperature. The second method is based on bending vibrations of a multi-layered plate. A simplified numerical calculus is jointly used with the previous inversion algorithm for the same purpose of elastic and damping characterization of poro-visco-elastic materials. Applications to light visco-elastic materials or various foams allow to check the relevance of these two methods compared to the existing ones and fix their limitations.