Characterization of elastic parameters of acoustical porous materials from beam bending vibrations

Dynamic visco-elastic characterization of porous material parameters shows a revival of interest since a few years. In this article, a methodology for the assessment of the visco-elastic parameters of soft, highly damped porous materials is presented. This method uses a frequency response function of a free-free bending beam. The global method is based on an inversion procedure. It consists of fitting the experimental data to the GLM computation model. In the experimental part of this work, it is explained how to take the attachment system and sensor mass into account and how to measure it. The assessment of the visco-elastic parameters needs a discrete laminae analytic model. The GLM model is described and used for a sensitivity study in relation to the visco-elastic parameters. This study gives indications for the beam dimensions design. The results, bending modulus and loss factor in the beam's main direction for various frequencies, obtained for two polymeric foams are shown and compared to results obtained with other techniques. The originality can be found in the experimental developments but also on technical developments of parameters assessment.