Measurement of the Rigidity Coefficients of a Melamine Foam

For an isotropic elastic solid, all the rigidity coefficients can be evaluated from the velocities of the shear wave and of the compressional wave. For an isotropic porous frame, the rigidity coefficients of the frame in vacuum can be evaluated from the velocities of the frame compressional Biot wave and the shear Biot wave when the porous frame is saturated by air. The velocity of the frame compressional Biot wave is evaluated at audible frequencies from the detection of the quarter compressional wavelength resonance generated with a point source in air for samples bonded on a rigid impervious backing. In a previous work, the second measured parameter was the velocity of the shear wave evaluated from the quarter shear wave resonance. In this work, the second parameter is the velocity of the Rayleigh waves slightly modified by the finite thickness of the samples, the observation of the shear resonances being difficult for the melamine foam.