Coherent elastic waves in a multiple scattering solid media

The propagation of elastic waves in materials containing randomly distributed particles is a fundamental topic that has been treated by many authors for several decades. In particular, the advent of metamaterials has highlighted the need to determine the effective properties of samples and in particular the effective density. In this context, we are interested in the propagation of elastic waves in an epoxy resin containing a monodisperse distribution of spherical dense particles. This kind of scatterer has two sub-wavelength resonances: the dipolar resonances in translation and in rotation. The influence of the dipolar resonance in translation on coherent longitudinal waves has already been studied previously in the team [1]. In the continuity of this work, we present here coherent transverse wave measurements and we highlight the influence of the two dipolar resonances on these coherent waves. For this, we use a new and original technique of characterization of the samples, called the technique "Sandwich" [2]. This technique, which has already shown its potential to characterize very attenuating homogeneous samples, is based on the study of Fabry-Perot interferences in the sample. The use of this technique allows us to determine not only the effective transverse wavenumber, but also the effective density and the effective shear modulus. [1] :Duranteau et al., Random acoustic metamaterial with a subwavelength dipolar resonance, Journal of Acoustical Society of America, 139, 2016 [2] :Simon et al., Viscoelatic shear modulus measurement of thin materials by interferometry at ultrasonic frequencies. Journal of Acoustical Society of America, 146, 201