RAYLEIGH-SCATTERING IN ELASTIC COMPOSITE-MATERIALS

This paper is devoted to long wave propagation in heterogeneous media. More specifically, we deal with Rayleigh diffraction in elastic mater ials with a periodic microstructure whose heterogeneities are in finit e concentration or show great contrasts in properties. This study is b ased on the homogenization method but contrary to the usual procedure in which only the first significant terms are used, the developments a re established up to the third order. We demonstrate that the terms of a superior order successively introduce effects of polarization, of c elerity dispersion and of attenuation and we thus bring to the fore a characteristic distance of mode conversion. Finally we demonstrate tha t the effect of dispersion alone appears in macroscopically isotropic materials.