Experimental verification of the theory of multilayered Rayleigh waves

A phenomenon which has been termed "multilayered Rayleigh modes" has been p resented in previous papers. This study aims to prove experimentally the ex istence of these waves in anisotropic periodically multilayered media. Thes e modes result from a combination of Floquet waves which propagate in a per iodically multilayered medium when all the Floquet waves are inhomogeneous. The experimental verification was done using an acousto-optic technique an d a measurement of the reflected field, which was obtained with a hydrophon e measurement system, on a carbon/epoxy composite plate. The experimental a nd calculated dispersion curves of the multilayered Rayleigh modes were the n drawn. The coincidence of the curves was found quite good, thus confirmin g our theory. However, two modes were found by the acousto-optic technique not to fit into the theory. One experimentally detected mode was found to c orrespond to the Lamb mode of the plate and the other was not experimentall y detected by the acousto-optic technique. Measurement of the reflected fie ld for this mode, which was obtained with a hydrophone measurement system, and its comparison with the predicted reflected field make it possible to v erify the existence of the mode. The combination of both experiments permit a good coincidence to be found. (C) 1999 American Institute of Physics. [S 0021-8979(99)01314-6].