FE modeling of Lamb waves propagation and diffraction in viscoelastic composite material plate

A Finite Element code is used in a stationary mode to compute, at single a frequency, the stress and displacement fields in a plate made of anisotropic viscoelastic materials. An appropriated spatial load at one boundary of the plate is applied to generate a guided Lamb wave mode. The number of frequency iterations (approximate to usually less than 30) is limited by the frequency content of the excitation. Then, the temporal response at any node of the plate can be reconstructed with inverse FFT. The velocity, attenuation and nature of one or several propagating modes can be identified in the classical frequency/wave number representation. This paper shows the effect of the attenuation on the propagation of Lamb waves in a cross-ply, carbon-epoxy material plate. Focus is made on some limitations that the attenuation causes on the detection of a delamination between plies.