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Abstract- This research develops a Lamb wave technique to determine the dispersion curves of a two layered bonded component: an aluminum sheet attached to a composite layer by means of a cohesive. A commercial finite element code (ABAQUS Explicit) is used to determine the dispersion curves of the Aluminum-cohesive-composite multilayer component. The finite element model includes three plain strain layers that the middle one is cohesive. Then a lamb wave is propagated in the model and some output signals are received. The dispersion curves are obtained by using 2D Fourier transformation of finite element model output signals. In addition, to produce various modes, experiments are carried out on a composite-aluminum assembly using two 2 MHz variable angle transducers. Comparison of modes obtained from finite element method and experiments shows that group velocities are almost identical. Hence, good agreement between finite element method results and experimental results indicates that finite element is reasonably accurate for determination of dispersion curves.

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The equations of Lamb wave propagation in an infinite isotropic micro plate with finite thickness on the basis of consistent coupled stress theory is presented in this study. By employing the characteristic length scale parameter, the effect of micro-plate size is considered, and thereby the effects of different plate dimensions on the dispersion of Lamb waves is illustrated. Lamb wave propagation velocity in aluminum nitride micro-plates has received many interests due to its applications in surface acoustic resonators. In the current work, at first, the dimensionless relations are developed through the definition of dimensionless parameters where the extracted curves can be applied to all thicknesses, propagation wavelengths and characteristic length scale parameters of a micro-plate. In addition, using the quasi-static approximation, the Lamb wave dispersion curves in both symmetric and asymmetric modes for an aluminum nitride micro plate are plotted and compared with the results from the classical theory. The integrity of the present formulation is verified by comparing the obtained results with the experimental data in the literature. Finally, by employing the dispersion curves and the reported experimental data, a novel method has been proposed to determine the size of characteristic length parameter in the consistent coupled stress theory.