Dynamics of incoherent elastic layers

A transversely isotropic plate is said incoherent when the transverse isotropy material axis is at an angle with the geometrical axis orthogonal to the plate cross section. In this paper two plate theories for the free-vibration of such plates are formulated. These theories are based on two different representations for the displacement field, both consisting in first-order polynomials in an axial coordinate along, respectively, the material axis and the geometrical axis. The effects of incoherence on free-wave propagation are investigated in a three-dimensional layer, and the results are used as a benchmark to test the accuracy of the two plate theories.