Evaluation of effective elastic properties of layered composite fiber-reinforced plastic plates by piezoelectrically induced guided waves and laser Doppler vibrometry

An approach to non-destructive evaluation of laminate composite plate elastic properties based on piezoelectrically induced elastic guided waves and laser Doppler vibrometry is presented and discussed. The reconstruction procedure is based on the genetic algorithm minimization of an objective function defined by the set of elastic moduli of the composite prepregs. The objective function defines discrepancy between theoretically calculated and experimentally measured dispersion characteristics of guided waves generated in the laminate anisotropic plate by piezoelectric wafer active sensors. The input data used for the identification are group velocities or wavelengths of the fundamental Lamb waves measured at varying excitation frequencies and propagation directions. The proposed approach has been experimentally tested on unidirectional and cross-ply carbon-fiber reinforced plastic plates and validated by conventional tensile tests.