Elastic parameter reconstruction in transversely isotropic plates based on laser-ultrasonic lamb wave dispersion and S1 Zero-Group-Velocity (ZGV) mode.

Elastic parameter inversion methods based on Lamb waves have been widely used to characterize the mechanical properties of plate-like composite structures. However, similar Lamb wave responses from multiple elastic parameters in transversely isotropic composites lead to an ill-posed inverse problem with reduced parameter distinguishability. This study proposes a stepwise inversion framework that combines the S1 Zero-Group-Velocity (ZGV) resonance frequency with multi-directional Lamb wave dispersion data for identifying the stiffness coefficients of transversely isotropic plates. A spectral-collocation-based forward model is applied to calculate Lamb wave dispersion curves and ZGV resonance frequencies. The sensitivities of the stiffness coefficients are evaluated with respect to propagation direction, mode type, and frequency-thickness product, thereby guiding the assignment of parameter-specific priorities. The framework is validated on unidirectional carbon fiber reinforced polymer (CFRP) plates through numerical simulations and laser-ultrasonic experiments. The reconstructed stiffness coefficients show good agreement with the reference values and strain-gauge measurements, with deviations below 4% in both numerical and experimental validations, demonstrating the reliability of the proposed method. The proposed inversion framework provides a feasible approach for characterizing elastic parameters in transversely isotropic composite plates, particularly through-thickness parameters, and may be extended to parameter reconstruction in multilayer composite structures.