Quantitative damage detection in cross-ply laminates using Lamb wave method

This paper investigates the effects of transverse cracking and delamination on the S0 mode velocity in GFRP and CFRP cross-ply laminates. We found experimentally that both the stiffness and the velocity decreased as the transverse crack density increased. In contrast, the stiffness decreased but the velocity increased as the delamination length increased. We analytically deduced the relationship between the velocity and the crack density from a combination of a shear-lag analysis and the classical plate theory. We also confirmed that the Lamb wave propagated through the 0° layers in the delaminated regions, and formulized the relationship between the velocity and the delamination length. The predicted crack density and delamination length using the measured velocity were in good agreement with the experimental results. This method is simple and promising for structural health monitoring of composite structures.