J0402-3-1 Delamination detection in composite laminates using the change in the frequency dispersion of broadband Lamb waves by mode conversions

The authors have constructed a broadband ultrasonic propagation system using MFC actuators and FBG sensors. These components can be integrated into composite laminates. In this research, we used this system to detect delamination damage in a CFRP quasi-isotropic laminate. First, we identified the multiple modes of Lamb waves in the laminate by transmitting and receiving the symmetric and antisymmetric modes separately. Then the mode conversions at both tips of a delamination were investigated. After that, we proposed a new delamination detection method based on mode conversions and carried out experiments on laminates with an artificial delamination. The frequency dispersions of the received modes changed depending on the delamination length owing to the mode conversions. Since these phenomena were also confirmed by FEA, our new method is effective in detecting a delamination in CFRP laminates.