Debonding Detection in a CFRP Skin-stringer Structure Using Dispersion Change of Lamb Waves Based on Mode Conversions

Abstract

In this research, the authors proposed a new debonding detection method in a CFRP skin-stringer structure. Ultrasonic Lamb waves were excited by a piezoelectric actuator and received in a highly sensitive FBG sensor, and the dispersion characteristics of the Lamb waves were evaluated over a broad bandwidth. The experimental results showed that the arrival time of S₁ mode was changed by the mode conversions when a debonding damage appeared in the skin-stringer structure. Then, the relationship between the debonding progress and the behavior of the S₁ mode was investigated by 2D FEA. As a result, it was found that the arrival time change of the S₁ mode was an effective damage index to estimate the debonding progress in the CFRP bonded structure.