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Noncontact Debonding Identification in Adhesive Joint using Guided Waves

This study proposes a debonding identification method in adhesive joints by utilizing a complete noncontact laser ultrasonic measurement system. This measurement system consists of a Q-switched Nd:YAG laser for ultrasonic wave generation and a laser Doppler vibrometer (LDV) for ultrasonic wave detection. The distance between the two laser beams, shot for wave generation and detection, is kept as a constant and they are synchronously scanned over the target adhesive joint. Energy features is then extracted from the acquired ultrasonic waves to present the difference induced by debonding problem. This proposed method has following advantages over the existing techniques: (1) it owns higher and more stable signal to noise ratio; and (2) debonding identification can be realized by spatial comparison and without relying on any baseline data got from pristine condition. It is successfully demonstrated by detecting debonding problem in several adhesive joint specimens.