Detection of Delaminations in CFRP Laminates by Using FBG Sensors as Lamb Wave Receiver

Lamb waves can propagate for long distance and change its waveform depending on the existence of damages within the propagation path. Hence, from the change in the waveform, the damages inside a structure can be detected. In this research, a new health monitoring system using piezo-actuators and fiber Bragg grating (FBG) sensors was developed. Piezo-actuators on the surface of a composite laminate generate Lamb waves into the laminate. Then the propagated waves were received by FBG sensors attached on it. From the change in the waveform, damages are detected. As preliminary researches, the appropriate gauge length of the FBG sensor for receiving Lamb waves was determined by theoretical calculations and experiments, and the directional sensitivity of the FBG sensor was evaluated. Then the authors succeeded in detecting a delamination in a CFRP cross-ply laminate by monitoring the change in the waveform received by an FBG sensor.