Abstract
For damage detection in CFRP laminates, health monitoring techniques using Lamb waves are effective. In this research, the authors constructed a new system combining a macro fiber composite (MFC) actuator and a fiber Bragg grating (FBG) sensor to employ broadband Lamb waves from DC to 1MHz. Then this system was applied to a CFRP quasi-isotropic laminate to examine the broadband characteristic. As a result, this system proved to be able to send and receive more broadband ultrasonic wave than conventional systems using bulk PZTs. Moreover, we investigated the frequency dispersion characteristic of Lamb waves propagating in the CFRP laminate in more detail by sending narrowband ultrasonic waves with different center frequencies. As a result, we could identify the modes of Lamb waves, comparing the measured frequency dispersion curves with the theoretical dispersion curves. After that, the dispersion curves were measured for the CFRP laminate that included an artificial delamination. Since the result measured in the damaged laminate had different dispersion from the result in the intact laminate, the delamination could be detected from the frequency dispersion curves. Hence this system can obtain more effective information for damage detection.
