Ultrasound and damage detection in CFRP using fiber Bragg grating sensors

Ultrasound detection using fiber Bragg gratings (FBGs) and its application to damage detection were investigated. Two types of FBG ultrasonic sensing system were constructed using different light source: a broadband light source and a tunable laser source. Ultrasonic waves generated with a piezoelectric transducer were propagated through a cross-ply CFRP and were detected by the FBG sensing systems at several ultrasonic source-sensor intervals. Furthermore, the FBG sensing systems were applied to ultrasonic inspection of an impact damaged cross-ply CFRP in order to examine their capability for damage detection. Both FBG sensing systems produced better detection of the damage in the composite than piezoelectric sensors. The FBG ultrasonic sensing system including a tunable laser possessed high sensitivity to ultrasonic wave and proved to be an alternative to conventional piezoelectric sensors in ultrasonic inspection of structural composite materials.