Contactless inspection of CFRP artificial disbonds using combined laser thermography and laser ultrasonics with optical microphone

Precise and efficient inspection of disband defect in sub-mm layers of composite structures is a big challenge for the non-destructive and testing industry. In this work, 16 artificial disbands (flat bottom holes), with different sizes and depths, in carbon fiber reinforced polymer (CFRP) composites were contactless detected using combined laser thermography and laser ultrasonics with optical microphone. The presented laser ultrasonic technique employed a membrane free optical microphone is a contactless and nondestructive technique and shows high detectability for flat bottom holes with deep depth in this preliminary investigation. Sizes and depths of the flat-bottom holes were determined by the presented laser ultrasonics technique. This investigation combined the high detection efficiency of laser thermography and high detection sensitivity of laser ultrasonics with the optical microphone together for the contactless inspection of artificial disbonds.