Air-coupled ultrasonic infrared thermography for inspecting impact damages in CFRP composite

Ultrasonic thermography or thermosonics is proved to be an effective non-destructive testing (NDT) method for inspecting carbon-fiber-reinforced polymer (CFRP) composites; however, the potential damages for the structure cannot be ignored, because of the contact vibration between the ultrasonic horn and the specimen. This work aims at developing a new excitation method for ultrasonic thermography-aircoupled ultrasonic excitation. CFRP laminates with impact damages are tested by air-coupled ultrasonic thermography, and the theoretical model of heat conduction is given. Results demonstrate good excitation performance for impact damages detection in CFRP composites. Moreover, the conventional ultrasonic thermography results are shown, and the prospect of air-coupled ultrasonic thermography is discussed.