Evaluation of carbon fiber composite repairs using asymmetric-frequency ultrasound waves

A novel asymmetric-frequency ultrasonic (AU) technique was developed for the nondestructive testing and evaluation of carbon fiber composite repairs. Experimental studies were conducted using the established AU system to repair specimens with and without natural debonding. The time-domain characteristics of the AU echo signals, cross-sectional imaging characteristics, and their variations from the repaired areas were analyzed. The results show that the echo signals from repaired zones had close to quasi-single period in AU-2F–5F mode. The cross-sectional geometric topologies of the repaired areas and morphologies of debonding in the specimens were visualized and evaluated well using the AU technique.