The rapid NDT of composite aircraft components remains an important issue for the passenger aircraft industry. This paper presents the use of two thermal techniques for the rapid in-service inspection of impact damaged composite aircraft components. The apparatus required for the currently established lock-in halogen lamp technique and the newly developed lock-in ultrasonic transducer technique is described together with an appreciation of the relevant theory. Experimental samples were prepared to simulate Barely Visible Impact Damage (BVID) in composite laminates to represent material flaws in the in-service environment. The samples were then evaluated using the two thermal methods and verified using ultrasonic c-scans. The paper concludes that ultrasonic lock-in thermography is a more powerful technique to detect BVID than halogen lamp lock-in thermography. Although thermal NDT techniques do not provide a comprehensive solution to all of the rapid NDT requirements they may eventually find application for use in combination with hand held ultrasonic equipment. It is also demonstrated that thermal NDT is up to 10 times quicker than underwater ultrasonic c-scanning and may ultimately provide a solution to the problem of rapid quantitative in-service and manufacturing process inspection of composite aircraft components.
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