Evaluation of NDT by Robotic Line Scan Thermography on Composite Aircraft Parts

Abstract

Non-destructive testing ensures the structural integrity and reliability of composite structures produced in the aerospace industry. Conventionally adopted inspection techniques, such as water-coupled ultrasonic installations using a water jet, are not optimized for the complex geometries of newly emerging composite parts and are characterized by long inspection times and expensive equipment investments. A promising alternative is line scan thermography (LST), which can serve as a relatively quick, low-cost and efficient NDT method for curved monolithic and sandwich CFRP panels with a limited thickness. This paper describes the evaluation of an industrial prototype developed to perform LST inspections on a couple of reference aircraft parts embedded with artificial defects. Initial tests have shown that the complete LST inspection of surface areas up to 1.4 m2 takes around 15 min. In this way, the inspection time of a bottom panel and monolithic root fairing could be cut back by 80% and 70% respectively compared to conventional ultrasonic inspection methods. Inspection depths up to 6 CFRP plies, approximately 1.5 mm, were achieved for artificial defects as small as 4 mm in diameter (except for the inclusion defects ‘separator film’and ‘polyethylene’). Results are expected to improve even further once the inspection hardware has been made more manoeuvrable and the inspection parameters have been tuned to their optimal values.