Spar disbond visualization in in-service composite UAV with ultrasonic propagation imager

Composite materials have been increasingly used for aircraft structures due to their major advantage of being lightweight compared to metallic materials. However, the drawback of composite materials is that they easily sustain disbond damages due to load and impacts during manufacture or service. An effective quality control management system for aircrafts is required for early detection and early response to such critical damages. This paper reports the application of the Ultrasonic Propagation Imager (UPI) for damage inspection of an in-service aircraft. The inspection task took place at a Korean air force base in May 2013 with the objective of determining the structural condition of the composite aircraft wing at various areas where disbond damages were suspected. The existence of many structural features such as multiple rivets and spars complicated the task since those additional structural features interfere with the laser ultrasonic waves. By developing a novel wavenumber domain filtering algorithm, we successfully detected the disbond damages on the aircraft wing. This result proved the feasibility of the UPI to serve as an effective structural health management system for real-world aircraft applications.