Practical Application of State-of-the-Art NDE Techniques: Evaluation of Graphite-Epoxy Composite Wing Covers

Abstract

The X-29 experimental aircraft, based at the NASA Dryden Flight Research Facility, Edwards Air Force Base, California, represents a demonstrator for several state-of-the-art aerospace technologies. The most obvious of these is the forward-swept wing configuration, made possible in this high-performance aircraft by the use of graphite fiber-reinforced epoxy composite laminate wing surfaces. During a routine inspection of the aircraft, a delamination was found in the wing on the right underside of the airplane. A NASA review board investigated the damage and recommended to repair the delamination and to closely monitor its integrity during the post-repair period. The local strain on the surface of the repaired part was measured with strain gages monitored in real time during subsequent flights and the area was periodically inspected nondestructively in a reproducible manner to test for failure of the repair or growth of the delamination. The Materials Characterization Instrumentation Section of the NASA Langley Research Center was called upon to acquire quantitative ultrasonic NDE data from the repaired delamination and to analyze it using the advanced techniques available at that facility. These measurements were in addition to more subjective conventional ultrasonic pulse-echo inspections.