Repair substantiation for a bonded composite repair to F111 lower wing skin

This paper presents the results obtained to date as part of a comprehensive repair-substantiation program currently in progress for a safety-critical repair to an F-111 lower wing skin. From the viewpoint of demonstrating compliance with certification requirements, this F-111 repair represents the most technically challenging bonded repair undertaken to date by the RAAF. It is particularly significant that the repair was designed and implemented entirely by RAAF personnel, on the basis of design principles and application procedures developed by DSTO. This constitutes an important milestone in technology transfer from DSTO to the RAAF. The repair substantiation involves both detailed finite element (FE) stress analyses and structural testing at three levels, ranging from coupon-size specimens (representative bonded joints) to quasi- full-scale specimens representing a spar-stiffened wing-box structure. The close coupling of analysis and testing is shown to lead to a time- and cost-efficient certification package, with a confidence level comparable with full-scale structural testing.