Design and analysis of adhesively bonded thick composite patch repair of corrosion grind-out and cracks on 2024 T3 clad aluminum aging aircraft structures

Many military and commercial aging aircrafts flying beyond their design life may experience severe crack and corrosion damage, and thus lead to catastrophic failures. In this paper, the design, fabrication and analysis of adhesively bonded thick composite patch repair of circular corrosion grind-out and a crack propagating on the periphery of the corrosion grind-out on thick 2024 T3 clad aluminum aircraft panel is presented. Thick orthogonal composite patch configurations of 7–25 plies were designed separately for crack and corrosion grind-out using CRAS. Using the principles of superimposition a single patch was designed to repair both the crack and corrosion grind-out. Finite element analysis (FEA) was performed on the test specimen subjected to uniaxial tensile loading. Stress distribution and displacements were obtained and analyzed. Dog-bone shaped tensile test panels were fabricated with damage and repaired with boron/epoxy patch of 11 plies. The patched and unpatched panels were subjected to tensile tests. The experimental and the FEA results show that the maximum skin stress decreases significantly and shifted away from damaged area after the application of composite patch. The load carrying capacity of patched specimen significantly increased over that for unpatched specimen.