C2024-20989 Fatigue Loading Of Test Specimens With Galvanically Induced Corrosion Damage Provides New Insight To Guide Fracture Mechanics Modeling

Thomas Curtin, Robert Adey, Ahmad Karayan, Joseph Indeck, Ethan Moore, Sharon Mellings - Airframe structural components commonly experience galvanic damage at dissimilar metal connections following deterioration of insulating sealants or breakdown in coating protection systems. Of particular concern is the often-hidden corrosion damage that occurs inside fastener holes. Aggressive electrolytes can develop in these occluded spaces leading to the formation of multiple crack initiation sites and a compromise in the structural integrity of the component. To investigate this type of damage, laboratory testing was undertaken to evaluate fatigue life in AA 7075-T651 dog-bone specimens that included side holes fitted with CFRP inserts. The CFRP insert was used to introduce galvanic damage under thin film atmospheric corrosion conditions but removed prior to actual fatigue testing. Fatigue tests were conducted under constant amplitude loading, at R-ratios of 0.05, 0.6, and 0.89, in both air a