04.1 - Aerospace Grade Materials, Structural Analysis, Fatigue and Damage Tolerance
A PROCESS-STRUCTURE-PROPERTY-PERFORMANCE FRAMEWORK FOR DIGITAL ENGINEERING-ENABLED REPAIR OF ALUMINUM PARTS
J. Lua¹, M.R. Rajanna¹, H. Yu, Virginia Tech, United States; A. Timmons², G. Murray², N. Phan²; ¹Global Engineering and Materials, Inc., United States ;²Naval Air Systems Command, United States
Aircraft corrosion maintenance and control are major drivers of sustainment cost and contributors to reduced aircraft availability. Structural repair based on either melting-based or solid-state approaches aims to restore the original geometry while achieving adequate post-repair mechanical performance. Unlike mainstream fusion-based additive manufacturing (AM) methods, additive friction stir deposition (AFSD) does not involve metal melting and solidification; therefore, defects such as lack of fusion, keyholing, and large residual stresses can be largely eliminated. AFSD integrates the friction stir principle with a material-feeding mechanism to enable location-specific material deposition, from which three-dimensional components can be built. AFSD is particularly well suited for the repair of damaged AA7075 components because it produces fully dense material in the as-deposited state with fine, equiaxed microstructures. Severe plastic deformation at elevated temperatures during deposition promotes dynamic recrystallization, typically resulting in refined microstructures with wrought-like mechanical properties. In addition, strong metallurgical bonding can be established between the deposited material and the substrate, eliminating weak interfaces commonly observed in repaired systems. The mechanical performance of AFSD-repaired components strongly depends on the distribution of process-induced defects and microstructure-driven constitutive behavior. Although AFSD offers significant flexibility to tailor microstructure through control of machine inputs, feedstock selection, and external thermal conditions during and after deposition, reliance on trial-and-error approaches to identify optimal repair strategies within a high-dimensional design space is both costly and time-consuming. For a given damage configuration and performance requirement, it is therefore critical to rapidly define an operational process window and associated thermal boundary conditions that min