When defense assets undergo structural repair, it is often due to corrosion. Although many technologies can remove and replace corroded material, these processes can reduce component strength or dimension. Welding, coating technologies, adhesives, and laser treatments have all demonstrated useful methods in recovering components, but drawbacks remain for each approach. Component removal and replacement are also costly and laborious processes that render defense assets unavailable for extended periods of time.

In 2021, SERDP research initiatives aim to identify and develop sustainable field repair technologies for damaged or corroded materials in advanced generation five and future aircraft composite and metallic structure or components. The following new projects are funded to produce repair technologies for use in the depot, field, or in situ on the defense asset that restore component strength and dimension without compromising chemical and mechanical properties.

• At the University of Delaware Center for Composite Materials, Shridhar Yarlagadda is working with the Naval Air Systems Command to evaluate highly aligned short fiber technology (TuFF) as a sustainable method for structural repair of defense assets. The project will set a foundation for repair approaches using TuFF that demonstrates repair of complex airframe structures on a representative geometry and retention of structural performance in static load cases. (Project Webpage)

• Brian Jordon from University of Alabama will use Additive Friction Stir Deposition (AFS-D), a transformative high deposition rate solid-state additive manufacturing process, to rapidly repair corrosion and mechanically damaged high strength aluminum alloy components. His team, which brings together a skillset of processing science, microstructural characterization, and mechanical testing research, will advance the fundamental understanding of this novel solid-state additive manufacturing process and fill technical gaps present in the additive repair of aluminum alloy components. (Project Webpage)

• Dr. Jason Patrick at North Carolina State University and his team will develop a sustainable self-healing composite system for completely restoring interlaminar fracture resistance that doesn’t compromise in-plane mechanical properties. Internal delamination damage in fiber-reinforce composites is one of the most significant problems reducing reliability of composite materials in lightweight structures, as it is difficult to identify and rarely possible to repair using common methods. Self-repairing structural composites pose a new solution. This team will advance understanding of self-healing composite systems by incorporating polymer mechanics/chemistry, emergent manufacturing, and advanced computing. (Project Webpage)

• Traditional powder-based methods of repairing aircraft components require expensive, energy-intensive equipment and typically have low efficiency rates. Dr. Timothy Eden at the Applied Research Laboratory of Penn State and his team will evaluate Wire Arc Additive Manufacturing (WAAM) as a method that offers significant energy and cost savings and higher material utilization. This project will advance the state-of-the-art for WAAM alloys by providing a better understanding of the microstructural evolution of aluminum alloys used in aircraft components. The team will conduct accurate modeling of the solidification and thermal process and produce and characterize WAAM materials. (Project Webpage)

Technologies that avoid replacement of damaged materials and parts reduce the environmental, safety, occupational and health risks associated with manufacturing and repair processes. SERDP research is developing smarter processes that simplify work schedules, cut costs, and reduce hazardous conditions to ensure higher operational readiness for all installations and warfighters.