TECHNOLOGY AREA(S): Air Platform ACQUISITION PROGRAM: JSF Joint Strike Fighter

OBJECTIVE: Develop innovative methods to quickly repair corroded fastener holes on Navy/Marine Corps aircraft structures, requiring minimal support equipment, and restoring the component�s previously un-corroded remaining useful life (fatigue), while maintaining acceptable static strength capability.

DESCRIPTION: Navy/Marine Corps aircraft operate in a highly corrosive marine environment. Some of these aircraft have hybrid (composite/aluminum) designs that exhibit accelerated galvanic corrosion damage compared to legacy all-metal airframes. The traditional corrosion repair method is time consuming and expensive, and, while structurally adequate, reduces the airframe strength capability. Current operational demands and budget constraints create the need for a faster, less expensive repair method that maintains structural integrity. Cost savings would be realized in a solution that allows minimal material removal and quick technician repair, reducing analysis and maintenance time.

The most commonly used corroded hole repair method involves oversizing to remove corrosion, manufacturing a custom bushing, Ion-Vapor Deposition (IVD) plating, and finally installing the bushing. The repair process can take upwards of two months and reduces the fastener hole edge distance, therefore lessening the static strength and fatigue life. To ensure safety of the repaired configuration, flight envelope restrictions or aircraft grounding may be enforced to prevent overloading the aircraft.

The desired rapid repair method will minimize modification to the existing structure and the creation of new, untested load paths. It should not require extensive special skills and training to employ for either the airframe repair or the installation. Quality control requirements that incorporate equipment and skills not presently in use by the Navy are not desired [Refs 4, 5].

The repair method being sought should restore the structure�s previously un-corroded remaining useful life (fatigue), while maintaining an acceptable static strength capability [Ref 6]. It will not interfere with the form, fit or function of attached or nearby structures or systems. Repair approaches that are portable and can be performed in the field are preferable. Those that require a large amount of Government-support equipment and capital expenditure are not desired.

PHASE I: Determine the feasibility of an innovative concept for rapid repair of corroded holes, through analysis and experimentation, to assess the expected strength and fatigue life benefits of the repair. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop and test a prototype of the proposed solution to assess actual performance benefits and demonstrate repeatability. Perform static strength and fatigue tests to provide sufficient data to qualify the repair process for Navy/Marine Corps fleet use. The static test should achieve at least equal ultimate and limit load capability to the original configuration. The fatigue test will cycle for at least as long as the original configuration under the same fleet/design usage spectrum. Provide a business case analysis to indicate the savings that can be achieved with the developed repair method.

PHASE III DUAL USE APPLICATIONS: Transition the prototype into a final product for Navy/Marine Corps fleet application. Complete the developed repair method at a fleet maintenance facility to define all process requirements in coordination with fleet maintainers and depot personnel. Distribute the product, support equipment, and process specifications to maintainers. Commercial aircraft and ships experience corrosion in fastener holes and would benefit from reduced maintenance costs, increased availability, and restored structural integrity.

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