N112-154 TITLE: Innovative Approaches for Predicting Galvanic Effects of Dissimilar Material Interfaces

TECHNOLOGY AREAS: Air Platform, Materials/Processes

OBJECTIVE: Develop and demonstrate an innovative analytical approach for determining the galvanic effects on dissimilar materials.

DESCRIPTION: Airframe structure is typically comprised of multiple materials forms each exhibiting unique electro-chemical properties. Examples may include graphite epoxy composites attached to metallic substructure. The differential in electro-chemical properties will result in galvanic activity, leading to a corrosive state accelerated with exposure in the aggressive Navy operational environment. The ongoing corrosive state results in material degradation and eventual structural failure, providing a substantial cost for fleet maintenance and reduced numbers of mission ready aircraft.

The current approach to airframe design is to select materials and structures for mechanical and thermal load performance based upon initial properties. Design analysis tools do not have the capability to account for degradation of these properties due to operational conditions. The current approach attempts to minimize the galvanic activity of structural designs by the utilization of sealants, coatings, and other barrier techniques, all of which typically degrade over time, resulting in corrosive damage. Areas of inadequate protection or high galvanic activity cannot be identified until the design is completed and fielded, leaving limited room to address basic design flaws in interfaces and material selection, and continuing the cycle of reactionary find/fix corrosion mitigation.

To address this issue, there is a desire to select the structure of the airframe to minimize galvanic activity from the design phase, thereby eliminating or minimizing potential corrosion issues. Therefore an innovative analytical solution that will enable the prediction of galvanic response to dissimilar materials is required.

PHASE I: Develop an analytical approach for predicting the galvanic effects on dissimilar materials. Demonstrate the feasibility of the approach by comparing predictive results with published data.

PHASE II: Fully develop the approach formulated in Phase I into a usable design tool. Provide verification of the ability of the design tool to predict the galvanic behavior of structural sub elements comprised of an array of dissimilar materials, including protective coatings, which are exposed to various chemical and thermal conditions. Verify the ability of the design tool to predict galvanic response of structures under mechanical loads.

PHASE III: Validate the design tool through an extensive test program. Transition the approach to airframe designers and manufactures.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The developed analytical tool has the potential to transition to the commercial aircraft market for the efficient design of airframe structure, resulting in improved component reliability and life extension due to the elimination of airframe corrosion.

REFERENCES:
1. "Military Airframe Costs � The Effects of Advanced Materials and Manufacturing Processes" Obaid Younossi, Micheal Kennedy, John C. Graser � United States, Project Air Force

2. "The Annual Cost of Corrosion for Navy and Marine Corps Aviation Equipment" David A. Forman, Eric F. Herzberg, James C. Tran, Amelia R. Kelly, Paul N. Chang, Norman T. O�Meara, Ph.D. � LMI Government Consulting, Report MEC70T3, May 2008

3. www.corrdefense.org

KEYWORDS: Corrosion, galvanic activity, dissimilar materials, cost reduction.

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