Date: Jan 13, 2014 Source: SBIR Success Stories (
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Air Force Requirement:
Degradation of outer mold line aircraft materials results in a significant increase in direct maintenance man-hours per flight hour, and reduced system performance. Development of crack-resistant, conductive gap fillers fits within the Air Force's goal of investing in low observable (LO) maintenance improvements to reduce sustainment costs and aircraft downtime. The combination of mechanical and thermal fatigue generates the most aggressive stresses for gap-fillers on aircraft, where temperatures can range from -65°F to 250°F.
One area of degradation involves cracking of conductive gap fillers used between aircraft skins and panels. Severe flight loads, combined with a wide range of operating temperatures and manufacturing tolerances can elevate mechanical and thermal strain on gap filler placed between aircraft panels (fixed and/or removable).
SBIR Technology:
Commercially available gap-fillers are initially effective, but degrade under thermal and mechanical fatigue. To reduce fatigue cracking in gap filler materials, TRI/Austin developed extremely tough elastomeric matrix resins. These materials exhibit a significant increase in fatigue crack resistance over the service temperature range. The thermal stability of the gap-fillers is improved as well. The new material is applied with conventional sealant gun hardware, as used for current commercial gap fillers and is available in two component kits with an application time of 30-60 minutes.
Potential Application:
Successful insertion of this innovative gap filler technology will help resolve specific Air Force operational challenge areas by increasing the mission ready rate for aircraft. It will also reduce the total ownership costs of fighter/bomber aircraft by reducing maintenance hours per flight hour. LO maintainability accounts for approximately one third of all fighter/bomber maintenance. The manpower required to maintain LO increases as aircraft age, which includes removing and reapplying gap filler to maintain a consistent mold line. Accomplishing this also fits within the objectives of The Air Force Life Cycle Management Center to provide systems that are more affordable to own, and easy to sustain and support.
These new gap-filler materials offer significant cost and production turnaround time advantages to the extant technology. The product TRI/Austin developed under this Air Force SBIR contract increases the fatigue durability a factor of four to six times better at sub-ambient (-65 oF) and ambient operational temperatures. It also improves thermal stability and weighs less yet is cost equivalent to commercial gap fillers. This technological advantage can lead to improved durability and reduction in maintenance requirements.
Company Impact:
TRI/Austin, Inc. is currently working, under an Air Force Defense Research and Development Rapid Innovation Fund (RIF) contract, with Lockheed Martin to insert one of these gap fillers into a fifth generation fighter aircraft. Modifications in the gap filler are being made that significantly decrease the density, which translates into overall weight reduction. TRI/Austin was awarded the 24-month RIF contract for $750K in September 2012. After finalizing the formulation for this platform, production of the gap filler will be scaled-up for on-aircraft evaluations. By teaming with, PPG-Aerospace, a major aerospace sealant manufacturer, TRI/Austin is well positioned to commercialize and transition the products, which will include several variants. "This new fatigue crack resistant gap filler compliments the TRI/Austin line of aerospace products tailored for applications requiring durability in extreme environments," said Mr. Rock Rushing, senior scientist at TRI/Austin. "This technology portfolio includes high temperature coatings, sealants, and adhesives."
