Tech Briefs

Stable, Thermally Conductive Fillers for Bolted Joints

A commercial structural epoxy [Super Koropon (or equivalent)] has been found to be a suitable filler material for bolted joints that are required to have large thermal conductances. The contact area of such a joint can be less than 1 percent of the apparent joint area, the exact value depending on the roughnesses of the mating surfaces. By occupying the valleys between contact peaks, the filler widens the effective cross section for thermal conduction. In comparison with prior thermal joint-filler materials, the present epoxy offers advantages of stability, ease of application, and —as a byproduct of its stability — lasting protection against corrosion. Moreover, unlike silicone greases that have been used previously, this epoxy does not migrate to contaminate adjacent surfaces. Because this epoxy in its uncured state wets metal joint surfaces and has low viscosity, it readily flows to fill the gaps between the mating surfaces: these characteristics affect the overall thermal conductance of the joint more than does the bulk thermal conductivity of the epoxy, which is not exceptional. The thermal conductances of metal-to-metal joints containing this epoxy were found to range between 5 and 8 times those of unfilled joints.

This work was done by Raymond J. LeVesque II; Cherie A. Jones; and Henry W. Babel of McDonnell Douglas Corp. for Johnson Space Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Materials category.

Title to this invention has been waived under the provisions of the National Aeronautics and Space Act [42 USC 2457 (f)], to
The Boeing Co.,
P.O. Box 2515/MS8WSB43
Seal Beach, CA 90740-1515

Refer to MSC-23066, volume and number of this NASA Tech Briefs issue, and the page number.

This Brief includes a Technical Support Package (TSP).

Stable, Thermally Conductive Fillers for Bolted Joints (reference MSC-23066) is currently available for download from the TSP library.

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