Electrically or Thermally Conductive Resins for Composite Structures

The development of graphite fibers with thermal conductivities along the fiber of greater than 1000 W/m degree K have allowed composites to reach in-plane thermal conductivities (11, k22) of 300 to 660 W/m degree K. These conductivities are two to four times those of the aluminum alloys currently used for spacecraft structure. However, the composites have very low thermal conductivities ( 2 W/m degree K) in the through-thickness direction (k33) because of the low transverse conductivity of the highly-crystalline graphite fibers and the low isotropic conductivity of the epoxy or cyanate ester matrix resins. While the low k33 values do not prevent the composite from thermally outperforming aluminum when the structures are "thin" (thickness/in-plane thermal path length, t/L less than or equal to 0.01, Ref. 1), higher k33 values would further increase performance and greatly broaden the range of applications where the 40% weight savings of composites (versus aluminum) could be invoked. This Phase I work will screen for and select a polymer modification approach to increasing the k33 values of a thermally conductive graphite composite and an adhesive, assess the effects of the modification on critical thermal, mechanical, and physical properties of composite and adhesive, and validate performance enhancement in a baseline hardware article.