SBIR-STTR Award

There is a need for lightweight CTC composites that can be tailored to manage rapidly generated, very high heat loads in electronic components and space and missile structures for navsea weapon systems. The innovation in this program is to utilize a high char yield mesophase pitch and b(4)c doped pitch as matrix precursors to fabricate c/c composites for navsea weapon systems. C/c composites of very high thermal conductivity will be fabricated by reinforcing a mesophase pitch carbon matrix with highly conducting p130x pitch based carbon fibers. The jp130x fibers have a thermal conductivity of about 1140 w/m.k. Mesophase pitch carbon will align the fibers to produce a "sheath effect" that should enhance the thermal conductivity and modulus of the fiber bundles. Addition of b(4)c to a pitch carbon matrix should Increase the thermal expansivity and elastic modulus of the matrix. The composities will be heated above 2000 degrees c to develop high thermal conductivity in the matrices. A final densification with cvi pyrocharbon is expected to further Increase the thermal conductivity of the composities and improve their strength and toughness. Structural evaluation and measurement of thermal and mechanical properties will provdie a data base. Phase I Research is expected to demonstrate the concepts and provide a basis for phase ii Research.

The results of the Phase I study showed the feasibility of fabricating carbon-carbon composites using high thermal conductivity fibers. Thermal conductivity values of up to 400 W/m.K in the composites were achieved along with excellent mechanical properties. The specific thermal conductivity of these composites was significantly higher than metal and organic matrix composites of similar architecture. The research in Phase II will be aimed at maximizing the in-plane thermal conductivity and to control the in-plane thermal expansivity of the carbon-carbon composites. High modulus pitch fibers will be used as reinforcements in pitch/PyC matrices. Mesophase pitch liquid crystals will be elongated parallel to the "2" direction of 2D high thermal conductivity preforms to enhance the "2" direction thermal conductivity and mechanical properties. Metal carbide particles will be added to the matrices to increase and control the in-plane thermal expansivity. The composites will be processed to promote a high degree of crystallinity, high thermal conductivity and good mechanical properties. The composites will be characterized by SEM and light microscopy and by measuring physical, thermal, electrical and mechanical properties. A system component such as a SEM E thermal plane will be fabricated and tested during the latter part of the program.