THE FABRICATION OF CARBON CARBON COMPOSITES USING A LIQUID-CRYSTAL MATRIX PRECURSOR

Carbon-carbon composites can be fabricated by the infiltration of an organic precursor into a fibre preform followed by pyrolysis to generate the carbon matrix. When the infiltration liquid is isotropic pitch, a transient liquid crystal phase is generated within the fibre preform during pyrolysis. An alternative approach is to produce suitable liquid crystal precursors separately, and then to infiltrate these directly into the preform. Such liquid crystal precursors can have higher carbon yields than the original pitch and pressure carbonisation can be avoided. Also a wider variety of microstructural features can be developed in the matrix. The problems arising in the fabrication processes are discussed and illustrated with examples from a current study.