Integrated mesophase injection and in situ transformation in fabrication of high-density carbon-carbon composites

The fabrication of high-density carbon-carbon composite by integrating mesophase injection and in situ transformation methods in different processing cycles was examined. Non-rigidized preform disks 30 mm thick and 68 mm in diameter were rigidized by an initial in situ transformation cycle to an average density of 0.92 g/cm³ after carbonization. The rigidized preforms were subsequently densified by 1-3 cycles of injection with the AR mesophase pitch. After each injection cycle, the flow-oriented mesophase matrix was stabilized and carbonized to 1150 °C. The composites from each injection cycle were further densified by a final in situ cycle. A final density of nearly 2 g/cm³ was attained after three injection cycles and a final in situ cycle. All the cycles except the third injection required only ambient or very moderate pressures.