Microstructural Studies of In-Situ Mesophase Transformation in the Fabrication of Carbon-Carbon Composites

摘要

Injection of a low viscosity, fully transformed mesophase pitch into a fiber preform can be an effective approach to fabrication of advanced, high- performance carbon-carbon (C/C) composites 1. Here, flow-induced microstructures can be stabilized by oxidation such that upon carbonization, the fibrous carbon needles running through the flow channels are retained. Using the injection and stabilization process, one can raise the density of C/C composites to reasonably high levels in a couple of cycles. While the injection method is effective in making highly densified materials with controlled microstructure, it is not without constraints. This method is best applied to uniform geometries such as aircraft brakes, and the use of rigidized preforms is required to resist compaction under injection pressure. Severe injection conditions with diminishing return in density gain could be encountered if the process has to be carried beyond two to three cycles.