Abstract: An improved method for producing low-cost carbon--carbon composites based on impregnating carbon fiber mat preforms with liquid dispersions or suspensions of fine carbon particles and subsequent mechanical consolidation is disclosed. A highly porous preform of carbon fibers is impregnated by a liquid suspension of colloidal graphite and dried in air at low temperatures. Multiple impregnation and drying densification cycles provide a soft, flexible carbon--carbon composite. Subsequent mechanical consolidation methods, such as pressing or rolling, combined with rigidization by resin or pitch impregnation and carbonization, render a thin carbon--carbon composite of high bulk density. Prior to rigidization, the composite may be sewn with carbon yarns for property enhancement.

Abstract: An improved method for producing low-cost carbon-carbon composites based on melt-impregnation of carbonaceous fiber preforms with low-melting point sugars is provided. Sugars such as fructose, ribose and sucrose are provided as impregnants via either ambient pressure or vacuum processing. Subsequent pyrolysis in air by heating to temperatures in the 325.degree. C. to 350.degree. C. range results in almost complete decomposition of the sugars to carbon. Frothing during the sugar melt-impregnation and pyrolysis process is minimized by the use of extended periods of isothermal pyrolysis or by the use of a catalyst. A hybrid process combining sugar melt-impregnation and pyrolysis with carbonaceous resin impregnation and pyrolysis is also provided as a densification enhancement.