METHOD OF FABRICATING CARBON COMPOSITES

摘要

An improved method of making a carbon composite product wherein a fabric comprised of oxidized or otherwise stabilized polyacrylonitrile fibers is heat treated and then coated with a closely controlled amount of a carbonaceous binder such as a polyimide resin. The fabric is then further heat treated to thermally fuse the resin to the fabric to form a rigid, easily handleable material. The carbonaceous binder is applied to the fabric in a manner whereby substantial encapsulation of the individual fibers is avoided. Next the material is cut into swatches of a predetermined size and shape and the segments are arranged into a basic or starting substrate having a volume greater than the desired volume of the end product. The basic substrate thus formed is then subjected to controlled temperatures and pressures to form a shaped substrate having a known fiber volume, a high degree of open porosity and a shape substantially corresponding to the shape desired of the end product. During this step, the fiber volume of the substrate is adjusted and the segments are fused together to temporarily hold them in position within the substrate. The shaped substrate thus formed is then pyrolyzed to form a carbon fibrous substrate which is densified in a freestanding configuration by the deposition of pyrolytic carbon interstitially thereof to form the desired end product. Because the portions of the fibers which are not encapsulated with binder are free to move, stresses generated in the substrate during pyrolyzation due to material shrinkage and the like are effectively distributed.