Carbon composite article and method of making same

A method of making a carbon composite product comprising the steps of:

• (a) forming a basic substrate from a multiplicity of stabilized polyacrylonitrile fibers, said basic substrate having a volume greater than the volume of the end product;
• (b) selectively depositing a precisely determined, small quantity of a carbonaceous binder material onto said fibers at a multiplicity of spaced apart bonding sites dispersed throughout said basic substrate, said amount of binder material contained in said basic substrate being limited to between approximately 1.0 weight percent and approximately 15.0 weight percent;
• (c) subjecting said basic substrate to controllable external pressures of up to 5,000 psi at a temperature of between approximately 300.degree. F. and approximately 410.degree. F. to compress said basic substrate into a shaped substrate having a fiber volume of between about 40 percent and about 80 percent and a shape substantially corresponding to the shape desired of the end product whereby adjacent fibers within said shaped substrate will be crimped and lightly fused together at their crossover points thereby interlocking them together and whereby said fibers will be further bonded together at bonding sites by said binder material, said shaped substrate thus formed being capable of further processing without the need of external fixturing means to retain its shaped configuration;
• (d) pyrolyzing said shaped substrate to carbonize said binder material and form a carbon fibrous substrate;
• and
• (e) maintaining said carbon fibrous substrate in the presence of a carbonaceous gas at a temperature of between approximately 1900.degree. F. and approximately 2300.degree. F. to deposit pyrolytic carbon interstitially in said carbon fiberous substrate, the fiber volume of said product thus produced being between about 20 percent and about 40 percent.

A method of making a precursor substrate for subsequent densification with pyrolytic carbon without the need for holding or shape retaining fixtures to produce a carbon composite final product comprising the steps of:

• (a) selectively depositing a precisely determined, small amount of a resin material onto a multiplicity of polyacrylonitrile fibers at spaced apart bonding sites, said fibers having been oxidized stabilized in a manner whereby the fibers retain thermoplasticity at a temperature of between 300.degree. F. and 410.degree. F.;
• (b) forming said multiplicity of fibers into a basic substrate having a volume greater than the volume of the end product, said amount of resin material contained in said basic substrate being limited to less than about 15.0 weight percent;
• (c) subjecting said basic substrate to controllable external pressures at a temperature of between approximately 300.degree. F. and approximately 410.degree. F. into a shaped substrate having a fiber volume of between about 40 percent and about 80 percent and a shape substantially corresponding to the shape desired of the end product to crimp and lightly fuse together adjacent thermoplastic fibers at their crossover points whereby said fibers will be interlocked together at their crossover points and will be further bonded together by said resin at said bonding sites;
• and
• (d) pyrolyzing said shaped substrate to form a carbon fibrous substrate having open porosity conductive to interstitial deposition therewithin of a pyrolytic material.

A composite article comprising a multiplicity of intercrossing stabilized PAN fibers interlocked together with adjacent fibers by:

• (a) mating deformations formed in the fibers at their crossover points within the article;
• (b) by a carbonaceous binder material deposited at a multiplicity of spaced apart bonding sites within the article said carbonaceous binder being limited to between approximately 1.0 weight percent and approximately 15.0 weight percent;
• and by
• (c) a coating of pyrolytic material substantially encapsulating said fibers at their crossover points within the article.