Manufacture of carbon/carbon composites by hot pressing
View Patent ↗A mixture of carbon-containing fibers, such as mesophase or isotropic pitch fibers, a suitable matrix material, such as a milled pitch is compressed while resistively heating the mixture to form a carbonized composite material. Preferably, the carbonized material has a density of at least about 1.30 g/cm 3 . Preferably, the composite material is formed in less than ten minutes. This is a significantly shorter time than for conventional processes, which typically take several days and achieve a lower density material. A treating component may be impregnated into the composite. Consequently, carbon/carbon composite materials having final densities of about 1.6–1.8 g/cm 3 or higher are readily achieved with one or two infiltration cycles using a pitch or other carbonaceous material to fill voids in the composite and rebaking.
1. A method of forming a composite material comprising:
combining a reinforcement material which includes carbon-containing fibers with a carbonizable matrix material to form a mixture;
heating the mixture to a sufficient temperature to melt at least a portion of the matrix material, the step of heating including:
applying an electric current to the mixture to generate heat within the mixture; and
while heating the mixture, applying a pressure of at least 35 kg/cm 2 to the mixture to form a compressed composite material;
increasing the density of the compressed composite by introducing a carbonizable material into voids in the compressed composite and then baking the compressed composite to achieve a density of at least about 1.30 g/cm 3 ;
graphitizing the compressed composite having a density of at least about 1.30 g/cm 3 in an inert atmosphere to a final temperature of at least 2000° C.; and
impregnating the compressed composite, having a density of at least about 1.30 g/cm 3 , with a treating component after graphitization.
2. The method of claim 1 wherein said treating component comprises at least one of a metal, a thermosettable resin, and combinations thereof.
3. The method of claim 2 wherein said metal comprises at least one of aluminum, copper, boron, and combinations thereof.
4. The method according to claim 2 wherein said thermosettable resin comprises phenolic resins, furan derived resins, epoxy resins, polyimides, cyanate esters, and combinations thereof.
5. The method according to claim 4 further comprising curing said thermosettable resin.
6. The method according to claim 1 wherein said compressed composite, having a density of at least about 1.45 g/cm 3 , comprises at least one friction additive.
7. The method according to claim 1 wherein said impregnation comprises subjecting said compressed composite, having a density of at least about 1.45 g/cm 3 , to vacuum.
8. The method according to claim 1 wherein said treating component comprises a thermosettable resin.
9. The method according to claim 1 further comprising heat treating said compressed composite, having a density of at least about 1.45 g/cm3, to a temperature greater than the highest use temperature of said composite material.