Patent ID: 7938992

Claim:
A method for the manufacture of pitch-densified carbon-carbon composite brake discs from carbon fiber preforms, the method comprising the following sequential steps: (a) providing a carbon-carbon composite preform made from nonwoven carbon fiber fabric, said preform being configured in the shape of a brake disc; (b) heat treating said preform at 1600-2540° C.; (c) directly following step (b), subjecting the heat-treated preform to Chemical Vapor Deposition/Chemical Vapor Infiltration processing to produce a carbonized fiber preform which: (i.) has a rough laminar microstructure and is densified to a density of about 1.4 grams per cubic centimeter; or (ii.) has a smooth laminar microstructure and is densified to a density of about 1.2 grams per cubic centimeter; or (iii.) has an isotropic microstructure and is densified to a density of about 1.1 grams per cubic centimeter; (d) infiltrating the preform with an isotropic low to medium char-yield pitch derived from coal tar, employing Vacuum Pitch Infiltration processing; (e) stabilizing the pitch-infiltrated preform by heating it in air at about 180° C. and then carbonizing the pitch-infiltrated preform at 900-2400° C.; (f) machining the surfaces of the resulting carbonized preform; and (g) repeating steps (d) through (f) at least two additional times, to raise the density of the carbon-carbon composite preform to at least approximately 1.75 g/cc, wherein the carbon-carbon composite brake disc preform is densified with an isotropic coal tar pitch to a density of approximately 1.3-1.6 grams per cubic centimeter in the first implementation of step (d) and wherein the carbon-carbon composite brake disc is densified with coal tar pitch to a density of at least approximately 1.75 grams per cubic centimeter in the third implementation of step (d).