Carbon/carbon composite for re-entry vehicle applications

Claim 1

A method for fabricating a re-entry vehicle nose-tip material which comprises the steps of (a) forming a billet of a three directional carbon-carbon material having a plurality of graphite bundles oriented in an axial "Z" direction and in a lateral "X" or "Y" direction, said axially oriented bundles each having three ends of graphite yarn with 0.030 in spacing between axial bundles and said laterally oriented bundles each having two ends of graphite yarn with 0.030 to 0.035 inches along the length; (b) heating said billet within a vacuum to a temperature of about 1500° C. to clean the surfaces of the fibers; (c) infiltrating said heated billet with carbon by passing said billet through an r.f. coil while heating at 0.001-0.003 atm. pressure in an atmosphere containing methane gas; (d) impregnating said infiltrated billet with coal tar pitch at a temperature of 250° C. and a pressure of 15,000 psi; (e) baking said impregnated billet at pressure and a temperature of approximately 650° C.; (f) graphitizing said baked billet at one atmospheric pressure to 2700° C.; and (g) repeating in sequence the cycle of steps (b) through (f) for from three to four times, thus forming a high density carbon-carbon composite.

Claim 2

A method for fabricating a re-entry vehicle nose-tip material which comprises the steps of (a) forming a billet of a three directional carbon-carbon material having a plurality of graphite bundles oriented in an axial "Z" direction and in a lateral "X" or "Y" direction, said axially oriented bundles each having three ends of graphite yarn with 0.030 in spacing between axial bundles and said laterally oriented bundles each having two ends of graphite yarn with 0.030 to 0.035 inches along the length; (b) heating said billet within a vacuum to a temperature of about 1500° C. to clean the surfaces of the fibers; (c) infiltrating said heated billet with carbon by passing said billet through an r.f. coil while heating at 0.001-0.003 atm. pressure in an atmosphere containing methane gas; (d) impregnating said infiltrated billet with coal tar pitch at a temperature of 250° C. and a pressure of 15,000 psi; (e) baking said impregnated billet at pressure and a temperature of approximately 650° C.; (f) graphitizing said baked billet at one atmospheric pressure to 2700° C.; and (g) repeating in sequence the cycle of steps (b) through (f) for from three to four times, thus forming a high density carbon-carbon composite.