Process for forming carbon composite materials
Processes for making carbon/carbon parts are provided. The process involves compression, carbonization and densification steps. Pressure may be applied to a fibrous preform prior to the carbonization step at a temperature less than an exothermic temperature to increase the fiber volume ratio of the fibrous preform. The densification steps may include filling the voids of the fibrous preform with a carbon matrix.
1. A method for forming a carbon composite preform comprising:
loading a fibrous preform comprising oxidized polyacrylonitrile (OPF) fibers extending in multiple directions and having pores extending therethrough into a stack having a first plate, a second plate and a spacer;
applying compression at an elevated temperature less than an exothermic temperature to the fibrous preform prior to a carbonization step to compress a thickness of the fibrous preform;
decompressing the fibrous preform; and
after the decompressing, carbonizing the fibrous preform in the carbonization step by heating the fibrous preform in a furnace to convert the fibers of the fibrous preform into carbon fibers.
2. The method of claim 1 , further comprising a step of densifying the fibrous preform by depositing a carbon matrix within the pores of the fibrous preform after carbonizing the fibrous preform.
3. The method of claim 1 , wherein the exothermic temperature is 180° C.
4. The method of claim 1 , wherein the elevated temperature is less than or equal to 180° C.
5. The method of claim 1 , wherein the applying is along a direction of a plurality of z-fibers of the fibrous preform.
6. The method of claim 1 , wherein the carbonizing comprises heating the furnace to at least 1600° C.
7. The method of claim 1 , wherein the applying is between about 60 and 180 minutes.
8. The method of claim 1 , wherein the applying is between about 5 lbs/in2 (psi) and about 150 psi.
9. The method of claim 1 , wherein the applying is by a dead weight; and
wherein the decompressing comprises removing the dead weight from the fibrous preform.
10. A method for forming a carbon composite preform comprising:
loading a fibrous preform comprising oxidized polyacrylonitrile (OPF) fibers extending in multiple directions and having pores extending therethrough into a stack having a first plate, a second plate and a spacer;
applying mechanical pressure at an elevated temperature less than 180° C. to the fibrous preform prior to a carbonization step to compress a thickness of the fibrous preform;
removing the mechanical pressure from the fibrous preform; and
after the removing, carbonizing the fibrous preform in the carbonization step by heating the fibrous preform in a furnace to at least 1600° C. to convert the fibers of the fibrous preform into carbon fibers for between 60 and 180 minutes.
11. The method of claim 10 , wherein the applying is between about 5 lbs/in2 (psi) and about 150 psi.
12. The method of claim 10 , wherein the applying is by a dead weight; and
wherein the removing the mechanical pressure comprises removing the dead weight from the fibrous preform.
13. The method of claim 10 , wherein during the loading, the fibrous preform has a fiber volume ratio between about 40% and about 45%.
14. The method of claim 10 , wherein after the carbonizing, the fibrous preform has a fiber volume ratio of about 20% to about 23%.