Facilitating pitch stabilization in densified carbon fiber preforms
A method of forming a densified preform or composite part is disclosed that includes partially densifying a porous preform, forming channels in the partially densified preform that open to an exterior surface of the partially densified preform, infiltrating a densifying agent, such as pitch, into at least some of the channels of the partially densified preform, at least partially stabilizing the densifying agent, including heating at a first temperature, such that cracks form within the densifying agent, and exposing the preform to an oxidizing agent, and heating the at least partially stabilized preform at a second temperature to carbonize at least the stabilized densifying agent. A partially densified preform including a densifying agent disposed at least in such channels also is disclosed.
1. A method comprising:
partially densifying a porous preform to form a partially densified preform;
forming a plurality of channels in the partially densified preform, wherein each channel of the plurality of channels opens to at least one exterior surface of the partially densified preform and defines a diameter of less than about 0.015 inch;
infiltrating a densifying agent into at least some channels of the plurality of channels formed in the partially densified preform to form an infiltrated preform;
at least partially stabilizing the densifying agent to form an at least partially stabilized preform by at least:
heating the infiltrated preform at a first temperature, such that the densifying agent disposed in the at least some channels shrinks to form a plurality of interconnected cracks, and
exposing the infiltrated preform to an oxidizing agent; and
heating the at least partially stabilized preform at a second temperature to carbonize at least the stabilized densifying agent to form a carbonized preform.
2. The method of claim 1 , wherein forming the plurality of channels comprises at least one of drilling or using laser ablation.
3. The method of claim 1 , wherein infiltrating the densifying agent comprises using at least one of resin transfer molding (RTM), vacuum pressure infiltration (VPI), or high pressure impregnation/carbonization (PIC).
4. The method of claim 1 , wherein the densifying agent comprises a pitch.
5. The method of claim 4 , wherein the pitch comprises a mesophase pitch, and wherein the mesophase pitch comprises at least one of coal tar, petroleum, or synthetic pitch.
6. The method of claim 1 , wherein partially densifying the porous preform comprises using at least one of chemical vapor deposition (CVD) or chemical vapor infiltration (CVI).
7. The method of claim 1 , wherein each channel of the plurality of channels is between about 0.25 inches and about 0.75 inches in length.
8. The method of claim 1 , wherein the first temperature is between about 170° C. and about 200° C., and the second temperature is between about 650° C. and about 900° C.
9. The method of claim 1 , wherein at least some interconnected cracks of the plurality of interconnected cracks open to at least one exterior surface of the at least partially stabilized preform.
10. The method of claim 1 , wherein exposing the infiltrated preform to the oxidizing agent comprises exposing the infiltrated preform to the oxidizing agent such that the oxidizing agent penetrates an inner portion of the infiltrated preform at least via at least some of the plurality of interconnected cracks.
11. The method of claim 1 , further comprising, after forming the carbonized preform, further densifying the carbonized preform using at least one of chemical vapor deposition (CVD) or chemical vapor infiltration (CVI) to form a carbon-carbon composite material.
12. The method of claim 1 , further comprising, after forming the carbonized preform, further densifying the carbonized preform by:
infusing at least one of phenolic resin or furfuryl alcohol in to remaining porosity of the carbonized preform; and
carbonizing the at least one of phenolic resin or furfuryl alcohol.
13. A method comprising:
infiltrating a densifying agent into at least some pores of a plurality of pores of a partially densified preform to form an infiltrated preform;
forming a plurality of channels at least partially in the densifying agent of the infiltrated preform, such that each channel of the plurality of channels opens to at least one exterior surface of the infiltrated preform and defines a diameter of less than about 0.015 inch;
at least partially stabilizing at least the densifying agent to form an at least partially stabilized preform by at least:
heating the infiltrated preform comprising the plurality of channels at a first temperature, and
exposing the infiltrated preform comprising the plurality of channels to an oxidizing agent to stabilize at least the densifying agent and form the at least partially stabilized preform;
heating the at least partially stabilized preform at a second temperature to carbonize at least the stabilized densifying agent to form a carbonized preform.
14. The method of claim 13 , wherein forming the plurality of channels comprises at least one of drilling or using laser ablation.
15. The method of claim 13 , wherein the first temperature is between about 170° C. and about 200° C., and the second temperature is between about 650° C. and about 900° C.
16. The method of claim 13 , wherein the densifying agent comprises a mesophase pitch.
17. The method of claim 13 , further comprising, prior to infiltrating the densifying agent, partially densifying a porous preform using at least one of chemical vapor deposition (CVD) or chemical vapor infiltration (CVI) to form the partially densified preform.