Method of fabrication of composites
AssigneeGeneral Atomics
InventorsHolger H. Streckert, Kirk P. Norton
Life of this patent
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Abstract
A method of making a fiber-reinforced ceramic matrix composite of complex shape by first rigidifying a fibrous arrangement made of woven or braided material by impregnating with a preceramic resin, and then curing and pyrolyzing the resin to form a rigid or stiff preform. The rigid preform is then densified by chemical vapor infiltration, e.g., using a forced-flow/thermal-gradient process. Using three-dimensional woven fabrics made of ceramic fibers, such as silicon carbide or silicon nitride, strong high-temperature resistant composites are produced having porosities from about 20 percent to less than about 5 percent.
Claims19
A method of making a fiber-reinforced ceramic matrix composite utilizing deposition of ceramic matrix material from a vaporous atmosphere without creating an array of gas channels in a supporting jig or the like, which comprises the steps of:
- a) combining a preceramic resin and fibrous reinforcing material to produce a body of desired shape;
- b) curing the resin at a first temperature to create a rigid preform;
- c) pyrolyzing said rigid preform at a higher temperature than said first temperature so that said rigid preform has a porosity between about 30 percent and about 50 percent of total volume of said desired shade;
- and
- d) then densifying said pyrolyzed preform by using chemical vapor infiltration to cause a vaporous substance to infiltrate pores within said pyrolyzed preform, without supporting said preform upon a device having passageways to channel said vaporous substance uniformly across the surface of said preform, and causing said vaporous substance to thermally react at locations within the pores to deposit ceramic matrix material therein and thereby produce a resulting composite having a total porosity of no greater than about 20 percent volume of the total volume of said desired shape.
A method of making a composite heat exchanger comprising the following steps:
- a) disposing tubes formed of continuous fibers about mandrels and impregnating said tubes with a preceramic resin;
- b) confining a plurality of said tubes within two sheets of woven fibers which sheets form a channel with said tubes aligned therewithin to thereby form a heat exchanger arrangement and impregnating said two sheets with said preceramic resin;
- c) curing and pyrolyzing said resin to form a rigid heat exchanger preform;
- d) removing said mandrels;
- and
- e) densifying said rigid preform by chemical vapor infiltration by causing a vaporous substance to infiltrate into the pores from the interior surface of said plurality of rigid tubes and thermally decompose within the pores of said tubes and of said sheets which form said channel of said preform to deposit a refractory matrix substance therewithin until such time that said preform has a porosity no greater than about 20 percent.
A method of making a fiber-reinforced ceramic matrix composite without gating vapor flow through a fabric preform, which method comprises the steps of
- a) applying a preceramic resin to fabric made from ceramic fibers to produce a body of desired near net shape, which preceramic resin is selected from the group consisting of polysilanes, polycarbosilanes, polysiloxanes, polysilazanes, and polyborazines;
- b) curing said resin at a first temperature to create a rigid preform of near net shape;
- c) pyrolyzing said rigid preform at a temperature above said first temperature and repeating said applying, curing and pyrolyzing steps so that said rigid preform has a porosity of between about 30 percent and about 50 percent of total volume of said near net shape;
- and
- d) densifying said pyrolyzed preform by using chemical vapor infiltration (CVI) to cause a vaporous substance to enter one surface thereof and flow through the interstices of said preform and thereby infiltrate pores within said pyrolyzed preform before exiting therefrom through another surface thereof, without supporting said preform upon a device formed with passageways to channel said vaporous substance uniformly across the surface of said preform, and causing said vaporous substance to thermally react at locations within the pores to deposit ceramic matrix material therein and thereby produce a resultant composite having a total porosity of no greater than about 20 percent volume of the total volume.
Dependencies are inferred from the claim text.