Ceramic matrix composite airfoil cooling

1. A method for forming an airfoil for a gas turbine engine, the method comprising:

laying up a ceramic matrix composite material to form an airfoil preform assembly, wherein the laying up the ceramic matrix composite material comprises laying up a plenum preform, laying up a filler pack preform, and laying up airfoil plies; the airfoil preform assembly including:

opposite pressure and suction sides extending radially along a span,

opposite leading and trailing edges extending radially along the span, the pressure and suction sides extending axially between the leading and trailing edges, and

a plenum defined within the airfoil preform assembly; and

processing the airfoil preform assembly to produce the airfoil,

wherein a cooling passage is defined within the airfoil, the cooling passage defined from the plenum to the trailing edge of the airfoil, the cooling passage defined proximate the suction side of the airfoil, the cooling passage comprising:

a first cavity extending radially within the trailing edge portion;

a second cavity defined aft of the first cavity, the second cavity extending radially within the trailing edge portion;

a crossover aperture defined from the plenum to the first cavity;

a channel defined from the first cavity to the second cavity, the channel extending axially between the first and second cavities; and

an ejection aperture defined from the outer surface of the airfoil to the second cavity;

wherein each of the airfoil plies, the plenum plies, and the filler pack comprise a ceramic matrix composite material such that the airfoil is formed from the ceramic matrix composite material, and

wherein the first cavity, the second cavity, and the channel are defined in the filler pack such that the first cavity, the second cavity, and the channel are separated from the outer surface by the airfoil plies.

2. The method of claim 1 , wherein a fugitive material insert is positioned within the ceramic matrix composite material as the material is laid up to form the airfoil preform, the fugitive material insert configured to define the first cavity, the channel, and the second cavity.

3. The method of claim 1 , wherein defining the cooling passage comprises machining the first cavity, the channel, and the second cavity within the filler pack preform before laying up the filler pack preform with the plenum preform and airfoil plies.

4. The method of claim 1 , further comprising machining the ejection aperture after applying an environmental barrier coating to the airfoil.

5. The method of claim 1 , wherein the ceramic matrix composite material comprises a plurality of airfoil plies, wherein the plurality of airfoil plies defining the pressure and suction sides of the airfoil preform assembly, and wherein the pressure and suction sides defining an outer surface of the airfoil preform assembly.

6. The method of claim 5 , wherein the airfoil preform assembly further comprises a trailing edge portion defined adjacent the trailing edge at an aft end of the airfoil preform assembly, wherein the trailing edge portion extends axially over a length, wherein the ceramic matrix composite material comprises a plurality of plenum plies, wherein the plurality of plenum plies define the plenum, and wherein the plenum is defined within the airfoil preform assembly forward of the trailing edge portion.

7. The method of claim 6 , wherein the ceramic matrix composite material further comprises a filler pack, the filler pack positioned between the plurality of airfoil plies and the plurality of plenum plies in the trailing edge portion, and wherein the first cavity, the second cavity, and the channel are defined in the filler pack such that the first cavity, the second cavity, and the channel are separated from the outer surface by the plurality of airfoil plies.

8. The method of claim 1 , further comprising, after processing the airfoil preform assembly:

performing a burn-out cycle; and

densifying the airfoil preform assembly.

9. The method of claim 8 , further comprising:

positioning a fugitive material insert within the ceramic matrix composite material as the material is laid up to form the airfoil preform assembly, the fugitive material insert configured to define at least a portion of the cooling passage; and

after performing the burn-out cycle and densifying the airfoil preform assembly, manipulating the airfoil to remove any remaining fugitive material of the fugitive material insert.

10. The method of claim 1 , wherein at least a portion of the cooling passage is defined by machining the ceramic matrix composite material.

11. The method of claim 1 , further comprising, prior to laying up the ceramic matrix composite material to form the airfoil preform assembly:

laying up a plurality of plenum plies to define a plenum preform;

compacting the plenum preform; and

processing the plenum preform.

12. The method of claim 1 , further comprising, prior to laying up the ceramic matrix composite material to form the airfoil preform assembly:

laying up a filler pack material to define a filler pack preform;

compacting the filler pack preform;

processing the filler pack preform to define a green state filler pack preform; and

defining one or more voids in the green state filler pack preform, wherein the one or more voids define at least a portion of the cooling passage.

13. The method of claim 12 , wherein defining one or more voids in the green state filler pack preform comprises machining the green state filler pack preform.

14. A method for forming an airfoil for a gas turbine engine, the method comprising:

forming a plenum preform from a ceramic matrix composite (CMC) material;

forming a filler pack preform from the CMC material;

preparing a plurality of airfoil plies, the plurality of airfoil plies formed from the CMC material;

laying up the plenum preform, the filler pack preform, and the plurality of airfoil plies to form an airfoil preform assembly, the airfoil preform assembly including

opposite pressure and suction sides extending radially along a span,

opposite leading and trailing edges extending radially along the span, the pressure and suction sides extending axially between the leading and trailing edges, the leading edge defining a forward end of the airfoil preform assembly, the trailing edge defining an aft end of the airfoil preform assembly,

a trailing edge portion defined adjacent the trailing edge, the trailing edge portion extending axially over a length, and

a plenum defined within the airfoil preform assembly forward of the trailing edge portion; and

processing the airfoil preform assembly to produce the airfoil,

wherein the pressure and suction sides define an outer surface of the airfoil, and

wherein a cooling passage is defined within the airfoil, the cooling passage defined from the plenum to the trailing edge of the airfoil, the cooling passage defined proximate the suction side of the airfoil, the cooling passage comprising:

a first cavity extending radially within the trailing edge portion;

a second cavity defined aft of the first cavity, the second cavity extending radially within the trailing edge portion;

a crossover aperture defined from the plenum to the first cavity;

a channel defined from the first cavity to the second cavity, the channel extending axially between the first and second cavities; and

an ejection aperture defined from the outer surface of the airfoil to the second cavity;

wherein each of the airfoil plies, the plenum plies, and the filler pack comprise a ceramic matrix composite material such that the airfoil is formed from the ceramic matrix composite material, and

wherein the first cavity, the second cavity, and the channel are defined in the filler pack such that the first cavity, the second cavity, and the channel are separated from the outer surface by the airfoil plies.

15. The method of claim 14 , wherein

a channel that extends along a majority of the length of the trailing edge portion.

16. A method for forming an airfoil for a gas turbine engine, the method comprising:

laying up a plurality of airfoil plies, a plurality of plenum plies, and a filler pack to form an airfoil preform assembly, the airfoil preform assembly including

opposite pressure and suction sides extending radially along a span,

opposite leading and trailing edges extending radially along the span, the pressure and suction sides extending axially between the leading and trailing edges, the leading edge defining a forward end of the airfoil preform assembly, the trailing edge defining an aft end of the airfoil preform assembly,

a trailing edge portion defined adjacent the trailing edge, the trailing edge portion extending axially over a length, and

a plenum defined within the airfoil preform assembly forward of the trailing edge portion; and

processing the airfoil preform assembly to produce the airfoil,

wherein the plurality of airfoil plies, the plurality of plenum plies, and the filler pack are

formed from a ceramic matrix composite (CMC) material,

wherein the filler pack is positioned between the airfoil plies and the plenum plies in the trailing edge portion of the airfoil preform assembly, and

wherein a plurality of cooling passages is defined within the airfoil, each cooling passage defined from the plenum to the trailing edge of the airfoil, and defined proximate the suction side of the airfoil, each cooling passage comprising:

a first cavity extending radially within the trailing edge portion;

a second cavity defined aft of the first cavity, the second cavity extending radially within the trailing edge portion;

a crossover aperture defined from the plenum to the first cavity;

a channel defined from the first cavity to the second cavity, the channel extending axially between the first and second cavities; and

an ejection aperture defined from the outer surface of the airfoil to the second cavity;

wherein each of the airfoil plies, the plenum plies, and the filler pack comprise a ceramic matrix composite material such that the airfoil is formed from the ceramic matrix composite material, and

wherein the first cavity, the second cavity, and the channel are defined in the filler pack such that the first cavity, the second cavity, and the channel are separated from the outer surface by the airfoil plies.