IP Library › Granted Patent US 7,258,530
Granted Patent B2
US 7,258,530 · App. 11/040,464 · Granted Aug 21, 2007

CMC component and method of fabrication

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Quick Facts
Patent No.
US 7,258,530
App. No.
11/040,464
Granted
Aug 21, 2007
Kind
B2
Abstract

An airfoil ( 44 ) formed of a plurality of pre-fired structural CMC panels ( 46, 48, 50, 52 ). Each panel is formed to have an open shape having opposed ends ( 54 ) that are free to move during the drying, curing and/or firing of the CMC material in order to minimize interlaminar stresses caused by anisotropic sintering shrinkage. The panels are at least partially pre-shrunk prior to being joined together to form the desired structure, such as an airfoil ( 42 ) for a gas turbine engine. The panels may be joined together using a backing member ( 30 ), using flanged ends ( 54 ) and a clamp ( 56 ), and/or with a bond material ( 36 ), for example.

Claims (47)

1. A method of fabricating a load-bearing structure from structural ceramic matrix composite (CMC) material, the method comprising:

forming at least one open member using a CMC material;

subjecting the open member to a process causing anisotropic shrinkage of the CMC material in a geometrically unconstrained state so that a first portion of the open member is free to move relative to a second portion of the open member to relieve interlaminar stresses resulting from the anisotropic shrinkage; and

joining the shrunk open member to an adjacent structural member to form a closed member;

further comprising pre-loading the shrunk open member during the joining step.

2. A method of fabricating a load-bearing structure from structural ceramic matrix composite (CMC) material, the method comprising:

forming at least one open member using a CMC material;

subjecting the open member to a process causing anisotropic shrinkage of the CMC material in a geometrically unconstrained state so that a first portion of the open member is free to move relative to a second portion of the open member to relieve interlaminar stresses resulting from the anisotropic shrinkage; and

joining the shrunk open member to an adjacent structural member to form a closed member;

further comprising forming the open member to have a generally C-shape defining an airfoil leading edge;

joining the shrunk open member to an adjacent panel member comprising one of a suction side panel and a pressure side panel with a clamp formed of CMC material; and

finish firing the shrunk open member and clamp together.

3. The method of claim 2 , further comprising pre-loading the shrunk open member during the joining step.

4. A method of fabricating a load-bearing structure form structural ceramic matrix composite (CMC) material, the method comprising:

forming at least one open member using a CMC material;

subjecting the open member to a process causing anisotropic shrinkage of the CMC material in a geometrically unconstrained state so that a first portion of the open member is free to move relative to a second portion of the open member to relieve interlaminar stresses resulting from the anisotropic shrinkage; and

joining the shrunk open member to an adjacent structural member to form a closed member;

further comprising forming the open member to have a generally C-shape defining an airfoil leading edge;

forming a first joint between a first end of the shrunk open member, a suction side panel member, and a first end of a rib member; and

forming a second joint between a second end of the shrunk open member, a pressure side panel member, and a second end of the rib member.

5. The method of claim 4 , further comprising performing the steps of forming a first joint and forming a second joint concurrently while applying a pre-load to the generally C-shape open member.

6. A method of fabricating a load-bearing structure from structural ceramic matrix composite (CMC) material, the method comprising:

forming at least one open member using a CMC material;

subjecting the open member to a process causing anisotropic shrinkage of the CMC material in a geometrically unconstrained state so that a first portion of the open member is free to move relative to a second portion of the open member to relieve interlaminar stresses resulting from the anisotropic shrinkage; and

joining the shrunk open member to an adjacent structural member to form a closed member;

further comprising forming the open member to have a generally V-shape defining an airfoil trailing edge;

forming a first joint between a first end of the shrunk open member, a suction side panel member, and a first end of a rib member; and

forming a second joint between a second end of the shrunk open member, a pressure side panel member, and a second end of the rib member.

7. The method of claim 6 , further comprising performing the steps of forming a first joint and forming a second joint concurrently while applying a pre-load to the generally V-shape open member.

8. A method of fabricating a load-bearing structure from structural ceramic matrix composite (CMC) material, the method comprising:

forming at least one open member using a CMC material;

subjecting the open member to a process causing anisotropic shrinkage of the CMC material in a geometrically unconstrained state so that a first portion of the open member is free to move relative to a second portion of the open member to relieve interlaminar stresses resulting from the anisotropic shrinkage; and

joining the shrunk open member to an adjacent structural member to form a closed member;

wherein the open shape is formed to comprise an airfoil shape comprising a gap, and wherein the step of joining further comprises applying a backing member to close the gap.

9. The method of claim 8 , further comprising applying a pre-load to the airfoil shape during the step of joining.

10. A method of fabricating a load-bearing structure from structural ceramic matrix composite (CMC) material, the method comprising:

forming at least one open member using a CMC material;

subjecting the open member to a process causing anisotropic shrinkage of the CMC material in a geometrically unconstrained state so that a first portion of the open member is free to move relative to a second portion of the open member to relieve interlaminar stresses resulting from the anisotropic shrinkage; and

joining the shrunk open member to an adjacent structural member to form a closed member; and

after forming the closed member, casting a ceramic core material in a core region of the closed member; and

finish firing the closed member and the ceramic core material together.

11. An apparatus at a stage of manufacture comprising:

an open member formed of CMC material having been subjected to a process causing at least some anisotropic shrinkage of the CMC material, the shrunk open member comprising opposed ends separated by a gap during the process to relieve interlaminar stresses developed as a result of the anisotropic shrinkage; and

a joining member subsequently attached between the opposed ends and imposing a preload on the member.

12. The apparatus of claim 11 , wherein the open member comprises a generally C-shape defining a leading edge shape of an airfoil.

13. The apparatus of claim 11 , wherein the open member comprises a generally V-shape defining a trailing edge shape of an airfoil.

14. The apparatus of claim 11 , wherein the open member comprises a flanged end and wherein the joining member comprises a flanged end, and further comprising a clamp joining the respective flanged ends of the open member and the joining member.