Ceramic matrix composite blade outer air seal segment using pre-densified tubes and method thereof

1 . A ceramic matrix composite (CMC) blade outer air seal (BOAS) segment, comprising:

a preform having:

a base layup formed of one or more fabric plies folded to form a first rib portion, a shoe portion having an upstream fold edge and a downstream fold edge, and a second rib portion;

one or more pre-densified CMC tubes disposed circumferentially between the first rib portion and the upstream fold edge and between the second rib portion and the downstream fold edge, respectively; and

an outer wrap formed of one or more fabric plies disposed to overwrap the first rib portion, the one or more pre-densified CMC tubes disposed circumferentially between the first rib portion and the upstream fold edge, the upstream fold edge, the downstream fold edge, the one or more pre-densified CMC tubes disposed circumferentially between the second rib portion and the downstream fold edge, and the second rib portion,

wherein ends of the base layup include L-shaped cuts to allow the ends to intersect and form a substantially U-shaped cross section forming the first and second rib portions.

2 . The CMC BOAS segment of claim 1 , wherein the preform has been densified by Chemical Vapor Infiltration (CVI), Melt Infiltration (MI), Polymer Infiltration and Pyrolysis (PIP), a hybrid of CVI/MI, or a hybrid of CVI/PIP.

3 . The CMC BOAS segment of claim 1 , wherein the pre-densified CMC tubes have flattened non-circular cross sections.

4 . The CMC BOAS segment of claim 1 , wherein one or more holes are formed to extend from the base layup between the first rib portion and the second rib portion to an interior of one of the pre-densified tubes.

5 . The CMC BOAS segment of claim 1 , wherein an end of one or more of the pre-densified tubes is sealed.

6 . The CMC BOAS segment of claim 1 , wherein the CMC BOAS segment comprises one sixth of a CMC BOAS wheel.

7 . A ceramic matrix composite (CMC) blade outer air seal (BOAS) segment, comprising:

a preform having:

a base layup formed of one or more fabric plies folded to form a first rib portion, a shoe portion having an upstream fold edge and a downstream fold edge, and a second rib portion;

one or more pre-densified CMC tubes disposed circumferentially between the first rib portion and the upstream fold edge and between the second rib portion and the downstream fold edge, respectively; and

an outer wrap formed of one or more fabric plies disposed to overwrap the first rib portion, the one or more pre-densified CMC tubes disposed circumferentially between the first rib portion and the upstream fold edge, the upstream fold edge, the downstream fold edge, the one or more pre-densified CMC tubes disposed circumferentially between the second rib portion and the downstream fold edge, and the second rib portion,

wherein the one or more pre-densified tubes are circumferentially offset relative to the base layup and the outer wrap.

8 . A method of forming a ceramic matrix composite (CMC) blade outer air seal (BOAS) segment, comprising:

forming a preform by:

folding a base layup formed of one or more fabric plies to form a first rib portion, a shoe portion having an upstream fold edge and a downstream fold edge, and a second rib portion;

disposing one or more pre-densified CMC tubes circumferentially between the first rib portion and the upstream fold edge and between the second rib portion and the downstream fold edge, respectively; and

disposing an outer wrap formed of one or more fabric plies to overwrap the first rib portion, the one or more pre-densified CMC tubes disposed circumferentially between the first rib portion and the upstream fold edge, the upstream fold edge, the downstream fold edge, the one or more pre-densified CMC tubes disposed circumferentially between the second rib portion and the downstream fold edge, and the second rib portion,

wherein ends of the base layup include L-shaped cuts and the method further comprises intersecting the L-shaped cuts to form a substantially U-shaped cross section forming the first and second rib portions.

9 . The method of claim 8 , further comprising densifying the preform by Chemical Vapor Infiltration (CVI), Melt Infiltration (MI), Polymer Infiltration and Pyrolysis (PIP), a hybrid of CVI/MI, or a hybrid of CVI/PIP.

10 . The method of claim 8 , wherein forming the preform further comprises forming one or more holes extending through the base layup between the first and second ribs to an interior of one of the pre-densified CMC tubes.

11 . The method of claim 8 , wherein at least one end of at least one of the pre-densified CMC tubes is sealed prior to being disposed circumferentially.

12 . A method of forming a ceramic matrix composite (CMC) blade outer air seal (BOAS) segment, comprising:

forming a preform by:

folding a base layup formed of one or more fabric plies to form a first rib portion, a shoe portion having an upstream fold edge and a downstream fold edge, and a second rib portion;

disposing one or more pre-densified CMC tubes circumferentially between the first rib portion and the upstream fold edge and between the second rib portion and the downstream fold edge, respectively; and

disposing an outer wrap formed of one or more fabric plies to overwrap the first rib portion, the one or more pre-densified CMC tubes disposed circumferentially between the first rib portion and the upstream fold edge, the upstream fold edge, the downstream fold edge, the one or more pre-densified CMC tubes disposed circumferentially between the second rib portion and the downstream fold edge, and the second rib portion; and

densifying the preform by Chemical Vapor Infiltration (CVI), Melt Infiltration (MI), Polymer Infiltration and Pyrolysis (PIP), a hybrid of CVI/MI, or a hybrid of CVI/PIP,

wherein at least one end of at least one of the pre-densified CMC tubes is blocked with fabric layup and sealed during the densifying of the preform.

13 . A method of forming a ceramic matrix composite (CMC) blade outer air seal (BOAS) segment, comprising:

forming a preform by:

folding a base layup formed of one or more fabric plies to form a first rib portion, a shoe portion having an upstream fold edge and a downstream fold edge, and a second rib portion;

disposing one or more pre-densified CMC tubes circumferentially between the first rib portion and the upstream fold edge and between the second rib portion and the downstream fold edge, respectively; and

disposing an outer wrap formed of one or more fabric plies to overwrap the first rib portion, the one or more pre-densified CMC tubes disposed circumferentially between the first rib portion and the upstream fold edge, the upstream fold edge, the downstream fold edge, the one or more pre-densified CMC tubes disposed circumferentially between the second rib portion and the downstream fold edge, and the second rib portion,

wherein disposing the one or more pre-densified CMC tubes circumferentially includes offsetting the pre-densified CMC tubes relative to the base layup and the outer wrap.

14 . A method of forming a ceramic matrix composite (CMC) blade outer air seal (BOAS) segment, comprising:

forming a preform by:

folding a base layup formed of one or more fabric plies to form a first rib portion, a shoe portion having an upstream fold edge and a downstream fold edge, and a second rib portion;

disposing one or more pre-densified CMC tubes having sealed ends circumferentially between the first rib portion and the upstream fold edge and between the second rib portion and the downstream fold edge, respectively, wherein the pre-densified CMC tubes have flattened non-circular cross sections;

disposing an outer wrap formed of one or more fabric plies to overwrap the first rib portion, the one or more pre-densified CMC tubes disposed circumferentially between the first rib portion and the upstream fold edge, the upstream fold edge, the downstream fold edge, the one or more pre-densified CMC tubes disposed circumferentially between the second rib portion and the downstream fold edge, and the second rib portion; and

forming one or more holes extending through the base layup between the first rib portion and the second rib portion to an interior of one of the pre-densified CMC tubes; and

densifying the preform by Chemical Vapor Infiltration (CVI), Melt Infiltration (MI), Polymer Infiltration and Pyrolysis (PIP), a hybrid of CVI/MI, or a hybrid of CVI/PIP,

wherein ends of the base layup include L-shaped cuts and the forming the preform further comprises intersecting the L-shaped cuts to form a substantially U-shaped cross section forming the first and second rib portions.