Methodology and tooling arrangements for increasing interlaminar shear strength in a ceramic matrix composite structure

Abstract

Methodology and tooling arrangements for increasing interlaminar shear strength in a ceramic matrix composite (CMC) structure are provided. The CMC structure may be formed by a plurality of layers of ceramic fibers disposed between a top surface and a bottom surface of the composite structure. A plurality of surface recesses are formed on the surfaces of the structure. For example, each of the surfaces of the composite structure may be urged against corresponding top and bottom surfaces of a tool having a plurality of asperities. The plurality of surface recesses causes an out-of-plane sub-surface fiber displacement along an entire thickness of the structure, and the sub-surface fiber displacement is arranged to increase an interlaminar shear strength of the structure.

1 . A method of fabricating a ceramic matrix composite structure, said method comprising:
 forming a ceramic matrix composite including a plurality of layers of ceramic fibers disposed between a top surface and a bottom surface of the composite structure;   urging each of the surfaces of the composite structure against corresponding top and bottom surfaces of a tool having a plurality of asperities;   as a result of said urging, the asperities forming a plurality of surface recesses on the surfaces of the structure, wherein the plurality of the surface recesses causes an out-of-plane sub-surface fiber displacement arranged to increase an interlaminar shear strength of the structure.   
     
     
         2 . The method of  claim 1 , wherein the urging is performed in response to a laminate consolidation pressure applied to the structure during a laminate consolidation stage. 
     
     
         3 . The method of  claim 1 , further comprising arranging the plurality of asperites over the surfaces of the tool in accordance with a respective pattern. 
     
     
         4 . The method of  claim 1 , further comprising selecting the respective pattern from the group consisting of a random pattern, a geometric pattern and a combination of said patterns. 
     
     
         5 . The method of  claim 1 , further comprising selecting at least one physical characteristic of the plurality of asperities, wherein the at least one physical characteristic includes at least one of the following: size and shape of the plurality of asperities. 
     
     
         6 . The method of  claim 1 , further comprising distributing the plurality of asperities over the respective top and bottom tool surfaces to establish a staggered asperity arrangement between said surfaces configured to produce a sinusoidal out-of-plane fiber displacement. 
     
     
         7 . The method of  claim 1 , further comprising arranging the plurality of asperities over the surfaces of the tool to form discrete surface recesses. 
     
     
         8 . The method of  claim 1 , further comprising arranging the plurality of asperities over the surfaces of the tool to form respective linearly extending recesses. 
     
     
         9 . The method of  claim 1 , further comprising arranging the plurality of asperities over the surfaces of the tool to form serpentinely extending recesses. 
     
     
         10 . A ceramic matrix composite structure comprising:
 a plurality of layers of ceramic fibers disposed between a top surface and a bottom surface of the composite structure; and   a plurality of surface recesses formed on the surfaces of the structure, wherein the plurality of the surface recesses causes an out-of-plane sub-surface fiber displacement along an entire thickness of the structure, wherein the sub-surface fiber displacement is arranged to increase an interlaminar shear strength of the structure.   
     
     
         11 . The structure of  claim 10 , wherein a depth of the surface recesses is based on a thickness of the structure, wherein the depth of the surface recesses comprises from 10 to 50 percent of a thickness of the CMC structure. 
     
     
         12 . The structure of  claim 10 , wherein a depth of the surface recesses ranges from approximately 0.5 mm to approximately 5 mm. 
     
     
         13 . The structure of  claim 10 , wherein a distance spacing between adjacent surface recesses is based on a thickness of the structure, wherein the distance spacing between adjacent surface recesses comprises 150 to 500 percent of a thickness of the CMC structure. 
     
     
         14 . The structure of  claim 10 , wherein the distance spacing between adjacent surface recesses is further based on a depth of the surface recesses, wherein the distance spacing between adjacent surface recesses comprises 300 to 1000 percent of the depth of said adjacent surface recesses. 
     
     
         15 . The structure of  claim 10 , wherein a distance spacing between adjacent surface recesses ranges from approximately 3 mm to approximately 15 mm. 
     
     
         16 . The structure of  claim 10 , wherein the surface recesses comprise discrete surface recesses. 
     
     
         17 . The structure of  claim 10 , wherein the surface recesses comprise respective linearly extending recesses. 
     
     
         18 . The structure of  claim 10 , wherein the surface recesses comprise respective serpentinely extending recesses. 
     
     
         19 . The structure of  claim 10 , wherein the plurality of top and bottom surface recesses are arranged with respect to one another to establish a staggered arrangement configured to produce a sinusoidal out-of-plane fiber displacement.