PARTICLE ENHANCED CERAMIC MATRIX COMPOSITE WITH NO PARTICLES ON SURFACE PLIES

1 . A method of forming a ceramic matrix composite, the method comprising:

preparing a plurality of fibrous ceramic plies by:

applying a binder solution loaded with ceramic particles to each of a first subset of plies; and

applying the binder solution without ceramic particles to each of a second subset of plies;

arranging the plurality of plies to form a preform with a gradient along a thickness direction of the preform by:

stacking the first subset of plies to form a first zone of the preform; and

stacking individual ones of the second subset of the plies on both sides of the first zone to form a second zone on each side of the first zone,

wherein loading of the ceramic particles is higher in the first zone than in the second zones; and

densifying the preform with a ceramic matrix.

2 . The method of claim 1 and further comprising:

applying the binder solution with the ceramic particles to a third subset of plies; and

stacking individual ones of the third subset of plies on both sides of the first zone and between the first and second zones to form third zones on each side of the first zone.

3 . The method of claim 2 , wherein arranging the preform comprises:

forming the first zone;

subsequently, forming the third zones; and

debulking the first zone and the third zones.

4 . The method of claim 3 and further comprising:

subsequently, forming the second zones; and

debulking the first zone, the second zones, and the third zones.

5 . The method of claim 2 , wherein arranging the preform comprises:

forming one of the second zones;

subsequently, forming one of the third zones;

subsequently, forming the first zone;

subsequently, forming an other of the third zones; and

subsequently, forming an other of the second zones.

6 . The method of claim 5 and further comprising: debulking the first zone, the second zones, and the third zones.

7 . The method of claim 6 and further comprising: removing migrant ceramic particles from the second zones using one of a brushing and blowing technique.

8 . The method of claim 1 , wherein the step of densifying the preform with a ceramic matrix comprises one or a combination of chemical vapor infiltration, melt infiltration, and polymer infiltration and pyrolysis.

9 . The method of claim 1 , wherein the binder solution comprises a solvent, a dispersant, and one of polyvinyl alcohol and polyvinyl butyral.

10 . The method of claim 9 , wherein the ceramic particles comprise one or a combination of silicon carbide, boron carbide, hafnium oxide, hafnium boride, aluminum oxide, ytterbium oxide, or zirconium boride.

11 . The method of claim 1 , wherein the step of applying the binder solution to each of the first subset and the second subset of plies comprises one of a spraying and pipetting technique.

12 . The method of claim 1 , wherein each of the first subset and the second subset of plies are impregnated with the binder solution.

13 . A gradient preform comprising:

a stacking arrangement of fibrous ceramic plies comprising:

a first zone comprising a first subset of plies; and

a second zone disposed on each side of the first zone, each second zone comprising a second subset of plies; and

ceramic particles dispersed throughout the first zone such that loading of the ceramic particles is higher in the first zone than in the second zones.

14 . The preform of claim 13 , wherein the plies are formed from tows of silicon carbide.

15 . The preform of claim 14 , wherein a tow architecture of each of the plies is one of harness-satin, plain, twill, braid, and unidirectional.

16 . The preform of claim 13 , wherein the ceramic particles comprise one or a combination of silicon carbide, boron carbide, hafnium oxide, hafnium boride, aluminum oxide, ytterbium oxide, or zirconium boride.

17 . The preform of claim 16 , wherein a size of the ceramic particles ranges from 0.5 microns to 100 microns.

18 . The preform of claim 13 , wherein a particle loading of the first zone ranges from 5 wt % to 15 wt %.

19 . The preform of claim 18 , wherein a particle loading of each of the second zones is less than 5 wt %.

20 . The preform of claim 13 and further comprising: a third zone disposed on both sides of the first zone and between the first zone and each of the second zone, each of the third zones comprising a third subset of plies.