PVB-based sacrificial tackifier for CMC
A tackified ceramic fabric sheet includes a pre-preg layer having a fabric of woven ceramic tows and a tackifier compound surrounding the tows and comprising 15% to 60% polyvinyl butyral with ethanol. The sheet further includes a removable first backing film layer on a first side of the pre-preg layer.
1 . A method of forming a ceramic matrix composite component, the method comprising:
forming a plurality of plies from a tackified ceramic fabric sheet, the tackified ceramic fabric sheet comprising:
a pre-preg layer comprising:
a fabric of woven ceramic tows;
a tackifier compound impregnating the fabric and comprising 15% to 60% polyvinyl butyral in ethanol, wherein the remainder of the tackifier compound is ethanol and wherein the tackifier compound is the sole impregnating compound; and
a removable first backing film layer on a first side of the pre-preg layer;
laying up the plurality of plies into a preform structure;
removing the ethanol from the plurality of plies while stabilizing the preform structure;
subsequently, removing the polyvinyl butyral; and
densifying the preform structure with a matrix.
2 . The method of claim 1 , wherein the step of laying up the plurality of plies comprises removing the first backing film layer from each of the plurality of plies such that the preform structure is formed from the pre-preg layer of each of the plurality of plies.
3 . The method of claim 1 , wherein the step of removing the ethanol while rigidizing the preform structure comprises one or a combination of heating the plurality of plies and applying a vacuum to the plurality of plies.
4 . The method of claim 1 , wherein the step of removing the polyvinyl butyral comprises burning off the polyvinyl butyral by heating the preform structure to a temperature ranging from 500° F. to 1350° F.
5 . The method of claim 4 , wherein the temperature ranges from 800° F. to 1150° F.
6 . The method of claim 4 , wherein the step of removing the polyvinyl butyral further comprises placing the preform structure in a nitrogen-rich environment.
7 . The method of claim 4 , wherein the step of removing the polyvinyl butyral further comprises placing the preform structure in an environment having a mixture of nitrogen gas and hydrogen gas.
8 . The method of claim 1 , wherein densifying the preform structure with a matrix is carried using one or a combination of chemical vapor infiltration, chemical vapor deposition, polymer infiltration and pyrolysis, and melt infiltration.
9 . The method of claim 1 , wherein the matrix comprises silicon carbide.
10 . The method of claim 1 , wherein the ceramic tows comprise silicon carbide.
11 . The method of claim 1 , wherein the tackifier compound comprises 30% to 40% polyvinyl butyral in ethanol.