	US 12,233,572 B2
	Methods to eliminate mudcracks in CMC matrix by humidity controlled atmosphere
Pathikumar Sellappan, Seal Beach, CA (US); and Sungbo Shim, Irvine, CA (US)
Assigned to Rolls-Royce High Temperature Composites, Inc., Cypress, CA (US)
Filed by Rolls-Royce High Temperature Composites Inc., Cypress, CA (US)
Filed on Sep. 9, 2020, as Appl. No. 17/015,840.
Claims priority of provisional application 62/898,187, filed on Sep. 10, 2019.
Prior Publication US 2021/0069931 A1, Mar. 11, 2021
Int. Cl. B28B 11/24 (2006.01); C04B 35/64 (2006.01)

CPC B28B 11/247 (2013.01) [C04B 35/64 (2013.01); C04B 2235/616 (2013.01); C04B 2235/65 (2013.01)]

11 Claims

1. A method of reducing dry crack formation in a ceramic matrix composite, the method comprising:

exposing an outer surface of a green body to a gaseous atmosphere having a first humidity for a first period of time at room temperature, the green body being a slurry-infiltrated ceramic fiber preform comprising a plurality of fiber plies or a plurality of prepreg tape layers comprising fibers, the first humidity being a relative humidity within a range of about 40 percent to 100 percent, the first period of time being within a range of about six hours to about 12 hours; and

reducing the humidity of the gaseous atmosphere, while the outer surface of the green body is exposed to the gaseous atmosphere at room temperature, from the first humidity to a second humidity over a second period of time, the second humidity being a relative humidity within a range of about 50 percent to about 65 percent or within a range of about 45 percent to about 60 percent, the second period of time being within a range of about 12 hours to about 18 hours.