CMC Cooling Holes via Sacrificial Fiber EBC Lining
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Solution Overview
Problem
Existing methods for forming holes in ceramic matrix composite components for high-temperature and high-pressure environments either weaken the material by cutting fibers or leave unprotected surfaces, and applying an environmental barrier coating can inadvertently plug the holes.
Innovation Solution
A sacrificial fiber with an environmental barrier coating is inserted into a ceramic preform, which is then formed into a composite body, and the fiber is removed, leaving the coating to define a hole that maintains the integrity of the ceramic fibers and protects against environmental attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If holes are formed by cutting or drilling in CMC components, then holes can be created for cooling purposes, but the ceramic fibers are cut and the environmental barrier coating is compromised, weakening the material
Solution Approach 1:
The environmental barrier coating is applied to the sacrificial fiber before the fiber is inserted into the CMC component. This preliminary coating ensures that when the sacrificial fiber is later removed, the coating remains as a protective lining in the hole, preventing material weakening that would occur with traditional post-hole coating methods
Solution Approach 2:
A sacrificial fiber is introduced as a temporary intermediary element during manufacturing. This fiber serves as a placeholder that maintains hole geometry and provides a substrate for environmental barrier coating application. The sacrificial fiber is subsequently removed, leaving the coating intact as the final protective structure
2Reliability
If an environmental barrier coating is applied after holes are formed, then the coating can protect the component, but the coating material inadvertently plugs the holes
Solution Approach 1:
The environmental barrier coating is applied to the sacrificial fiber before it is inserted into the CMC component. This preliminary coating ensures that when the sacrificial fiber is later removed, the coating remains as a protective lining in the hole, preventing material weakening that would occur with traditional post-hole coating methods
Solution Approach 2:
The sacrificial fiber acts as an intermediary that carries the environmental barrier coating into the hole position. By removing the sacrificial fiber after coating application, the coating is left as a hollow-lined structure that maintains both protection and hole functionality
3Reliability
If sacrificial fiber with environmental barrier coating is used to form holes, then the coating protects against environmental attacks and maintains fiber integrity, but the manufacturing process becomes more complex
Solution Approach 1:
The environmental barrier coating and sacrificial fiber are combined into a single integrated component before insertion. This merging allows the coating to be applied in advance and ensures it remains attached to the sacrificial fiber throughout the manufacturing process, simplifying the overall process despite the additional initial step
Solution Approach 2:
The sacrificial fiber with pre-applied coating serves as a temporary mediator that simplifies the final structure. By using this intermediary, the complex requirement of creating protected holes without plugging is resolved through a single removal step rather than multiple complex operations
Data Source
AI summary
A method for forming a hole in a ceramic matrix composite (CMC) component may be provided. A sacrificial fiber having an environmental barrier coating on an outer surface thereof may be inserted into a porous ceramic preform that includes ceramic fibers. The ceramic preform may be formed into a ceramic matrix composite body. The sacrificial fiber may be removed from the ceramic matrix composite body, the environmental barrier coating of the sacrificial fiber defining an opening in the ceramic matrix composite body. A ceramic matrix composite component may be provided. The ceramic matrix composite component may include an environmental barrier coating of a sacrificial fiber, where the environmental barrier coating forms a lining of a hole passing partly or entirely through a thickness of the ceramic matrix composite body.