Graphite-PVB Fugitive Cores for Complex CMC Cooling Channels
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Solution Overview
Problem
Current methods for creating cooling structures in ceramic matrix composite (CMC) components are expensive and limited in flexibility, unable to form complex shapes and are not cost-effective.
Innovation Solution
Incorporating fugitive graphite-polyvinyl butyral (PVB) core inserts into CMC preforms, which are then treated to remove PVB and retain graphite, forming internal cavities for cooling channels, allowing for complex and efficient cooling structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If drilling and machining holes, pockets or channels into surfaces are used to create cooling structures, then cooling channels can be formed, but the manufacturing cost increases and manufacturing complexity increases
Solution Approach 1:
The core insert is placed into the preform before densification, establishing the cooling channel geometry in advance. This preliminary positioning allows the cavity to form naturally during densification without requiring subsequent expensive machining operations to create the cooling structures.
Solution Approach 2:
The core insert is removed after densification to create the cooling cavity. This extraction approach allows the cooling channel to be formed by removing the sacrificial core material rather than by adding material through machining, significantly reducing manufacturing cost and complexity.
2Ease of manufacture
If plates are used to cover the resultant structures after drilling, then cooling structures can be formed, but device complexity and manufacturing cost increase
Solution Approach 1:
Instead of adding plates to cover drilled holes, the invention removes the core insert after densification to create the cooling cavity. This extraction approach eliminates the need for additional cover plates and assembly steps, reducing both device complexity and manufacturing cost.
Solution Approach 2:
The cooling channel formation is merged with the densification process itself. The core insert serves as a placeholder that defines the cavity geometry, and its removal after densification creates the cooling channel as an integrated feature rather than a separate assembly step.
3Adaptability or versatility
If mandrels are inserted during layup of plies, then internal cavities can be formed, but manufacturing cost increases and flexibility is limited
Solution Approach 1:
The core insert material composition is changed to include both graphite and PVB in specific proportions. This parameter change allows the core to survive the initial layup process while enabling complete removal after densification, providing both manufacturing ease and design flexibility.
Solution Approach 2:
The core insert uses a composite material of graphite and PVB. The graphite provides structural integrity during manufacturing while the PVB can be completely removed after densification. This composite approach enables complex cooling structures with both cost effectiveness and design flexibility.
4Shape
If current methods are used to create cooling structures, then cooling channels can be formed, but the ability to create complex shapes is limited
Solution Approach 1:
The core insert is fabricated with the desired complex cooling channel geometry before being placed in the preform. This preliminary shaping allows complex geometries to be created using standard molding techniques rather than requiring complex machining or assembly operations.
Solution Approach 2:
The core insert is completely removed after densification to create the cooling cavity. This extraction approach allows the full complexity of the core insert geometry to be transferred to the cooling channel, enabling complex shapes that would be difficult or expensive to create by other methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the creation of flexible, complex cooling channels within CMC components, enhancing cooling efficiency and reducing costs by eliminating the need for expensive machining and cover plates.
Implementation Method 1
subjecting the preform with the one or more integrated core inserts to a heat treatment to remove polyvinyl butyral while retaining graphite
Data Source
Figure 1~2
Figure 3~4
AI summary
The preparation of ceramic matrix composite (CMCs) is disclosed in which a ceramic matrix composite (CMC) preform is made with one or more integrated core inserts (30) made of a fugitive material comprising graphite and polyvinyl butyral. The preform with integrated core inserts (30) is subjected to a heat treatment to remove the polyvinyl butyral (e.g., by melting or burning) while retaining the graphite. Removal of the polyvinyl butyral results in formation of one or more internal cavities within the preform in which the retained graphite aids in maintaining the shape of the internal cavities. The preform can then be subjected to densification to form a composite and the remaining graphite can be removed from the internal cavities.