Forced-Flow CVI Tooling for Faster Preform Densification
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Solution Overview
Problem
The challenge in chemical vapor infiltration (CVI) is the lengthy processing time required to form a ceramic matrix, necessitating means to accelerate this process.
Innovation Solution
A tooling assembly comprising a hollow base plate, solid cover plate, and seal plates with support bars is used to create a pressure gradient for forced-flow CVI, enabling faster deposition of reactive precursors within fibrous preforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional diffusion-based CVI process is used, then complete infiltration of reactive precursors into preforms is achieved, but processing time is excessively long
Solution Approach 1:
The patent applies pneumatic principles by using pressure differentials to drive forced-flow of reactive precursors through the preforms. Gas-phase precursors are forced into the preform under pressure, creating a pressure gradient that accelerates infiltration from hours to minutes, resolving the contradiction between complete infiltration and processing time
Solution Approach 2:
The patent changes the flow regime parameter from passive diffusion to forced convection by applying pressure gradients. This parameter change transforms the infiltration mechanism, enabling rapid penetration of reactive precursors into preform interiors while maintaining complete infiltration, thus improving productivity without sacrificing process completeness
2Loss of time
If forced-flow CVI is implemented, then infiltration time is reduced, but tooling complexity increases due to sealing requirements
Solution Approach 1:
The tooling is segmented into modular components: base plate, cover plate, and individual seal plates that can be independently positioned between preform layers. This segmentation allows simplified assembly and disassembly while maintaining effective sealing, reducing the perceived complexity of the forced-flow tooling system
Solution Approach 2:
Seal plates act as intermediary elements between the preform layers, creating the necessary pressure barriers to enable forced-flow without requiring complex integrated sealing systems. These simple plate intermediaries facilitate pressure gradient creation while keeping the overall tooling structure relatively simple
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
This approach significantly reduces the time required to densify preforms by facilitating rapid infiltration and deposition of reactive gases, enhancing the fabrication of ceramic matrix composites (CMCs).
Implementation Method 1
A tooling assembly for use in infiltrating a plurality of hollow fibrous preforms includes a hollow base plate disposed at a first end of the tooling assembly relative to a direction of a flow of reactive gas
Implementation Method 2
directing the flow of reactive gas into a hollow interior of the stack
Implementation Method 3
Chemical vapor infiltration (CVI) is a well-known process used in the fabrication of ceramic matrix composites (CMCs). During CVI, one or more porous ceramic preforms can be placed in a reactor and exposed to reactive precursors carried in a gaseous flow through the reactor. The gaseous flow diffuses into the porous preforms to and the reactants deposit to form a matrix
Implementation Method 4
a plurality of seal plates in physical contact with disposed between adjacent ones of the plurality of fibrous preforms
Data Source
AI summary
A tooling assembly for use in infiltrating a plurality of hollow fibrous preforms includes a hollow base plate disposed at a first end of the tooling assembly relative to a direction of a flow of reactive gas, a solid cover plate disposed at an opposing second end of the tooling assembly, a plurality of seal plates in physical contact with disposed between adjacent ones of the plurality of fibrous preforms, and a plurality of support bars extending between the base plate and the cover plate and disposed about a periphery of the tooling assembly.