Slotted Annular Preforms for Uniform CVD Densification
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Solution Overview
Problem
Conventional chemical vapor infiltration and deposition (CVI/CVD) processes for making composite structures like carbon/carbon brake disks face challenges with non-uniform densification across thickness, improper microstructure formation, and long processing times.
Innovation Solution
The method involves forming porous structures with annular geometry and using slotted seal plates and preforms to create entrance and exit channels for a pressure gradient chemical vapor deposition process, combined with high-flow and thermal gradient processes to enhance densification, ensuring uniformity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CVI/CVD processes are used to densify porous structures, then composite structures like carbon/carbon brake disks can be produced, but the densification is non-uniform across the thickness of the porous structure
Solution Approach 1:
The porous structure is divided into multiple sections with different porosity levels - a first porous structure with higher porosity and a second porous structure with lower porosity. This segmentation allows different regions to densify at appropriate rates, achieving uniform overall densification while maintaining productivity.
Solution Approach 2:
Different regions of the porous structure are given different local properties - specifically, different porosity levels in different radial zones. The first porous structure has higher porosity to allow faster gas penetration and densification, while the second has lower porosity to control densification rate, creating locally optimized densification characteristics.
2Manufacturing precision
If conventional CVI/CVD processes are used with pressure gradients, then gas can be driven into porous structures for deposition, but the porous structure does not form a desired microstructure
Solution Approach 1:
The preform is segmented into multiple porous structures stacked in sequence, each with controlled porosity. This segmentation enables precise control over gas flow paths and deposition patterns, allowing desired microstructure formation without requiring complex process parameters.
Solution Approach 2:
The porosity parameter is deliberately changed across different radial zones of the preform. By varying porosity from the center outward (or vice versa), the gas flow distribution and deposition rate are controlled to produce the desired microstructure with appropriate fiber-matrix distribution.
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 allows for faster and more uniform densification of porous structures, improving the quality and speed of the composite material production process.
Implementation Method 1
a pressure differential driving the gas mixture into the porous structures
Implementation Method 2
undergoes a reaction such as thermal decomposition, hydrogen reduction, co-reduction, oxidation, carbidization, or nitridation to deposit a binding matrix
Implementation Method 3
Chemical vapor infiltration and deposition (CVI/CVD) is a known process for making composite structures
Implementation Method 4
A gas may be urged into the first entrance channel, through the porous structure, and out the exit channel
Data Source
AI summary
A method of making a fibrous part is provided. The method may comprise forming a porous structure with an annular geometry. A first entrance channel and a second entrance channel may be formed with the entrance channels defined by a surface of the preform. The entrance channels may also extend in a radial direction from an inner diameter of the annular porous structure partially across the surface. An exit channel may be formed between the entrance channels and defined by the surface. The exit channel may extend in a radial direction from an outer diameter of the annular porous structure partially across the surface.