CVI Tooling Hole Gradients for Uniform CMC Infiltration
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Solution Overview
Problem
Existing tooling for chemical vapor infiltration (CVI) of ceramic matrix composites (CMCs) fails to ensure uniform deposition of the ceramic matrix due to insufficient infiltration of vaporous precursors in complex-shaped preforms, leading to variations in deposition rate and mechanical behavior.
Innovation Solution
The use of tooling fixtures with varied infiltration hole parameters, including varying hole lengths, diameters, and spacings, to create a continuous path gradient that minimizes reactant gas decay and ensures uniform IFC deposition across the preform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform holes are used in the tooling fixture, then the structure is simple and easy to manufacture, but the infiltration is non-uniform and resin-rich regions form
Solution Approach 1:
The patent applies local quality by varying the hole dimensions (diameter, length, or both) at different locations within the tooling fixture. Specifically, holes in regions prone to resin accumulation are made smaller or longer to restrict excessive resin flow, while holes in other regions maintain larger dimensions to ensure adequate infiltration. This localized variation in hole geometry enables uniform resin distribution throughout the composite workpiece while maintaining a relatively simple overall fixture structure.
2Productivity
If larger holes are used in the tooling fixture, then resin infiltration is enhanced, but resin-rich regions form and voids are not eliminated
Solution Approach 1:
The patent implements local quality by strategically varying hole dimensions across different regions of the tooling fixture. In areas where resin flow is excessive or where voids are likely to form, holes are made smaller or longer to control and restrict resin infiltration. In other areas, larger holes maintain adequate infiltration rates. This spatially differentiated approach ensures both sufficient overall infiltration and uniform resin distribution, eliminating resin-rich regions and voids.
Solution Approach 2:
The patent applies parameter changes by modifying the geometric parameters of the holes (diameter, length, aspect ratio) at different locations within the tooling fixture. By changing these dimensional parameters locally rather than using uniform dimensions throughout, the system optimizes resin flow control in each specific region, preventing both excessive infiltration (resin-rich regions) and insufficient infiltration (voids).
3Manufacturing precision
If smaller holes are used in the tooling fixture, then resin-rich regions are prevented, but infiltration is insufficient and voids remain
Solution Approach 1:
The patent applies local quality by using smaller or longer holes only in specific regions where resin accumulation is problematic, while maintaining larger hole dimensions in other regions to ensure adequate infiltration rates. This selective approach prevents resin-rich regions in critical areas without compromising overall infiltration efficiency, thereby eliminating both uniformity issues and void formation.
4Manufacturing precision
If the tooling fixture thickness is increased, then more holes can be incorporated for better infiltration control, but the fixture becomes more complex and harder to manufacture
Solution Approach 1:
The patent applies dimensionality change by utilizing the thickness dimension of the tooling fixture to arrange holes at multiple levels or depths. Instead of simply increasing the number of holes in a single plane, the invention strategically positions holes at different thickness locations, allowing for three-dimensional control of resin flow patterns. This approach provides enhanced infiltration control while avoiding excessive fixture complexity, as the dimensional arrangement is integrated into the overall fixture design rather than adding separate components.
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
The solution achieves more uniform IFC deposition, enhancing the mechanical consistency and durability of CMC parts by optimizing the infiltration process.
Implementation Method 1
Chemical vapor infiltration (CVI) is a popular process used to manufacture ceramic matrix composite (CMC) materials. The CVI process involves the decomposition of a vapor phase precursor and the subsequent deposition of the reaction product onto the substrate
Implementation Method 2
The CVI process involves the decomposition of a vapor phase precursor and the subsequent deposition of the reaction product onto the substrate
Implementation Method 3
resin-rich regions, also known as hot spots, form at the periphery of the CMC workpiece while the interior regions fail to infiltrate completely
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A tooling fixture (10A) suitable for use in infiltrating a fibrous preform (12) with a flow of reactant gas includes an outer surface (16A) and an inner surface (14A) defining a thickness (TA) therebetween, and a plurality of holes (18A) extending through the thickness (TA) of the tooling fixture (10A). The plurality of holes (18A) includes a first hole (18A) having cylindrical geometry with a first pair of dimensions comprising a first length (LA) and a first diameter (DA), a second hole having cylindrical geometry with a second pair of dimensions comprising a second length and a second diameter, and a third hole having cylindrical geometry with a third pair of dimensions comprising a third length and a third diameter. At least one dimension of the first pair of dimensions is different from at least one dimension of the second pair of dimensions, and at least one dimension of the second pair of dimensions is different from at least one dimension of the third pair of dimensions.