3D Woven CMC Preforms With Pre-Weakened Regions for Faster Machining
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Solution Overview
Problem
Existing methods for forming slots and cavities in ceramic matrix composites (CMCs) are inefficient due to the need for machining techniques that are slow because of the material's density and porosity, necessitating a means to locally increase porosity for faster machining.
Innovation Solution
Introduce fugitive yarns during the weaving process to create pre-weakened regions with higher porosity, which are then decomposed to facilitate quicker machining operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If machining techniques such as grinding or drilling are used to form slots and cavities in CMC components, then features like seals and cavities can be produced, but the machining speed is slow due to the density and porosity of the material
Solution Approach 1:
The patent applies local quality by creating regions with different porosity levels within the CMC component. Fugitive yarns are selectively placed in specific regions that will later be removed, creating localized high-porosity zones. This allows machining operations to proceed faster in these specific regions while maintaining the overall structural integrity and appropriate density of the bulk material.
Solution Approach 2:
The patent implements preliminary action by incorporating fugitive yarns during the weaving process itself, before the CMC component is fully manufactured. These yarns are strategically positioned to create pre-determined high-porosity regions. Subsequently, the fugitive yarns are removed (decomposed), leaving behind voids that facilitate faster machining. This preliminary preparation eliminates the need to create porosity during or after machining, thereby improving machining speed.
2Productivity
If means are introduced to locally increase porosity to facilitate faster machining, then machining speed improves, but the manufacturing process complexity increases
Solution Approach 1:
The patent merges the porosity creation step with the existing weaving process by incorporating fugitive yarns directly into the preform during manufacturing. This integration means that the same equipment and processes used to create the CMC structure also create the high-porosity regions, eliminating the need for separate porosity-introduction steps and reducing overall process complexity.
Solution Approach 2:
The patent uses fugitive yarns as temporary, disposable elements that serve their purpose (creating porosity) and are then removed. These yarns are typically made from inexpensive, easily decomposable materials that leave no harmful residue. Their temporary nature allows them to be integrated into the process without permanent complexity, as they are simply removed after serving their function.
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 localized introduction of fugitive yarns allows for faster machining by reducing porosity in specific regions, thereby accelerating the formation of slots and cavities in CMCs.
Implementation Method 1
subsequently, decomposing the fugitive yarns to transform the region into a pre-weakened region, the pre-weakened region having a higher porosity than a remainder of the preform
Data Source
AI summary
A method of forming a ceramic matrix composite includes forming a preform by weaving a plurality of warp tows with a plurality of weft tows, weaving a plurality of fugitive yarns into a region of the preform in at least one of a warp position or weft position, and subsequently, decomposing the fugitive yarns to transform the region into a pre-weakened region, the pre-weakened region having a higher porosity than a remainder of the preform.