Ribbonized Ceramic Tows for Uniform Pore Distribution in CMC Fabrics
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Solution Overview
Problem
The microstructure of ceramic matrix composites is dictated by the fiber tow structure, leading to a default bimodal pore distribution with inter-tow porosity exceeding intra-tow porosity, which causes stress concentrations and uneven matrix deposition during processes like CVI, PIP, and MI.
Innovation Solution
Transforming ceramic tows from a first geometry to a second geometry by reducing one dimension and increasing the orthogonal dimension, resulting in a flattened or ribbonized tow, which is then woven or braided to create a ceramic fabric with reduced inter-tow pore size and increased intra-tow porosity, homogenizing the pore distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional ceramic tows with circular cross-section are used, then the manufacturing process is simple, but the inter-tow porosity exceeds intra-tow porosity causing stress concentrations and uneven matrix deposition
Solution Approach 1:
The patent transforms the tow cross-sectional geometry from circular to flattened/ribbonized shape by changing dimensional parameters. Specifically, the tow width is increased while the thickness is reduced, creating a controlled geometric transformation that modifies the pore distribution characteristics and enables more uniform matrix infiltration throughout the composite structure.
Solution Approach 2:
The invention introduces a dimensional transformation by flattening the tow cross-section, effectively changing from a roughly equidimensional circular shape to an anisotropic flattened shape with distinct width and thickness dimensions. This dimensional change creates a more favorable pore distribution architecture that reduces the disparity between intra-tow and inter-tow porosity.
2Strength
If ceramic tows are flattened to reduce inter-tow pore size, then stress concentrations are reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies parameter changes by systematically modifying the tow cross-sectional dimensions through flattening. The width is expanded and thickness is reduced to specific ranges that optimize the mechanical properties, particularly interlaminar tensile strength, while maintaining manufacturability through controlled processing parameters.
Solution Approach 2:
The invention implements local quality optimization by creating a specific flattened geometry in the tow cross-section that addresses the local stress concentration problem at inter-tow interfaces. The flattened shape locally modifies the pore distribution and stress fields in critical regions, improving interlaminar strength without requiring complete restructuring of the entire manufacturing system.
3Manufacturing precision
If ceramic tows are flattened to increase intra-tow porosity, then matrix deposition uniformity improves, but the processing time increases
Solution Approach 1:
The patent utilizes parameter changes in the tow geometry (flattening ratio, width-to-thickness ratio) to optimize matrix deposition characteristics. The flattened configuration creates more uniform pore pathways that facilitate consistent matrix infiltration, reducing the need for extended processing times while maintaining deposition uniformity across the composite structure.
Data Source
AI summary
A method of preparing a ceramic fabric for use in a ceramic matrix composite includes transforming a ceramic tow from a first tow geometry to a second tow geometry, thereby reducing a first dimension of the ceramic tow and increasing a second dimension of the ceramic tow orthogonal to the first dimension to produce a flattened tow. The method includes weaving or braiding the flattened ceramic tow to form a ceramic fabric.