Spiked Preform Tooling for Uniform CVI Infiltration
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Solution Overview
Problem
In the processing of ceramic matrix composites, large voids between fibrous tow bundles lead to uneven matrix infiltration during chemical vapor infiltration (CVI), resulting in porous midplanes and detrimental defects due to the tortuous pore network, which slows down the infiltration process and reduces uniformity.
Innovation Solution
A tooling assembly with a spiked array is used to perforate the fibrous preform, creating holes that allow reactant vapors to penetrate more evenly, comprising a plate with metallic spikes extending into receiving holes in a fixture, facilitating even matrix deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CVI processing is used on woven preforms, then matrix infiltration occurs, but the pore network is highly tortuous leading to uneven deposition and porous midplanes
Solution Approach 1:
The preform is segmented into multiple regions through the introduction of mandrels that create discrete infiltration channels. This divides the continuous tortuous pore network into separate, more direct pathways, allowing reactant vapors to access different regions of the preform more uniformly and reducing the tortuosity effect.
Solution Approach 2:
Mandrels are introduced as intermediary objects within the preform structure. These mandrels act as mediators that redirect the flow of reactant vapors through the preform, creating alternative infiltration pathways that bypass the highly tortuous original pore network and enable more uniform matrix deposition.
2Productivity
If conventional CVI processing is used on woven preforms, then matrix infiltration occurs, but processing time is prolonged due to slow and uneven deposition
Solution Approach 1:
By segmenting the infiltration process into multiple channels through mandrel placement, the total infiltration path is divided into parallel shorter paths. This segmentation allows reactant vapors to infiltrate multiple regions simultaneously, reducing the overall infiltration time while maintaining uniform deposition.
Solution Approach 2:
The infiltration process is transformed from a primarily two-dimensional surface-deposition process into a three-dimensional process by introducing mandrels that create internal infiltration channels. This dimensional change allows reactant vapors to access the midplane regions directly through the thickness of the preform, significantly reducing infiltration time and improving uniformity.
3Reliability
If conventional CVI processing is used on woven preforms, then matrix infiltration occurs, but large voids between tows become large defects detrimental to composite properties
Solution Approach 1:
Mandrels serve as intermediary structures that occupy the large void spaces between tows during infiltration. By placing mandrels in these void regions, the infiltration process is redirected to fill these previously problematic areas, transforming large voids into regions of uniform matrix deposition and eliminating detrimental defects.
Solution Approach 2:
The mandrels are placed in advance within the preform structure before infiltration begins. This preliminary action pre-establishes the infiltration pathways and ensures that the large voids between tows are targeted for matrix deposition, preventing these voids from becoming defects in the final composite.
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 perforation of the preform significantly reduces processing time by 25-75% while achieving similar density, ensuring more uniform matrix infiltration and reducing porosity, thereby enhancing the properties of the composite.
Implementation Method 1
In the processing of ceramic matrix composites, there is a need to infiltrate matrix within and around fibrous tow bundles to replace pore volume with dense matrix material... The pore network through a woven system is often highly tortuous for infiltrating reactant vapors
Data Source
AI summary
A tooling assembly for perforating a fibrous preform comprises a tooling fixture comprising a plurality of receiving holes, and a spiked array comprising a plate and a plurality of metallic spikes projecting away from the plate and toward the tooling fixture, each of the plurality of metallic spikes corresponding to and extending towards one of the plurality of receiving holes. The spiked array is engageable with the tooling fixture such that the plurality of spikes extend at least partially into respective ones of the plurality of receiving holes.