Ceramic Needle Array for Clean Z-Channel Formation in CMC Preforms
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Solution Overview
Problem
The use of metallic needles for forming z-channels in ceramic matrix composites (CMCs) leads to contamination and deformation of the preform due to residual metallic particles, which have different thermal and mechanical properties, creating defects that adversely affect the composite's properties.
Innovation Solution
A needle array is developed using a bundle of ceramic filaments with a metallic sheath and a sharpened ceramic tip, allowing for removable and contaminant-free z-channel formation in fibrous preforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metallic needles are used to form z-channels in ceramic preforms, then z-channels can be created for improved reactant gas pathways, but metallic particles contaminate and deform the preform, creating defects that deteriorate composite properties
Solution Approach 1:
The harmful metallic material is extracted and replaced with ceramic material that matches the preform composition. The needle is constructed with a ceramic filament bundle core and ceramic tip, eliminating metallic contamination while maintaining the z-channel formation function.
Solution Approach 2:
The material composition parameter of the needle is changed from metallic to ceramic. The tip is specifically formed with ceramic material having similar thermal and mechanical properties to the preform, fundamentally changing the interaction between needle and preform to eliminate contamination.
2Productivity
If metallic needles are used to perforate the preform, then z-channels can be formed efficiently, but the preform ceramic material and metallic particles have dissimilar thermal and mechanical properties, creating detrimental defects
Solution Approach 1:
Homogeneity is achieved by making the needle tip material (ceramic) similar to the preform material (ceramic). This ensures matching thermal and mechanical properties, eliminating the dissimilarity that causes defects while maintaining perforation efficiency through the sharpened tip design.
Solution Approach 2:
The needle is constructed as a composite structure with a ceramic filament bundle core and a ceramic tip coating or formation. This composite approach combines the structural integrity needed for perforation with the material compatibility needed to avoid contamination and defects.
3Strength
If a sheath is applied to the ceramic filament bundle, then structural integrity is improved, but the sheath must be removable to prevent contamination
Solution Approach 1:
The harmful metallic sheath is extracted and replaced with a ceramic-based sheath or tip formation. The ceramic sheath material is compatible with the preform, eliminating contamination risks while maintaining the structural support function during perforation.
Solution Approach 2:
The sheath material parameter is changed from metallic to ceramic. This material substitution maintains the structural integrity function while changing the chemical compatibility parameter to prevent contamination of the ceramic preform.
Data Source
Figure 1
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Figure 4~5
AI summary
A needle array (30) suitable for perforating a fibrous preform includes a backplate (32) and a plurality of needles (26) individually removably attached to and extending away from the backplate (32). Each of the plurality of needles (26) includes a bundle (14) of ceramic filaments, a metallic sheath (20) surrounding a first end of the bundle (14) abutting the backplate (32), and a sharpened point (24) on the second end of the bundle (14), the second end being oppositely disposed from the first end.