Ceramic Matrix Composite Barrier Layer Design
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Solution Overview
Problem
Ceramic matrix composites (CMCs) face degradation issues due to melt infiltration reactions, particularly silicon attack, which affects their mechanical and chemical properties, especially at high temperatures, limiting their durability and performance in applications like gas turbine engines.
Innovation Solution
A ceramic matrix composite structure is developed with a rigidization barrier layer sandwiched between the rigidization and infiltration layers, using CVI methods to deposit layers such as silicon nitride or silicon-nitro-carbide, reducing porosity and preventing melt infiltration reactions, and incorporating fiber interface coatings to enhance fiber protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If melt infiltration is used to enhance CMC density and properties, then the CMC achieves better mechanical performance, but silicon attack reactions occur causing degradation of the composite and fiber
Solution Approach 1:
A barrier layer composed of silicon nitride or silicon-nitro-carbide is introduced as an intermediary between the rigidization layer and the infiltration layer. This barrier layer prevents direct contact and chemical reaction between the melt infiltration materials (silicon) and the fiber/rigidization layer, thereby eliminating silicon attack while still allowing the melt infiltration process to enhance the overall density and mechanical properties of the CMC.
2Reliability
If multiple layers are added to protect against melt attack, then fiber protection is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The barrier layer is integrated into the existing multi-layer structure by combining it with the rigidization layer and infiltration layer sequence. Rather than adding a completely separate protective system, the barrier layer is merged into the layered architecture, allowing it to function as part of the standard manufacturing process flow. This integration reduces the perceived complexity increase while maintaining effective fiber protection.
3Manufacturing precision
If CVI method is used to deposit barrier and rigidization layers, then manufacturing precision is improved, but production time increases
Solution Approach 1:
The barrier layer and rigidization layer are deposited in a predetermined sequence using CVI, with the barrier layer being applied first followed by the rigidization layer. This preliminary arrangement of layers during manufacturing ensures that when melt infiltration occurs later, the protective barrier is already in place, eliminating the need for additional protective measures and reducing overall production time despite the extra deposition step.
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 results in CMCs with improved interlaminar tensile strength, fatigue resistance, and extended lifespan, exceeding 20,000 hours, while maintaining high-temperature resistance and ease of manufacturing, thus addressing the degradation issues and enhancing their suitability for high-temperature applications.
Implementation Method 1
fiber interfaces of a fiber preform may be coated using chemical vapor infiltration (CVI). Illustratively, a rigidization layer may also be applied by CVI
Implementation Method 2
particulates or other matter may be introduced by slurry and/or melt infiltration
Data Source
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AI summary
A ceramic matrix composite comprising: a matrix; a fiber preform embedded within the matrix; and wherein the matrix includes a rigidization layer, an infiltration layer, and a barrier layer sandwiched between the rigidization layer and the infiltration layer. The infiltration layer step illustratively may include particulate infiltration and melt infiltration. The illustrative method may further include the step of coating the fiber with an interface coating or layer. Illustratively, each of the fiber interface layer, the rigidization layer and the barrier layer may be deposited by any suitable method including without limitation CVI. The illustrative method of manufacturing a CMC may produce a relatively dense CMC, for example having a porosity of less than about 5% by volume, n some embodiments of the CMC and/or the method there will be a fiber interface coating or layer. Illustratively, the type and need for such an interface coating is generally a function of the type of fiber used. For example, a fiber interface coating, illustratively of boron nitride (BN) or pyrolytic carbon (PyC), is recommended or required for use with SiC or SiNC fiber. In the case of carbon fibers, a carbon interface illustratively might be used. In the case of oxide fibers, an interface layer illustratively may or may not be used. In any event, the fiber interface coating or layer illustratively may be deposited by for example chemical vapor infiltration (CVI) or other suitable method on the surface of the fiber. Illustratively, the fiber interface coating or layer generally encapsulates, surrounds or coats the fiber. lllustratively, the fiber interface coating or layer comprises between about 0.09 % and about 11 % of the total volume of the CMC. [0010] Illustratively, the rigidization layer or portion of the CMC and/ or method may be provided, deposited or introduced by for example CVI. Illustratively, the rigidization barrier may be any suitable material for example and without limitation it may comprise SiC. Illustratively, the rigidization layer comprises between about 14 % and about 41 % of the total volume of the CMC.