Pre-ceramic Polymer Infiltration for C/SiC Composite Fabrication
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Solution Overview
Problem
The high cost and lengthy processing times associated with chemical vapor deposition (CVD) reactors hinder the widespread adoption of large fiber reinforced ceramic matrix composite (CMC) structures, particularly carbon/silicon carbide (C/SiC) systems, due to their complexity, specificity, and high operational costs.
Innovation Solution
A method involving pre-impregnated carbon/carbon (C/C) prepreg materials processed through polymer infiltration and pyrolysis (PIP) to create SiC-matrix C/SiC structures without the need for a discrete fiber/matrix interface, utilizing existing autoclaves and inert furnaces for cost-effective and efficient fabrication of high-strength CMC structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical vapor deposition (CVD) process is used to create C/SiC composites, then fiber/matrix interface and matrix are created with proper properties, but processing time is lengthy and cost is high
Solution Approach 1:
The patent applies preliminary action by pre-impregnating carbon fibers with a pre-ceramic polymer (such as polyacrylonitrile) before the actual ceramic matrix formation. This preliminary impregnation step allows the polymer to be distributed uniformly throughout the fiber structure in advance, eliminating the need for lengthy CVD processing later. The pre-ceramic polymer is then converted to the final ceramic matrix through pyrolysis, achieving both interface quality and matrix formation in a more efficient sequence.
Solution Approach 2:
The patent replaces the complex chemical vapor deposition system with a simpler thermal processing approach. Instead of using CVD reactors that require precise chemical control, temperature, and pressure regulation, the invention uses conventional furnaces to perform pyrolysis of the pre-ceramic polymer. This substitution of the processing mechanism dramatically simplifies the equipment requirements and reduces both processing time and operational cost while maintaining the necessary material properties.
2Manufacturing precision
If CVD reactors are used for C/SiC composite fabrication, then acceptable structural thickness and density are achieved, but equipment complexity and operational cost increase significantly
Solution Approach 1:
The patent employs a disposable pre-ceramic polymer coating that is applied to the carbon fibers and then consumed during pyrolysis to form the final ceramic matrix. This approach replaces the need for expensive, complex CVD reactors with simple, conventional furnace equipment. The pre-ceramic polymer serves as a temporary intermediary that is completely converted during processing, eliminating the need for sophisticated reaction chambers and control systems.
Solution Approach 2:
The patent changes the processing parameters from chemical vapor deposition conditions (requiring precise control of temperature, pressure, and chemical composition) to simple thermal pyrolysis conditions. By controlling only the temperature ramp and hold parameters during pyrolysis, the invention achieves the desired structural thickness and density without requiring complex CVD reactor systems. This parameter simplification directly reduces equipment complexity and operational cost.
3Reliability
If CVD process is used to produce C/SiC structures, then proper fiber/matrix interface is created, but cost of running the reactor is significantly higher than conventional furnaces
Solution Approach 1:
The patent replaces the energy-intensive CVD process with a more efficient thermal pyrolysis process. Instead of requiring continuous chemical vapor deposition under controlled atmospheric conditions, the invention uses conventional furnace heating to decompose the pre-ceramic polymer in place. This substitution reduces the energy input requirements and eliminates the need for expensive CVD reactor operation, thereby significantly lowering operational costs while maintaining interface quality through the controlled pyrolysis transformation.
Solution Approach 2:
The patent uses a disposable pre-ceramic polymer coating that is applied economically and then completely consumed during pyrolysis to form the final matrix. This eliminates the need for expensive CVD reactor operation and associated energy costs. The pre-ceramic polymer serves as an inexpensive intermediary material that is transformed into the final ceramic matrix through simple thermal decomposition, dramatically reducing the operational cost compared to using CVD reactors throughout the entire process.
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
This approach enables the production of high-strength CMC structures with reduced processing time and costs, improved scale-up capabilities, and eliminates the need for CVD reactors, allowing for the fabrication of larger complex parts with enhanced efficiency and lower equipment costs.
Implementation Method 1
pyrolyzing the applied pre-ceramic polymer to fabricate a ceramic matrix composite structure
Implementation Method 2
polymer infiltration and pyrolysis (PIP) to create SiC-matrix
Data Source
AI summary
Methods are disclosed herein to fabricate high-strength ceramic matrix composite (CMC) structures by combining, in one example, pre-impregnated (prepreg) material with a pre-ceramic polymer. The prepreg is processed to a first density, and the densification is completed with repeated polymer infiltration and pyrolysis (PIP) cycles of the pre-ceramic polymer to fabricate a CMC structure. Advantageously, the present invention allows for fabrication of ceramic matrix composites more efficiently and to a larger scale than previously available.