Pitch-Based C-C Composite Brake Disc Densification
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Solution Overview
Problem
Carbon-carbon composites densified with pitches exhibit higher wear rates, leading to frequent replacement of friction materials, which increases operating costs.
Innovation Solution
A method involving sequential steps: providing a carbon fiber brake disc preform, heat-treating, infiltrating with pitch using VPI or RTM, carbonizing, optionally stabilizing, machining, repeating densification cycles, and finally densifying with CVI/CVD to achieve a density higher than 1.7 g/cc, improving the binding of the pitch matrix and reducing wear rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pitch densification is used to manufacture carbon-carbon composites, then manufacturing cost is reduced and processing is simplified, but wear rate increases leading to frequent replacement
Solution Approach 1:
The patent applies multiple parameter changes to resolve the contradiction: (1) Changes pitch density parameters by selecting specific gravity ranges (1.7-2.1 g/cm³) to optimize matrix binding; (2) Changes carbonization temperature parameters (900-1500°C) to control matrix structure; (3) Changes processing cycle parameters through repeated infiltration-carbonization cycles to achieve optimal density and wear resistance while maintaining manufacturing feasibility
Solution Approach 2:
The patent creates a composite structure by combining carbon fiber preform with pitch-based carbon matrix through repeated infiltration and carbonization cycles. This composite approach allows the pitch matrix to provide cost-effective manufacturing while the optimized carbon-fiber-c composite structure delivers improved wear resistance and reliability
2Ease of manufacture
If pitch densification is used to manufacture carbon-carbon composites, then manufacturing cost is reduced, but service life decreases due to higher wear rates
Solution Approach 1:
The patent employs periodic action through repeated cycles of pitch infiltration followed by carbonization. Multiple cycles (typically 2-5 times) allow progressive densification and optimization of the matrix structure, transforming the pitch-based composite from high-wear to low-wear performance while maintaining cost-effective manufacturing through the use of pitch materials
Solution Approach 2:
The patent changes critical parameters including pitch specific gravity (1.7-2.1 g/cm³), carbonization temperature (900-1500°C), and number of infiltration cycles to optimize both manufacturing cost and service life. These parameter optimizations enable the pitch-based composite to achieve extended service life comparable to or exceeding traditional CVD/CVI processes
3Volume of stationary object
If pitch infiltration is used to densify carbon preform, then density increases to 1.1-1.5 g/cc, but wear rate increases and friction material must be replaced more frequently
Solution Approach 1:
The patent applies preliminary action by performing multiple pitch infiltration and carbonization cycles before final product completion. Each cycle progressively densifies the matrix and improves its binding characteristics, preparing the composite structure to achieve low wear rates while maintaining the cost advantages of pitch-based manufacturing
Solution Approach 2:
The patent optimizes density parameters by controlling pitch specific gravity (1.7-2.1 g/cm³) and carbonization conditions to achieve a final composite density that balances structural integrity with wear resistance. This parameter optimization ensures that increased density does not correlate with increased wear rate, but rather with improved service life
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 method significantly reduces wear rates and improves the strength and oxidation resistance of carbon-carbon composite brake discs, enhancing their friction performance and economic viability.
Implementation Method 1
infiltrating the carbon fiber preform with a pitch feedstock by vacuum pressure infiltration (VPI) or resin transfer molding (RTM) processing
Implementation Method 2
infiltrating the carbon fiber preform with a pitch feedstock by vacuum pressure infiltration (VPI) or resin transfer molding (RTM) processing
Implementation Method 3
carbonizing the pitch-infiltrated carbon fiber preform at 1200-2200° C. in an inert atmosphere
Implementation Method 4
densifying the preform by chemical vapor deposition (CVD) or chemical vapor infiltration (CVI) to a density higher than 1.7 g/cc
Implementation Method 5
densifying the preform by chemical vapor deposition (CVD) or chemical vapor infiltration (CVI) to a density higher than 1.7 g/cc
Implementation Method 6
heat-treating the carbon fiber preform at 1200-2540° C.
Data Source
AI summary
A method of manufacturing pitch-based carbon-carbon composite useful as a brake disc, includes (a) providing annular carbon fiber brake disc preform; (b) heat-treating the carbon fiber preform; (c) infiltrating the carbon fiber preform with pitch feedstock by VPI or RTM processing; (d) carbonizing the pitch-infiltrated carbon fiber preform; (e) repeating steps (c) and (d) to achieve a density in the carbon fiber preform of approximately 1.5 g/cc to below 1.7 g/cc; and (f) densifying the preform by CVI/CVD processing to a density higher than 1.7 g/cc. Employing lower cost VPI and/or RTM processing in early pitch densification cycles and using more expensive CVI/CVD processing only in the last densification cycle provides C-C composites in which the pitch-based components resist pullout, resulting in a longer wearing composite.