Lecture Summary:
Today's lecture focused on Carbon-Carbon Composites (CC Composites), which are critically important in high-temperature applications such as those found in aerospace and automotive industries. CC Composites are unique in that both the matrix and reinforcing fibers are made of carbon. The lecture covered an introduction to CC Composites, discussed various matrices, processing techniques, advantages, and applications.
Key Points from the Lecture:
Introduction to Carbon-Carbon Composites
- Definition and Composition: Carbon-Carbon Composites consist of carbon fiber reinforcement and a carbon matrix.
- Properties: High strength, high stiffness, low density, good shear strength, and excellent high-temperature performance.
Different Types of Carbon Matrices
- Thermoset resins: Includes phenolic and fluorine resins.
- Metal Matrix Composites: Not discussed in detail concerning CC.
- Ceramic Matrix Composites: Different process but similar in needing high-temperature capability.
Carbon Fiber Types
- Sources: Made from rayon, PAN (Polyacrylonitrile), and pitch.
- Properties: Extremely strong yet lightweight, critical for high-strength applications.
Processing Techniques
- Impregnation and Pyrolysis:
- Using thermoset resins or thermoplastic pitches.
- Process involves heating, resulting in pyrolysis and graphitization.
- Chemical Vapor Deposition (CVD) and Chemical Vapor Infiltration (CVI):
- Techniques for creating high-purity carbon matrices.
- Physical Properties:
- Thermal stability, low shrinkage, and high carbon yield are desired properties in the carbon matrix.
Advantages of Carbon-Carbon Composites
- High-Temperature Performance: Can withstand up to 3000°C.
- Strength and Stiffness: Maintain structural integrity under extreme stress.
- Thermal Properties: Low thermal expansion and high thermal shock resistance.
Applications
- Aerospace: Used in the Space Shuttle and other re-entry vehicles.
- Automotive: Braking systems and high-performance engine parts.
- Industrial: High-temperature furnaces and processing equipment.
Structural Considerations
- Laminates and Orientation: Various forms including 2D mats and 3D structures for tailored mechanical properties.
- Designations and Codes: Explain the composition, orientation, and treatment temperatures of composites through standardized codes.
Technical Details Covered:
- Impregnation Processes: Detailed steps on how resins are impregnated, cured, and pyrolyzed into the carbon matrix.
- CVD and CVI Techniques: Thorough explanation of gaseous phase deposition processes used in creating high-purity carbon materials.
- Strength and Durability Tests: Discussion on specific strengths and stress tests, highlighting the material's resilience at elevated temperatures.
This lecture provided an extensive overview of the manufacturing processes, material properties, and usage scenarios of Carbon-Carbon Composites, underlining their critical role in modern high-temperature and high-strength applications.