Carbon fiber (carbon content >90%), known as "black gold", is a high-performance inorganic fiber made from organic polymers via high-temperature treatment. It excels in lightweight (1/4 density of steel), high strength (7-9x steel), and corrosion resistance, playing a key role in aerospace, automotive, and sports industries.
I. Basic Concepts & Properties
1. Composition & Structure
• Precursor types:
◦ PAN-based (90% global output): High strength/modulus (aerospace mainstream).
◦ Pitch-based: Ultra-high modulus (spacecraft, high-temp use).
◦ Viscose-based: Historic, rarely used now.
2. Key Advantages
• Lightweight & high strength: Specific strength/modulus top among materials.
• High-temp resistance: Stable at thousands of °C (ideal for spacecraft).
• Corrosion resistance: Durable in salt/humid/acidity.
• Low thermal expansion: Near-zero after graphitization (>2000°C).
3. Main Limitations
• Brittleness: Cracks expand easily (no plastic deformation warning).
• Anisotropy: Mechanical differences between axial/transverse directions.
II. Development History
• Early exploration (1879-1950): Edison used carbonized fibers for lamp filaments; 1950s US Union Carbide rediscovered its potential.
• Tech breakthroughs (1950s-1980s):
◦ 1959: Japan’s Akio Kondo made PAN-based carbon fiber.
◦ 1970: Toray (Japan) + Union Carbide produced T300 (aerospace staple).
◦ 1972: First civilian use (carbon fiber golf clubs/fishing rods).
◦ 1980s: Toray’s T800/T1000 and US Hexcel’s IM7 marked maturity.
III. Production Process
1. Precursor Fiber Production
• Polymerization: Acrylonitrile monomers + solvent (e.g., DMSO) polymerize at ~60°C.
• Spinning: Wet spinning (large tow, ≥48K) or dry-jet wet spinning (small tow, 1K/3K, high-performance).
• Post-treatment: Washing, hot drawing, oiling, drying.
2. Carbon Fiber Production
• Pre-oxidation: 200-300°C (air, 1h) to stabilize structure.
• Carbonization: Low-temp (400-700°C, inert gas) → high-temp (1200-1500°C) to form graphite microcrystals.
• Optional graphitization (>2000°C): Boosts modulus/conductivity.
• Surface treatment + sizing: Enhance matrix bonding and processability.
IV. Application Fields
1. Aerospace
• Commercial aircraft: Boeing 787/Airbus A350 (50% carbon fiber use).
• Military aircraft: F-35 (36% carbon fiber, improves stealth).
• Spacecraft: China’s Tiangong Station, SpaceX Starship.
2. Automotive
• High-end EVs: BMW i3 (30% weight reduction), Tesla Model S (50kg/vehicle).
• New energy: eVTOL (e.g., EHang EH216-S, all-carbon fuselage).
3. Sports & Leisure
• Early civilian use: Fishing rods (1972), carbon fiber bicycles (40% lighter than aluminum), tennis rackets (Yonex), golf clubs (TaylorMade).
4. Others
• Wind power: Key for blades; China accounts for >50% global use.
• Pressure vessels: Hydrogen storage (high strength/corrosion resistance).
V. Market & Trends
1. Market Structure
• Japan: Toray/Toho Tenax/Mitsubishi (70% global small-tow capacity; Toray 35-40%).
• US: Hexcel/Cytec (20% global market).
• China: 2024 capacity 150,000 tons (48.6% global, world’s largest producer).
2. Trends
• Cost reduction: Via low-cost precursors and recycled carbon fiber.
• High performance: Develop higher strength/modulus (e.g., Toray M40X, Hexcel HM50).
• Green development: Reduce energy use and pollution.
VI. Future Outlook
• Aerospace: More use in new aircraft (e.g., next-gen airliners).
• Automotive: Rapid growth in NEVs (battery packs, lightweight bodies).
• Civilian market: Expanding to household goods/electronics as prices drop.
