What is Carbon Fiber
Carbon fiber is a high-performance material composed mainly of carbon atoms arranged in a crystalline structure. It is renowned for its high strength, lightweight, and high stiffness, making it essential in aerospace, automotive, sports equipment, and industrial applications. This guide explains what is carbon fiber, carbon fiber properties, carbon fiber structure, mechanical and physical data, manufacturing processes, composites, and practical uses.
Carbon Fiber Structure and Chemical Composition
The carbon fiber chemical structure consists of carbon atoms forming hexagonal graphite microcrystals aligned along the fiber axis. This alignment provides exceptional carbon fiber tensile strength, elastic modulus of carbon fiber, and breaking strength.
Carbon fibre elements: Carbon (>90%), trace hydrogen, nitrogen, oxygen
Density: 1.6–2.0 g/cm³ (density carbon fibre)
Fiber diameter: 5–10 µm
Crystallite size: 5–10 nm
Bonding: Strong sp² covalent bonds enhance carbon fiber strength
Common precursors:
Polyacrylonitrile (PAN): High-strength fibers
Pitch: High-modulus fibers
Rayon: Moderate strength fibers
Mechanical Properties of Carbon Fiber
| Property | Typical Values | Keywords |
|---|---|---|
| Tensile Strength | 3,500–7,000 MPa | carbon fiber tensile strength, carbon fibre tensile strength |
| Elastic Modulus | 230–700 GPa | carbon fiber elastic modulus, modulus of carbon fiber, tensile modulus of carbon fiber |
| Ultimate Tensile Strength | 3,500–7,000 MPa | carbon fiber ultimate tensile strength, carbon fiber ultimate strength |
| Breaking Strength | Comparable to tensile strength | carbon fiber breaking strength |
| Strain at Failure | 1.5–2.0% | carbon fiber properties |
| Yield Strength | Not applicable (brittle) | carbon fiber yield strength, yield stress of carbon fiber, carbon fibre yield stress |
| Density | 1.6–2.0 g/cm³ | carbon fiber density, density carbon fibre |
| Thermal Conductivity | 10–100 W/m·K | carbon fiber characteristics |
| Coefficient of Thermal Expansion | -0.1 to 1×10⁻⁶ /°C | carbon fiber properties |
Is carbon fiber a metal? No. Carbon fiber is a non-metallic material with some conductive properties along fiber axes.
Material Properties of Carbon Fiber
Carbon fiber material properties include:
High strength-to-weight ratio: Stronger than steel but lighter
High stiffness: Maintains shape under load
Low density: Crucial for aerospace and automotive
Chemical resistance: Resistant to acids, alkalis, solvents
Thermal stability: 200–400°C depending on resin
Electrical and thermal conductivity: Varies with fiber alignment
Dimensional stability: Low thermal expansion ensures precision
Carbon Fiber Manufacturing Process
Precursor Spinning: From PAN, pitch, or rayon
Stabilization: Heating 200–300°C in air to create thermally stable ladder polymer
Carbonization: Heating 1,000–1,500°C in inert atmosphere
Graphitization (Optional): 2,500–3,000°C for higher modulus
Surface Treatment & Sizing: Enhances adhesion to polymer matrices
Tailoring carbon fiber structure during manufacturing allows production of high-strength, intermediate, or high-modulus fibers.
Carbon Fiber Composites
Carbon fibers are embedded in resins to form carbon fiber reinforced polymers (CFRP):
Composite density: 1.55–1.6 g/cm³ (carbon fibre composite density)
Tensile Strength: 500–1,500 MPa (unidirectional)
Elastic Modulus: 70–200 GPa
Fiber Volume Fraction: 50–65%
Weave Types: Plain, twill, unidirectional
Thermal Resistance: 200–400°C depending on resin
Carbon fabric properties vary with weave, influencing modulus, tensile strength, and impact resistance.
Applications – What is Carbon Fiber Used For
Carbon fiber is used where lightweight and high strength are critical:
Aerospace
Aircraft fuselage panels: ~50% weight reduction vs aluminum
Boeing 787: ~50% CFRP by weight
Satellite structures: High stiffness, low density
Automotive
Formula 1 monocoques: Tensile strength >1,000 MPa
Body panels: 30–50% lighter than steel
Wind Energy
Turbine blades >50 meters: Stiffness >100 GPa
Sports Equipment
Bicycles: 0.8–1.5 kg frames, tensile strength >1,000 MPa
Tennis rackets: Modulus ~50–100 GPa
Industrial
Pressure vessels: Operating pressure 200–500 bar
Bridge reinforcement: Load-bearing improvement 20–50%
Consumer & Medical
Lightweight laptops, prosthetics, surgical instruments
Advantages and Limitations
Advantages:
Exceptional strength-to-weight ratio
High stiffness and dimensional stability
Corrosion and chemical resistance
Tailorable properties for directional loads
Limitations:
Brittle, low impact resistance
High cost vs metals
Complex manufacturing
Limited recyclability
Future Trends
High-modulus fibers for aerospace and wind turbines
Recycling technologies for sustainability
Hybrid composites with glass or aramid
Automated manufacturing: 3D weaving, robotic filament winding