Carbon Fiber Properties
Carbon fiber properties define why this material is widely used in aerospace, automotive, wind energy, sports equipment, and industrial applications. These properties include mechanical performance, physical characteristics, chemical composition, and behavior in composites.
Understanding carbon fiber properties is critical for engineers and designers who aim to optimize performance while minimizing weight.
Mechanical Properties of Carbon Fiber
Carbon fibers are renowned for their high-strength and stiffness. Key mechanical properties include:
| Property | Typical Values | Description |
|---|---|---|
| Tensile Strength | 3,500–7,000 MPa | Maximum stress before fiber fracture (carbon fiber tensile strength) |
| Elastic Modulus | 230–700 GPa | Fiber stiffness; depends on graphitization (modulus of carbon fiber) |
| Ultimate Tensile Strength | 3,500–7,000 MPa | Maximum stress fibers withstand before breaking (carbon fiber ultimate tensile strength) |
| Breaking Strength | Comparable to tensile strength | Indicates fiber brittleness (carbon fiber breaking strength) |
| Strain at Failure | 1.5–2.0% | Elongation before fracture (carbon fiber properties) |
| Yield Strength | Not applicable | Fibers are brittle; no plastic deformation (carbon fiber yield strength) |
Notes: Carbon fibers are extremely strong but brittle, which is why they are usually embedded in polymer matrices for composites.
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Physical characteristics make carbon fibers lightweight yet strong:
Density: 1.6–2.0 g/cm³ (density carbon fibre, carbon fibre composite density)
Diameter: 5–10 µm
Thermal conductivity: 10–100 W/m·K along fiber axis
Coefficient of Thermal Expansion: -0.1 to 1×10⁻⁶ /°C
Electrical conductivity: Variable along fiber orientation
These physical properties make carbon fiber ideal for applications requiring weight reduction, thermal stability, and structural efficiency.
Chemical Properties
Carbon fiber chemical structure:
Primarily carbon atoms (>90%)
Trace amounts of hydrogen, oxygen, and nitrogen
Graphitic structure contributes to high stiffness and chemical resistance
Carbon fiber characteristics:
Resistant to most chemicals and corrosion
Thermally stable up to 200–400°C (depending on resin)
Maintains dimensional stability under varying temperatures
Carbon Fiber in Composites
Carbon fibers are usually used in composites (CFRP – Carbon Fiber Reinforced Polymers) to enhance properties:
| Composite Property | Typical Values | Notes |
|---|---|---|
| Density | 1.55–1.6 g/cm³ | Depending on fiber volume fraction |
| Tensile Strength | 500–1,500 MPa | Unidirectional fibers provide highest strength |
| Elastic Modulus | 70–200 GPa | Depends on weave and fiber alignment |
| Fiber Volume Fraction | 50–65% | Optimal range for mechanical performance |
Carbon fabric properties vary by weave (plain, twill, unidirectional) which affects modulus, impact resistance, and flexibility.
Applications Related to Carbon Fiber Properties
Carbon fiber properties determine its use in:
Aerospace: Fuselage panels, wings; 50% weight reduction vs aluminum
Automotive: Formula 1 monocoques, body panels; tensile strength >1,000 MPa
Wind Energy: Turbine blades; stiffness >100 GPa
Sports: Bicycles, tennis rackets; modulus 50–100 GPa
Industrial: Pressure vessels, bridge reinforcement; load-bearing improvement 20–50%
Advantages and Limitations of Carbon Fiber
Advantages:
Exceptional strength-to-weight ratio
High stiffness and dimensional stability
Corrosion and chemical resistance
Tailorable properties for directional load
Limitations:
Brittle, low impact resistance
High production cost
Complex manufacturing
Limited recyclability