Smart composite fibres are advanced materials designed to deliver high performance in strength, durability, and resistance while remaining relatively lightweight. These fibres are essential in modern engineering, especially where performance, efficiency, and safety are key. Among the most widely used smart fibres are carbon fibres, glass fibres (E-glass and S-glass), and aramid fibres (meta and para). Each type has unique properties, advantages, and applications that make them vital to industries ranging from aerospace to sports equipment.
Carbon Fibre
Characteristics
Carbon fibre is one of the strongest and lightest reinforcement materials available. Known for its excellent stiffness and tensile strength, it is widely used in performance-driven fields such as aerospace, automotive, and marine engineering. Although costly, its weight-to-strength ratio makes it invaluable in areas where handling, speed, and durability are crucial.
Manufacturing & Structure
Carbon fibre is produced through processes such as carbonization at high temperatures (1000–2000 °C). It can be fabricated into monocoque structures (where the outer shell provides structural support), body panels, or reinforcement layers. Often, it is combined with fibreglass to reduce costs while retaining performance advantages.
The unique feature of carbon fibre is its ability to be arranged directionally, allowing engineers to design components with maximum resistance to specific stresses. Compared to metals like steel, which have inherent weaknesses, carbon fibre’s adaptability eliminates many structural vulnerabilities.
Categories and Properties
Carbon fibres are classified by modulus, tensile strength, and heat treatment:
- Low modulus/strength fibres: ~1000 °C treatment
- High strength fibres: ~1500 °C treatment
- High modulus fibres: ~2000 °C treatment
There are two main production sources:
- PAN-based fibres – high strength and heat resistance
- Pitch-based fibres – high modulus with greater stiffness
Property Comparison (PAN vs. Pitch):
- Tenacity: 18–70 g/de (PAN) vs. 14–30 g/de (Pitch)
- Modulus: 1640–3850 g/de (PAN) vs. 1000–5850 g/de (Pitch)
- Elongation: 0.4–2.4% (PAN) vs. 0.2–1.3% (Pitch)
- Continuous operating temperature: 570–1000 °F (both)
Applications
- Woven Fabric: aerospace, automotive supercars, sports & recreational equipment, marine, engineering components
- Yarn/Fibre: reinforcement composites, rubber products, filtration systems
Glass Fibre
Characteristics
Glass fibres are produced from silicon oxide mixed with other oxides, offering high strength, good corrosion and temperature resistance, and a significantly lower cost compared to carbon fibre. Two major types are:
- E-glass: valued for electrical properties, the most widely used
- S-glass: stronger, stiffer, and more temperature resistant
Glass fibre is far more affordable (~15 DKK/kg for woven mats), making it a popular reinforcement material in industries requiring a balance of strength and cost.
Structural & Physical Properties
Glass fibres have a high surface-area-to-weight ratio, giving them excellent reinforcement potential but making them more susceptible to chemical attack. Their amorphous structure ensures uniform properties along and across the fibre. However, surface scratches, moisture, and microcracks can reduce their tensile strength.
Unlike carbon fibre, glass fibres can elongate more before breaking, making them more ductile. The viscosity of molten glass during production is a key factor; if too high, fibres break during drawing, and if too low, droplets form instead of fibres.
Applications
- Woven Fabric: automotive parts, reinforcement of plastics/rubber/cement, filtration, thermal insulation, printed circuit boards
- Needle Felts: aerospace insulation, cushioning, filtration, acoustic insulation
Aramid Fibre
Characteristics
Aramid fibres, made from aromatic polyamides (PPTA), are known for their extreme toughness, hardness, and resistance to penetration. They are widely recognized in protective gear such as bulletproof vests, helmets, and flame-resistant clothing. Though costly (~400 DKK/kg) and challenging to process, their mechanical performance justifies their use in high-risk environments.
Structural & Physical Properties
Aramid fibres are created by spinning PPTA liquid crystals in strong acids, then stretching them at high temperatures. The result is bright yellow filaments with low density and very high specific strength. All grades show excellent impact resistance, with lower modulus types being especially suited for ballistic applications.
Aramid is also making strides in rigging for yachts, where its lightness and strength allow cables to be 50% smaller in diameter than steel while retaining equal or greater durability.
Applications
- Flame- and heat-resistant clothing and helmets
- Ropes and cables
- Bulletproof vests and protective armour
- Fibre-reinforced concrete
Conclusion
Smart composite fibres—carbon, glass, and aramid—have transformed modern engineering by combining lightweight construction with exceptional mechanical strength.
- Carbon fibre offers unmatched stiffness and directional performance but at high cost.
- Glass fibre provides a cost-effective, versatile option with strong insulation properties.
- Aramid fibre excels in impact resistance and protective applications despite its expense and processing challenges.
Each fibre type serves distinct purposes, and together they form the foundation of advanced materials in aerospace, automotive, marine, defense, and consumer industries. Their continued development promises even more innovative applications in the future.
Comparison Table: Carbon vs. Glass vs. Aramid Fibres
| Property / Fibre Type | Carbon Fibre | Glass Fibre | Aramid Fibre |
|---|---|---|---|
| Cost (weaved mats) | ~500 DKK/kg (most expensive) | ~15 DKK/kg (very cheap) | ~400 DKK/kg (high) |
| Tensile Strength | 2000–5000 MPa | Moderate (varies with type) | ~3600 MPa |
| Density / Weight | Very low (lightest) | Higher than carbon and aramid | Very low (lightweight) |
| Stiffness / Modulus | Extremely high (especially high-modulus grades) | Good, less than carbon | Medium–high, lower modulus grades available |
| Elongation (Ductility) | Low (brittle) | Higher (more ductile) | Low–medium |
| Resistance to Impact | Moderate | Moderate | Excellent (used in armour) |
| Heat Resistance | High (570–1000 °F) | Good (depends on type) | High (used in protective clothing) |
| Main Applications | Aerospace, supercars, sports equipment, marine | Automotive, insulation, PCBs, reinforcement | Bulletproof vests, helmets, ropes, heat-protective clothing |