Reinforcements

In the Pultrusion process all continuous fibres can be used, however carbon and glass fibres are becoming more common.

The mechanical properties of the pultruded composite profile are largely determinated by the type of reinforcement (unidirectional glass fibre roving or carbon fibre tow), its for (UD, mat, woven fabric, multiaxial fabric etc.) and its position and orientation in the cross-section, and of course the fibre content has a very remarkable effect.

Carbon/graphite fibres

Today carbon fibres are widely used in high performance applications, such us racing and aerospace industry. In racing industry we can mention of course F1, however also racing ski-poles are using high modulus carbon fibres.

Exel is using today all carbon fibres in its pultrusion process; High Strength (HS), High Modulus (HM) PAN type carbon fibres and also Ultra High Modulus (UHM) pitch type carbon fibres.

The pultruded carbon fibre products have

  • Light (80 % lighter than steel and 45 % lighter than aluminium)
  • Extremely strong (UTS upto 3000 Mpa), high specific strength
  • Extremely stiff (E from 80-400+ Gpa), high specific stiffness
  • Very low coefficient of thermal expansion
  • Low maintenance
  • Weather proof
  • Low water absorption
  • Good fatigue and creep properties
  • High vibration damping

The pultruded carbon fibre profiles are much stronger than steel, lighter than aluminium and may be stiffer than steel (stiffness range 100-400+ GPa).

Typical properties of carbon fibres

Type Density Tensile strength Tensile modulus
  [kg/dm3] [Gpa] [Gpa]
HS1 1.75 3.31 228
HS2 1.80 5.0 248
IM 1.74 4.50 296
HM1 1.81 2.41 393
HM2 1.96 1.52 483
UHM 2.15 2.24 724

 

Glass fibres

Glass fibre (also called fibreglass and glassfiber) is the most widely used reinforcement material in pultrusion industry. Glass fibre is used as a reinforcing agent for many polymer products; the resulting composite material, properly known as fiber-reinforced polymer (FRP) or glass-reinforced plastic (GRP), is called "Fibreglass" in popular usage. Glass fiber is formed when thin strands of silica-based or other formulation glass is extruded into many fibres with small diameters suitable for textile processing.

Glass fibre has good tensile, compression and impact properties.

  Specific gravity Tensile strength Tensile modulus Coefficient of thermal expansion
    [Mpa] [Gpa] 10-6/K
E-glass 2.58 3 450 72.5 5.0
ECR-glass 2.62 3 625 72.5 5.0
S-glass 2.48 4 590 86.0 5.6

 

Typical properties of Fibreglass (GRP) profiles and tubes are

  • Light weight (75 % lighter than steel, and 30 % lighter than aluminium)
  • Very good specific strength
  • Very good specific stiffness
  • Low coefficient of thermal expansion
  • Thermal insulation
  • Non-magnetic
  • Good chemical resistance
  • Low maintenance
  • Weather proof
  • Low water absorption (high fibre content)
  • Cost effective

Exel is using glass fibres in different forms:

  • Roving
  • Woven roving
  • Mats

Combinations of roving, mats and woven roving.

Aramid fibres

Aramid fibres have low density (1.45 kg/dm3) and high tensile strength. Aramid fibres have very good impact strength properties and they are used in anti-ballistic applications. Comparison of properties of pultruded profiles

Fibre Unit Carbon Glass Aramid
Density [kg/dm3] 1.5-1.6 1.9-2.0 1.3
Tensile Modulus [Gpa] 80-400+ 38-45 70-75
Tensile strength [Mpa] 1500-3000+ 800-1200 800-1500
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Exel Oyj, Vantaa head office, Mäkituvantie 5, FI-01510 Vantaa, Finland, Tel +358 20 7541 200, Fax +358 20 7541 201