Carbon Fibres

1. Introduction

Carbon is a high-tensile fiber or whisker made by heating rayon or polyacrylonitrile fibers or petroleum residues to appropriate temperatures. Fibers may be 7 to 8 microns in diameter and are more that 90% carbonized. carbon fibre, also called graphite fibre ia basically very thin strands of carbon, consisting of strong crystalline regions within the fibre. It is very well oriented carbon atoms.

2. Properties of Carbon Fibres
  • Fineness: Diameter of carbon fibre is usually 5-10 µm.
  • Tensile Strength: is maximum stress that a material can withstand while being stretched or pulled before breaking. Carbon fibre has tensile strength of around 4137 MPa compared to normal steel 2693 MPa. Carbon fibre (Toray T1000G) (the strongest man-made fibre) has 6370 MPa/fibre.
  • Weight: Carbon fibre is light weight. Carbon fibre has high strength to weight ration (also known as specific strength), which is 2457 kNm/kg, as compared, glass has 1307 kNm/kg and steel has 254 kNm/kg.
  • Elasticity: Elasticity of carbon fibre is poor, as carbon is very rigid fibre.
  • Dimensional Stability: Carbon fibre is dimensionally stable, hence used as composite to make spare parts of missiles, automobiles, aircrafts etc.
  • Moisture regain: Moisture regain is the ratio between the weight of water with the oven dry weight of the material expressed in percentage. Moisture regain value for carbon fibre is zero, for comparison, it can be seen that moisture regain value for jute is 13.75.
  • Thermal Conductivity: Carbon fibre has fairly good thermal conductivity. Nanotubes of carbon are used as high conducting materials.
3. Production of Carbon Fibres

The raw material used to make carbon fibre is called the precursor. About 90% of the carbon fibres produced are made from polyacrylonitrite (PAN). The remaining 10% are made from rayon or petroleum pitch. Carbon fibres are made by heatign rayon or polyacrylonitrile fibre to appropriate temperatures.

4. Application / Uses of Carbon Fibres
  • Aerospace, road and marine support, sports goods
  • Missile, aircraft brakes, large telescopes
  • Audio equipments, loudspeakers
  • Medical Application
  • Chemical Industry

Reference: 1. High Performance Fibres 2. NPTEL