Carbon fiber is a kind of fibrous carbon material with more than 90% carbon content. It is prepared by pre-oxidation, carbonization and graphitization of organic fibers, such as polypropylene fine (PAN) fibers, viscose fibers and asphalt fibers. It is composed of graphite microcrystals with preferred orientation and has high strength and modulus of elasticity (rigidity).
Its specific gravity is generally 1.70 g/cm3-1.80 g/cm3, strength is 1200 MPa-7000 MPa, modulus of elasticity is 200 GPa-400 GPa, coefficient of thermal expansion is close to zero, and even can be negative (~1.5 x 10-6 power).
Carbon fibers have high axial strength and modulus, no creep, good fatigue resistance, between non-metal and metal in specific heat and conductivity, small thermal expansion coefficient, good corrosion resistance, low fiber density and good X-ray transmission.