Carbon fiber has the characteristics of strong tensile resistance of carbon material and soft processability of fiber, and is a new material with excellent mechanical properties. The tensile strength of carbon fiber is about 2 to 7 GPa and the tensile modulus is about 200 to 700 GPa. The density is about 1.5 to 2.0 grams per cubic centimeter, which is mainly determined by the temperature of carbonization treatment, except for the structure of the precursor silk. Generally, after graphitization treatment at high temperature 3000 °C, the density can reach 2.0 grams per cubic centimeter. In addition, its weight is very light, its specific gravity is lighter than aluminum, less than 1/4 of steel, and its specific strength is 20 times that of iron. The coefficient of thermal expansion of carbon fiber is different from other fibers, and it has anisotropic characteristics. The specific heat capacity of carbon fiber is generally 7.12. Thermal conductivity decreases with increasing temperature, parallel 1 is negative in fiber direction (0. 72 to 0.90), while perpendicular to the fiber direction is positive (32 to 22) The specific resistance of carbon fiber is related to the type of fiber, at 25 ° C, the high modulus is 775, and the high-strength carbon fiber is 1500 per centimeter. This results in carbon fiber having a higher specific strength and specific modulus among all high-performance fibers. Compared with titanium, steel, zhao and other metal materials, carbon fiber has the characteristics of high strength, high modulus, low density and small linear expansion coefficient in physical properties.