Material characteristics of carbon fiber
Carbon fiber is a kind of new material with excellent mechanical properties due to its two characteristics: carbon material, high tensile strength and soft fiber workability. The tensile strength of carbon fiber is about 2 to 7GPa, and the tensile modulus is about 200 to 700GPa. The density is about 1.5 to 2 grams per cubic centimeter, which is mainly determined by the temperature of the carbonization process except for the structure of the precursor. Generally treated by high temperature 3000 degrees graphitization, the density can reach 2 grams per cubic mile. Coupled with its weight is very light, it is lighter than aluminum, less than 1/4 of steel, than the strength of iron is 20 times. The coefficient of thermal expansion of carbon fiber is different from that of other fibers, and it has anisotropic characteristics. The specific heat capacity of carbon fiber is generally 7.12. The thermal conductivity decreases with increasing temperature and is negative (0.72 to 0.90) parallel to the fiber direction, while the direction perpendicular to the fiber is positive (32 to 22). The specific resistance of carbon fibers is related to the type of fiber. At 25 degrees centigrade, the high modulus is 775, and the high strength carbon fiber is 1500 per centimeter.
This allows carbon fibers to have the highest specific strength and specific modulus in all high-performance fibers. Compared with the metal materials such as titanium, steel and aluminium, carbon fiber has the characteristics of high strength, high modulus, low density and low coefficient of linear expansion. It can be called the "king of new materials". In addition to carbon fiber with general characteristics of carbon material, its appearance has obvious anisotropy and soft, can be processed into a variety of fabrics, and the proportion of small, along the fiber axis show a very high strength carbon fiber reinforced epoxy resin composites, the strength and modulus of composite indicator in the existing structural materials is the highest. The tensile strength of carbon fiber resin composite materials are generally in more than 3500 MPa, is 7 to 9 times that of steel, the tensile modulus of 230 to 430G were also higher than that of steel; therefore the specific strength of CFRP material intensity and density can be achieved above 2000 MPa, the specific strength of A3 steel is only 59 MPa.