Structural characteristics of carbon fiber with ultrahigh tensile strength and high modulus

Abstract The structure of carbon fiber with ultrahigh tensile strength and high modulus was investigated and compared with M40J using SEM, Raman, XRD and TEM. The tensile strength and modulus of the carbon fiber prepared are 7.68 and 362 GPa respectively, which is the highest combination of mechanical properties of polyacrylonitrile-based carbon fiber up to now. Smooth surface, nearly perfect circular cross-section, irregular lattice structure and low degree of graphitization positively contribute to the tensile strength. The tensile strength is also benefited from compact but small crystal size with moderate crystal orientation. Evenly distribution of wave-like graphene layers and amorphous carbon effectively decreases boundary defects, and thus largely increases the tensile strength of carbon fibers.