ABSTRACT Because of their superior mechanical properties, carbon fibers are widely used as reinforcement material for the matrix. Carbon fibers with both high strength and high modulus are proposed to grant the composite high strength and high modulus simultaneously. Carbon fibers with a tensile modulus of 330–390 GPa and a tensile strength exceeding 5.0 GPa were successfully fabricated through continuous preoxidation, carbonization, and graphitization of wet‐spun polyacrylonitrile fibers. Raman spectroscopy was used to analyze the carbon structure of the fibers. The results showed that the tensile modulus was strongly correlated with the width of the G band, while the tensile strength was mainly influenced by the intensity of the D band. Furthermore, the elongation at break was closely associated with the width of both D and G bands as well as the D band intensity. The increase in these Raman parameters reflected a higher degree of structural disorder, which contributed to a tougher carbon matrix and thereby enhanced the elongation at break. The carbon fiber exhibited graphitic crystallites with Lc values of 2.0–2.4 nm and La values of 5.0–5.8 nm. Microstructural analysis revealed that the fibers consisted of small graphitic crystallites dispersed within a disordered carbon matrix. Adjacent basic structural units were interconnected via continuous carbon layers, contributing to the material's relatively high tensile strength. These findings establish a fundamental structure–property relationship, offering critical insights for the design of next‐generation high‐performance carbon fibers.
Wang et al. (Thu,) studied this question.