To thoroughly analyze the mechanical properties and surface conditions of HF50S carbon fibers, the tensile properties, surface morphology, surface chemical element, surface energy, sizing agent properties, and Naval Ordnance Laboratory (NOL) ring of their composites were characterized. Furthermore, the aforementioned properties were exhaustively compared with those of T1000G carbon fibers. The results showed that the tensile strength, modulus, and elongation of the HF50S carbon fibers were 6638 MPa, 297 GPa, and 2.2%, respectively, thus demonstrating that the mechanical properties of the HF50S carbon fibers were on par with those of the T1000G carbon fibers, in addition, the coefficient of variation (Cv) indices of HF50S carbon fiber were below 3%, indicating good stability. The HF50S carbon fibers have a smooth surface without grooves, which is analogous to that of the T1000G carbon fibers prepared by the typical dry jet–wet spinning process. The main component of the sizing agent of the HF50S carbon fibers is an epoxy resin, which is also used for the preparation of epoxy matrix composites. Because the HF50S carbon fiber surface has greater O and N contents than the T1000G carbon fiber surface, the HF50S carbon fibers have more active functional groups and higher surface activity. The surface energy of the HF50S carbon fibers is 30.13 mJ/m2, which is higher than that of the T1000G carbon fibers (28.42 mJ/m2). Owing to the higher strength and surface activity of the HF50S carbon fibers than those of the T1000G carbon fibers, the strength and strength conversion of NOL ring based on the former are slightly higher than those of that prepared using the latter.

    Abstract
    1 Introduction
    2 Materials and methods
    3 Results and discussion
        3.1 Mechanical properties
        3.2 Surface morphology
        3.3 Surface chemical properties
        3.4 Surface sizing agent
        3.5 Surface energy
        3.6 NOL performance
    4 Conclusions
    References

• Hongxing Gu(Harbin Institute of Technology, Jiangsu Hengshen Co., Ltd.)
• Ming Zhang(Harbin Institute of Technology, Jiangsu Hengshen Co., Ltd.)
• Shubin Zhang(Harbin Institute of Technology, Jiangsu Hengshen Co., Ltd.)
• Jingyao Qi(Harbin Institute of Technology)