Influence of Surface Characteristics and Radial Microstructure of Domestic T800G Fiber on Mechanical Properties of Epoxy-based Composites

The mechanical properties of high-performance CFRCs depend on the fiber's intrinsic structure and the fiber-matrix interface, and the two are synergistically regulated. This study compared the effects of differences in the microstructure of two types of domestic dry-jet wet-spun T800G carbon fibers (Type A and Type B) on the 0° tensile and compression-after-impact (CAI) properties of two epoxy resin-based composites. It was found that although type B fiber has higher surface roughness, chemical activity and interfacial shear strength, its strong interfacial bonding did not improve the composite's mechanical performance, and the fiber strength conversion rate (72%) was lower than that of type A (85%), the CAI was also lower (305 MPa vs. 335 MPa). The analysis showed that the excessive interfacial bonding inhibited the energy dissipation during loading. The pronounced "hard-skin, soft-core" radial structure exacerbated strain mismatch, inducing core collapse and stress concentration. In contrast, the interfacial strength of type A fiber is moderate, the fiber potential can be fully utilized through fiber pull-out and interfacial delamination. The mechanical property trends of the composites remain consistent across both resin systems, with the synergistic effect of fiber structure and interface playing the leading role. The study reveals the limitations of simply improving the interfacial bonding, and optimizing the homogenization of fibers and the synergy of interfaces is the key to improving the performance of composites.