Effect of fiber surface treatment on the microstructure and mechanical properties of mesophase pitch-based C/C composites

The CVI coating and 400°C air oxidation were used to treat carbon fiber surface and the influence of fiber surface treatment on the microstructure and flexural property of mesophase pitch-based 2D C/C composites were studied by polarized light microscopy (PLM), scanning electron microscopy (SEM) and mechanical properties test techniques, respectively. The results showed that the fracture behaviors of the C/C composites with different fiber surface treatment were ductile rupture, and the flexural strength of composites of CVI coating surface treatment was lower than that of 400°C air oxidation. The microstructure of matrix carbon was of the optical active pyrolytic carbon and the flow, and domain of mesophase pitch carbon formed multilayer interface in the composite. So the fracture was matrix cohesive damage. The microstructure of matrix carbon made of small domains and domains of mesophase pitch carbon by surface treatment of 400°C air oxidation led to the mixed damage of matrix cohesive damage and interfacial debonding damage.