Microstructure evolution and mechanical properties of C/C-SiC composites prepared with different prefabricated structures

C/C-SiC composites were prepared by chemical vapor infiltration （CVI） and reactive melt infiltration （RMI） using carbon fiber preforms with stitched and needle-punched structures. The microstructure and pore characteristics of C/C porous composites obtained from the two structural preforms， as well as the microstructure and flexural properties of C/C-SiC composites， were systematically studied. Results show that the pore size of stitched C/C porous composite is multimodal distribution， and the pores are mostly inter-bundle pores. The pore size of needle-punched C/C porous composite is unimodal distribution. Due to the addition of mesh， some inter-bundle pores are transformed into connected small pore networks. The simulated absolute permeability in the Z direction of the latter is slightly greater than that of the former， which is conducive to the subsequent RMI densification process of the latter （high density， low open-porosity and low residual metal）. The average flexural strength of stitched C/C-SiC composites is higher than that of needle-punched C/C-SiC composites， both of which exhibit a “pseudo plastic” fracture mode. The needle-punched C/C-SiC composite has a higher density and lower residual Si content， but its fiber volume content is lower， and the integrity of long straight fibers is poor， resulting in lower load-bearing property of the composite.