Mechanical property and toughening mechanism of 2.5D C/C-SiC composites with high textured pyrocarbon interface

The application of C/C-SiC composites remains a challenge because of the poor mechanical properties induced by the liquid silicon infiltration method. In this study, a thick high textured pyrolytic carbon (HT PyC) interface manufactured by chemical vapor infiltration (CVI) was used to protect the carbon fibers and improve the flexural properties. The microstructure of HT PyC, its flexural properties, and its associated strengthening and toughening mechanisms were analyzed on the C/C-SiC composites. The results showed that the bending strength of the C/C-SiC composites was 344.74 MPa, which is nearly 31.82% higher than that of C/C composites. The fracture mode transformed from brittle fracture to pseudoplastic fracture owing to the addition of SiC, and the C/C-SiC composites maintained a better toughness compared to C/C composites. Multiple mechanisms of strength and toughness improvement were found to be responsible for the excellent performance of the C/C-SiC composites. The HT PyC interface played a critical role in the excellent flexural properties. The strong bonding among the carbon layers and high interfacial strength between the fiber and HT PyC led to the increase of strength. Besides, the improvement in toughness was attributed to the multiple effects of the carbon-layers deformation, cracks deflection and propagation caused by the bridging areas, sublayers, nano- and micro-scale cracks.