Effects of SiC interphase on the mechanical and ablation properties of C/C-ZrC-ZrB₂-SiC composites prepared by precursor infiltration and pyrolysis

Carbon/Carbon (C/C) composites modified with ZrC-ZrB₂-SiC particles were prepared by precursor infiltration and pyrolysis (PIP) process. Effects of SiC interphase on the mechanical and ablation properties of C/C-ZrC-ZrB₂-SiC composites were investigated. The SiC interphase was deposited through low pressure chemical vapor infiltration (LPCVI). It was found that as the SiC interphase was introduced into the modified C/C composites, the flexural strength increased by 24% and the failure mode showed brittle fracture. The mechanisms for the strengthening of the modified C/C composites with SiC interphase were identified as (I) the deposition of SiC interphase in short-cut webs that strengthened the bonding between fibers and matrix promoting to stress transfer, and (II) the production of weak bonding between fiber bundles and matrix in non-woven webs improved the utilization of carbon fiber strength. SiC interphase increased adhesion between the ablation products and matrix, it could enhance the ablation resistance of the modified C/C composites in short term under the action of the evaporation. However, the long-time ablation resistance was reduced since the ceramic particles could not be incorporated into the composites during preparation due to the existence of SiC interphase.