Evolution of Pseudoplastic Crack Propagation Mechanism and Ablation Behavior of C/Sic-Hfc Composites Induced by the Sic Interlayer

Abstract

In this study, C/SiC-HfC composites with different thicknesses of the SiC interlayer (about 0, 0.5, 1.0, and 1.5 μm) were prepared by the joint process of chemical vapor infiltration and precursor impregnation pyrolysis. The bending and ablation behavior of these composites were characterized and investigated. A pseudoplastic crack propagation model during the bending process was established based on the microstructure of the fracture and the stress intensity factor approach to understand the failure process of the composites. When the thickness of the SiC interlayer increased to 1.5 μm, the linear ablation rate of C/SiC-HfC composites increased from 5.04 ± 0.24 to 8.25 ± 0.16 μm/s. Surprisingly, the flexural strength of the composites increased from 115.13 ± 6.34 to 286.09 ± 17.56 MPa (an increase of 148%), due to the excellent mechanical properties of SiC and the consumption of crack propagation energy by type II cracks near the SiC-HfC interface. After ablation, the strength retention rate of C/SiC-HfC composites first increased and then decreased with the enhancement of SiC layer thickness (increased from 71.82% to 85.36%, then decreased to 66.75%). In addition, due to the release of residual stress inside the high-temperature environment of ablation, the pseudoplastic characteristics of C/SiC-HfC composites were enhanced. C/SiC-HfC composites exhibit a high strength retention rate after failure.

Keywords: C/SiC-HfC composites, Ablation behavior, crack propagation, pseudoplastic, flexural strength