Mechanical, thermophysical, and ablation properties of C/HfC–SiC composites with various SiC/HfC ratios

Abstract

The mechanical, thermophysical, and ablation properties of 2.5D C/HfC–SiC composites with various SiC/HfC ratios are studied. The S7‐C/HfC–SiC composite with a high SiC/HfC volume ratio of 30.4/15.2 has the highest flexural strength of 203.4 ± 26.8 MPa and fracture toughness of 10.0 ± .5 MPa·m1/2. All C/HfC–SiC composites have a similar low thermal conductivity of ∼2 W·m−1·K−1 and their CTEs are in the range of .45–4.0 × 10−6/K from 30°C to 1400°C. S5‐C/HfC–SiC with medium SiC/HfC ratio possesses the lowest mass ablation rate of .29 ± .02 mg·cm−2·s−1 and linear ablation rate of .003 ± .0002 mm/s. The C/HfC–SiC composites are endowed with a pitting corrosion feature according to the morphology and composition evolution of the ablated surface, which results from both high temperature and stagnation pressure gradients in the radial direction of the oxyacetylene torch.