Effect of HfC on the ablative and mechanical properties of C/C composites

The ablation and mechanical behavior of the carbon/carbon (C/C) and hafnium carbide (HfC) modified C/C (HfC-C/C) composites were evaluated by oxyacetylene flame and the three-point bending tests. The effect of impact damage on their mechanical behavior was also investigated. To produce the HfC-C/C composites, the refractory carbide precursor was introduced to the preforms by impregnating with HfOCl₂·8H₂O solution. Both the C/C and the HfC-C/C preforms were densified by thermal gradient chemical vapor infiltration. Results indicated that, although the linear and mass ablation rates exhibited by the HfC-C/C composites were lower than those for the C/C composites by 55% and 21%, respectively, the maximum flexural load for the C/C composites was significantly higher by 33% than that of HfC-C/C composites. The influence of pre-impact loading on mechanical behavior was greater for the HfC-C/C composites than for the C/C composites.