Ablation properties of three dimensional needled C/SiC composites by the chemical vapor infiltration

The ablation property of three dimensional needled carbon/silicon carbide composites with a density of 2.15 g/cm³ and a porosity of 16.0% fabricated by the chemical vapor infiltration was studied using oxyacetylene ablation equipment. The linear and mass ablation rates were 0.03 mm/s and 0.0047 g/s on average, respectively. Ablated surfaces of the samples were investigated using scanning electron microscopy and energy dispersive spectroscopy. At the ablation centre, the SiC matrix was erode out due to the combined results of the sublimation and mechanical erosion of SiC, and the C framework can be observed obviously and the C fibers is a needle-shape. The ablation of the composites was dominated by sublimation and mechanical erosion. Between the ablation center and the edge, the end of the C fibers parallel to the ablated surface is a needle-shape and the root becomes thinner. The main ablation mechanisms are thermo-oxidation and mechanical erosion. At the edge, composites were ablated slightly. There were many ablation products and SiC matrix melt on the ablated surface, preventing the ablating of the substrate material. The main ablation mechanism is thermo-oxidation ablation.