Microstructure Evolution and Ablation Mechanism of C/C and C/C-SiC Composites Under a Hypersonic Flowing Propane Torch

The high-velocity oxygen fuel thermal spray system can provide a hypersonic flowing environment in which the temperature, pressure, and speed are all sufficiently high to represent a more realistic environment of hypersonic vehicles than that produced by traditional oxyacetylene flame. In this work, the ablation resistance of C/C and C/C-SiC composites under hypersonic flowing propane flame is investigated, and the microstructure evolution during the ablation process is examined. It is found that different ablation regions are formed depending on the size, and the distributions of temperature and pressure on the front surface of the samples. With the increase of ablation time, a dense and continuous oxide layer forms, which acts as a barrier to prevent the interaction of oxidizing gases and composites, and can also block the conducted heat and resist high temperature scouring of hypersonic flowing flame. In addition, a numerical analysis is performed using ANSYS Fluent software to investigate the fields of velocity, pressure, and temperature on the front surface and around the carbon fibers of the sample. The simulation results further demonstrate the evolution of microstructures of C/C and C/C-SiC composites.