A mesoscopic thermochemical ablation-erosion coupling model of 3D woven C/C composites under high-speed airflow shear

Aircrafts suffer from severe aerodynamic heating and aerodynamic force in the hypersonic environment, leading to the thermochemical ablation and aerodynamic erosion of thermal protection materials. Characterizing the ablation and erosion performances of thermal protection materials is of great significance for the engineering design of thermal protection systems. In the paper, the ablation tests of 3D woven C/C composites were firstly conducted using an oxygen-acetylene ablation test rig, and the surface ablation morphology and recession were characterized and analyzed. Then, the analysis method of mesoscopic ablation morphology is established, considering the component ablation rate difference and the reaction/diffusion competition mechanism. Based on the mesoscopic structure characteristics and surface ablation behavior, an aerodynamic erosion model is developed to analyze material failure under supersonic airflow shear, and an aerodynamic erosion criterion for 3D woven C/C composites considering aerodynamic force and surface ablation roughness is proposed. A mesoscopic ablation-erosion coupling method and the corresponding numerical program are developed. Finally, the effects of different aerodynamic shear pressures on surface recession, roughness, and mass loss are investigated, and the mechanical erosion factor is calculated via numerical methods. Combined with the classical macroscopic thermochemical ablation model, the total surface recession caused by ablation and erosion is calculated. The accuracy of the total surface recession calculated by the numerical model is verified by comparison with experimental results. This study can provide guidance for the analysis of surface ablation-erosion performance of thermal protective materials, as well as the engineering design of thermal protection systems.