Pyrolysis and ablation behavior of an innovative thermal ablation/insulation gradient composite coating structure: From numerical model to design optimization

Thermal protection coating is the one of ideal materials for large-area ablation regions of spacecraft. A thermal ablation/insulation gradient composite (TAIGC) coating structure is presented, which integrates the advantages of thermal ablation and insulation coatings. In this study, a multi-stage pyrolysis kinetics model was developed to investigate the pyrolysis characteristics based on the thermal analysis kinetics equations. The ablation and thermal protection mechanisms were revealed by analyzing the microstructural evolution of the TAIGC coating structure during thermal exposure tests. Based upon the principles of mass and energy conservation, a coupled ablation and heat transfer model with multi-stage pyrolysis and gas diffusion mechanisms was proposed. Based on the comparison of the temperature–time curves from the simulations and the experimental data, the proposed model could satisfactorily predict the pyrolysis and ablation response of the TAIGC coating structure undergoing ablation. Furthermore, the redesign and optimization of the TAIGC coating structure were conducted using the proposed model. This work can provide a theoretical basis for the high-fidelity design and ablation performance evaluation of multilayer thermal protection coating structures.