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This work conducts ablation experiments and multi-scale numerical simulations of C/SiC composite materials under CW laser action. The highest surface temperature, macroscopic and microscopic ablation morphology, and approximate ablation threshold for C/SiC composites at different power densities were obtained. A multi-scale ablation calculation method for C/SiC composite materials under CW laser action was established using the level-set method. At the meso-scale, a macro-mesoscopic cross-scale surface ablation model was established, taking into account factors such as solid heat transfer, heat exchange of chemical reactions, differential temperature rise process between internal fibers and matrix, and differences in ablation behavior of two-dimensional plain weave fabrics. The experimental and microscale simulation results indicate that different ablation behaviors (oxidation and sublimation) occur in different regions, resulting in "shoot tip" fibers and residual matrix pore morphology. This work can provide theoretical and experimental basis for the design and precision machining of C/SiC materials. [ABSTRACT FROM AUTHOR]

In this study, the CW laser is used as a local heat source to simulate the extreme thermal environment generated by shock wave interference at discontinuities in spacecraft. The ablation behavior of the thermal protection material (C/SiC) is investigated under the combined impact of high-temperature airflow and the local extreme heat source. A novel multi-field coupling numerical computation software was presented to examine this strong coupling process of fluid-solid-thermal-ablation. The program was modified using the ALE + umeshmotion ablation calculation method in the ABAQUS software to mimic the process of the material's ablative boundary retreating under the action of the CW laser until the target was perforated. ANSYS Fluent software was used to do the numerical analysis of the high-speed airflow. The results of wind tunnel experiments and numerical simulations indicate that, compared to the effect of local heat sources in static air, irregular ablation pits are formed on the material surface under the action of local heat sources in high-temperature flow fields, resulting in higher ablation rates due to mechanical denudation effects. Analysis of the localization characteristics of the flow field near the ablation pit reveals that the shock wave generated downstream of the ablation pit leads to an increase in gas temperature, pressure, and density. When the ablation amount reaches a certain threshold, the gas in the ablation pit forms vortices, leading to an increase in local heat flow and pressure. [ABSTRACT FROM AUTHOR]

• Local structural heat sources with different heat flux densities are used to simulate local extreme environments at discontinuities in spacecrafts. • The thermal response, ablation law, and multi-scale ablation morphology of typical thermal protection materials (C/SiC) under the action of local heat sources are analyzed. • Improve the ablation retreat program (Umeshmotion+ALE) in the ABAQUS software so that C/SiC composite materials with large ablation amount until material perforation can be simulated numerically. This study uses ablation testing on C/SiC composite materials under local structured thermal sources with a wide range of heat flux densities, simulating the harsh local conditions caused by discontinuous structural interference on spacecrafts. The thermal response, ablation laws, and ablative perforation time of C/SiC composite materials are obtained under different heat flux densities. The experimental findings demonstrate that there are notable differences in the morphology of the ablation pits under various heat flux conditions. As the heat flux density increases, the temperature of the local structure heat source action center on the target surface increases, the depth and outer diameter of the erosion pits increase, and the wall surface of the erosion pits gradually tends to be smooth. Under the influence of local structural heat sources, the creation of material ablation pits and the process of material perforation are predicted using the improved Umeshmotion+ALE+birth and death element method. For various conditions, the temperature field results and ablation morphology are well predicted by the numerical simulation results. Numerical calculations can be used to analyze the thermal stress and oxidation sublimation contribution rates of targets under the action of structural heat sources. [ABSTRACT FROM AUTHOR]