极端环境下变密度炭化复合材料的烧蚀机理及性能优化研究

When the reentry capsule, suffering severe aerodynamic heating, reenters the Earth's atmosphere at the approximate second cosmic escape velocity, the low density charring composite materials is the best choice in this thermal protection system (TPS). In order to increase the thermal protection efficiency, the density of charring composites has to be changed with the varying reentry aerodynamic heating environment. So it's imperative to explore the ablation mechanism and performance optimization of the variable density charring composite materials. Taking the phenolic impregnated carbon ablator (PICA) with variable density for example in this project, the heat-fluid-solid-chemistry coupling mechanism of the pyrolytic layer and surface ablation mechanism in the PICA with variable density will be revealed with the application of the integration of materials, structure, flow field and chemical reaction, which is on the base of composite material mechanics, heat transfer, computational fluid dynamics, high temperature experimental mechanics, ablation and other multi-disciplinary theories. The correlation between material density distribution and thermal protection efficiency is found out, the law for effect of chemical non-equilibrium and catalysis on the material ablation is discovered, and the ablation mechanism of variable density charring composite materials in extreme environment is revealed through multiple ways, including physical and mechanical performance test of the variable density charring composites, ablation test and numerical simulation. Based on the above, characterization parameter for thermal protection efficiency of these materials in TPS is refined, and the optimization and evaluation system of these materials will be further established. This research will contribute to the development of interdisciplines, which will own not only the significance of theory research, but also the crucial national defense value.

以第二宇宙速度再入的返回舱服役于气动加热的极端环境中，其热防护材料首选低密度炭化复合材料。为提高防热效率，炭化复合材料的密度需随热环境而变，变密度炭化复合材料烧蚀机理及性能优化的科学问题尚未解决，亟待研究。本项目以变密度PICA复合材料为主要研究对象，基于复合材料力学、高温实验力学、传热学、稀薄气体动力学、烧蚀学等多学科的交叉与渗透，通过变密度炭化复合材料的高温物理性能、力学性能测试及烧蚀试验、数值模拟，从材料、流场、传热、化学反应一体化的角度揭示变密度多孔热解层中热-流-固-化耦合机理，发现稀薄气体的化学非平衡与催化效应对材料表面烧蚀的影响规律，建立极端环境下变密度炭化复合材料的烧蚀模型，弄清炭化材料密度分布与热防护效率的关系；进一步提炼变密度炭化材料热防护效率的表征参量，构建炭化材料热防护性能的优化及评价系统。本项目将推进多学科的交叉，具有重要的理论研究意义，又具有重要的国防应用价值。

高超声速飞行器服役于气动加热的极端环境中，其热防护材料首选低密度炭化复合材料。为提高防热效率，炭化复合材料的密度需随热环境而变，变密度炭化复合材料烧蚀机理及性能优化的科学问题尚未解决，亟待研究。本项目以变密度PICA复合材料为主要研究对象，基于复合材料力学、高温实验力学、传热学、稀薄气体动力学、烧蚀学等多学科的交叉与渗透，通过变密度炭化复合材料的高温物理性能、力学性能测试及烧蚀试验、数值模拟，从材料、流场、传热、化学反应一体化的角度揭示了变密度多孔热解层中热-流-固-化耦合机理，发现了稀薄气体的化学非平衡与催化效应对材料表面烧蚀的影响规律，建立了极端环境下变密度炭化复合材料的烧蚀模型，弄清了炭化材料密度分布与热防护效率的关系；进一步提炼变密度炭化材料热防护效率的表征参量，构建了炭化材料热防护性能的优化及评价系统。通过本项目研究，充分发挥自主创新能力，使得热防护材料选择、热结构设计及产品性能评价都将有理可依、有据可寻，对实现防热系统的精细化设计具有重要意义，为未来深空探测返回舱、进入船及高马赫数武器的热防护设计提供有效的技术支撑。本研究还将推进复合材料力学、传热学、烧蚀学等多学科的交叉与渗透，具有重要的理论意义和航天工程应用价值。

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