CMC-SiC轻质点阵热防护系统防隔热承载一体化设计与热力耦合效能评价方法

In the future, thermal protection systems (TPS) of hypersonic vehicles will develop towards the direction of ultra-high temperature resistance, integration of structure and function, and lightweight. In extreme environments, the combined effect of high heat and high load on TPS is more prominent. The project intends to conduct mechanical experiments of CMC-SiC materials by using in situ X-ray computed microtomography (μCT) at ultra-high temperature, reveal the evolution mechanism of microcrack damage in materials, establish ultra-high temperature thermal-mechanical coupling constitutive theory and failure criterion, and develop corresponding numerical simulation method for CMC-SiC materials and their lightweight lattice TPS to investigate the thermal-mechanical response laws of CMC-SiC lightweight lattice TPS at ultra-high temperatures. Then considering the thermal insulation and loading-bearing capacities, thermal-mechanical coupling efficiency evolution method will be established, and optimization design method integrated thermal insulation and loading-bearing capacities will be developed. It is expected to obtain some innovative research results on ultra-high temperature in situ experimental characterization, constitutive theory, failure criterion of CMC-SiC materials and thermal-mechanical efficiency evolution method of lightweight lattice TPS, which will provide theoretical and experimental basis for integrated design of thermal insulation and load-bearing capacities of CMC-SiC lattice TPS in aerospace.

未来高超声速飞行器热防护系统(TPS)向耐更高温、结构功能一体化、轻量化方向发展。极端环境下，TPS受高热/高载联合作用问题更加突出。针对CMC-SiC点阵TPS超高温防隔热和承载问题，本项目拟开展CMC-SiC材料超高温在位μCT力学实验，揭示材料内部微裂纹损伤演化机制，建立CMC-SiC材料超高温热力耦合本构理论及失效准则，并在此基础上发展CMC-SiC材料及其轻质点阵TPS超高温热力耦合数值仿真方法。探索CMC-SiC轻质点阵TPS在超高温环境下的热力耦合响应规律，建立综合考虑防隔热和承载性能的热力耦合效能评价方法，发展CMC-SiC轻质点阵TPS的防隔热承载一体化优化设计方法。本项目期望在CMC-SiC材料超高温在位实验表征、本构理论与失效准则及CMC-SiC点阵TPS热力耦合效能评价方法获得原创性成果，为航空航天领域对轻质点阵TPS防隔热承载一体化设计需求提供理论基础和实验依据

高超声速飞行器高马赫数飞行过程中，表面受严酷气动加热作用，翼前缘、头锥等关键部位温度高达 1500℃以上，在飞行器内部结构内部产生高温及温度梯度，高温使结构承载性能下降，温度梯度在结构内部产生较大的热应力及变形，对高超声速飞行器的安全性产生极大影响。针对高超声速飞行器对耐高温热防护材料与结构的迫切需求，分别开展CMC-SiC 超高温在位热力耦合加载μCT力学测试与实验表征方法、CMC-SiC超高温热力耦合唯象本构理论、CMC-SiC 轻质点阵TPS防隔热承载一体化设计与热力耦合效能评价方法研究。以C/SiC复合材料开展μCT室温及1000℃高温环境下在位拉伸加载测试，在位观察材料缺陷及其演变。室温下，在施加载荷之前，复合材料中最初存在着空隙缺陷，位于两个平纹织物层压板之间，当拉伸载荷增加到2.0KN时，复合材料中的损伤开始沿着初始缺陷发展。采用深度卷积网络算法（DCNN）对CT图像进行分割，提出了一种检测纤维纱线接触时凹点的算法。凹点可以用来判断分割图像中是否有接触的纤维纱。针对C/SiC编织复合材料，首次建立了超高温无氧非线性唯象本构理论，该理论考虑了拉压异性、单边裂纹闭合效应、正交各向异性以及热硬化效应。该理论认为C/SiC编织复合材料的非线性来源于材料内部微裂纹的萌生、扩展，在无氧超高温环境下，温度小于一定值时，温度对裂纹密度影响不大，裂纹的形成、演化只与应力状态有关。压缩应力抑制非线性（裂纹扩展），而拉伸或剪切应力分量则导致非线性行为。在无氧环境下，温度升到至一定值时，C/SiC编织复合材料的非线性降低，也就是热硬化效应。设计了C/SiC点阵热防护系统，实现隔热承载一体化设计。提出结构效率概念作为评价点阵式热防护系统热学和力学综合性能的指标。研究结果表明，芯子倾角为30°时，点阵热防护系统综合性能最好。本项目将为航空航天领域中结构的超高温热防护问题提供新的解决方案，为CMC-SiC材料与结构在我国高端装备的应用提供理论基础和实验依据。