Woven-fiber ceramic materials have shown remarkable results in the design of insulative lay-up structures for flexible thermal protection systems. A deeper understanding of heat transfer through the different insulation layers is key for predicting the performance of heat shields. In this article, a thermo-mechanical multiscale model is developed to predict the out-of-plane thermal conductivity at the micro- and meso-levels of transversely loaded two-dimensional woven ceramic fabrics. Knudsen effects within the multiscale structure are studied by adjusting gas pressure conditions. Alumina-based Nextel-BF20 and silicon carbide Hi-Nicalon with a 5-harness satin weave pattern are modeled by finite-element analysis. The computational results are validated experimentally by applying the anisotropic transient plane source method. We find that out-of-plane thermal conductivity decreases significantly with gas pressure due to Knudsen effects in the confined air within the fibrous structure. The dependence of thermal conductivity of fabrics on fiber volume fraction is shown to decrease markedly with pressure reduction. The proposed multiscale modeling approach yields a notable accuracy improvement, with respect to simplified series-parallel models, when compared with our experimental measurements. The FEA model is applicable to other fabric materials and loading conditions and presents an opportunity to study how changes at the fiber level affect the overall thermal behavior of woven fabrics.

机织陶瓷纤维材料在用于柔性热保护系统的隔热叠层结构的设计中已显示出显著成果。深入了解通过不同隔热层的热传递是预测隔热板性能的关键。在本文中，开发了一种热机械多尺度模型，以预测横向加载的二维机织陶瓷织物的微观和内观水平的平面外热导率。通过调节气压条件研究了多尺度结构内的克努森效应。通过有限元分析对具有5线缎纹编织图案的氧化铝基Nextel-BF20和碳化硅Hi-Nicalon进行建模。应用各向异性瞬态平面源法对计算结果进行了实验验证。我们发现，由于纤维结构内封闭空气中的克努森效应，面外热导率随气压显着降低。织物的热导率对纤维体积分数的依赖性显示出随着压力降低而显着降低。与我们的实验测量结果相比，相对于简化的串并联模型，提出的多尺度建模方法可显着提高准确性。FEA模型适用于其他织物材料和负载条件，并为研究纤维水平的变化如何影响机织织物的整体热性能提供了机会。织物的热导率对纤维体积分数的依赖性显示出随着压力降低而显着降低。与我们的实验测量结果相比，相对于简化的串并联模型，提出的多尺度建模方法可显着提高准确性。FEA模型适用于其他织物材料和负载条件，并为研究纤维水平的变化如何影响机织织物的整体热性能提供了机会。织物的热导率对纤维体积分数的依赖性显示出随着压力降低而显着降低。与我们的实验测量结果相比，相对于简化的串并联模型，提出的多尺度建模方法可显着提高准确性。FEA模型适用于其他织物材料和负载条件，并为研究纤维水平的变化如何影响机织织物的整体热性能提供了机会。