界面层及其建模方式对编织结构CMC材料导热系数影响研究

Effects of Interface and Its Modeling Method on Thermal Conductivity of Braided CMC Materials

关键词:  陶瓷基复合材料  编织结构  界面层  热分析  导热系数  各向异性

Key words:  Ceramic matrix composite  Braided structure  Interface  Thermal analysis  Thermal conductivity  Anisotropy

摘要:

针对编织结构陶瓷基复合材料（Ceramic matrix composite，CMC）中基体、纤维束和界面层等组分的不同传热特征，以及考虑到界面层结构极薄的尺寸特征，探究了界面层及其在细观结构代表单元中的引入方式对编织结构CMC材料内部热量传输特征和各向异性导热系数的影响。研究中对比分析了不考虑界面层、含隐式界面层和含显式界面层等三种代表性体积单元模型的温度场、热流密度场及各向异性等效导热系数，获取了界面层导热系数对CMC材料整体导热系数的影响规律。研究结果表明：编织结构CMC材料内部温度场存在明显的不均匀性，不同模型计算获取的热流密度场具有明显区别。同时基于三个模型获取的各向异性导热系数也具有较大差异，显示界面层方法预估精度较高。此外，随着界面层导热系数增加，CMC材料整体各向异性导热系数明显增加，其对水平经纱Y方向上等效导热系数的影响最大。

Abstract:

Different components of the braided ceramic matrix composites（CMC）， including the matrix， the fiber and the interface， have different heat transfer properties. Considering the thin-wall characteristic of interface， the effects of the interface and its modeling method on the heat conduction characteristics and the anisotropic thermal conductivity were studied. Three different representative volume element （RVE） models were built， that is， the model without interface， the model with implicit interface and the model with explicit interface. The temperature distributions， heat flux distributions and effective anisotropic thermal conductivities of these three models were compared. The effects of interface’s thermal conductivity on the thermal conductivities of whole CMC material were also studied. The results show that， the internal temperature field is quite non-uniform. The heat flux distributions of these three models have significant difference. At the same time， the anisotropic thermal conductivities based on these three models are also different with each other. The modeling method with explicit interface has better accuracy in predicting the effective thermal conductivity of braided CMC materials. Additionally， as the thermal conductivity of interface increases， the anisotropic thermal conductivities of whole CMC material increase significantly， especially the effective thermal conductivity on the Y axis （the direction along horizontal warp yarns）.