Abstract: When the braided structural CMC material is applied to high-temperature components of aero-engines such as turbine blades, the internal structure of the braided composites will cause the temperature fluctuation. 2.5D braided composite was taken as an example to investigate the temperature field fluctuation characteristics of composite materials. The homogeneous plate model on the basis of effective thermal conductivity and the plate model on the basis of full-size microscopic structure of the braided material were constructed respectively. The temperature distribution and the internal heat transfer characteristics of the two plate models were calculated and compared. Moreover, the effects of the structural parameters (e.g., the angle of the internal braided structure) and the thermal property parameters (e.g., the ratio of axial to radial thermal conductivity of fiber bundle and the thermal conductivity ratio of fiber bundle to matrix) on the temperature fluctuation of materials were also studied. In addition, the test experiment on temperature field of the braided structural plate was carried out. The results show that comparing with the temperature field calculated based on the effective thermal conductivity, the temperature field obtained based on the full-size braided structural plate model shows more obvious fluctuation. When the average internal temperature gradient inside the plate is 25383K/m, the amplitude of the temperature fluctuation on the surface reaches to 12.41K, the value of the highest temperature increases from 906.96K to 911.60K and the direction of heat transfer inside the plate is significantly deflected along the yarn. Meanwhile, with the warp braiding angle increasing, the amplitude of the temperature fluctuation decreases. However, the high temperature region on the surface and the frequency of the fluctuation along the axial direction of the warp increase. As the ratio of axial to radial thermal conductivity of fiber bundle increases, the high temperature region on the surface of the material is almost unchanged, but the amplitude of the temperature fluctuation decreases slightly and the uniformity of the temperature is enhanced. As the thermal conductivity ratio of fiber bundle to matrix increases, the high temperature region of the material surface increases, but the amplitude of the temperature fluctuation decreases greatly and the uniformity of the temperature is greatly improved. In this paper, when the boundary temperature reaches to 1600K, the method based on effective thermal conductivity cannot estimate the temperature field of the braided materials correctly.

Key words: Aeroengine;Turbine blade;Composite materials;Heat transfer;Braided structure;Temperature distribution;Anisotropy

摘要： 考虑到编织结构陶瓷基复合材料（CMC）在涡轮叶片等航空发动机高温部件应用时，材料内部编织结构特征会导致高温部件的温度场存在波动性。为了研究复合材料温度场的波动特征，以2.5D编织结构复合材料为例，分别建立了基于等效导热系数的均匀化平板模型和基于材料全尺寸细观编织结构的平板模型，计算对比了两种平板模型的温度场分布及内部热量传输特征，同时探究了材料内部编织结构的角度、纤维束轴向与径向导热系数比、纤维束与基体导热系数比等材料结构特征参数和热物性特征参数对材料表面温度波动的影响规律，并开展了编织结构平板的温度场测试实验。研究结果表明：与基于等效导热系数计算得到的平板温度场相比，基于全尺寸编织结构平板模型得到的温度场存在明显的波动特征，当平板内部平均温度梯度为25383K/m时，表面温度波动幅值达到12.41K，表面最高温度由906.96K增加到911.60K，并且在平板内部热量的传输方向沿着纱线发生明显的偏转。同时，随着纱线编织角度的增加，材料表面温度波动幅值下降，但表面的高温区域增加，沿着经纱轴向的温度波动频次增加。随着纤维束轴径向导热系数比的增加，材料表面的高温区域基本不变，温度波动幅值小幅下降，均匀性增强；随着纤维束与基体导热系数比的增加，材料表面的高温区域增加，温度波动幅值降幅较大，均匀性得到较大提高。在本文的研究范围内，当边界温度达到1600K时，基于等效导热系数的方法无法准确地预估复合材料的温度场。

关键词: 航空发动机;涡轮叶片;复合材料;热传导;编织结构;温度分布;各向异性