温度参数下轴编C/C复合材料的超高温热结构性能分析

Analysis of Ultra High Temperature Thermo-Structural Characteristics of Four-Directional Carbon/Carbon Composites with Temperature Parameter

关键词:  轴编C/C复合材料  高温热结构性能  代表性体积单元  周期性边界条件  等效热结构参数

Key words:  Four-directional carbon/carbon composites  High temperature thermo-structural characteristics  Representative volume element  Periodic boundary condition  Effective thermo-structural properties

摘要:

为了研究轴编碳/碳（C/C）复合材料的超高温热结构性能，开展了2800℃超高温载荷下复合材料的拉伸实验，表征了复合材料组分材料的高温失效形貌；提出了立方体单胞和正六棱柱单胞的温度周期性边界条件的算法和预测复合材料等效热结构参数的方法，在材料属性各向同性正六棱柱单胞模型上验证了方法的正确性；最后建立了轴编C/C复合材料的代表性体积单元，计算了复合材料随温度载荷变化下的等效热结构参数，与实验数据进行了对比分析。分析表明：开展的轴编C/C复合材料的超高温拉伸实验，可以得到复合材料在2800℃载荷下复合材料的等效刚度值，同时分析了轴向试件和径向试件的高温失效机理，径向试件的纤维束拉伸强度对复合材料的径向拉伸强度起到决定性的作用。在应用位移以及温度周期性边界条件的基础上，提出的方法可以得到随温度载荷变化下复合材料的等效热结构参数，得出复合材料在横向满足近似各向同性的特性，预测结果表明只改变温度参数下复合材料的等效热导率不会发生改变。提出的方法同样也适用于其他编织复合材料的热结构性能研究。

Abstract:

To study the ultra high temperature thermo-structural characteristics of the four-directional carbon/carbon （4D C/C） composites， the tensile experiment of composites loaded with 2800℃ were carried out， and the failure morphology of component materials of composites were observed.The algorithm for the equations of periodic temperature boundary conditions imposed in the cubic unit cell and hexagonal unit cell and the method for predicting the effective thermo-structural properties of the 4D C/C composites were proposed.The accuracy of the method was verified on the isotropic material property of the hexagonal unit cell.Finally， the representative volume element of the 4D C/C composites was created， the effective thermo-structural properties of the 4D C/C composites were calculated with temperature.The results were compared with the experimental results.The analysis shows that the effective elastic properties of the composites and the failure mechanism of the axial and the radial samples of the 4D C/C composites can be analyzed by the ultra high temperature tensile experiment with 2800°C.The tensile strength of the fiber bundle of the radial sample plays a decisive role in the radial tensile strength.Based on the application of periodic displacement boundary conditions and periodic temperature boundary conditions， the effective thermo-structural properties of composites can be obtained by the proposed method loaded with temperature.The 4D C/C composites satisfy the characteristics of isotropic in the lateral direction.The effective thermal conductivity of the composites will not change when only the temperature parameter is changed.The proposed method is also applicable to analyze the thermo-structural properties of other braided composites.