防热复合材料高温力学性能

INVESTIGATION OF THE THERMO-MECHANICAL PROPERTIES OF THERMAL PROTECTIVE COMPOSITES UNDER HIGH TEMPERATURE

通过对高温环境下防热材料内部热化学烧蚀机理的分析,利用Eshelby等效夹杂方法研究了组元材料烧蚀-相变特性和高温力学性能的变化规律。假设材料热化学反应后的热解(热氧化)生成相介质统计均匀分布,考虑了烧蚀反应产生的气孔与固体相介质之间的相互作用,预报了单向纤维增强复合材料微结构与宏观性能之间的变化关系,并进行了数值计算。研究结果表明:单向复合材料纵向杨氏模量随温度升高而衰减,并与加温速率有关,典型热防护材料的高温力学性能的理论预报与实验数据进行比较,结果吻合较好,说明理论模型正确,为防热复合材料热结构分析奠定了基础。

According to the analysis of the ablative mechanism of thermal protective materials under high temperature, the ablation-phase transformation properties and the thermomechanical behavior of the component materials are investigated by Eshelby equivalent inclusion method. Through the hypothesis of the statistical uniform distribution of the phases consisting of solid products of thermodestruction at high temperatures and pores in the materials, the interaction among different phases by complicated internal physico-chemical processes in a matrix and fibers is considered. The exact relationship between the micro-structure and the macro-behavior for composites reinforced with unidirectional continuous fibres is proposed, and the numerical solution is given. With the model, the following high-temperature phenomena have been described: degradation of elastic moduli of the composite in the reinforcing direction in heating, and dependence of heat properties of the composite not only on temperature but also on duration of heating. Comparison of the theoretical and experimental results for typical ablative materials showed that the model allows one to forecast the thermomechanical characteristics of the composites according to the properties of their matrices and fibers. It is helpful for the analysis of the composite materials high-temperate structure.