Investigation of the thermo-mechanical properties of thermal protective composites under high temperature

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.