Study Of The Thermal Properties Of Several Typical Aerospace Thermal Protection Materials

The design of reusable thermal protection systems is a key technology for the development of reusable launchers.Thermal properties parameters such as thermal conductivity and specific heat capacity are important parameters to quantitatively evaluate the thermal conductivity and heat absorption capability of materials,and are also the main basis for the screening of thermal protection materials and the design of thermal protection structures.Obtaining thermal properties parameters of thermal protection materials scientifically,accurately and efficiently is a crucial step to assess the reusable performance of space vehicles.In this paper,the method of determining the thermal properties of aerospace thermal protection materials is studied with some typical aerospace materials as the research objects.The main work is as follows: first,based on the idea of the inverse problem of heat conduction equation,the inverse model of thermal conductivity and specific heat capacity of the material with temperature is established by using the finite element method combined with the optimization algorithm;in the positive problem of heat conduction equation,the specific heat capacity and thermal conductivity are assumed to be segmental functions of temperature,and the temperature response of the material under the given heat flow condition is calculated by using the finite element simulation as the basic analysis tool.response;meanwhile,in the heat conduction equation inverse problem study,based on the quartz lamp radiation heating test system,the material temperature measurement data are obtained,and the thermal conductivity and specific heat capacity are inverse performed by using multi-island genetic algorithm and sequential quadratic programming method.Secondly,in order to explore the reliability and stability of the inverse model,the influence of three factors,such as the initial value of the inverse parameters,the number of thermocouples and the measurement error,on the inverse values was focused on.The results show that the initial value has a small effect on the inversion results,and the inversion accuracy improves with the increase of the number of thermocouples and decreases with the increase of the measurement error,but good inversion results can be obtained even within a large measurement error,which verifies the reliability and robustness of the inversion model.Then,the inversion model was experimentally verified with the aid of a quartz lamp radiation heating test system,using typical aerospace materials such as stainless steel M304,high-temperature alloy GH4169,and aluminum 5A06 as research objects.By comparing the change pattern of the inversion temperature value with the measured temperature value,it can be found that the change trend of the inversion temperature curve is basically consistent with the measured temperature curve.In addition,the measured values of thermal conductivity and specific heat capacity at each point after inversion are in general agreement with those of other instrumental measurement methods,which further demonstrates the feasibility and accuracy of the method.Also,the macroscopic morphology and density changes of each material before and after the test were further analyzed.Finally,the anti-insulation performance of the anti-insulation integrated structure was explored,focusing on the thermogravimetric and DSC curves of the anti-insulation integrated structure.The optimized design method for minimizing the mass scale of the material structure under the material test temperature permitting condition is discussed,and the ideas for the dimensional design of the anti-insulation integrated structure are provided.