Study On Design And Verification Technology Of Lightweight Silicon Based Integrated Structure For Thermal Protection And Insulation

The design of thermal protection structure is the key to the thermal management of aircraft,and it is the most difficult problem in the process of developing hypersonic vehicle.When the aircraft is flying at high speed,the surface temperature of the aircraft will increase greatly.At the same time,the working temperature of the electronic and electrical equipment inside the body should not exceed 85℃ to ensure the normal operation of the aircraft internal equipment.Such a high temperature difference will bring severe challenges to aircraft thermal protection,the existing thermal protection structure design criteria and thermal insulation materials can not meet the design requirements,so the development of high-performance thermal protection structure becomes extremely urgent.According to the demand of thermal protection structure,the strength and stiffness of the integrated structure are simulated by finite element method,and the type and material of the structure are determined.On this basis,the configuration of the lightweight and efficient thermal protection structure is designed.The thermal mechanical coupling calculation of the thermal protection structure is carried out by using ABAQUS software,the connection form is analyzed,and the configuration of the efficient passive thermal protection structure is designed.According to the results of the finite element simulation,the light silicon-based thermal insulation material system is determined.High silica microfiber of Uygur cotton was prepared by flame injection method,and the Microfiber with finer diameter and lower thermal conductivity was obtained.By controlling the hydrochloric acid concentration,acid leaching time and temperature in the process of acid treatment,the optimal process parameters were obtained to ensure the best content of silica in high silica microfiber Uygur cotton.By adjusting the beating time and adding some fiber cotton a with better performance to the pulp,the density of the felt was reduced and the light fiber cotton was obtained.The synthesis technology of aerogel/silica fiber composites was studied,and the effects of precursors on the physical and chemical properties of aerogel composites were discussed.It is found that tetraethyl orthosilicate(TEOS)can control the preparation process of aerogels.The two-gel aging process can improve the crosslinking degree of the gel network structure and improve the heat insulation performance.In order to obtain large size aerogel composites with excellent overall performance,supercritical drying process was optimized.The evaluation method of lightweight silicon based thermal insulation material is proposed.The performance of high silica microfiber mat and silica aerogel insulation material is evaluated by this method.The heat insulation performance of high silica microfiber mat and silica aerogel/silicon fiber composite material at medium temperature and high temperature and short time working conditions is given.Low density,high silica microfiber cotton felt,and silica aerogel/silicon fiber composite materials were synthesized.A test method for thermal insulation properties of insulating materials was put forward,and the heat insulation properties of silicon based thermal insulation materials were tested.The effectiveness of the lightweight and efficient passive thermal protection structure is evaluated.Based on the thermo mechanical coupling calculation results of the thermal protection structure,the reliability and thermal insulation effectiveness of the bonding and mechanical connection modes were studied.The skin material,the connector material,the heat insulation efficiency and the connection form of the external block aerogel/silicon fiber composite material were verified.Based on the principle of equivalent density,the thermal insulation performance of lightweight silicon-based thermal protection structure is analyzed,and the technical indexes such as plate thickness,quality,temperature and time are given to meet the use requirements,and the configuration scheme with minimum weight gain is determined.The database of thermal protection material system with friendly man-machine interface is constructed,which is convenient for researchers to query the thermal insulation performance of various thermal insulation materials and improve the efficiency of scientific research.The database can realize the functions of material selection,temperature time curve and configuration information query,guide the design of thermal protection structure,and provide technical support and guidance for the follow-up research.