Experimental Determination And Numerical Studies On Typical Thermal Protection Structure Materials

With the continuous improvement of the application of space vehicles,their light speed and service environment become increasingly harsh,leading to increasingly prominent thermal protection problems in space structures.For example,the truss structure of the space station is damaged due to excessive thermal deformation,and the battery of the satellite battery is detached due to excessive deformation.Therefore,effective thermal protection system is one of the important technologies to ensure the normal service of aircraft.Based on the typical thermal protection material ceramic matrix composite materials yuan as the research object to carry out the experimental study on its surface structure and mechanical properties,microscopic and calculation parameters of Weibull distribution to obtain the related technology,and through the finite element simulation of carbon/silicon carbide(C/SiC)unidirectional composite material,plain weave and satin weave formulation of composite material under different temperature condition of the damage mechanism of development.The main work of the paper is as follows:(1)For typical thermal protection materials,precursor impregnation cracking(PIP)carbon/silicon carbide(C/SiC)ceramic matrix composites(CMCs)were studied.The mechanical properties and microscopic properties of fiber bundles in PIP-C/SiC composites were studied by PIP process.The impact of the structure.The fiber bundle is placed in a high temperature furnace for cyclic heat treatment,strictly in accordance with the manufacturing process of the PIP-C/SiC composite material.A series of tensile tests were then performed on each of the treated fiber bundles to obtain their in-situ mechanical properties under each cycle heat treatment.Through numerical simulation and experimental tests,it was found that the average strength of the fiber bundles treated in the same cycle was significantly higher than the average strength of the fiber bundles in situ.Based on this characterization,the tensile strength of these fiber bundles was correlated with the heat treatment of different cycles by Weibull distribution and least squares fitting.The microstructure of the fiber bundle surface was studied under scanning electron microscopy(SEM)to explain the experimental results.(2)In view of the precursor impregnation pyrolysis of silicon carbide(PIP-SiC/SiC)SiC ceramic matrix composites,studied the PIP-components in SiC/SiC composites is silicon carbide(SiC)monofilament tensile properties and the microstructure change process,follow the PIP process processing,silicon carbide fiber and carbon fiber for cyclic heat treatment of fiber,and in the monofilament tensile tester for silicon carbide monofilament 10 mm,15 mm,20 mm,25 mm and 30 mm of fracture strength,comparing with the carbon fiber monofilament,The two-weibull distribution was used to fit the silicon carbide and carbon fiber monofilament treated with normal temperature and thermal cycle,and the Weibull modulus of normal temperature and PIP at each stage was obtained,which provided a reliable basis for engineering calculation.At the same time,the microstructure of the surface and fracture of the fiber monofilament after cyclic heat treatment was analyzed to explain the experimental results.(3)Based on the finite element numerical simulation method(FEM),two kinds of PIP-C/SiC woven composites(plain weave and woven fabrics)were studied by F language programming UMAT subroutine for damage failure analysis of composite panel.The damage failure behavior of satin-coded composites under different temperature loading conditions,numerical simulation results show that the stress on the woven composites increases from room temperature to 1300 ℃;In this paper,the stress and strain field analysis of ceramic matrix composite material components and structures under mechanical,manufacturing and other service and manufacturing conditions is given.The Weibull modulus measured in the experiment provides the basis for the calculation.The failure mechanism calculation methods of three typical thermal protection structures provide the calculation support for the corresponding engineering design and strength check.