Design And Investigation On Heat Transfer Performance Of C/SiC Sandwich Composites

According to the requirements of lightweight and multi-functions of thermal protection system for the high-speed flight vehicle,a new graded corrugated truss core composite sandwich structure which combine the characteristic of lattice structure with functionally graded materials was presented.Two different graded corrugated truss core including the gradient property along Y and Z direction were designed.Considering the coupling of heat conduction,heat radiation and heat convection,three-dimensional heat transfer model of the sandwich structure was established based on Discrete Ordinates Radiation Model and Laminar Flow Model.The calculation method of heat transfer coefficient of the graded lattice core sandwich structure was developed.In order to verify the calculation method,the numerical results were compared with the experiment data.Firstly,the transient and steady-state temperature field of C/SiC sandwich composites was studied at different temperature.The heat transfer coefficient of corrugated-core sandwich structure were discussed under different boundary conditions and fillings.The heat transfer increases with the temperature increase.The heat transfer coefficient of the sandwich structure increases gradually with the temperature.The ability of thermal insulation for the sandwich structure was improved as the thermal conductivity of filling decreased.Secondly,the effect of meso size of the graded lattice core sandwich structure on the heat transfer coefficient were discussed.It is found that the heat transfer coefficient of structure becomes larger with the increase of the volume of core at low temperature.However,the heat transfer coefficient of structure becomes smaller with the increase of the volume of core at high temperature.Finally,the corrugated truss core sandwich structure with gradient in Z direction was established.The influence of the air fluid velocity on the heat transfer coefficient was studied.The contribution of cavity radiation to the heat transfer and the influence of internal surface emissivity of the structure on heat transfer coefficient were investigated.The results show that the heat transfer coefficient of structure decreases with the increase of air flow velocity.Furthermore the cavity radiation makes more contributions to the heat transfer with increase of temperature.The ability of thermal insulation for the sandwich structure was promoted as the internal surface emissivity decreased.