Analysis Of Thermal Deformation And Profile Accuracy Of Honeycomb Sandwich Reflectors

With the continuous development of satellite communication technologies,human beings have higher and higher requirements for antenna accuracy,which has gradually increased the caliber and quality of satellite-borne antennas.With the development of materials science,a honeycomb sandwich structure using a carbon fiber composite material as an antenna skin is gradually applied by major communication satellites,the carbon fiber skin honeycomb sandwich structure has the characteristics of light weight,high strength,strong resistance to thermal deformation,etc.It can serve in long-term service environments with cyclical changes in high and low temperatures.In this paper,the thermal deformation and the accuracy of the surface of the carbon fiber aluminum honeycomb sandwich structure are studied.Firstly,according to the honeycomb plane projection shape and molding process,a double-walled thick hexagonal honeycomb is selected as the structural form of this honeycomb.At the same time,the commonly used hard aluminum-5A02 aluminum alloy as a honeycomb material in the aerospace field.Due to the complex mechanical and thermal properties of the honeycomb structure,it is necessary to calculated the quivalent mechanical and thermal properties of the honeycomb structure.Based on the equivalent theory of Y model,the calculation formula of honeycomb equivalent mechanical parameters is given.According to ABAQUS finite element calculation and S-P formula,the analytical method of the effective thermal conductivity of honeycomb structure under the coupling of thermal conduction and thermal radiation is obtained under the premise of ignoring air heat conduction and convection radiation.According to the principle of volume mixing,the formula for the equivalent specific heat capacity of a regular hexagonal double-walled honeycomb structure is obtained.The relationship between the honeycomb equivalent thermal expansion coefficient and the thermal expansion coefficient of the honeycomb core material itself was obtained by using ABAQUS finite element analysis.Secondly,the experimental performance of the mechanical properties of the reflector skin M55 carbon fiber laminate was tested at low temperature-80?,room temperature and high temperature 120?,including: elastic modulus,Poisson's ratio,in-plane shear modulus and out-of-plane shear modulus,the relationship between the mechanical properties of M55 laminates and the temperature was also obtained.The thermal properties of M55 carbon fiber laminates and 5A02 aluminum alloyswere measured at-80?~120?,including: specific heat capacity,thermal conductivity and thermal expansion coefficient,and the response laws of thermal performance and temperature are obtained;The measured properties of the honeycomb core material are brought into the honeycomb equivalent theory,accurate cellular equivalent parameters were obtained,including: equivalent density,equivalent specific heat capacity,equivalent thermal conductivity and equivalent thermal expansion coefficient,we get the change rule under-80?~120? at the same time.Finally,The ABAQUS was used to analyze the thermal deformation of the small reflector model of the reflector,and the RMS value of the reflector with small size was obtained through precision fitting.By comparing with the RMS value of the experimental measurement,we can derived the deviations between experimental and simulated values.Meanwhile the accuracy of the calculation of the cellular equivalent parameter was verified.According to the analysis of the influencing factors of profile accuracy,including: temperature gradient,thermal expansion coefficient,honeycomb height,number of plies,adhesive layer thickness and ply angle deviation.It is concluded that the thermal expansion coefficient in the honeycomb height direction is the most important factor affecting the reflector accuracy,at the same time,the optimal reflector structure is obtained.The finite element model of the full-size reflector is established based on the actual assembly conditions of the reflector,it is concluded that the buried block and the fastener assembled on the reflector face can effectively reduce the deformation of the working face,the RMS value of the full-surface reflector's profile accuracy obtained by precision fitting is obtained,it shows that the reflector has good thermal deformation resistance and high profile accuracy.