| With the development of large space vehicles,higher requirements are put forward for their lightweight.Since the tank accounts for more than 60%of the overall weight of the rocket,the material and structural design of the tank directly affect the weight of the rocket,and composite materials have gradually become one of the main structural materials due to their light weight,high strength,and integral manufacturing.The high-quality manufacture of large-scale composite material integral tank poses severe challenges to the design and manufacture of its forming tooling.On the one hand,there may be tooling deformation caused by winding tension during the winding forming process of large tank,and it is necessary to ensure the integral stiffness of the forming tooling;On the other hand,during the curing and molding process of large tank,the thermal expansion coefficient of the tooling material needs to be matched with it to avoid the reduction of molding accuracy caused by the uncoordinated deformation,and it is necessary to realize the problem of removing the molding tool from the bottom cover of the cured tank.Therefore,this paper focuses on the high-quality manufacturing needs ofφ3.35m large composite integrated tank,and carries out the research on the design of removable composite tooling and its curing process.The main research work and conclusions of this paper are as follows:(1)Using DSC,TMA,DMA,thermal dilatometer and other test methods,the change curve of the physical parameters of the rocket tank tooling composite material during the curing process was measured,and the curing kinetic equation and the relationship between the physical parameters and the temperature or curing degree were calculated.It can provide material parameters for the optimization of composite tank tooling structure and the prediction of temperature field and curing deformation of subsequent monomer tooling.(2)The optimization design of composite tooling structure for large tank is studied and determined.Firstly,based on the simplified winding tension calculation formula,the external winding force on the forming tooling during the winding process of the tank is determined.At the same time,the stress on the forming tooling caused by the curing shrinkage process of the composite container is simulated by ABAQUS finite element simulation software,so as to provide a numerical simulation basis for the subsequent optimization design of the tooling structure that meets the stiffness requirements.Based on the geometric structure of the bottom cover of the integral composite tank,the tooling structure of the tank is designed to meet the requirements of disassembly.The bolt distribution is optimized by using the orthogonal test method,and the bolt layout scheme meeting the requirements of integral stiffness is obtained;Further,taking the lightest weight on the premise of meeting the stiffness of tank tooling as the optimization objective,Opti Struct optimization software is applied to optimize the ply scheme of tank tooling,The optimized tank tooling has a volume of 2.9×10~8mm~3 reduced to 1.89×10~8mm~3,weight loss 34.7%.(3)The curing temperature field and curing deformation prediction model of the composite material monomer tooling are established,and the molding process optimization is carried out based on the orthogonal experimental design method,and the reasonable molding process window is clarified as follows:the heating rate was 0.5°C/min,the molding temperature was 130°C,and the holding time was 120min.The simulation results show that with the increase of the layer thickness,the internal temperature difference of the composite single tooling gradually increases,and the maximum temperature difference is 5℃.The maximum deformation of the composite monomer panel tooling and the monomer melon tooling based on the ply scheme optimization results are 0.61mm and 1.35mm respectively.The engineering trial production of composite single wall panel tooling scale parts was further carried out and the profile accuracy was tested.The results showed that the deformation trend of composite monomer panel tooling scale parts obtained by the curing deformation prediction model was the same as that of the experimental test results,both ends were convex,and the maximum deformation was0.14mm and 0.15mm respectively.The simulation error was 6.7%.The accuracy of the curing process and its deformation prediction model was verified. |
