Study On Automatic Placement Technology Of Sandwich Panel With Variable Stiffness For Satellite

With the application of composite structures in the aerospace field,the traditional components of linear lay-out molding are challenging to meet the higher stiffness requirements of aerospace structures due to their poor design flexibility and low bearing efficiency.Compared with the linear layer form,the curved layer can develop the mechanical advantage of the fiber direction better,and improve the equivalent stiffness of the spacecraft structure within a certain range of quality,so the space structure formed by curve laying has superior design potential.In this thesis,the continuous skin honeycomb panel of the spacecraft main load-bearing structure and the grid sandwich panel of solar wing main structure are taken as the research objects and in order to improve the first-order modal frequency of the structures,the variable stiffness design method is studied,which lays a theoretical foundation for the application of variable stiffness fiber placement technology in spacecraft structures.The stiffness of the sandwich panel skin is designed and the simulation model of the sandwich panel is established.According to the constitutive equation of composite laminate,the meaning of fiber angle change is defined,and the corresponding relationship between the fundamental modal frequency and fiber angle is deduced by using the modal formula.Based on the non-linear constant curvature arc curve,the reference path of laminated structure is defined,the continuous skin laminated plate and grid sandwich panel are planed by using the translation method,and the expression methods of two kinds of variable stiffness sandwich plates are defined by reference to the expression method of linear layers.Based on the idea of equivalent model and ABAQUS redevelopment method based on parametric programming,the equivalent finite element models of two kinds of sandwich plates are established.The modes of variable stiffness / constant stiffness are analyzed and compared between the continuous skin honeycomb plate with four edges fixed and the grid plate with eight points fixed in-plane.It is found that the fundamental frequency of the shape of the variable stiffness sandwich plate with the starting angle less than the ending angle curve is improved.By analyzing the grid sandwich panels of orthogonal plies and symmetric plies,it is found that orthogonal plies are more suitable for grid sandwich panels.In order to explore the influence of curve angle combination on the fundamental modal frequency of two kinds of sandwich plates,the starting angle and ending angle of curve are optimized based on response surface method.After optimization,the maximum lifting percentages of fundamental modal frequency of two components are 12.33% and 31.18% respectively.Through the modal analysis of different boundary conditions of solar wing base plates,it is found that the fundamental modal frequency of the grid sandwich panel is determined by the form of fixed point and the way of curve laying.In addition,based on Tsai Wu criterion,the strength of the continuous skin honeycomb panel is checked,and it is found that the fiber variable angle improves the strength and stiffness of the continuous skin honeycomb panel.The laboratory thermoplastic laying robot equipment is improved,and the thermoplastic and thermosetting laying equipment is obtained.By comparing the modal analysis results of the continuous skin honeycomb plate and the grid sandwich panel,the design process of the experiment pieces is determined,and the placement path planning and CAM programming of the variable stiffness sandwich panel skin are carried out according to the model simulation.Based on the experiments of laying speed,laying pressure,laying temperature and curve curvature radius,the reasons for the defects of variable angle fiber laying,such as folds in the inner side of fiber curvature,warpage in the outer side of fiber curvature and adhesive peeling off,are summarized and analyzed.The experimental results of equivalent skin placement of grid sandwich panels with variable stiffness show that,when the laying pressure is 0.5MPa,the laying temperature is about 70?,and the laying speed is about 15mm/s,the surface performance is the best,and the conclusion that the limit radius of curve laying under the robot equipment is about 700 mm is obtained.According to the optimal process parameters,the actual skin samples are manufactured.By comparing the model simulation,the correctness of the design model is verified to a certain extent,which provides a certain process and experimental basis for the future manufacturing of actual samples.