Analysis Of Sandwich Structures And Research Of Structural Design For Satellite

With the increasing of spacecraft functions and the development of processing technology,material and analysis methods, spacecraft structures are being more complex, lighter, more flexibilityand larger scale. The research works for some technological problems of design for satellite structureare as follows:Honeycomb sandwich structures are widely applied to the satellite structures. During the finiteelement analysis (FEA) for honeycomb sandwich structures, the equivalent elastic constants directlyinfluence the accuracy of results. Three equivalent methods, including Reissner theory, Hoff theoryand sandwich theory, are used. Static analysis and mode analysis for honeycomb sandwich plates areperformed. The calculation results of each equivalent theory are compared with the results of3-Dsolid element model in different load cases, including the displacement, the stress and the normalfrequency. Results show that the sandwich theory is better than the other two equivalent theories.A research method of stability problem of honeycomb sandwich structures based on the FEA ispresented. The buckling factors of honeycomb sandwich structures with fixed size core are obtainedwith different faceplate thicknesses using homogenization core models. The solutions obtained withthe FEA approach are compared with the results from the conventional analytical formulas. Theresults obtained by two kinds of methods are basically consistent. The finite element modelsconsidering the geometry characteristics of the core are used. And the effect of the core's geometrycharacteristics on the stability problem is discussed. A local instability phenomenon, called cell-wallbuckling, is introduced. A prediction analytical approach for the phenomenon is presented. And theresults are compared with that of the FEA to validate the proposed approach. The stability problem ofsatellite sandwich bearing cylinder under the multi-axis inertial loads is researched. The finite elementresults are obtained with different faceplate thicknesses and different ratios of vertical and horizontalinertial load. The related analysis equation for the multi-axis inertial loads is given. It can guide thebearing cylinder design.Design for structure connection stiffness and the equivalent method of the important connectionpart influence the design requirements satisfied or not, and the accuracy of results. The hydrazinetanks are apposed in the bearing cylinder. The stiffness and strength of hydrazine tank brackets arechanged through the strengthen frames. Compared with four different design schemes of thehydrazine tank bracket structure, the installation way is researched. The design principle of "the lowerstrong, the upper weak" for hydrazine tank system is proposed. To satisfy the design requirements, the hydrazine tank bracket structure is further improved.The connection modes of satellite structure are classified. The equivalent method of theimportant connection part is researched. Four equivalent methods, including MPC(Multi-PointConstraint) method, beam element method, bush element method and fastener element method,areused to simulate the bolt joints for normal mode analysis and linear static analysis. The advantagesand disadvantages of each equivalent method are listed.A multiobjective optimization method is presented for trusses of spacecraft antenna withappended structures. To set up an accurate finite element model for optimization design, the effect ofappended structure stiffness on the truss structure dynamic characters must be discussed. Thestructural topological configuration is decided iteratively using the surrogate model and theman-machine interactive method. For the surrogate model, optimal Latin hypercube sampling methodis used as the design of experiments strategy, and radial basis functions are selected as theapproximation method. The multiobjective evolutionary algorithm NSGA-II which produces a set ofPareto front points and Pareto solutions is employed as the optimization strategy to tradeoff theminimization of weight and the maximization of natural frequency. The optimum solution is visuallychosen with the level diagrams (considering the design preference and no considering the designpreference). This method not only can maintain good design efficiency, but also increase the globalsearch capability. And it is very useful for the multiobjective optimization design of spacecraftstructure.Finally, for defining the vibration environment which is needed for spacecraft structure designand experiment verified, the load responses of spacecraft and launch-vehicle interfaces need to begiven in the coupled analysis. According to the dynamic characters, the equivalent models instead ofthe finite element model are used. The equivalent models consist of some single-degree-of-freedommass-springs. Based on the concept of modal efficient mass, the calculation formulas of theparameters of equivalent models are derived. Taken a satellite as an example, the equivalent modelsand the finite element model are respectively used in the coupled analysis of spacecraft andlaunch-vehicle. Then the results of the above two models are compared. It is demonstrated that theequivalent models can be used to replace the complex finite element model.