Mechanical Analysis Method And Mechanical Property Of Spacecraft Structure Containing Cavity

With the increasing development of the aerospace industry and the increasing demand for aerospace engineering,the functions and structures of spacecraft systems have become increasingly complex.To reduce the total mass of the spacecraft structure,improve the overall efficiency of the spacecraft system,and reduce the cost of flight missions,the design method of multifunctional structure,which integrates functional components such as the battery,thermal control,electromagnetic,and cable subsystems into the honeycomb sandwich structure for carrying loading,can be adopted.Since it is necessary to manufacture a cavity in the core of the multifunctional structure to embed various electronic devices,the stiffness of the sandwich structure is decreased.Meanwhile,the honeycomb core containing its cavity is prone to appear geometric and material nonlinearity under a load of tensile,bending,shear,explosion,and shock during the flight of the spacecraft.There is no complete theoretical system for the analysis of the mechanical properties of the sandwich structure containing a cavity,which limits the analysis and design of multifunctional structures.Therefore,it is necessary to research the mechanical analysis method and mechanical property of the spacecraft structure containing a cavity.The high-order sandwich beam model is proposed,which considers the shear deformation in the skins and the core,as well as the longitudinal rigidity in the skins,the longitudinal and transverse rigidity in the core.The displacement function of the sandwich beam is determined by the continuity conditions of displacement and shear stress between the skin and the core,and the boundary condition of shear stress on the top and bottom surfaces of the sandwich beam.The Chebyshev quadrature element method is adopted to derive the discrete governing equation of the perfect sandwich beam.The mechanical properties of the perfect sandwich beam are analyzed.The results demonstrate that the Chebyshev quadrature element method based on the high-order sandwich beam model can improve the accuracy of the statics analysis of the sandwich beam.The top and bottom skins of the sandwich beam mainly undergo normal stress,while the shear stress primarily exists in the core.In the slender sandwich beam,the core has no obvious transverse deformation,while in the short beam,the transverse deformation of the core is significant.The Chebyshev quadrature element method based on the high-order sandwich beam model is applied to the sandwich beam containing cavity.The discrete governing equation is obtained,and the mechanical analysis method of the sandwich beam containing a cavity is established.The analysis of the overall mechanical performance of the sandwich beam containing cavity with different boundary conditions,geometric parameters,and material properties subjected to various loadings is carried out to further verify the correctness and the applicability of the Chebyshev quadrature element method based on the high-order sandwich beam model.The results demonstrate that the existence of the cavity reduces the stiffness of the sandwich beam,which increases the displacement and decreases the natural frequency of the sandwich beam.When the size of the cavity is constant,the closer the cavity is to the two ends of the sandwich beam,the more significant the decrease in stiffness.For the multifunctional structure employing the sandwich beam containing cavity,the cavity should be kept in the middle of the sandwich beam to minimize the decrease in stiffness to meet the stiffness requirements of the structure.Based on Reissner beam theory,the analysis method of in-plane elastic properties of the honeycomb core considering the geometric nonlinearity is established,which considers the axial deformation,bending deformation,shear deformation of the honeycomb wall,and the deformation of the node between the honeycomb walls simultaneously.It is verified by comparing with the existing methods and experimental results that the proposed method is suitable for predicting the in-plane elastic properties of thin/thick-walled honeycombs with different geometric parameters under small and large deformation.The results demonstrate that the in-plane equivalent elastic modulus of the honeycombs increases with the increase of strain and does not remain constant under large deformation.The in-plane elastoplastic analysis method of thin-walled honeycomb core considering geometric nonlinearity is established based on nonlinear Euler beam theory and elastoplastic theory.The solution algorithm is researched to obtain the stress-strain relationship and Poisson’s ratio of the thin-walled honeycombs.The results demonstrate that with the increase of strain,the geometric nonlinearity causes the overall stiffness of honeycombs to increase.Then it decreases gradually due to the plastic deformation.