Structural Design Of Cryogenic Composite Tank For Space Vehicle

Considering the trends in the development of the cryogenic composite tanks for space vehicle and the practical problems in engineering applications,the structural design method of the cryogenic composite tanks are studied to investigate the failure law of the cryogenic composite tank under the thermo-mechanical coupling loads via the theoretical analysis and the finite element simulation.Meanwhile,the structural analysis method,the stability analysis method and the optimal design method for the cryogenic composite tank under low temperatures are developed.The main research contents are as follows:Based on the micromechanics finite element method,a multi-scale hierarchical analysis method for the cryogenic composite tank under low temperature is established.This method is developed by designing the mechanical performance test matrix for a single layer composite,selecting the appropriate representative vo xel,deriving the corresponding boundary conditions and computing the mechanical properties of the composites at different temperatures.The meso-scopic stress field of the macro-structure under the known response is obtained b y superposing the stress field of the six elements for the representative bod y on the meso-scale,which enables one to predict the strength parameters of the composite.A multi-scale hierarchical progressive damage analysis method for the unlined cryogenic composite tank under low temperature is developed.Since the macroscopic progressive damage analysis method is unable to consider the failure problem of the substrate,a multi-scale hierarchical progressive damage analysis method is proposed based on the first order shear lamination theory and the multi-scale hierarchical analysis method.Then,the influences of the adjacent ply angle,the different failure criteria,and the different material parameters on the composite under low temperature are analyzed based on the meso maximum stress criterion and the ultimate failure criterion of substrate perforation.Based on multi-scale hierarchical analysis method,a structural optimization design method for the cryogenic composite tanks under low temperature is proposed and the traditional mesh theory is improved.The mechanical properties for the cryogenic composite tank subjected to the thermo-mechanical coupling loads are studied via the multi-scale hierarchical analysis method.On this basis,the objective function and the general process of the structural optimization design method are designed for the cryogenic composite tanks by using the multi-scale hierarchical analysis method.Meanwhile,the stability of the cryogenic composite tanks under low temperature is analyzed by considering geometric nonlinearity and material nonlinearity.Finally,a finite element model and an analysis method for the composite mesh structure are proposed.A bearing capacity test of the composite grid structure for partial section of tank is carried out.Based on the stiffness equivalent analysis model of the composite mesh structure,both finite element analysis model and analysis method are studied.Furthermore,the bearing capacity test of composite grid structure for partial section of tank is carried out,whose results are compared with those of the finite element analysis,to implying the feasibility of the composite mesh structure analysis method.The work of this thesis can provide theoretical basis and technical support for the composite tank design of the new space launch vehicle,and also provide ideas for the overcoming design challenges of the cryogenic composite tank.The results have significance value in both theoretical and application.