Braided Composite Cylindrical Shell Stability Analysis

Stability of the braid composite cylindrical shell is a complicated problem which needs to be urgently solved in aerospace industry now. In this paper, a theoretical analysis of this problem is presented in detail. Then, various stability problems of the braid composite cylindrical shell are analyzed and studied.First, 3-cell analytical model is used to estimate the mechanical properties and elastic constants and to analyze the effects of the 3-D braid parameters on the properties. Those results are compared with the theoretic results in FGM model and the experimental results.Then, the classical stability theory for brail composite cylindrical shells under axial compression is discussed. First, higher-order shear deformation theory and Reddy's simplified higher-order shear deformation theory of the flat shell is adopted to obtain the buckling governing equations. Then the geometric nonlinear theory and the geometric and material dual-nonlinear theory with shear effects are introduced (the buckling governing equations are get). The simplified geometric nonlinear theory and the small defection theory are discussed as emphases. In the small deflection theory, by buckling analysis, the classical buckling critical load of integrative braid composite cylindrical shells under axial compression is get.According to the experience and the results of FEM,a revised formula for calculating buckling critical load is presented. The simplified geometric nonlinear theory is used in post-buckling analysis. Galerkin method is employed to derive the eigenvalue equation of the shell containing initial geometrical imperfections. The buckling critical load is get.The program for calculating the buckling critical load is developed and the numerical example is given.. Some useful conclusions are get.Finally, the modern stability theory for braid composite cylindrical shells under axial compression is discussed. First, the dynamic stability of braid composite cylindrical shells with the influences of some main factors is introduced.The general governing equations for the nonlinear dynamic stability is obtained.by the Hamilton Principle.The creep buckling analysis of braid composite cylindrical shells under axial compression and the dynamic stability under nonconservation force are discussed as emphases.In creep buckling question,by means of theoretical analysis,the instaneous critical load and durable critical load of viscoelastic braid composite cylindrical shell under axial compression are obtained and the numerical example is given. In the buckling question under nonconservation force,a simply example( the dynamic stability question under the uniformly follower forces withsmall deformation % linear elastic, straight normal.) is considered.The variationalequation of braid composite cylindrical shells subjectd to uniformly follower forces is deduced based on the variation principle of quasinatural frequency of elastic nonconservative system self-excited vibration.The calculated formulas of the flutter load and quasinatural frequency of shells are obtained. The program for calculating the flutter load is developed.The numerical example is given and some useful conclusions are obtained.