Buckling And Postbuckling Behavior Of Compositecylindrical Shell Structures In Naval Architectureand Ocean Engineering

Currently there is a wide range of naval structures being developed using fibre-reinforced polymer composites, due to considerable strength-to-weight ratio. There has been considerable attention in the structural instability of relatively thick shells. Many current potential applications involve the moderately thick shell type configuration. For example, large patrol boats, hovercraft, minecountermeasure vessels and corvettes that are built completely of composite material, to mention a few. Other new or potential uses for composites are in the superstructures, advanced mast systems, bulkheads, decks, propellers, propulsion shafts and rudders for large surface combatants such as frigates and destroyers. In submarines, the future applications of composites may include control surfaces and mast systems. Navies are also exploring the feasibility of using composites for internal equipment and fittings, such as machinery, heat exchangers, equipment foundations, values, pumps, pipes and ducts. A new class of composite material known as braided composites have been received considerable attention. Textile composites are manufactured by fabrication methods derived from the textile industry. Unlike laminated composites, in which cracking and debonding may occur at high temperature due to the material property mismatch at the interface of two discrete materials, the textile composites are able to eliminate the delamination due to the inter-lacing of the tows in the through-thickness direction. Braided composites are now developed for general use as structural components in naval ship and submarine, offshore structures due to their light weight and easy handling secure their place in the industry.As a primary load carrying structure, the buckling and postbuckling behavior of laminated or braided cylindrical shell subjected to mechanical load is a vital safety consideration, and improvement of its prediction accuracy behavior is thus essential for reliable design.This paper consists of two parts: A boundary layer theory of shell buckling is extended to the case of general shear deformable anisotropic laminated cylindrical shell of finite length subjected to axial compression, external pressure, torsion, respectively. The material properties of each layer of the shell are assumed to be linearly elastic, anisotropic and fiber-reinforced. The governing equations are based on Reddy's higher order shear deformation shell theory with von Kármán-Donnell-type of kinematic nonlinearity and including the extension/twist, extension/flexural and flexural/twist couplings. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling response of perfect and imperfect, moderately thick, anisotropic laminated cylindrical shells with different values of shell parameters and stacking sequence.Then, established a micro-macro-mechanical model, a 3D braided composite may be as a cell system and the geometry of each cell is deeply dependent on its position in the cross-section of the cylindrical shell. The material properties of epoxy are expressed as a linear function of temperature. A postbuckling analysis is presented for a 3D braided composite cylindrical shell of finite length subjected to axial compression, external pressure, torsion, combined loading of external pressure and axial compression in thermal environments, respectively. The governing equations are based on Reddy's higher order shear deformation shell theory with a von Kármán-Donnell-type of kinematic nonlinearity and including thermal effects. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling behavior of perfect and imperfect, braided composite cylindrical shells with different values of geometric parameter and of fiber volume fraction in different cases of thermal environmental conditions. The results show that the shell has lower buckling loads and postbuckling paths when the temperature-dependent properties are taken into account. The results reveal that the temperature changes, the fiber volume fraction, and the shell geometric parameter have a significant effect on the buckling load and postbuckling behavior of braided composite cylindrical shells.Finally, based on the present perturbation technique combined with perturbation method, the computer program packages are made by using FORTRAN computer language, this paper provides comprehensive first-ever-known results which are helpful in better understanding the postbuckling behavior of the 3D braided and fiber-reinforced shells.