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TIP ANGLE EFFECT ON BUCKLING AND DEFORMATION OF LAMINATED COMPOSITE ANGLEGRID PLATES
Abstract
Grid structures are widely used in many engineering fields. Typically, a single grid plate is employed as an orthotropic layer to strengthen plates and shells or as an independent structural element. In contrast with conventional grids, laminated grid plates are constituted from several grid layers with various orientations. Therefore, the grid layers with different orientations can be utilized to enhance stiffness and coupling effects of a weight sensitive structure. In the present study, to investigate the efficiency of the laminated anglegrids, the deformation and buckling responses of a conventional and several laminated anglegrid plates are evaluated. The first-order shear deformation plate theory along with Ritz method is employed to achieve the buckling load and maximum deflection of the plates. The effectiveness of modifying the tip angle of anglegrid layers on mechanical behaviors of the conventional and laminated grids is also studied. The analytical results of buckling load are compared and validated by finite element method. The results indicate that thoughtful selection of stacking sequences of the laminated grids and appropriate tip angle considerably improves the behavior of the laminated grids in comparison with conventional grids.
This study presents the multi‐objective optimization of weight and cost concerning the vibration behavior of a sandwich structure. In this regard, the maximization of frequency against the minimization of the structure's weight or cost is considered the objective functions in the optimization algorithm. For this purpose, a sandwich structure with two composite skins and an orthotropic grid core is designed. The design variables including the core geometrical variables, and the type of the applied composite materials for each group of stiffeners of the core. The first‐order shear deformation theory and the Ritz method have been used to obtain the natural frequencies of the plates. Eventually, optimization has been performed using the genetic algorithm.
For a long time, a single grid layer, such as isogrid, have been utilized to strengthen a shell or plate or as an independent structural member for various applications. Laminated grid structures consist of several grid layers that can have different in-plane orientations or can be made from different materials. Therefore, using laminated configuration instead of conventional grids yields to an extensive variety of configurations with different coupling effects and cost. In the current paper, to evaluate the appropriateness of laminated isogrids, the vibration and stability behaviors of a conventional isogrid are compared with corresponding laminated isogrid plate. The first-order shear deformation plate theory as well as the Ritz theorem is utilized to achieve the critical buckling loads and free vibration frequencies of the plates. The influence of increasing the number of isogrid plies and changing pattern geometries on mechanical behaviors of the laminated isogrid plate is also investigated. The results imply that utilization of the laminated isogrids remarkably enhances the buckling load and free vibration frequency values of the plates.
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