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In this paper the correlation of deformation energy and critical buckling loads is examined. An advanced analysis technique is derived for the investigation of z-section frames typically applied in composite aircraft fuselage. This technique is verified through closed form solutions of z-section columns under quasi-static loading conditions. The method is applied to study the effects of flange width and laminate thickness on the critical failure modes of composite frames. Therein, the focus is on composite structural elements favourable for deformation kinematics in aerospace applications subjected to crash loads. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper, a three-dimensional elasticity approach is employed to investigate buckling of heterogeneous functionally graded plates under biaxial compression, shear, tension-compression, and shear-compression load conditions. In this regard, a formulation that employs a full compatible three-dimensional Hermitian element with 168 degrees of freedom and guarantees continuity of the strain and stress components is used. It is known that all of the available famous commercial finite element softwares and the proposed series solutions satisfy continuity conditions of the displacement rather than the stress components. Buckling occurrence is detected based on checking both the instability onset and equilibrium criteria. Results are extracted based on a Galerkin-type orthogonality. Therefore, they are more accurate than those obtained based on the traditional Ritz method. The presented three-dimensional finite element analysis and the extracted results are quite new. A vast variety of results including results of biaxial compression, compression-tension, shear, and shear-compression load cases is considered and discussed in detail. [Copyright &y& Elsevier]

Abstract: The paper deals with the theoretical prediction of buckling loads for symmetric angle-ply and cross-ply laminated flat composite columns, consisting of two portions of different widths connected by fillets. The buckling loads of the column under axial compression were obtained for the following end conditions: simply supported, simply-clamped, clamped-clamped, and clamped free. Based on the first order shear deformation theory (FSDT), finite elements method (FEM) with FORTRAN computer language was exploited to obtain the critical buckling loads. The effects of orientation angles, fillet radius, column thickness and wideness, and modulus ratios on the buckling load were investigated. The results were presented in both graphical and tabular forms. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with multiobjective optimization of symmetrically angle-ply square laminated plates subjected to biaxial compressive and uniform thermal loads. The design objective is the maximization of the buckling load for weighted sum of the biaxial compressive and thermal loads. The design variable is the fiber orientations in the layers. The performance index is formulated as the weighted sum of individual objectives in order to obtain optimal solutions of the design problem. The first-order shear deformation theory (FSDT) is used in the mathematical formulation of buckling analysis of laminated plates. The modified feasible direction (MFD) method is used for optimization routine. For this purpose, a program based on FORTRAN is used. Finally, the effect of different weighting factors, number of layers, aspect ratios, load ratios and boundary conditions on the optimal design is investigated. [Copyright &y& Elsevier]