An analytical solution for stability analysis of unrestrained tapered thin-walled FML profile

The main purpose of this study is to compare the lateral buckling behavior of laterally unrestrained Fiber-Metal Laminate (FML) and composite thin-walled beam with varying cross-section under transverse loading. It is supposed that all section walls (the web and both flanges) are composed of two metal layers at the outer sides of the fiber-reinforced polymer laminates. The classical lamination theory and Vlasov’s model for thin-walled cross-section have been adopted to derive the coupled governing differential equations for the lateral deflection and twist angle. Employing an auxiliary function, the two governing equations are reduced to a single fourth-order differential equation in terms of twist angle. To estimate the lateral buckling load, Galerkin’s method is then applied to the resulting torsion equilibrium equation. Eventually, the lateral stability resistance of FML and laminated composite web-tapered I-beam under uniformly distributed load has been compared to each other considering the effects of some significant parameters such as laminate stacking sequence, metal volume fraction, transverse load position, and web tapering ratio. The results show that increasing the metal volume fraction leads to enhance the linear buckling strength of glass-reinforced aluminum laminate I-beam under transverse loading. For the optimum lamination, it is seen that the lateral buckling load increases approximately 25% by raising the metal volume percentage from 0% to 20%.