Buckling and initial post‐buckling of thin‐walled composite beams

The buckling and initial post-buckling behaviour of thin-walled composite beams is analysed in this paper. The governing equations are based on the main assumption that the displacement components in the plane perpendicular to the axial direction are of the type of rigid-body motion. The shear strain in the middle surface of the beam wall is taken into account as the shear stiffness of the composite material is low. The governing equations are solved by a perturbation method. For the case of simply supported ends, double Fourier series are used to solve the equations for perturbation terms of different orders. Then, some formulas derived by Budiansky in the notation of functional analysis are cited to calculate the initial post-buckling parameters. The experimental results of five specimens of circular open cross-section are compared with the numerical results.