Improvement Of The Post-buckling Strength Of The Composite Wall Structure And Its Arc-length Method

On a background of strength and stability design of composite airfoil used in ×× remodel aeroplane, this paper made an exhaustive study on the buckling/post-buckling analysis of composite thin-walled structures adopting non-linear FEM based on the large-deformation plate/shell theory , while also made an effective improvement on the widely used arc-length method in the post-buckling analysis. Main subjects considered are as follows:1. A finite element formula for a quadrilateral plate/shell element with drilling degree of freedom is proposed which considers the membrana-strain item produced by in-plane displacement in order to the FEA of box-like structures.2. Buckling/post-buckling behavior of various cross section box beams and composite box-like structures is researched. From the numerical results, the effects of the configurations, ply-angle, ply numbers on the buckling/post-buckling behavior of box-like structures are discussed.3. Based on the conventional arc-length method, this paper describes a high-efficient arc-length method for introducing the change of the stiffness parameter and extrn-interpolation using the information of the known convergence points to the arc-length increment solution. This method has well adaptability and higher efficiency in plates / shells post-buckling analysis of achieving not only the whole load-deflection path but also the convergence value to the required load level.The method and numerical conclusions provided in the paper are valuable for engineers dealing with design of composite structures. The improved arc-length in this paper is applicable for geometrical non-linear analysis of general structures.