Buckling of composite laminates with multiple delaminations: Part I Theoretical and numerical analysis

Abstract Buckling of composite laminates containing multiple delaminations are analyzed theoretically based on the proposed equivalent model. From the exact analysis in which the nonlinear contact effect between the two portions above and beneath the delamination is included, it is found that (1) the two portions above and below the delamination undergoes exactly identical global deflection; (2) the composite laminate is subjected to Mode II delamination propagation due to in-plane slipping. According to such observations, an equivalent model which is perfect, delamination free is proposed to replace the delaminated portion of the laminate. The substitute model has the same geometric size and is stacked in the same sequence as that of the delaminated portion. The exact solution of the global deflection mode also suggests that the stiffness of the substitute model is taken as the sum of the stiffness of the two portions above and beneath the delamination. Buckling of composite laminates simply supported at the four sides with a single delamination is examined for different delamination length and depth using equivalent model, exact model and the finite element model. A good agreement between them demonstrates the efficiency and accuracy of the presented equivalent model. Using the established equivalent model, buckling of composite laminates with multiple delaminations along thickness and horizontal directions are investigated. Parametric studies are executed analytically and numerically to inspect the influence of delamination conditions, such as the number of delamination as well as the depth, the position and the length of each delamination, on the buckling performance of the composite laminates.