| Delaminations are very common in composite laminates. Under compressive loading, the thin delaminated layer and/or the base layer can buckle and/or deflect, causing high interlaminar stresses at the disbond boundary. An approximate method is developed for buckling loads and natural frequencies analysis for a slit beam and the buckling load analysis for the composite plate having an elliptic delamination. A Modified Gram-Schmidt method is presented to use the algebraic orthogonal polynomials in eigenvalue analysis. An exact method for the free vibration and buckling analysis of a slit beam is also given.;The approximate method developed in this work provides solutions similar to the solutions from finite element codes, but computations are reduced considerably. In this way, all possible instability modes which are predominantly either local, global, or coupled and local (mixed) buckling in terms of global stresses are considered. The buckling load analysis is extended for an anisotropic base laminate with an anisotropic delaminated sublaminate. The influence of the geometry such as that of the location of the delamination across the thickness, its inclination, position of the delamination, boundary conditions, and material properties are studied. The computations are done by supercomputer.;In this study, kinematically admissible displacement functions for the sublaminate and the base laminate are determined so that displacement, slope, shear force, and bending moment are compatible at the global boundary and at the boundary of delamination. Such selected functions provide information about all buckling modes in terms of global stresses in a very simple, inexpensive, and accurate way. It is to be noted that an algebraic polynomial is reduced to another polynomial with factors which satisfy the boundary conditions.;For the convergence study of a delaminated composite plate, different aspect ratios of the plate, different configurations of the plate, different sizes of the delamination, and different number of terms for displacement functions are considered.;As expected, the buckling loads for delaminated composite plates are found to be lower for smaller delaminations. The buckling loads resulting from satisfying the continuity conditions only at the boundary of the delamination are lower than the buckling loads satisfying both the continuity conditions and the equilibrium conditions at the boundary of the delamination. In this work and for presentation of results, only continuity conditions are applied to the displacement functions. Thus, additional constraints imposed by satisfying equilibrium conditions are avoided. |
