A novel technique for modeling the mechanical behavior of partially delaminated composite plates is proposed and adopted for addressing the postbuckling problem of such plates under compressive in-plane loading. The new method considers a laminate as two sublaminates on the two sides of the plane of an existing delamination. The model assumes that the sublaminates are bonded to each other except in the delaminated region. The sublaminates are separately modeled using a first-order-shear deformation theory and to address both pre and postbuckling regimes, a strain definition capable of accommodating large rotations is used. The equilibrium equations are obtained using a modified Ritz method in conjunction with the stationary total potential energy principle. The modified Ritz method makes use of a combination of continuous and noncontiguous functions to accurately represent highly local deformations that can be expected in a delaminated region. The bonding between the sublaminates is simulated using a penalty method and by adding the energy terms corresponding to an elastic adhesion between the sublaminates to the expression of the total potential energy. Numerical examples are presented and compared with the results obtained using 3D finite element analyses.
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