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This is the first of two companion papers that examine the elastic buckling and post-buckling behavior of thin unsymmetric cross-ply laminates. When cured in a flat mold these panels possess two cylindrical equilibrium configurations. From stability perspective this problem is identified as a bifurcation buckling problem. As explained in literature thermal mismatch between plies and existing geometric imperfections triggered this behavior. Therefore, and according to Koiter it is necessary to measure and account for these geometric imperfections to accurately predict the cured shapes. Since imperfection measurement is challenging and cannot be possible in the stage of design. This work applies a unified finite element methodology based on Koiter's theory to predict the cured shapes. This methodology is consistently applied in commonly used finite element computer codes, ABAQUS, ANSYS and LS-DYNA, and their predictions are compared.

This is the second of two companion papers that examine the elastic buckling and post buckling behavior of unsymmetric cross-ply laminates. The existence of geometric imperfection and thermal mismatch between plies result in these panels to retain two equilibrium configurations despite being cured in a flat mold. These equilibrium configurations conform to cylindrical shapes of orthogonal and opposite curvatures. Under externally applied load a panel undergoes snap-through behavior from one equilibrium shape to the other. The unified finite element methodology based on Koiter's theory and presented in the first companion paper is extended to predict the required force responsible for snap-through behavior. Accordingly, ABAQUS, ANSYS and LS-DYNA finite element codes are used to predict the critical snap-through forces and their predictions are compared.