Postbuckling Behavior of Anisotropic Laminated Plates Under Pure Shear and Shear Combined with Compressive Loading

In the current work a postbuckling analysis for anisotropic plates under combined compressive and shear loading is presented. A pair of governing equations in the von Karman sense are solved in conjunction with simply supported boundaries. A series of computations is carried out for plates having different lay-ups, dif- ferent materials, and different aspect ratios. The emphasis of these investigations is put on the effect of shear direction on the postbuckling behavior of the plates. The results of the computations reveal that the post- buckling behavior of anisotropic plates is completely different when the applied shear directions are alternated for the plate under either shear loading or combined loading. HE postbucking behavior of composite plates under shear loading has been studied experimentally by a few investigators.1"3 It was reported that the ultimate loads of plates made of boron/epoxy, carbon/epoxy, or graphite /epoxy could be considerably higher than the initial buckling loads. However, so far, few postbuckling analyses are available for anisotropic plates under shear or combined loading. In previous work4"6 it was pointed out that the shear direction has a significant influence on the initial buckling behavior of anisotropic plates under pure shear or under the combination of compressive and shear loading. Thus it is natural to raise the question: How does the shear direction affect the postbuckling behavior of the anisotropic plates? The present work answers the question. In the current work a postbuckling analysis for plates of composite material with midplane symmetric lay-up is presented. A pair of governing equations in the von Karman sense, in which the effects of boundary moments are included, are solved in conjunction with simply-supported boundaries. As examples, a series of computations are carried out for plates having different fiber directions, different stacking sequences of layers, different materials, and different aspect ratios. The results reveal that the direction of applied shear with respect to the fibers of the layers is very important for postbuckling behavior of anisotropic plates under shear loading or the combination of compression and shear. This means that the postbuckling behavior of anisotropic plates will depend greatly upon the directions of the shear acting on the plates.