Analytical Study of Bifurcation and Nonlinear Behavior of Sandwich Columns

Buckling behavior of axially compressed sandwich columns exhibits a variety of interesting phenomena. The column can buckle in a long wave "overall mode" or a short-wave "wrinkling mode," the latter involving severe bending of the facings and transverse deformation of the core. The full-range nonlinear behavior of these structures is investigated in the elastic range taking typical examples. Columns can be, though not always, imperfection sensitive when wrinkling is the principal mode of buckling. The columns buckling in the overall mode collapse by the formation of localized wrinkles in the postbuckling range. An interesting new finding of this study is that, for certain combinations of core compliance and facing thickness, there can be a bifurcation from the prebuckling path at a load smaller than that predicted by the linear stability analysis. In this scenario, if wrinkling is the dominant mode of buckling, the column turns out to be imperfection sensitive.