Buckling, postbuckling, and failure of stiffened panels under shear and compression

A theoretical/analytical capability for prediction of buckling, postbuckling, and failure of flat and shallow-curved, edge-stiffened laminated composite plates under combined axial compression and shear is discussed. The initial buckling predictions are based on linear elasticity; however, the postbuckling calculations include the material nonlinearity present in the composite. Specifically, three in-plane Ramberg-Osgood stress-strain relations are used to describe the laminae and the matrix material between laminae is modeled with one Ramberg-Osgood relationship for transverse shear. Accurate representations of stress and strain distributions permit comparison to material allowables; thus, failure predictions can be made.