Buckling and Postbucking Behavior of Laminated Composite Stringer Stiffened Curved Panels under Axial Compression-Experiments and Design Guidelines

It is well known [1] that non-closely stiffened panels can have considerable postbuckling reserve strength, enabling them to carry loads significantly in excess of their initial buckling load. If appropriately designed, their load carrying capacity will even appreciably exceed that corresponding to an equivalent weight unstiffened shell (i.e. a shell of identical radius and thicker skin and which is also more sensitive to geometrical imperfections). In these shells, initial buckling of their panels takes place in a local mode, i.e. skin buckling between stiffeners, and not in an overall mode, i.e., an Euler or wide column mode. The design of aerospace structures places great emphasis on exploiting the behavior and on mass minimization of such panels to reduce lifecycle costs. An optimum (minimum mass) design approach based on initial buckling, stress or strain, and stiffness constraints, typically yields an idealized structural configuration characterized by almost equal critical loads for local and overall buckling. This, of course, results in little postbuckling strength capacity and susceptibility to premature failure. However, an alternative optimum design approach can be imposed to achieve lower mass designs for a given loading by requiring the initial local buckling to occur considerably below the design load an