Validity of the Reduced Bending Stiffness Method for Stacked Laminates

Abstract

Unsymmetrical laminates are unavoidable in practical applications of composite materials. Fuselages require a smooth surface on the outside and can be typically only stiffened by attaching reinforcements on the inside. Here, the stringer feet are often stacked on top of the skin surface. In those cases, the reduced bending stiffness (RBS) method has been applied to avoid more complex computational methods for the approximation of critical buckling loads. However, the validity of the RBS method has not been evaluated for stacked laminates but for single unsymmetrical laminates only. This topic is addressed in the present work by investigating a stacked laminate consisting of two by itself symmetrical cross-ply laminates under uniaxial compression. The panel is simply supported. The effects of prebuckling deformation are neglected. The results show perfect agreement for the special case investigated; thus, the utilisation of the reduced bending stiffness method can be recommended.