Residual strength of aircraft panels with multiple site damage

Multiple site damage (MSD) is a type of cracking that may be found in aging airplanes which can adversely affect the damage tolerance of an airframe structure. In this paper the behavior of MSD is studied by examining the interaction of cracks in stiffened and riveted panels. The hybrid finite element method, in conjunction with the complex variable theory of elasticity, is used to provide accurate and efficient solutions to these problems. Typical results include stress intensity factors at the crack tips, stress concentration factors in the stiffeners, and rivet loads for a stiffened structure with multiple cracks. Particular emphasis is placed on the derivation and interpretation of residual strength diagrams. This study produces a better understanding of the interaction between multiple cracks and provides insight for avoiding MSD in future designs.