| In this thesis, a hybrid finite element method is developed for the damage tolerance analysis of aging aircraft with multiple site damage (MSD). The method is versatile enough to take into account the effects of complex geometry variations, different stiffener and fastener configurations as well as the singular behaviors near multiple crack tips. By incorporating the analytical solutions into the variational formulation, the hybrid finite element method provides an accurate and efficient way for calculating stress intensity factors at crack tips, residual strengths of stiffened panel structures and rivet load distributions.; The hybrid finite element method is first applied to analyze the effect of using riveted skin patches to repair a structure containing a single crack. The behavior of multiple site damage is then studied by examining the interaction of cracks in stiffened and riveted panels using the hybrid finite element technique. Finally, a lap joint structure with multiple site damage is investigated. The analysis relates multiple cracking, MSD, crack linkup and residual strength for a stiffened panel structure and provides a better understanding of the behavior of structures before and after the linkup to adjacent cracks. |
