Motivated by a need for understanding the damage tolerance of unitized structures fabricated using the modern additive manufacturing process, fracture analysis of curvilinearly stiffened panels, unitized structures, with different crack lengths were performed by using a global-local finite element method under three different load cases: a) shear, b) normal, and c) combined load cases. It was observed that, in most of the cases, 85% data storage space and the same amount in CPU time requirement could be saved using the global-local finite element method compared to the standard global finite element analysis. It was also observed that the fracture mode in panels with different crack lengths was essentially Mode-Ⅰ under the normal load case; Mode-Ⅱ under the shear load case; and again Mode-Ⅰ under the combined load case. Under the maximum combined loading condition, the largest effective stress intensity factor of the panel with a crack of recommended size was very smaller than the critical stress intensity factor. Therefore, considering the critical stress intensity factor, the stiffened panel was an optimum design satisfying damage tolerance constraints.
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