Development of design charts for stress intensity factors at tips of multi-site cracks in unstiffened curved panels

•The multi-site damage curved panel stress intensity factor calculated by Modified Virtual Crack Closure Integral method.•The buildup of design charts for stress intensity factors at tips of multi-site cracks in curved panel without stiffener.•Thus the curves can be used for design as well as for the purpose of evaluating the multi-site damage configurations.

Multi-site damage need to be addressed and evaluated in order to assess the integrity of aging aircraft structures. One of the problems recognized in the recent times is the effect of interaction between two or more cracks in the close neighborhood in such structures. The present paper deals with such a problem and presents numerical estimates of stress intensity factors at a crack tip in an un-stiffened curved panel with a secondary crack in the vicinity of a primary crack. The results are presented in the form of design charts. These results should be useful in evaluation in the damage tolerance evaluation of aircraft structures with multi-site damage.