Damage tolerance implications of corrosion pillowing on fuselage lap joints

A previous study showed that pillowing, caused by the presence of corrosion products, can significantly increase the stress in fuselage lap joints, which raises concerns about the effect on aircraft safety. In the present study finite element techniques were used to determine the effect that pillowing has on the stress-intensity factor for cracks located at rivet holes in lap joints. The stress caused by the internal pressure and riveting process was taken into account while the fuselage curvature was ignored. The results indicate that corrosion pillowing increases the stress-intensity factor for the crack edge along the skin-faying surface with a concurrent decrease on the opposite side. This difference suggests that a crack will grow more rapidly along the faying surface than in the through-the-thickness direction, thus forming a semielliptical crack front with a very high aspect ratio. This type of crack is more difficult to detect.