Corrosion pillowing in aircraft fuselage lap joints

This paper presents the results of studies that have been carried out at the National Research Council on the effect that corrosion pillowing has on the structural integrity of fuselage lap joints. Modeling of corrosion pillowing using finite element techniques showed that the stress near the rivet holes increased to the yield strength of the material (Al 2024-T3) when the corrosion present was above 6% thickness loss. In addition, the analysis showed that pillowing resulted in a stress gradient through the skin thickness, which suggested that semi-elliptical cracks with a high aspect ratio could form. During teardowns of service-exposed lap joints, these types of cracks were found to occur at numerous holes and a closer examination of some of the fracture surfaces revealed the presence of fatigue striations. Therefore a new source of multi-site damage other than fatigue was identified.Peer reviewed: YesNRC publication: Ye