The Significance of Laminar Corrosion Defects in Aircraft

Laminar corrosion defects, such as intergranular penetrations and stress corrosion cracks, are common in ageing aircraft. These defects are most commonly found in extruded and rolled sections made from high strength aluminium alloys; typical examples include wing and tailplane spar caps in widespread use in ageing aircraft. They present a significant problem in that the assessment of their significance is difficult, not only because their orientation (most commonly parallel to the direction of applied stress) makes analysis difficult using conventional stress analysis techniques, but because of the inherent variability of the laminar cracking process. The paper summarises progress in AMRL research which is investigating analytical and experimental approaches to laminar defect/fatigue interactions.