Residual strength of unstiffened aluminum panels with multiple site damage

This study investigated the residual strength of unstiffened aluminum panels with widths of 381 mm and 229 mm containing multiple site damage (MSD). The MSD usually occurs at rivet holes, or other stress concentration locations within an aircraft structure. This study simulated rivet holes with MSD, by using holes of constant diameter with small cracks, evenly spaced across the midspan of specimens. The panels were prepared by either fatiguing MSD damage at rivet holes or simulating fatigue damage by saw cuts at each hole. Each specimen was subjected to a monotonically increasing tensile load until failure occurred across the midspan of the gauge section. Five different failure criteria which do not model the stable crack extension were evaluated to predict the residual strength (failure load) for each specimen geometry. These criteria provided a wide range of residual strength predictions for wide and narrow panels with MSD. A failure criterion which involved the plastic zone (yielding) of the lead and MSD cracks gave the most accurate prediction of failure load for panels with MSD damage. The width of the specimens did not affect, in general, the trends in the prediction of failure loads from the five failure criteria. (C) 1997 Published by Elsevier Science Ltd.