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 damag e (MSD). The MSD usually occurs at rivet holes, or other stress concen tration locations within an aircraft structure. This study simulated r ivet holes with MSD, by using holes of constant diameter with small cr acks, evenly spaced across the midspan of specimens. The panels were p repared by either fatiguing MSD damage at rivet holes or simulating fa tigue 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 whic h do not model the stable crack extension were evaluated to predict th e residual strength (failure load) for each specimen geometry. These c riteria provided a wide range of residual strength predictions for wid e and narrow panels with MSD. A failure criterion which involved the p lastic zone (yielding) of the lead and MSD cracks gave the most accura te prediction of failure load for panels with MSD damage. The width of the specimens did not affect, in general, the trends in the predictio n of failure loads from the five failure criteria. (C) 1997 Published by Elsevier Science Ltd.