Convex/probabilistic models of uncertainties in geometric imperfections ofstiffened composite panels

Thin-walled stiffened composite panels, which are among the most utilized s tructural elements in engineering, possess the unfortunate property of bein g highly sensitive to geometric imperfections, Existing analysis codes can predict the buckling load of a structure with specified initial imperfectio ns. However, it is impossible to determine the amplitude and shape of imper fections of nonexistent composite panels that are only being designed. This is due to a variety of uncertainties that are involved in fabrication of p anels. Because of the very nature of the manufacturing processes, it is har d to imagine that a given process could ever produce two identical panels. Currently, however, rather than analyzing the manufacturing processes that lead to imperfections, panels are typically designed using probabilistic mo dels to account for the uncertainties in imperfections. An efficient approa ch is presented that employs a convex model of the uncertainties in the imp erfections. This approach can replace the computationally expensive probabi listic approach typically used in the study of imperfection sensitive struc tures. Several example problems are solved to show the accuracy of the pred ictions of the convex model. A Monte Carlo simulation has also been perform ed to validate the results obtained by the convex model and show the effort and cost reductions obtained by the use of such models.