A Benchmark Example for Collapse Analysis of Stiffened Composite Panels

Eight different finite element implementations used by the partners within the COCOMAT consortium are employed to simulate the behavior of curved stiffened composite panels loaded in compression. The aim is to define a suitable benchmark example and compare the abilities of the different finite element codes to simulate the structural behavior in the postbuckling range. The benchmark example is defined and presented together with the results and conclusions. It is found that the results obtained with an imperfection-free model are sensitive to differences in the finite element implementation. On the other hand, when a realistic geometry imperfection is introduced it is found that the load-shortening curve varies in a fairly narrow band, depending on the program used. Comparing the curves from the analysis with the experimental data, it is concluded that no program or method is superior to the others, or that any program gives poor or inaccurate results compared to the others. The results obtained give some information about the expected accuracy in results when experienced users choose different software to analyze this benchmark problem. The partners also observe a lack of convergence in some cases and conclude that understanding how damping parameters and time steps should be chosen is very important.