Experiments on Buckling and Postbuckling of Thin-walled Cfrp Structures Using Advanced Measurement Systems

The aircraft and space industry strives for significantly reduced development and operating costs. Reduction of structural weight at safe design is one possibility to reach this objective which is aimed by the following two running research projects: the EC project "COCOMAT" and the ESA study "Probabilistic Aspects of Buckling Knock Down Factors". These projects develop improved concepts and tools for a fast and reliable simulation of the buckling and the postbuckling behavior of thin-walled structures up to collapse, respectively, which allow the exploitation of considerable reserves in primary fibre composite structures in aerospace applications. For the validation of the concepts and tools, a sound database of experiments is needed which is also performed within these projects. This paper focuses on the experimental activities within these projects performed at the buckling test facility of the Institute of Composite Structures and Adaptive Systems (DLR). It presents an overview about the DLR buckling, postbuckling and collapse tests which are already finished and gives an outlook to the results which are expected until the end of the running projects. This paper explains the working of the buckling test facility, the advanced measurement systems, which are running in parallel to the tests, and gives exemplarily two test results. The structures considered are unstiffened cylinders (ESA study) as well as panels, which are understood as sections of cylinders, stiffened by stringers (COCOMAT project). The unstiffened cylinders are more related to space applications (e.g. Ariane busters or parts of the international space station ISS) and the stiffened panels focus more on aircraft structures (e.g. fuselage). The load case considered for all investigations presented in this paper is axial compression under static loading although the test facility is also ready to apply torsion and internal pressure, as well as dynamic axial impact.