Production and characterization of complex folded cellular structures made of sheet metal
Final Report Abstract
This research project focused on the development of a folding process for the production of complex cellular structures from flat metal sheets with thicknesses greater than 0.5 mm, as well as methods for characterizing these folded structures intended for use as sandwich core materials. Previous research work on the manufacturing of folded sandwich cores exclusively considered feedstock materials with thinner material thicknesses of less than 0.2 mm. With these low sheet thicknesses, material thickening during the folding process in the area of bending corners can be neglected. In contrast, folded structures from thicker metal sheets promise disproportionately increasing buckling strength compared to the material thickness and thus great potential for use as lightweight load-bearing structures or crash elements. Given this background, the project partners developed a process route for manufacturing complex metallic structures with sheet thicknesses greater than 0.5 mm. For this purpose, experimental and numerical investigations first identified roll pinching as the most suitable method for forming pre-structures for the actual folding process. Furthermore, different folding cell geometries were analysed with regard to their potential performance and manufacturability. In this context, a new numerical model with reduced model complexity was developed for rapid evaluation of different geometries and thus for providing a tool for optimization and geometry finding in terms of the thick-walled sheet folded cores. As a result of the analysis, folding cells with three main axis pairs (MAP) proved to be most advantageous, since with this cell geometry folding edges only perform translational and no rotational movements during the folding process. The folding tool, which was newly developed for use in forming presses, exploits this property to ensure force transmission into the folding cell during the complete press stroke. The structural properties of the folded metal sheet sandwich cores were first determined by numerical methods and finally confirmed by experimental investigations on the test components produced. The compression and shear tests carried out here with core structures produced from different materials showed excellent weight-specific mechanical properties, which were significantly higher above strength and stiffness values of conventional cellular core materials with sheet thicknesses below 0.2 mm.
Publications
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Virtual process chain for optimization of sandwich foldcores under flatwise compression. Thin-Walled Structures, 157, 107121.
Muhs, Fabian; Thissen, Simon & Middendorf, Peter
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Evaluation of Forming Methods for the Pre-shaping of Miura-Structures Made of Sheet Metal Materials. Lecture Notes in Production Engineering, 75-84. Springer International Publishing.
Görz, M.; Liewald, M. & Riedmüller, K. R.
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Numerical analysis of imperfections in Miura Ori sandwich cores using isogeometric analysis. Proceedings of the IASS 2020/21. Vol. 2020: Deployable, foldable and tensegrity structures. pp. 1164-1174. Surrey, UK. ISSN 2518-6582.
Thissen, S. & Middendorf, P.
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Numerical characterization and optimization of the anisotropy of foldcores under shear loading. Proceedings of the IASS 2020/21. Vol. 2020: Deployable, foldable and tensegrity structures. pp. 1145-1157. Surrey, UK. ISSN 2518-6582.
Muhs, F. & Middendorf, P.
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Numerical analysis of sheet metal folded sandwich core structures. Proceedings of IASS Annual Symposia. Vol 2022: Next Generation Parametric Design. pp. 1- 7(7). ISSN 2518-6582.
Thissen, S.; Görz, M. & Middendorf, P.
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Herstellung von zellulären Faltstrukturen aus Blech. Zeitschrift für wirtschaftlichen Fabrikbetrieb, 118(9), 554-560.
Görz, Marcel; Thissen, Simon; Clauß, Philipp; Rouven, Riedmüller Kim; Liewald, Mathias & Middendorf, Peter
