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Cost-optimal design and automated production of sandwich structures for wind turbine rotor blades

: Wang, P.; Braun, R.; Dörsch, C.; Rosemann, H.; Sayer, F.; Bagemiel, O.; Prissok, F.; Stoll, R.; Brandes, J.; Fröse, E.

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20th International Conference on Composite Materials, ICCM 2015. Proceedings. Online resource : 19-24 July 2015, Copenhagen, Denmark
Copenhagen, 2015
Paper 5203-3, 12 pp.
International Conference on Composite Materials (ICCM) <20, 2015, Copenhagen>
Conference Paper, Electronic Publication
Fraunhofer IWES ()

The publicly funded research project BladeMaker aims at industrializing the production of wind turbine rotor blades to achieve a reproducible high quality and cost reductions. Along with other processes it addresses the automated production of sandwich structures through an in-situ foaming process of the core. For the skins, two alternative processes are presented: two-sided infusion of dry non-crimp fabrics and automated tape laying of prepreg tapes. Manual lay-up of pre-manufactured PVC foam kits is replaced by an automated application of liquid, in-situ expanding polyurethane (PU) foam directly into the mold. The benefits are considerably lower material costs, easier material transportation and the reduction of scrap. This innovative process also brings new challenges in terms of material performance and structural design, since the density-specific material properties of PUs are in general lower than of the typically used PVC-foams. Material properties of PUs depend on the selection of the specific PU system as well as on foaming parameters and especially on the density. A parameter study for a representative sandwich element has been carried out to make a trade-off between structural performance, weight and costs. Assuming that global buckling of the sandwich plate and skin wrinkling of the sandwich skins are the two dimensioning failure modes, the critical loads were calculated for different core thicknesses and PU densities. The main requirement was to achieve at least the same critical load with a PU-sandwich as with the PVC-sandwich. Finally, the material costs and the structural mass were evaluated to determine the cheapest and the lightest configuration. The contribution of additional flow meshes and resin uptake of the core material was taken into account. Results for the representative sandwich element show that the mass difference is small and that PU sandwich structures allow for significant cost reductions.