On the use of structural optimization to drive the transition to sustainable core materials in wind turbine blades

Abstract Structural design of modern wind turbine blades poses a serious engineering challenge. Key contributing factors include the use of complex laminated composite materials, the double-curved geometry of modern aerodynamically efficient designs, and the length scale of current commercial offshore blades exceeding 100 m. Yet, developing even larger wind turbines is key to increase the energy output at lower cost. Moreover, it is important that blades are designed as sustainable, which implies transitioning away from many of the materials currently used in designs. To encourage collaboration and innovation for reaching these goals, Gurit Wind Systems has published an in-house developed 98-meter blade model: the Gurit98m. The objective of this work is to introduce the Gurit98m model and demonstrate a use case concerning transitioning to recycled PET foam as the core material as well as discover the optimal distribution of PET core in the model. For this purpose, a gradient-based thickness optimization approach is applied, aiming to minimize the mass of the core materials under buckling, tip displacement, and static failure constraints for twelve different load cases. Moreover, shear crimping and face wrinkling sandwich failure criteria are included as failure criteria, which is a novelty in thickness optimization of wind turbine blades. Structural optimization is performed on different versions of the Gurit98m model, containing one, two, and three shear webs respectively. The optimizations results reveal possible mass reductions, identify critical criteria, and show ideal PET distribution tendencies for the three designs, which can be used as a starting point for more detailed design.