The impact of shear web configuration on the optimization potential of wind turbine blades with sustainable core materials

Balsa wood has long been the preferred core material for wind turbine blade sandwich laminates due to its superior through-thickness mechanical performance. However, increasing demand and supply limitations are making continued use of balsa wood unsustainable. PolyEthylene Terephthalate (PET) foam presents a more sustainable alternative to balsa wood, but its inferior through-thickness performance makes this transition non-trivial. This work aims to support the transition by demonstrating a structural optimization approach to efficiently generate PET blade designs. Three different optimization problems are solved on variants of the Gurit98m open-source blade model containing one, two, and three shear webs, respectively, yielding novel insight to their corresponding optimal distribution of PET core material. A continuous layer thickness parametrization is used with adjoint gradient-based methods, allowing unprecedented fidelity with each blade optimization problem containing more than 11,000 design variables, several structural criteria, a novel ply-group-based ply-drop constraint system, and twelve design load cases. Bill of material costs are reduced by more than 13% in all models and most constraints have reached their defined limit at the optimization process termination. The resulting laminates are shown to meet the structural requirements, including core driven failure modes, and provide a detailed starting point for designing PET blades.