Automated Model Generation of Large Wind Turbine Blades: Advantage of Solid over Shell Elements

Abstract

Due to market demand the size of wind turbines has been rapidly increasing due to the expected reduction in cost of energy for larger turbines. This leads to blades of extreme complexity, both in terms of geometry and materials. The increased structural complexity of larger turbines requires a better understanding of their behaviour, thus demanding the usage of higher fidelity numerical models. The behaviour of these structures is usually investigated using Outer Mold Layer (OML) shell models, however different studies have identified significant drawbacks of this approach. One of the drawbacks is related with the mechanical response of the blade under torsional loads, which shows a lower stiffness when simulated using OML based shell elements when compared to solid elements [1]. The second issue with the shell approach is related to the correct representation of the adhesive joints in the blade, since the inner surfaces that make contact with the adhesive are not directly modelled. This is usually resolved by changing the geometry of the modelled adhesive and scaling its stiffness, ensuring the correct stiffness of the blade’s section, or by using multi-point constraints to connect the adhesive with the OML shell. Finally, the usage of solid elements allows a better representation of the stress state within the composite materials, which increases its fidelity and is essential when predicting damage progression and failure. In this work, a novel approach to create FE blade models, which allows both shell, solid and hybrid modelling strategies to be employed is presented