Numerical Modelling of Wind Turbine Blade to Evaluate Damage due to Impact Loads /

Abstract

Effect of change in ply orientation of wind turbine blades made with Kevlar Composite has been studied with emphasis on damage tolerance of the materials due to impact loads. Three different types of ply stacking orientation have been considered in this research to see how changing the ply orientation effects the damage tolerance of a composite. These orientations include plies oriented symmetrically, unsymmetrically and in Principal directions. The wind turbine blade is modeled after the 5 MW NREL wind turbine which was developed by National Renewable Energy Laboratory US for research purposes. This turbine has a power generation capacity of 5MW as the name suggest with a hub height of 90m and a rotor radius of about 63m. Composite modeling was done using ANSYS Composite PrepPost (ACP) in which composites having varying ply orientation were modeled. Modeling of composite in ACP enables the study of damage in individual ply which is very helpful in determining the cause of the failure. After the composite modeling, the impact analysis was performed using ANSYS Explicit Dynamics to see how the impact loads effect the materials. Deformation and equivalent stresses for different cases were studied after the completion of simulation to get an idea about how well or worse the subject modeled materials have performed. In all the simulations, there was significant elastic deformation observed but no plastic deformation was observed in any of the case. It was noted that the composites having plies oriented symmetrically or oriented at principal angles showed inferior impact resistance properties as compared to plies oriented at 0 and -45 degrees. There were several constraints to this simulation which include no consideration of material impurities or thermal stresses. Also, better results can be obtained by increasing the computational power which will enable to get a more refined mesh consequently resulting in improved simulation results.