On the effect of dielectric breakdown in UD CFRPs subjected to lightning strike using an experimentally validated model

To meet worldwide increases in energy demands Wind Turbine (WT) manufacturers are producing turbines with longer blades to generate more electrical energy. To lightweight these blades, Carbon Fibre Reinforced Polymers (CFRP) have been introduced in load carrying structures such as the WT blade sparcaps. The introduction of CFRPs presents new challenges in integrating protection from lightning strikes. The semi-conductive nature of CFRPs adds an additional electrical path to ground, and the anisotropic nature of the material properties, in particular the thermal and electrical conductivities, create large amounts of resistive heating. The aim of this paper is to develop and validate a modelling approach to predict lightning damage in unidirectional (UD) CFRP materials. The proposed modelling approach includes the electric field dependency to simulate dielectric breakdown. The model predictions are validated against experimental data and observations obtained from simulated direct lightning strike tests conducted on UD CFRP laminates. A comparison between the experimental results and the proposed model shows good ability to accurately predict the shape, volume and depth of the inflicted damage. Furthermore, the proposed model is benchmarked against conventional damage models reported in literature, and a clear improvement of the predictive capability is demonstrated, especially with respect to the predicted depth of damage.