Estimation of contact resistivity in lightning protection equipotential Bonding joints of wind turbine blades

Modern lightning protection systems for wind turbine blades with conducting structural elements, e.g., carbon fiber reinforced polymer (CFRP) spar caps, contain equipotential bonding joints to prevent sparking during strikes. Significant current levels are experienced through the joints and the characterization of the electrical contact at the bonding regions is essential for reliable protection. Therefore, this article aims to characterize the contact resistivity of several equipotential bonding joints. The proposed methodology first measures the total resistance of the samples, and then the bulk resistance of the conductive elements is computed using the finite-element method. The latter is required to predict the spreading effects in CFRP components due to the strong anisotropic nature of such materials. After that, the contact resistance is calculated by subtracting the predicted bulk resistances from the measured total resistances. The developed procedure was applied to three typical equipotential bonding materials: expanded copper foil (ECF), biaxial (BIAX) CFRP, and unidirectional (UD) CFRP. Both ECF and BIAX CFRP showed superior contact quality than the UD CFRP, with one to two orders of magnitude smaller contact resistivity.</p

Experimental characterisation of contact resistivity for CFRP wind turbine Spars9 equipotential bonding

This study aims to characterize the contact resistance of several equipotential bonding interfaces between the Carbon Fibre Reinforced Polymer (CFRP) spar and the Lightning Protection System (LPS). The total resistance of the coupons is measured, and the contact resistance is computed using the Finite Element Method (FEM). The latter is necessary to predict the resistance of CFRP components, which is not a trivial task because of the strong anisotropic nature of such materials. The developed methodology has been applied to a range of bonding materials: Expanded Copper Foil (ECF), Biaxial (Biax) CFRP and Unidirectional (UD) CFRP. It allows to propose the most reliable solutions for equipotential bonding applications.</p

The influence of graphene oxide filler on the electrical and thermal properties of unidirectional carbon fibre/epoxy laminates: effect of out-of-plane alignment of the graphene oxide nanoparticles

The influence of out‐of‐plane alignment of graphene oxide (GO) platelets used as matrix filler on the through‐thickness electrical and thermal conductivity of unidirectional carbon fiber‐reinforced polymers (CFRPs) composites has been investigated. By utilizing an external AC field, the orientation of GO flakes was altered to take advantage of the higher electrical and thermal conductivity along the graphene basal planes. Commercially available GO was dispersed in quantities up to 5 wt% into the epoxy matrix prior to vacuum infusion into dry carbon fabric to form CFRP laminates. Both GO‐modified CFRP laminates containing randomly oriented GO and aligned GO‐modified CFRP (A‐GO/CFRP) laminates were manufactured to assess the influence of the application of the electric field. Measurements of the electrical conductivity revealed markedly increased values for the A‐GO/CFRP even with low filler contents. The thermal conductivity, albeit increased in A‐GO/CFRP, only resulted in modest improvements. Mechanical tests of the interlaminar shear strength (ILSS) showed that the A‐GO/CFRP laminates exhibited significantly improved behavior and retained higher ILSS values (than the randomly aligned GO/CFRP laminates) even at high filler contents