Wind Blade Repair Optimization

Abstract

Wind Turbine blades are constantly exposed to extremely adverse environmental conditions throughout their operation. As a result, they inevitably suffer damage from erosion, exposure as well as more acute incidents such as lightning strikes and extreme wind speeds. Damage must be repaired in the shortest possible time frame to reduce blade downtime. However, current repair processes are highly variable and not optimized for the unique geometry of each repair or environmental conditions. The goal of this study is to optimize the cure cycle to produce a homogeneously cured repair patch in the shortest time and to identify key cure cycle parameters, such as heating rate, cure temperature, hold time, etc., that significantly affect the time and quality of the repair. The effect of each cure cycle parameter on the repair time is investigated individually within a combined experimental-numerical framework. Extensive material characterization of the neat resin is conducted. First, the resin and the curing agent are separately exposed to environmental conditions to measure the moisture absorption capacity. Then, the curing behavior of the resin is characterized using Differential Scanning Calorimetry (DSC) as a function of different environmental conditions. Lastly, Finite element (FE) curing simulations of a single-side scarf repair, are performed within Abaqus through user-written subroutines, to investigate the effect of cure cycle parameters and environmental conditions on the blade repair time. The effect of each parameter is quantified in terms of peak exothermic temperature, spatial distribution of cure and temperature within the repair and the total repair time. Experimental validation in lab conditions is proposed to validate the FE and to gauge the quality of the repair resulting from the optimized cure cycle.