Intermediate‐Scale Fatigue Testing and Structural Health Monitoring of a Retrofitted Shear‐Web in the Root‐End‐Section of a Wind Turbine Blade

ABSTRACT Reliable wind turbine blades with low risk of structural failure require a robust structural failure assessment methodology, involving thorough experimental testing combined with non‐destructive inspection (NDI) techniques for structural health monitoring (SHM). In this study, multiple NDI techniques are demonstrated and compared on an intermediate‐scale fatigue‐rated multi‐axial test rig. Here the effectiveness of a retrofitted shear‐web inserted in the max‐chord region between the trailing edge sandwich panels is demonstrated on the inner 15 m root section of a 34 m wind turbine blade from SSP technology A/S. A dual degree‐of‐freedom load configuration, chosen to maximize out‐of‐plane trailing edge panel deformations, is used to provoke and drive disbonding at the foot of the shear‐web. The disbond propagation is monitored with strain gauges, a wire potentiometer, acoustic emission sensors and digital image correlation (DIC). The wire potentiometer clearly detects disbond growth when trailing edge panel breathing deformation increases from 7.5 to 34 mm. AE sensor data also aligns well with potentiometer outputs, with acoustic sensors offering large coverage and easy blade instrumentation. Simple, reliable and cost‐effective sensor technologies are of key importance for field deployment of structural health monitoring. Combining intermediate scale‐blade testing, as presented in this study, with efficient sensing and continuous monitoring systems provides information that enhances blade reliability through a basic understanding of structural blade behavior.