Structural health monitoring techniques for wind turbine blades

Wind turbine blades are made of fiberglass material to be cost effective, but they can be damaged by moisture absorption, fatigue, wind gusts or lightening strikes. It is important to detect the damage before the blade fails catastrophically which could destroy the entire wind turbine. In this paper, four different algorithms are tested for detecting damage on wind turbine blades. These are the transmittance function, resonant comparison, operational deflection shape, and wave propagation methods. The methods are all based on measuring the vibration response of the blade when it is excited using piezoceramic actuator patches bonded to the blade. The vibration response of the blade is measured using either piezoceramic sensor patches bonded to the blade, or a scanning laser doppler vibrometer. The sensitivity of the techniques to detect a reversible damage simulated by a steel plate clamped to a section of a wind turbine blade is compared in this paper.