“…Even though several available sensor types can be applied for CM of blades, e.g., strain gauges, vibrational sensors, fiber optics, and acoustic emission sensors [11,12], the CM of blades is still in the developmental stage [13]. Laboratory testing [14] and prototype testing have been made, and studies of the rentability have been performed [15], but the long-term reliability and durability have yet to be tested, and only a few turbines have blade CM systems installed. Therefore, methods that rely solely on online CM will have limited applicability for blades of wind turbines currently installed, unless CM systems are installed later, which is more expensive compared to sensors embedded during production [11].…”