Assessment of different health monitoring techniques for damage characterization in a spar cap- shear web thick adhesive joint of a wind turbine blade

Abstract

Developing an effective blade structural health monitoring (SHM) system is important for the wind energy industry. This has challenged the scientific communities for years, and still, the problem has not been solved. This research aims to find a solution to this problem and provide a basis for further research in this field. The failure rate and the downtime associated with wind turbine blades are relatively high. Within the framework of preventive maintenance, it is necessary to inspect wind turbine blades periodically. Blade inspection needs special tools, skilled manpower, vessels, and lifting equipment; therefore, it is costly. This is the main reason that the wind energy industry would like to minimize the number of periodic blade inspections by using a reliable SHM system. An issue that complicates the SHM of wind turbine blades is the complexity of blade geometry. Different parts of a wind turbine blade are connected using adhesive. These adhesive joints, e.g., leading edge, trailing edge, and spar capshear web adhesive joints, are important parts of the blade structure and play an essential role in the integrity of the blade. These joints are very vulnerable to fatigue damage. Manufacturing flaws and impact can instigate and accelerate fatigue damage in a wind turbine blade. Impacts may happen during the transportation or installation of the blades, especially for offshore wind turbines. In this study, vibration, acoustic, and infrared thermography are used to characterize fatigue damage in test specimens representative of the spar cap-shear web adhesive joint of a wind turbine blade. To create different levels of damage, the test specimens were subjected to fatigue tension tests. To study the effect of impact on damage propagation, the test specimens were subjected to different levels of impact using a Gas Canon machine before being subjected to fatigue tests. During the fatigue tests, a Polytech laser vibrometer, Vallen acoustic system, and FLIR infrared thermographic system were used for vibration, acoustic and thermographic analysis...