A practical approach to fracture analysis at the trailing edge of wind turbine rotor blades



Wind turbine rotor blades are commonly manufactured from composite materials by a moulding process. Typically, the wind turbine blade is produced in two halves, which are eventually adhesively joined along their edges. Investigations of operating wind turbine blades show that debonding of the trailing edge joint is a common failure type, and information on specific reasons is scarce. This paper is concerned with the estimation of the strain energy release rates (SERRs) in trailing edges of wind turbine blades in order to gain insight into the driving failure mechanisms. A method based on the virtual crack closure technique (VCCT) is proposed, which can be used to identify critical areas in the adhesive joint of a trailing edge. The paper gives an overview of methods applicable for fracture cases comprising non-parallel crack faces in the realm of linear fracture mechanics. Furthermore, the VCCT is discussed in detail and validated against numerical analyses in 2D and 3D. Finally, the SERR of a typical blade section subjected to various loading conditions is investigated and assessed in order to identify potential design drivers for trailing edge details. Analysis of the blade section model suggests that mode III action is governing and accordingly that flapwise shear and torsion are the most important load cases.Copyright © 2013 John Wiley & Sons, Ltd.