Influence of Structural Configurations on the Shear Fatigue Damage of the Blade Trailing-Edge Adhesive Joint

Abstract

Wind turbines are under continuous development for large-scale deployment and oceanization, leading to the requirement of longer blades. The economic losses caused by blade replacement and shutdown have increased. The downtime caused by blade issues in a wind turbine is 8-20% of the total downtime. Many of these blade issues originate from the cracking of the blade trailing edge. The edge is more susceptible to damage due to the complex geometry, manufacturing technique, and operation conditions. The traditional design method and the expensive experimental research are not suitable for the accurate damage analysis of the trailing-edge adhesive because of simplifying assumptions and costs. This study aimed to investigate the influence of trailing-edge structural configurations on the shear fatigue life of the trailing-edge adhesive joint using finite element and stress transformation matrix (STM) methods. The structural configurations of the blade trailing edge included the position of unidirectional fiber layer (UD), chamfer of bonding line, prefabricated components, and outer over-lamination of the trailing edge. In this study, the finite element method was used to simulate the blade structure. The shell element was used for laminates, and the solid element was used for the trailing-edge adhesive joint. The basic shear fatigue properties of the adhesive were obtained by standard component tests. The shear fatigue life of the blade trailing-edge adhesive joint under given load conditions was calculated using the fatigue properties of the adhesive and STM method. The results showed that the angle of chamfering, location of UD, rigidity of the preform, and outer over-lamination all had an obvious influence on the fatigue damage of trailing-edge adhesive. The findings of this study can be used to guide blade structure design and blade production and maintenance.

Durability and Damage Tolerance Analysis Approaches for Wind Turbine Blade Trailing Edge Life Prediction: A Technical Review

“…Wind turbine blades are designed to last at least 20 years, resulting in load cycles between 10 7 and 10 9 [45,48], making the blade very susceptible to fatigue. As such, the most common composite materials have been tested for fatigue properties and are reported in the Department of Energy/Montana State University (DOE/MSU) [49] and OptiDat [50] databases.…”

“…All three types still have the same basic concept of two composite shells held together with an adhesive. The most common type is Type A [48]. The DNV design standard requires all bonded joints including the trailing edge to be analyzed for both the extreme and fatigue load cases with all failure modes evaluated including adhesive, adherent and interface failures [17].…”

“…Rafiee and Hashemi-Tahero [6] conducted a finite element analysis on the trailing edge joint with various bondline widths and reported a change in failure mode from cohesive for short bondline widths to adherent delamination in large bondline widths. Besides bondline thickness and bondline width, the shape of the flow front also plays a crucial role in determining the specific mode of joint failure [48,70]. Certain geometries can lead to specific failure modes, such as cohesive failure versus adhesive failure at the interface.…”

A Comprehensive Analysis of Wind Turbine Blade Damage

“…This process is depicted in Figure 9 [46]. The shear effect also can be critical for the trailing edge adhesive joint, because it is more susceptible to damage due to the complex geometry, manufacturing technique and operating conditions [47].…”