## 1 Introduction
In 2013, [PERSON] [22] investigated the mechanical properties of the adhesive joint in the carbon/epoxy wind turbine blade under the combined bending, and tensile loads were studied by the finite element method. The effects of the properties and geometric details (including fillets and defects) of the bonding material were studied based on the interlaminar stress of the bonding layer. In 2014, [PERSON] and [PERSON] [23] used the finite element analysis method combined with fracture mechanics to study the failure of the adhesive joint of the wind turbine blade. The results of a numerical calculation based on fracture mechanics showed that, before the ultimate design state was reached, the edge of the adhesive bond line began to break and expand gradually due to a high level of shear stress. In 2016, [PERSON] and [PERSON] [18] investigated mainly the damage behavior of the blade trailing-edge adhesive joint using fracture mechanics. They proposed a method based on linear fracture mechanics, which used small-scale experimental results to predict large-scale failure. Some experimental tests were also performed on the blade trailing edge to examine the damage of the blade trailing edge. In 2016, [PERSON] [2] studied the initiation of trailing-edge failure in full-scale wind turbine blade test for the accurate failure analysis of the trailing edge. The test results and simulation analysis results were compared to select the accurate simulation analysis method. Of course, some researchers tested only the local part of the blade to study the damage of the trailing edge because of the high cost of full-scale blade testing. In 2018, [PERSON] [24] carried out static and fatigue tests on the blade submodel to analyze the failure and damage mechanism of the blade trailing edge. Also, the test results were compared with the simulation results to modify the simulation analysis method. However, the test was expensive, and the complex dynamic fatigue load could not be accurately reproduced in the experiment. In the traditional methods of adhesive fatigue analysis, such as design guidelines [25], the variable-amplitude load can be converted into a constant-amplitude load by the damage equivalent method under certain assumptions. For a given constant-amplitude dynamic load, the previous methods can be used to accurately analyze the fatigue damage of the blade trailing-edge adhesive. However, the wind turbine load is irregular. If, similar to the traditional design method, the variable-amplitude load is converted into a constant-amplitude load for analysis, it may lead to the inaccuracy caused by load simplification. When analyzing the fatigue damage of the structural adhesive under a dynamic fatigue load, the finite element method combined with the stress transformation matrix method (FEM-STM method) [26] can be used to achieve the stress state of the adhesive with time without simplifying the dynamic fatigue load. The purpose of this study was to examine the influence of trailing-edge configuration on shear fatigue life of trailing-edge bonding using the FEM-STM method. The trailing edge had four main structural configurations: the position of unidirectional fiber layer (UD), chamfer of bonding line, prefabricated components, and outer over-lamination of the trailing edge. The combination of shell and solid elements was used to build the blade models of various configurations. The shell element simulated the laminated plate of the shell, and the solid element simulated the adhesive of the trailing edge. Blades with 33% relative thickness were selected for the blade model. Many single-lap standard test specimens were produced to obtain the basic shear fatigue properties of the adhesive joint. The shear S-N curve of the adhesive was evaluated using the fatigue test equipment. The shear fatigue life of the blade trailing-edge adhesive joint was assessed using the FEM-STM method.