# Numerical Analysis of Fatigue Life of Wind Turbine Blades Reinforced with Graphene Platelets
## 1 Introduction  
Since the industrial revolution in the 18 th century, the rapid growth of science, technology, and industry has accelerated the development of human civilization. However, we now face serious energy crises and climate change owing to rapidly increasing energy demands and the greenhouse gas emissions caused by fossil fuel consumption. Renewable energy has attracted attention as a key alternative to address these problems. Specifically, wind energy has been established as a major axis of the renewable energy industry along with solar energy based on its low carbon emission characteristics and large-scale power generation potential. With a recent sharp increase in demand for wind energy, various strategies have been adopted to increase economic feasibility and efficiency. Among them,large wind turbines have been evaluated as a representative approach to increasing power generation efficiency. Large wind turbines, however, increase operational loads and the weight of the structure, presenting new engineering challenges in design and manufacturing processes. To address these problems, academia and industry have explored various methods. One of them is to ensure structural safety and economic feasibility by applying cutting-edge new materials with ultralight and high-strength properties to wind turbine blades. Wind turbine blades represent 10 to 15% of the total manufacturing cost and 8% of the total weight [1]. Given that they are key structures that have the largest impact on the power generation efficiency of wind turbines, various studies have been conducted by applying cutting-edge new materials to them. For example, [PERSON] et al. [2] examined the applicability of basalt fibers to wind turbine blades by comparing them with conventional glass and carbon fibers. [PERSON] et al. [3] analyzed the structural performance of the wind turbine blades reinforced with nanopowder and hybrid fibers composed of glass, carbon, and basalt. [PERSON] et al. [4] experimentally verified that the structural integrity of wind turbine blades is effectively improved via carbon fiber reinforcement. [PERSON] et al. [5] analyzed the bending behavior of the wind turbine blades reinforced with SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\). [PERSON] et al. [6; 7] and [PERSON] et al. [8] conducted research on the application of bamboo epoxy composite laminates to wind turbine blades and verified that they are applicable as alternative materials by providing sufficient strength and stiffness when compared to conventional fiberglass composites. Recently, a number of studies have been conducted on the application of carbon-based nanomaterials to wind turbine blades. As a representative case, [PERSON] and [PERSON] [9] analyzed the applicability of carbon nanotube (CNT)/polymer composites to wind turbine blades, considering structural and functional requirements. [PERSON] et al. [10] suggested that the application of CNT-based composites to wind turbine blades can improve the mechanical performance and fatigue resistance of the blades. [PERSON] et al. [11] comprehensively analyzed various potentials, such as mechanical performance, excellent fatigue resistance, and environmental resistance, when CNT-based composites are applied to wind turbine blades based on the experimental results and theoretical modeling reported in the existing literature. Furthermore, there are research cases in the literature where graphene platelets (GPLs), which attract attention as carbon-based, cutting-edge nanomaterials along with CNTs, are applied to wind turbine blades. For example, [PERSON] and [PERSON] [12] parametrically investigated the vibration characteristics of blades based on functionally graded GPL-reinforced composites (FG-GPLRCs) according to the GPL distribution pattern, weight fraction, and geometry. [PERSON] et al. [13] systematically analyzed the nonlinear coupled resonance characteristics of GPL-reinforced rotating blades according to various variables.