# Numerical Analysis of Fatigue Life of Wind Turbine Blades Reinforced with Graphene Platelets
## 4 Results and Discussion  
### Fatigue Life of Wind Turbine Blades with Conventional Fiberglass Composites  
Prior to assessing the fatigue life of the GPL-reinforced wind turbine blade, the fatigue life of the blade based on the conventional fiberglass composite was calculated using the aforementioned method to validate the method proposed in this study. It was then compared with the fatigue life results presented in Resor [24] to validate the proposed method. In general, the fatigue life of wind turbine blades is evaluated to be lower near the root when compared to the area near the tip. In this study, fatigue life was also assessed at the locations selected in Resor [24] (Table 8). Figure 7 shows the fatigue life distribution of the fiberglass composite-based wind turbine blade according to the location in the span direction. It can be observed that the lowest fatigue life was calculated at location 5 for GFRP and CFRP. Compared with the fatigue life results presented in Resor [24], some differences were observed. This appears to be due to the difference in fatigue life assessment methods and applied loading conditions. Given that the changing tendency of the fatigue life of the blade in the span direction is generally similar to the results of Resor [24], however, the reliability and validity of the proposed method can be confirmed.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Localation** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** \\ \hline Span location (m) & 0 & 1.3667 & 4.1 & 6.8333 & 10.25 & 14.35 & 18.45 & 22.55 \\ \hline \end{tabular}
\end{table}
Table 8: Spanwise location for fatigue life assessment.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Peak** & **Cycle** & \(\sigma_{\text{max}}\) & \(\sigma_{\text{min}}\) & \(\sigma_{\text{m}}\) & \(\sigma_{\text{a}}\) & \(\sigma_{\text{e}}\) & **N** & \\  & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** & **(Cycle)** & **D** \\ \hline
4 & 16 & 197.33 & 19.73 & 108.53 & 88.80 & 105.09 & \(6.86\times 10^{6}\) & \(1.46\times 10^{-7}\) \\  & & 156.42 & 145.33 & 150.87 & 5.54 & 7.07 & \(3.64\times 10^{18}\) & \(2.75\times 10^{-19}\) \\  & & 127.17 & 35.26 & 81.21 & 45.95 & 51.99 & \(7.82\times 10^{9}\) & \(1.28\times 10^{-10}\) \\  & & 155.41 & 65.59 & 110.50 & 44.91 & 53.33 & \(6.07\times 10^{9}\) & \(1.65\times 10^{-10}\) \\  & & 181.65 & 91.35 & 136.50 & 45.15 & 56.08 & \(3.66\times 10^{9}\) & \(2.73\times 10^{-10}\) \\  & & 140.60 & 14.59 & 77.59 & 63.01 & 70.86 & \(3.53\times 10^{8}\) & \(2.83\times 10^{-9}\) \\  & & 199.31 & 174.74 & 187.03 & 12.29 & 16.77 & \(6.41\times 10^{14}\) & \(1.56\times 10^{-15}\) \\  & & 77.50 & 17.45 & 47.48 & 30.02 & 32.21 & \(9.39\times 10^{11}\) & \(1.06\times 10^{-12}\) \\  & & 119.65 & 10.48 & 65.06 & 54.59 & 60.18 & \(1.81\times 10^{9}\) & \(5.53\times 10^{-10}\) \\  & & 189.78 & 31.79 & 110.79 & 78.99 & 93.85 & \(2.13\times 10^{7}\) & \(4.70\times 10^{-8}\) \\  & & 190.16 & 38.82 & 114.49 & 75.67 & 90.46 & \(3.07\times 10^{7}\) & \(3.26\times 10^{-8}\) \\  & & 185.96 & 61.33 & 123.65 & 62.31 & 75.68 & \(1.83\times 10^{8}\) & \(5.47\times 10^{-9}\) \\  & & 181.90 & 27.95 & 104.92 & 76.98 & 90.55 & \(3.04\times 10^{7}\) & \(3.29\times 10^{-8}\) \\  & & 171.72 & 111.92 & 141.82 & 29.90 & 37.49 & \(2.05\times 10^{11}\) & \(4.87\times 10^{-12}\) \\  & & & & & & & & \\
178.48 & 24.53 & 101.51 & 76.97 & 90.03 & \(3.22\times 10^{7}\) & \(3.10\times 10^{-8}\) \\  & & & & & & & & \\
185.92 & 49.14 & 117.53 & 68.39 & 82.19 & 8.02 \(\times\) 10\({}^{7}\) & \(1.25\times 10^{-8}\) \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\ \end{tabular}
\end{table}
Table 7: _Cont._