# Effectiveness of Nanotechnology Treatments in Composite Aircraft Applications
## 3 Corrosion and Fatigue Test
### Fatigue Test
From Equation (1) and for all three load types, it is possible to obtain the global \(k_{t}\) value obtained during the test as:  
\[k_{t}=\sqrt[E]{\left(\frac{10^{A-logN}+D}{S}\right)} \tag{2}\]  
\(k_{t}\) is determined by the effect of the sample shape (the presence of a hole introduces a \(k_{t\text{-}shape}\) (around 2.44 in our specific case)), the presence of corrosion through \(k_{t\text{-}corr}\), and a possible stress release through \(k_{t\text{-}release}\):  
\[k_{t}=k_{t\text{-}shape}\cdot\,k_{t\text{-}corr}\cdot\,k_{t\text{-}release}^{-1} \tag{3}\]  
Figure 5: Load type 1: \(F_{max}=11\), kN \(F_{min}=0\), and kN \(f=5\) Hz. Figure 6: Load type 2: \(F_{max}=9\) kN, \(F_{min}=0\) kN, and \(f=5\) Hz. Corrosion protection through primers or through innovative nanotechnological treatment is responsible for \(k_{t-release}\), which reduces the total \(k_{t}\). Table 3 shows the results obtained. From the table, it can be seen that the average kt-shape obtained through the uncorroded samples MC010, MC011, MC012, and MF000 was approximately 2.36, in line with the kt-shape value obtained through the finite element method for which a kt-shape equal to 2.44 was obtained. The average kt value of the raw corroded specimens corresponding to the MCF001, MCF002, MCF003 specimens was 3.2, which led to the determination of the average value of the kt-corr, which was approximately 1.36. Comparable values were obtained in [18]. Then, considering the specimens treated with a primer, it was possible to estimate the kt-release relative to that treatment, which turned out to be 1.04, indicative of the fact that the primer could reduce the corrosive effect by only about 4%. Some signs of the loss of protective efficacy of the primer had already been seen during the corrosive bath phase when the formation of bubbles under the protective layer was noted. As regards the specimens treated with MCF007, MCF008, and MCF009 nanotechnologies, the average value of kt was 2.58, which allowed us to calculate an average value of kt-release of about 1.19, with a maximum of 1.23 for higher loads where corrosion was less aggressive, and 1.14 at the lowest load. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Name** & **Load Type** & **N** & \(k_{t}\) & \(k_{t-shape}\) & \(k_{t-corr}\) & \(k_{t-release}\) \\ \hline MF000 & 1 & 5570 & 2.32 & 2.32 & 1.00 & 1.00 \\ MCS010 & 1 & 4533 & 2.47 & 2.47 & 1.00 & 1.00 \\ MCS011 & 2 & 16,694 & 2.21 & 2.21 & 1.00 & 1.00 \\ MCS012 & 3 & 100,170 & 2.42 & 2.42 & 1.00 & 1.00 \\ MCF001 & 1 & 2312 & 3.05 & 2.47 & 1.23 & 1.00 \\ MCF002 & 2 & 6041 & 2.96 & 2.21 & 1.34 & 1.00 \\ MCF003 & 3 & 20,791 & 3.58 & 2.42 & 1.48 & 1.00 \\ MCF004 & 1 & 2476 & 2.99 & 2.47 & 1.23 & 1.02 \\ MCF005 & 2 & 7631 & 2.77 & 2.21 & 1.34 & 1.07 \\ MCF006 & 3 & 22,986 & 3.49 & 2.42 & 1.48 & 1.03 \\ MCF007 & 1 & 4467 & 2.49 & 2.47 & 1.23 & 1.23 \\ MCF008 & 2 & 11,775 & 2.44 & 2.21 & 1.34 & 1.21 \\ MCF009 & 3 & 34,329 & 3.14 & 2.42 & 1.48 & 1.14 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Experimental stress concentration and release factors. Figure 7: Load type 3: \(F_{max}=6\) kN, \(F_{min}=0\) kN, \(f=5\) Hz. Figure 8 shows the S-N curves considered for the different cases discussed. In blue are the specimens not subject to corrosion, in black are the corroed and unprotected specimens, in green are the specimens protected with primer, and finally, in red are the specimens protected with nanotechnologies and subjected to the corrosion test. In all specimens subjected to corrosive immersion, a greater effect of corrosion was observed at lower loads (load types 2 and 3), confirming not only an increase in the stress concentration factor (kt) but also a change in the slope, as indicated also in [9].