# Evaluation of Pressure Effect on Accelerated Aging Tests of Polymer-Insulated Aircraft Wires
## 6 Conclusions  
In this paper, the degradation behavior of insulated wires was studied using accelerated wet arc tracking tests. It was found that the degradation of the insulation material is progressive and visibly evidenced by material erosion and the formation of tree paths or tracks through the insulation. Insulated wires for low-pressure aircraft applications are currently tested at standard pressure, so this paper analyzed the feasibility of studying the behavior of the samples in low-pressure environments. To this end, three degradation indicators were proposed and analyzed based on the use of optoelectronic sensors. These indicators are based on the surface discharge inception voltage (SDIV), the intensity of the images acquired with a CMOS sensor, and the intensity of the solar blind UV light. Although the system is fully automated and the environmental conditions are controlled, the reproducibility of wet tests presents several challenges due to several causes. These include issues related to the notches made in the wire specimens, which, although carefully prepared, are always difficult to reproduce. Variability in the material properties of the test specimens, such as the surface finish, thickness, or composition, can lead to inconsistencies in tracking performance, as these properties directly affect the dielectric strength and tracking resistance. In addition, the uneven deposition of the electrolyte solution, whether due to the application process or environmental factors such as humidity and airflow, can result in localized areas of higher conductivity. All of these factors can contribute to premature or unpredictable arcing. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Pressure** & **Sample** & **Slope** & **Intercept** & \(\mathbf{R^{2}}\) & **Pressure** & **Sample** & **Slope** & **Intercept** & \(\mathbf{R^{2}}\) \\ \hline \multirow{8}{*}{16 kPa} & 1 & \(-\)0.00822 & 0.823 & 0.098 & & 1 & \(-\)0.02265 & 1.286 & 0.250 \\  & 2 & \(-\)0.00143 & 0.813 & 0.001 & & 2 & \(-\)0.03929 & 1.228 & 0.209 \\  & 3 & \(-\)0.01754 & 0.659 & 0.153 & & 3 & \(-\)0.04939 & 1.082 & 0.328 \\  & 4 & \(-\)0.00514 & 0.572 & 0.261 & & 4 & \(-\)0.01219 & 0.806 & 0.322 \\  & 5 & \(-\)0.01198 & 0.653 & 0.347 & & 5 & \(-\)0.01828 & 0.950 & 0.490 \\  & 6 & \(-\)0.04043 & 0.626 & 0.858 & & 6 & \(-\)0.04875 & 0.754 & 0.639 \\  & 7 & \(-\)0.01925 & 0.636 & 0.234 & & 7 & \(-\)0.02187 & 0.835 & 0.127 \\  & 8 & \(-\)0.00095 & 0.557 & 0.006 & & 8 & \(-\)0.01172 & 0.864 & 0.174 \\ \cline{2-10}  & \multirow{2}{*}{1-8} & \multirow{2}{*}{\(-\)0.013} & \multirow{2}{*}{0.584} & \multirow{2}{*}{0.200} & Mean & & & & \\  & & & & & & values & 1-8 & \(-\)0.028 & 0.855 & 0.254 \\ \hline \multirow{8}{*}{72 kPa} & 1 & \(-\)0.02874 & 1.627 & 0.250 & & 1 & \(-\)0.03445 & 1.820 & 0.218 \\  & 2 & \(-\)0.06789 & 1.540 & 0.659 & & 2 & \(-\)0.02836 & 1.730 & 0.176 \\  & 3 & \(-\)0.07332 & 1.385 & 0.496 & & 3 & \(-\)0.11379 & 1.8 The experimental results showed that, despite the inherent dispersion between samples and degradation cycles, the SDIV performed best, showing an overall decrease along with the degradation process, followed by the intensity measured with the solar blind UV sensor. A novel aspect of this research was to vary the atmospheric pressures from 100 kPa to 16 kPa (the pressure associated with the cruising altitude of commercial aircraft) to observe changes in the sensitivity of degradation perception. The experimental results presented in this paper show that the sensitivity of the proposed methods is affected by atmospheric pressure, such that higher pressures accentuate the visibility of degradation effects in the form of a greater increase in the intensity captured by the solar blind UV sensor and a greater reduction in the slope of the SDIV value versus the number of degradation cycles (the slope is \(-\)0.013 at 16 kPa, while it is \(-\)0.047 at 100 kPa).