## 3 Results and Discussion  
### Tensile Properties  
The final aspects of the specimens tested are presented in Figure 8 and the tensile properties obtained in the experimental analysis are shown in Figure 9. The values represented in Figure 9 represent the mean of the measurements for the three tested specimens. Figure 8: Specimens after failure. Figure 7: The finite element model. The unexposed pipe, evaluated in air at room temperature, serves as the baseline and shows the highest strength. The graphs from Figure 9a show that pipes exposed to saltwater experience a noticeable reduction in strength (18%), especially at higher temperatures. While the reduction is more pronounced at 50 \({}^{\circ}\)C, the effect is slightly less at room temperature, suggesting that the damaging effects of saltwater increase with heat. Similarly, exposure to an alkaline solution weakens the GFRP pipes, with a more severe  
Figure 9: Experimental results: (**a**) circumferential ultimate tensile strength (UTS), (**b**) circumferential modulus (E), (**c**) Poisson’s ratio (\(v_{yx}\)). The uncertainty range is represented as error bars, calculated using the standard deviation of the measured values. drop in strength at elevated temperatures (UTS decreases with 21%). However, under cooler conditions, the alkaline solution has a milder impact. This indicates that chemical degradation is accelerated by heat. Interestingly, the pipes exposed to air at 50 \({}^{\circ}\)C retain most of their strength, showing only a moderate reduction. This suggests that while high temperatures alone do cause some weakening, the absence of a corrosive medium such as saltwater or alkaline solution helps maintain a higher level of structural integrity. The second graph from Figure 9 shows that exposure to different environmental conditions causes a noticeable reduction in stiffness. Samples exposed to saltwater show a reduction in the elastic modulus, particularly at elevated temperatures (\(E\) decreases with 14%), suggesting that saltwater accelerates material degradation, which affects the pipe's ability to withstand deformation. The alkaline solution further reduces the modulus, especially at 50 \({}^{\circ}\)C (\(E\) decreases with 21%), where the lowest stiffness is observed. In the case of the Poisson's ratio (Figure 9c), it can be observed that exposure to saltwater, particularly at 50 \({}^{\circ}\)C, lowers the Poisson's ratio, implying that the material becomes less prone to lateral expansion under stress. The alkaline solution has a similar effect, with the lowest values observed at higher temperatures. However, under 20 \({}^{\circ}\)C conditions, the Poisson's ratio values in the saltwater and alkaline solution are closer to the unexposed specimen, indicating less material degradation at room temperature. Similarly, in the scientific paper [2], it was found that at higher temperatures (50 \({}^{\circ}\)C), the UTS tends to decrease compared to lower temperatures (20 \({}^{\circ}\)C). Additionally, the tensile modulus in the axial direction was higher at 20 \({}^{\circ}\)C, indicating a stiffer material response under cooler conditions. Also, these findings are consistent with those reported in [27], which show that environmental shifts, such as transitioning from tap water to seawater or alkaline solutions, have a significant impact on the tensile strength. These studies notably highlight that alkaline environments cause the greatest reduction in the tensile strength. The previous study of the authors [2] highlighted that the temperature played an essential role in affecting the mechanical properties, while the type of solution--especially alkaline--had a significant effect on the flexural and tensile moduli. In saltwater environments, the flexural modulus was higher compared to other conditions, possibly due to the formation of a corrosive precipitate, as confirmed by XRD and FTIR analyses.