Effects of different loading types and high temperatures on the bending behavior of GFRP box profiles

The widespread use of fiber-reinforced polymer (FRP) materials in the construction industry is steadily increasing. While these materials possess numerous superior properties, it is well-known that their strength decreases under the influence of temperature. In this study, glass fiber reinforced plastic (GFRP) box profiles were first subjected to bending tests when they reached -30 to 200 oC. In the second, after reaching the target temperature, they were kept at the target temperature for 30-60 minutes and subjected to bending tests when they returned to room temperature. To investigate the effect of loading type, both three-point and four-point bending tests were conducted. Due to the temperature effect, the surface changes of the profiles were examined under a microscope. Finally, the compatibility of mathematical formulas with the experimental data was determined using correlation and regression analyses. The results of the study show a decrease in bending strength with increasing temperature, while an increase in bending strength was observed under cold conditions. It was found that exposure time had a more significant effect at lower temperatures, while at higher temperatures, thermal degradation dominated the failure mechanism regardless of exposure time. Additionally, it was observed that the loading effect is crucial, and therefore, both loading types should be considered.