Experimental Investigation and Prediction for Bending Creep of Glass Fiber-Reinforced Polymer Pultruded Tube

This study experimentally investigates the bending creep behavior of a pultruded tube made of glass fiber-reinforced polymer (GFRP) and provides the corresponding fitting model as well as the life prediction equation. In the experiment process, the static bending test is performed first to determine the ultimate load-bearing capacities. Then, the creep experiments lasting 3000 h are conducted for GFRP pultruded tubes with 50%, 55%, 60%, and 65% fiber contents, subjected to four different load levels, i.e., 20%, 32.5%, 45%, 57.5%, and 70%, of the ultimate load-bearing capacity. The results indicate that the creep behavior exhibits linear viscoelasticity for load levels below 45%, while the specimens under load levels of 57.5% and 70% experienced creep failure before 1500 h. The test results indicate that for GFRP tubes, the higher the load level, the more pronounced the creep deformation, and specimens with a higher fiber content exhibit better creep resistance compared to those with lower fiber content. When the load level is less than 45%, the creep behavior appears as linear viscoelasticity. However, at a load level of 57.5%, the specimens experience shear failure, and at a load level of 70%, the specimens undergo overall bending failure. In addition, the prediction equation of creep deflection for GFRP pultruded tubes in linear viscoelasticity is developed by utilizing the Bailey–Norton model and the Findley model, and the prediction equation of creep life is acquired by fitting the experimental data with an exponential function