Experimental and modeling study on creep behavior of GFRP pipes dependent on temperature and stress

This study investigates the influence of temperature and stress level on the creep behavior of glass fiber reinforced plastic (GFRP) pipes with varying fiber contents. Using constant-load testing devices and environmental chambers, creep experiments were conducted for 1,000 h under three temperature conditions (30 °C, 50 °C, and 70 °C) and three stress levels (10 %, 30 %, and 50 % of the ultimate strength). The experimental data were fitted using the Zener, Burgers, and HKK models, and the time-dependent strain evolution of the pipes from 1,000 to 5,000 h was predicted. The results demonstrate that both temperature and stress level significantly affect the creep performance of GFRP pipes. The creep rate increases with higher temperatures and stress levels, and under high-temperature, high-stress conditions, the pipes experience rapid failure. All three models—Zener, Burgers, and HKK—effectively describe the creep behavior of the pipes with different fiber contents. The Burgers and HKK models exhibit superior fitting accuracy, and their long-term strain predictions are in close agreement. This study establishes a methodological framework for evaluating the long-term mechanical performance of GFRP pipes and provides valuable insights for predicting their creep behavior.