Interlaminar Shear Property and Strength Prediction Model for Hybrid Fiber-Reinforced Polymer Bar after Exposure to Simulated Concrete Environments

AbstractThe load-transfer mechanism in the fiber-reinforced polymer (FRP) bars is different from that of the conventional steel bars. The efficiency of stress transfer in FRP bars mainly depends on the mechanical properties of matrix resin, fibers, and fiber/matrix interface, which are easily degraded after long-term exposure to concrete environment. Herein, the interlaminar shear properties of a novel carbon/glass hybrid fiber-reinforced polymer (C/G-HFRP) bar were experimentally investigated by the accelerated aging tests at 60°C to study the effects of the ratio of carbon to glass fiber volume fractions, distribution configuration of carbon fiber, total fiber volume fraction, exposure environment, and exposure period. Water uptake tests, scanning electron microscopy, and Fourier transform infrared spectroscopy were employed to explore the degradation mechanisms of exposed samples. The results indicated that the interlaminar shear strength (ILSS) retention of exposed C/G-HFRP bars was higher than that of the single glass-FRP bar, which was decided by tooth force and friction. In addition, the degradation of C/G-HFRP bars was also related to water uptake rate, and then waterproof coating and fiber modification are recommended to improve the durability of C/G-HFRP bars. Finally, a model of ILSS retention was proposed for the C/G-HFRP bars after exposure to different concrete environments.