Tensile Strength and Degradation of GFRP Bars under Combined Effects of Mechanical Load and Alkaline Solution.

Dongxu Liu,Lizhi Sun,Qingping Jin,Yonghong Gao,Peixia Chen,Aihua Du

doi:10.3390/ma13163533

Abstract

Mechanical properties of glass fiber reinforced polymer (GFRP) composites degrade under the combined effects of mechanical load and alkaline solution, affecting the service ability and safety of GFRP reinforced structures. In this study, GFRP bars were loaded with cyclic tension at different stress levels and immersed in alkaline solution for days to investigate the tensile properties and degradation law of GFRP bars. The degradation mechanisms were studied at micro-, meso- and macro-scales with scanning electron microscopy (SEM) and three-dimensional X-ray microscopy, respectively. The results show that tensile strength and degradation rate of GFRP bars are mainly dependent on the different stress levels and alkaline solution. When stress level is higher, the tensile strength degrades more quickly, especially in the early stages of soaking. With the loading and immersion time, the elastic modulus and Poisson’s ratio increase at first and then decrease. The ultimate tensile strain is relatively stable, whereas the ultimate elongation is significantly reduced. A strength-degradation model was proposed and fit well with experimental data, demonstrating that the model can be applied to predict tensile strength degradation under combined effects of the load and alkaline solution.

Highlights

Glass fiber-reinforced polymer (GFRP), composed of resin and glass fibers, has many advantages such as light weight, high strength and diamagnetism [1], which can be applied as alternative or supplementary material for steel rebar in civil engineering [2]
Through alkali, acid- and salt-resistance tests, the result was found that tensile strength degradation of GFRP bars is more severe in alkaline environment
After 40% σ b cyclic loading, by immersing in alkaline solution, which indicated that increasing the cyclic load can increase the damage to the fibers and resins, accelerate the hydrolysis reaction of the resins and alkaline solution and reduce the bonding force between the fiber and resin, resulting in the tensile strength degradation of GFRP bars

Summary

Introduction

Glass fiber-reinforced polymer (GFRP), composed of resin and glass fibers, has many advantages such as light weight, high strength and diamagnetism [1], which can be applied as alternative or supplementary material for steel rebar in civil engineering [2]. Exposed GFRP bars to an alkaline solution and sustained 10% stress level on specimens and observed the significant degradation of tensile strength of GFRP bars during the test. The above research demonstrates that the combined effects of alkaline solution and the loading on the tensile properties of GFRP bars are not much different from the single factor effect of alkaline environment within a certain period of time and at a specific stress level. When stress level is high, the resin matrix formed micro-cracks, corrosion resistance of GFRP bars is mainly affected by the stress and the service life of GFRP bars is greatly reduced [22]. Most studies focus on mechanical properties by accelerated test and pay little attention to the combined effects between the load and alkaline solution in natural environment. Based on the Arrhenius equation, a modified life prediction model was proposed and validated for the GFRP ultimate tensile strength

Materials

Procedures

Results and Discussion

Apparent Phenomena of GFRP Bars after the Corrosion

Corrosion Reaction of GFRP Bars in Alkaline Solution

Mechanical Properties of GFRP Bars under Loading and Alkaline Solution

Degradation Model of Tensile Strength of GFRP Bars

Literature

Figure

Conclusions