Effect of freeze-thaw/dry-wet environment on mechanical properties of epoxy resin adhesive

Epoxy resin adhesive (ERA) is an important bond material for carbon fiber reinforced polymer (CFRP) strengthened bridge structures, and its mechanical properties often degrade when used in harsh environments. Fifty-two ERA specimens were prepared and tested to investigate the influences of freeze-thaw (F-T), chlorine dry-wet (D-W), and F-T/D-W on mechanic properties of the ERA. Static tensile tests were conducted after the ERAs were exposed to these environments for 30, 60, 90, and 120 cycles. The experimental results showed that failure of all specimens demonstrated characteristics of brittle failure. Compared with the control group, the tensile strength increased around 40.7, 22.8, and 11.3%, and the elastic modulus increased around 39.2, 34.6, and 38.3% after 120 cycles of the F-T, D-W, and F-T/D-W exposure, respectively. Meanwhile, the stress-strain relationship of the environmental specimens exhibited nonlinear characteristics. However, the stress-strain relationship of the control group without any environmental treatment showed linear. By contrast, the deformation capacity of the environmental specimens was weaker than those of the control group, except for the specimens under the 120 D-W cycles. In addition, variation for the strain energy and tensile strength retention rate of the environmental specimens demonstrated similar trends with the tensile strength, which increased first and then decreased from 30, 60, 90, to 120 cycles. Finally, a strength degradation model of the ERA was proposed to predict the tensile strength under the F-T, D-W, and F-T/D-W exposure.