Fatigue performance of a cold-curing structural epoxy adhesive subjected to moist environments

This paper presents the results of an experimental program designed to study the effects of aging and a wet environment on the fatigue behavior of epoxy resins used in bridge applications. Specimens were manufactured, cured, and treated, before the experiments, under a variety of conditions, in room and in water environments, in order to simulate the aging of adhesives in bridges for a period of up to 100 years. Experimental results indicated that a typical power law S-N equation could describe the fatigue stress vs. life behavior of the examined material under different gravimetric conditions. The slope of the curve was found to be in the range of that of other polymers and polymeric composite materials. The cyclic strain behavior and hysteresis loops were obtained under different gravimetric conditions and at different stress levels and the effects of both parameters on the viscoelastic behavior of the material have been thoroughly discussed. The fatigue failure surfaces were also recorded using a digital handheld microscope to reveal the damage mechanisms. The results of this work showed that the examined epoxy resin could sufficiently sustain fatigue loads with maximum cyclic stress levels of more than 25% of their quasi-static strength for more than 2 million cycles.