Experimental study of quasi-static and dynamic tensile behavior of epoxy resin under cyclic hygrothermal aging

Fiber-reinforced polymer (FRP) structures used in aviation are typically exposed to cyclic hygrothermal environments in which they may be subjected to impact loads that threaten flight safety. Although the effects of hygrothermal aging on the mechanical behavior of FRPs have been extensively explored, few authors have discussed the impact-induced behavior of composites after long-term hygrothermal aging, and hardly any study has examined the effect of the strain rate of neat epoxy resin after hygrothermal aging. This study examines the quasi-static and dynamic tensile properties of TDE86 epoxy resin under cyclic hygrothermal aging for the first time. The resin specimens were aged for 0, 1, 7, 14, 28, 56, 70, and 140 days, representing specimens that were unaged, and had been in service for one month, six months, one year, two years, four years, five years, and 10 years respectively. The strain rate at which they were tested ranged from 7.5 × 10−6 s−1 to 1000 s−1. This yielded the hygroscopic law, the process of evolution of crack-induced damage, and the viscoelastic behavior of the specimens, including the hygrothermal effect and the effect of the strain rate of the epoxy resin. This information can be used to predict the hygrothermal behavior of FRPs based on the micromechanics method.