Effect of graphene on the creep and stress relaxation behaviors of epoxy-nanocomposite in viscoplastic deformation regime

In this study, the creep and stress relaxation behaviors of epoxy nanocomposites reinforced with functional graphene in the viscoplastic deformation regime were investigated. Determining these behaviors, which are important indicators of viscoelastic and viscoplastic behaviors, is critical for durability and reliability in the long-term behavior of polymer-based nanocomposites. The effect of graphene, which has been used in many research fields in recent years and has superior mechanical, thermal, and electrical properties, on these time-dependent behaviors has been experimentally determined. To ensure that the nanocomposites with a content of 0.1 wt% functional graphene remained in viscoplastic deformation, the creep measurement was experimentally measured at 200 MPa constant stress level, and stress relaxation tests were experimentally conducted at 35.5% constant strain level for the 7200s. The results were compared with pure epoxy and observed a 48.5% improvement in creep resistance and a 21.9% improvement in stress drop with 0.1% f-GNF reinforcement to epoxy in the viscoplastic area. In this study, different from the studies in the viscoelastic and yield region generally discussed in the literature, the creep and stress relaxation behaviors of nanocomposites in the viscoplastic area were determined and important results were revealed for the determination of comprehensive material behavior in the design of nanocomposite structures.