Modeling of long-term creep behavior of structural epoxy adhesives

The mechanical properties of polymeric materials change over time, especially when they are subjected to long-term loading regimes. It is imperative that reliable accelerated tests be developed to determine the long-term time-dependent performance of polymers under different environmental conditions. The long-term creep behaviors of a neat epoxy resin and a commercial structural adhesive for bonding aluminum substrates were investigated. The time-temperature superposition method produced a master curve, allowing for the long-term creep compliance to be estimated. The physics-based coupling model was utilized and found to fit well with the long-term creep master curve. The equivalence of the temperature and moisture effects on the creep compliance of the epoxy adhesives was also addressed. Finally, a methodology for predicting the long-term creep behavior of epoxy adhesives was proposed.