Atomistic investigation on interfacial deterioration of epoxy-bonded interface under hygrothermal environment

The fiber reinforced polymer (FRP) has been increasingly used for strengthening concrete infrastructure through external bonding by using epoxy adhesive. The long-term durability of FRP-concrete structure is seriously degraded under hygrothermal environment at high level of temperature and humidity, which is mainly caused by interfacial debonding between concrete and epoxy. The microscopic information on local interfacial deterioration is important for understanding the failure mechanism of epoxy-bonded FRP-concrete structure under hygrothermal environment, which is still lacking at this stage. This paper aims to understand the effect of hygrothermal environment on nanoscale mechanical and interfacial behavior of epoxy-bonded interface by using molecular dynamics simulation. The interface model is conditioned in dry and wet environment at room and elevated temperature. By simulating interfacial debonding process, the structural and mechanical properties of epoxy-bonded interface are examined, which degrades most seriously in wet environment at elevated temperature, resulting in significant decrease of interfacial adhesion. The mechanistic knowledge provided in this paper could contribute to the understanding of environment-affected structural failure of FRP-concrte system from the nanoscale perspective, and it is believed to be applicable to similar FRP-strengthened structure.