Deterioration of FRP/RPUF interfacial bond strength under moisture intrusion: An analysis from the perspective of adsorption

Abstract

Fiber-reinforced polymer (FRP) / rigid polyurethane foam (RPUF) interface is a typical bonding interface composed of two layers of material. Adsorption theory is widely used in the analysis of such interfacial bonding. The mechanism of influence of water on the interfacial bonding strength of FRP/RPUF was discussed from the perspective of adsorption effect. Water intrusion experiments of FRP/RPUF interface samples were conducted at 98 °C for 672 h. The change characteristics of interfacial mechanical properties were obtained by compression-shear test, and the change characteristics of active groups were obtained by X-ray photoelectron spectroscopy (XPS) analysis. Based on the XPS results, the functional groups between interfaces were directionally regulated, and the contribution of active groups to surface free energy was evaluated. A molecular dynamics simulation method was used to simulate the process of water intrusion into the interface. Experiments and simulations show that water intrusion will cause a significant decrease in the macroscopic mechanical properties of the interface. The chemical adsorption caused by active functional groups of oxygen and nitrogen has little effect on the interface bonding strength and decreases with the water intrusion. Interface bonding mainly depends on the physical adsorption caused by non-bonded interaction. The simulation results show that the hydrogen bond energy makes a significant contribution to the interface binding energy. The invasion of water molecules will recombine the original hydrogen bonds of the interface system, resulting in the decrease of the stability of the interface structure.