FRP-soil interfacial mechanical properties with molecular dynamics simulations: Insights into friction and creep behavior

The fiber-reinforced polymer (FRP) has attracted much attention in civil engineering due to its durability and cost-effectiveness. The soil-FRP structure interface plays an essential role when the FRP is adopted in geotechnical engineering, but its fundamental interfacial behavior remains unclear. In the present study, the atomistic models of silica representing sand, water film representing the lubricated condition, and cross-linked epoxy representing FRP are constructed to investigate the FRP-sand interfacial properties at the nano-scale through molecular dynamics (MD) simulations. The epoxy model geometry and forcefield are first validated by comparing the thermodynamic and mechanical parameters with experimental and simulation measurements. The silica-epoxy interfacial tribological and rheological behavior is then explored by conducting friction and creep simulations under dry and lubricated conditions. The friction force has been found linearly dependent on the normal load and increases with the sliding velocity while decreasing against water content. The modified Amontons law for the adhering surface could describe the silica-epoxy interfacial friction well. The shear stress level influences the creep characteristics with primary, secondary, and tertiary (or rupture) creep modes. The results of this study at the nano-scale can be further developed to enhance the current contact laws of sand-FRP structure in micromechanics-based modeling approaches.