A micromechanical-based study on the tribological and creep-relaxation behavior of sand-FRP composite interfaces

Fiber-reinforced polymer (FRP) composites have a promising potential to be utilized to extend the lifespan of geostructures in harsh environments due to their high durability, satisfactory strength and cost-effectiveness. The FRP-soil interaction is critical to model soil-structure interaction problems and assess the performance of foundation systems where composites are used. In this paper, the contact behavior of sand-FRP interfaces at the fundamental level of the grain-scale was investigated with a custom-built micromechanical testing apparatus, with an emphasis on the normal contact response, the tangential load – displacement relationship as well as creep and relaxation behavior. Leighton Buzzard sand (LBS), a typical silica sand, and custom manufactured glass fiber reinforced laminated FRP plates were used in the study. It was shown that the surface texture, thickness, and fiber orientation of the FRP composite plates have important influences on the tribological behavior of the sand-FRP interfaces, and plowing damage was observed to be a dominant mechanism from the shearing tests, particularly at higher normal loads. The results also suggested that creep and relaxation had a significant influence on the interface behavior of sand-FRP and these phenomena should be considered in the long-term design of FRP included composite geostructures.