Environmental effects on the bond at the interface between FRP and wood

The advantages of fiber reinforced polymer (FRP), such as high specific strength, resistance against corrosion and formability, have made it a more acceptable alternative to conventional materials regarding repairing and retrofitting of structures. Although investigations in recent years have proved the concern of civil engineers about the environmental effects on the bond between FRP and concrete or masonry (especially moisture and temperature), only few researches have been reported on FRP-wood interfaces. This research investigated the effect of five different environments on the bond at the interface between FRP and wood. A series of pull-out tests were performed on 375 wood specimens bonded with aramid, carbon and glass fibers (wet lay-up) and one type of epoxy resin. Then, these samples were immersed in chemical solutions with pH of 2.5, 7, 10 and 12.5 and substitute sea water for 2, 4, 6, 8, 10 and 13 weeks to estimate bond strength reduction. The effect of dry heat was also investigated. The results of such experimental tests illustrated that an acidic solution had the most effect on the bond between carbon-FRP and wood by 57% reduction. Sea water and fresh water had almost the same effect on the specimens bonded with glass and aramid-FRP (40% reduction), and they had the least influence on the bond between carbon-FRP and wood. Further, alkaline solutions had the most effect on the specimens bonded with glass-FRP. In addition, dry heat did not affect the bond between FRP and wood considerably.