Influence of freeze–thaw cycling on the bond strength of steel–FRP lap joints

The long term durability of FRP strengthened steel structures under freeze thaw cycles is a key parameter in their design. This paper presents an experimental investigation of the effect of freeze–thaw exposure on the bond strength and the mode of failure of steel–CFRP lap joints. A total of 48 single lap shear specimens were prepared and exposed to varying numbers of freeze–thaw cycles before being tested to failure at room temperature. The results show that the freeze–thaw cycling decreases the bond strength by about 28% and leads to variations in the mode of failure. A separate set of tests was also conducted on adhesive tensile specimens under similar conditions as those of the steel–CFRP joints, which showed a reduction in the initial elastic modulus after exposure to freeze–thaw cycling. A simple shear stress–slip model is used to predict the failure load of the specimens, which reveals a good correlation with the experimental results.