Abstract:To investigate the effects of load history on the bonding properties of carbon fiber reinforced polymer (CFRP) steel interface, long-term loading tests of CFRP-steel plate double-lap specimens were conducted under four interfacial shear stress levels and six types on loading time, and static tensile tests were carried out on the specimens which reached the specified loading time. Based on the axial strain data of CFRP, the distribution of interfacial shear stress and bond-slip curves were given. In view of the effect of interfacial creep damage on the bond-slip constitutive relations, coefficients β, η, and γ were introduced into bilinear model, and corresponding expressions were obtained by regression analysis. Results show that the creep deformation of the adhesive caused the redistribution of the interfacial stress. With the increase of time, the peak value of interfacial shear stress decreased and the strain of CFRP increased. After loading for 90 days, the interfacial shear stress of the specimens in groups B, C, D, and E at 12.5 mm decreased by 26.6%, 59.2%, 73.8%, and 85.4%, respectively. When the level of interfacial shear stress was high, the influence of interfacial creep damage on bond-slip curves should be considered, where higher interfacial shear stress and longer duration led to more significant creep damages. When the bonding length of CFRP was longer than the effective bonding length, the interfacial creep damage had no obvious effect on its ultimate bond strength.