Influences of the joint and epoxy adhesive type on the CFRP-steel interfacial behavior

The bond behavior of the interface between carbon fiber reinforced polymer (CFRP) and steel is an important factor affecting the strengthening effect. In this study, the double-shear and single-shear bonded joints were used to research the influences of test methods and epoxy adhesives on the CFRP-steel interfacial behavior. The test parameters included the joint type, adhesive type and adhesive thickness. The failure mode, ultimate load, strain on the CFRP, interfacial shear stress and bond-slip curve were compared. Test results show that the joint type affects the ultimate load, CFRP strain and interfacial shear stress but has no influence on the bond-slip relationship and failure mode. The ultimate loads of the interfaces tested by the double-shear bonded joints are higher than those of the single-shear bonded joints, and the ratio of the ultimate load is determined by the stiffness ratio between the CFRP plate and steel substrate. The adhesive type can affect the failure mode, ultimate load, shapes of the shear stress distribution and bond-slip curve. The ultimate load of the bonded joints with the adhesive A can reach two times that of the joints with the adhesive S. Compared to the specimen with the adhesive S, the specimen with the adhesive A has a lower peak shear stress but much longer stress transfer length. The bond-slip relationships are approximately bilinear and trapezoidal shape, respectively, for the specimens with the adhesives S and A.