Shear-Peeling Bond Strength between Continuous Fiber Sheet and Concrete

Abstract

Fiber-reinforced polymer (FRP) sheets can be externally bonded to reinforced concrete structural members to increase strength. However, the bond between the FRP sheet and concrete may adversely affect the performance of flexurally strengthened members when there are diagonal tension cracks in the members. This study investigates the bond strength between the FRP sheet and concrete interface for both shear bond and peeling conditions. In the experiment, 27 rectangular specimens with FRP sheets bonded on two sides were tested in uniaxial tensile loading. The specimens were designed for different step angles at the middle to ensure that the interface acts for both shear and peeling conditions. Three types of woven composite sheets made of aramid and carbon were used to allow the study of various sheet stiffnesses and strengths. The results showed that the bond strength decreases considerably due to the peeling effect. Step angle and fiber stiffness greatly influence the bond strength between the FRP sheet and concrete interface for combined shear and peeling conditions. The highest bond strength was observed for the lowest axial stiffness of the laminate. Based on the test results, a modification to an existing bond strength model is proposed that improves the prediction of the bond strength between FRP laminate and concrete for shear-peeling conditions.