Shear-Peeling Bond Strength between Continuous Fiber Sheet and Concrete

Diagonal tension cracks in reinforced concrete members may adversely affect the performance of flexurally strengthened members by fiber-reinforced polymer (FRP) materials. The interface between the FRP sheet and concrete may experience both shear bond and peeling for such conditions. This study presents the experimental results of bond strength between the FRP sheet and concrete interface for both shear bond and peeling conditions. Twenty-seven 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 (Aramid I and Aramid 2) and carbon were used in this investigation. The three different sheets were chosen to allow various sheet stiffnesses and strengths to be studied. The results revealed that the bond strength decreases considerably due to the peeling effect. In addition, the step angle and fiber stiffness play an important role in the bond strength for a combined effect. The highest bond strength was observed for the lowest axial stiffness of the laminate. Based on the test results, a modification has been proposed to one of the existing bond strength models. The proposed modification improves the prediction of the bond strength between FRP laminate and concrete.