The purpose of this investigation is to study the bond between Carbon Fiber Reinforced Polymer (CFRP) sheets and concrete. An experimental investigation was conducted in order to determine the effects of bonded length, concrete strength, and number of plies of CFRP. The specimens used in the study were unreinforced concrete beams that were externally reinforced with CFRP sheets and tested in flexure. Strain gauges were used to monitor the strain at different locations on the CFRP sheet. From this information, strain distribution curves were plotted for different levels of load. After the initial experimental investigation was completed, more specimens were tested to verify results. These specimens were conducted to address the effects of the width of sheet, 0º/90º wrapping technique, and surface preparation.

The failure mode for all of the specimens in the initial investigation resulted from peeling of the CFRP sheet. However, some of the specimens in the verification stage failed by fiber rupture. It was found that the bonded length did not have an effect on the bond strength due to the existence of an effective bonded length. The effective bonded length is defined as the length of sheet that contributes to the bond strength. The concrete strength also did not affect the bond, as the peeling failure occurred in the concrete-epoxy interface. The number of plies (stiffness) of CFRP reinforcement had a considerable influence on the bond. A model was developed based on the stiffness of the CFRP sheet. This model was used to create a design procedure to make sure that the service stress in the CFRP sheet is less than the calculated peeling stress. The width of the sheet was found to have no effect on the bond strength. The 0°/90° wrapping technique and improved surface preparation was found to improve the bond strength to the point where failure occurred by fiber rupture. It was concluded that more experimental evidence is needed to provide a complete answer to the problem. Suggestions were made for future research in order to build on the current study.