Experimental and analytical studies on peeling and spalling resistance of unidirectional FRP sheets bonded to concrete

In this paper, the peeling and spalling resistance of unidirectional fiber reinforced polymer (FRP) sheets externally bonded to concrete surface are investigated experimentally through a series of peeling tests. A peeling load is applied on the FRP sheet by a circular rod placed into the central notch of the beam. The effects of different FRP composites, adhesives, surface treatments and strength of concrete on peeling behavior are investigated. Three different modes of debonding failure are identified: debonding within concrete surface, debonding in concrete-adhesive interface, and debonding in FRP composites-adhesive interface. It is observed that the failure pattern debonding within concrete layer yields a higher peeling load carrying capacity. Moreover, a typical failure due to the FRP rupture is also observed experimentally. Based on the experimental results, a theoretical analysis is conducted on specimens representing the peeling behavior and spalling resistance. Load carrying capacity is expressed as the function of peel angle based on geometrical analysis and equilibrium of forces between FRP sheets and the circular rod. Interfacial fracture energy is calculated analytically using membrane-peeling method. Finally, a close agreement between the predicted and the experimental results is demonstrated by means of some numerical examples.