CFRP sheets bonded to natural stone: interfacial phenomena

The effectiveness of the reinforcing technique consisting of fiber reinforced polymer sheets bonded to the structural elements depends on a good connection at the joint. This has to be able to ensure the transfer length of the shear stress in order to avoid a premature failure due to debonding. In this paper, the bond phenomenon at the interface is examined with reference to the calcarenite stone and carbon fiber reinforced polymer (CFRP) sheets in order to evaluate the possibility of utilizing this technique on masonry structural members, consisting of calcarenite ashlars and mortar. An experimental investigation is carried out on nine specimens obtained by applying unidirectional CFRP sheets to calcarenite squared-stone by using epoxy resin layers. All specimens were submitted to tensile force until the failure of the bond joint took place. Results allow us to deduce the local bond stress versus slip relationship, which is an important step toward understanding bond behavior at the joint interface.