Peel and Shear Fracture Characterization of Debonding in FRP Plated Concrete Affected by Moisture

The objective of this paper is to develop a new mechanistic understanding of moisture affected debonding failures in carbon fiber reinforced polymer (CFRP) plated concrete systems by mechanically testing accelerated moisture conditioned mesoscale peel and shear interface fracture specimens. Central to the investigation is the use of interface fracture toughness as the quantification parameter of the CFRP-epoxy-concrete trilayer system, which is considered a bond property, to analyze, compare, and correlate physical observations. Results have shown that fracture toughness of the CFRP bonded concrete systems significantly degrades, and its value becomes asymptotic with increasing moisture ingress. This asymptotic behavior is associated with certain moisture concentration levels as predicted by a three-dimensional moisture diffusion simulation. The generally observed debonding mode by concrete delamination for the dry specimens changes to an epoxy/concrete interface separation mode for the wet specimens. Finite element fracture computation, mixed-mode characterization, and kink criterion implementation synergistically suggest that the interface separation mode is attributed to an interfacial material toughening and an interface weakening mechanism as a consequence of moisture diffusion.