Failure modes of sheet bonded fiber reinforced polymer applied to brick masonry

CFRP reinforcement sheets are proposed as reinforcement for unreinforced brick masonry subjected to out of plane loads. The investigation consisted of testing unidirectional sheet bonded carbon fiber as a reinforcing material for brick masonry prisms. Two types of brick and FRP materials were utilized in these experiments. The masonry materials exhibited high and low porosity, indicated by initial rate of absorption tests, while high and low modulus FRP materials were used. Strain gauge and full field photoelastic strain analysis was conducted to obtain a record of the strain transfer from the FRP to the masonry. From this analysis, a finite element model was then constructed to predict the mode and magnitude of failure. Results indicate that shear failure of the brick or debonding of the FRP were the general failure modes of the composite specimens tested. When comparing the results of different brick types, it is seen that, in the molded brick, the failure mode was shear failure of the brick at the end of the FRP reinforcement. In these specimens, it is clearly seen in the photoelastic strain results that strain transfer into the brick occurred in an area adjacent to the FRP. Failure in the extruded brick specimens was governed by the debonding of the FRP at the interface with the prism. It is conjectured that the viscosity of the epoxy and the porosity of the brick, characterized by initial rate of absorption tests, directly affect the bond of the composite structure and, therefore, the failure mode. Photoelastic results reveal that strain transfer does occur at high loads when the FRP remains bonded to the masonry. A linearly elastic finite element model was generated to match the experimental results and predict the failure mode for future design purposes. This model can be used for various configurations of FRP in the future.