Analytical Description of the Bond Behavior of Thermally Preconditioned Carbon FRCM Applied onto Masonry Substrates

In the last few years, externally bonded fabric-reinforced cementitious matrix (FRCM) composites have been increasingly employed as externally bonded (EB) reinforcement of existing concrete and masonry structures. Failure of EB FRCM reinforcement is generally caused by composite debonding at the matrix-fiber interface. The stress transfer mechanism at the joint interface is analytically described within the fracture mechanics framework assuming a pure Mode-II loading condition and a zero-thickness interface, which allows for formulating the bond differential equation. Its solution requires the knowledge of the cohesive material law (CML) of the specific interface studied, often obtained by calibration of direct shear (DS) test results. In this paper, a rigid-trilinear CML is used to analytically describe the bond behavior of four control and four thermally preconditioned carbon FRCM-masonry joints subjected to single-lap direct shear test. Thermal preconditioning consists of 250-min-long exposure up to 300 ℃. Stress responses obtained from the DS tests are used to calibrate the CML of the matrix-fiber interface, which is then used to solve the bond differential equation. Comparison between the analytical and experimental stress responses of control and conditioned specimens sheds light on the effect of temperature exposure on the bond behavior of carbon FRCM-masonry joints.