Non-linear analytical model for FRCM coupons in tension

Externally bonded FRCM (Fiber Reinforced Cementitious Matrix) materials are nowadays quite diffused to reinforce existing structures: taking as reference FRP (Fiber Reinforced Polymer), the replacement of an organic matrix with mortar is more compatible with masonry substrates, and the reversibility of the reinforcement is more appealing for the architectural heritage conservation. At the same time, due to the low strength of the mortar layers, complex failure mechanisms are observed for FRCMs, which still need comprehensive theoretical investigations. Indeed, not only the mortar-fiber interface may behave non-linearly, but also the mortar may crack and affect the overall behavior. The tensile test on coupons is commonly used as a direct approach to characterize the properties of the reinforcing package, and there is a wide consensus on approximating the global behavior with a trilinear law; however, the different test set-ups and the inhomogeneity of the material itself bring about large dispersion of the experimental results. This paper aims at proposing a simplified analytical model to consider the damage mechanisms in FRCM coupons in tension, including interface slippage, mortar cracking, and their simultaneous occurrence. The accuracy of the model is then verified by comparing the results with experimental data. The conditions under which such failure mechanisms occur and the effects of material properties are also investigated with a view to complement the understanding of experimental observations from a theoretical perspective.