Asymmetric Interfacial Behavior of FRCM Systems Subjected to the Single-Lap Shear Test

Abstract The single-lap shear test is the most representative method for characterizing fabric-reinforced cementitious matrix (FRCM) systems under standard service conditions, as it tackles the interaction between the textile reinforcement and the matrix for a specific substrate. Owing to its inherently asymmetric configuration, the slip and the shear stress at the external interface are lower than that at the internal one. To account for this feature, the model defines two distinct textile–matrix shear stress–slip relationships that represent the bond behaviors caused by different boundary conditions on mortar layers. The model considers rigid mortar, does not prescribe a ratio between the fracture energies of the two interfaces, as in previous approaches, and semiautomatically back-calibrates the two shear stress–slip relationships by maximizing the fit between the predicted load–slip response and experimental data. The novelty of the model lies in the capacity to describe the asymmetric behavior of the internal and external interfaces, neglecting mortar deformability and keeping the computational cost as low as possible. Model validation is performed using an experimental campaign on six glass FRCM systems with different mortars and textile treatments that was carried out in a previous work by the authors. The results highlight the key roles of mortar granulometry and aggregate skeleton in governing the shear stress distribution along the interfaces during the ascending and softening phases, as well as the interaction between mortar layers. Overall, the model accurately reproduces experimental responses while providing insight into local fracture mechanisms, offering a refined framework for modeling FRCM bond behavior.