Effect of matrix type, coating, and test setup on bond behavior of glass-fiber-based FRCM systems

This study considers a comprehensive characterization campaign on six fiber reinforced cementitious matrix (FRCM) systems, all using the same glass-fiber textile (dry or epoxy-coated) combined with lime-, gypsum-, and cement-based matrices. In addition to the mechanical and physical characterization of the constituent materials, single-lap shear tests and textile pull-out tests were performed and compared. The main objective of this paper is to observe to what extent mortar matrix properties and fiber coating affect fiber–matrix bond in asymmetric and symmetric test setups. For this reason, an analytical model was employed to calibrate the Cohesive Material Laws (CML). Findings highlight the significant role that mortar granulometry, elasticity moduli, and tensile strength had on the global behavior and on the CMLs. As expected, the epoxy coating increased peak bond strength but shifted the failure mode from pseudo-ductile to brittle, and the test setup influenced both the global and local behavior. The test setup influenced the CMLs related to lime- and cement-based mortars, with coarser granulometries and higher elasticity modulus in tension and in compression, more significantly than the CML related to the gypsum matrix. This outcome suggests that the mortar characteristics not only affect the behavior of a composite system but also affect its response under different boundary conditions, leading to the difficulty of retrieving a CML that should remain constant regardless of the test employed. For these reasons, a model capable of accounting for the mortar characteristics and the test setups should be implemented in future work.