A numerical study on the effect of the interface material model on the tensile behaviour of FRCM strips

Fibre Reinforced Cementitious Matrix (FRCM) composites are becoming increasingly popular for strengthening masonry structures for which the compatibility of the inorganic matrix with the chemical and physical properties of the support makes it advantageous to adopt such systems. However, despite the large use of FRCMs for strengthening applications, the characterization and modelling of the mechanical response in tension of these systems is an open issue. In fact, the constitutive tensile law of the composite shows to be affected by different variables, such as the clamping system adopted during tensile test, the gauge length used for recording strains, the number of yarns and the planarity of the textile within the composite thickness. In addition to these parameters, which influence the experimental tensile characterization, few information is available on the constitutive law that rules the fibre-matrix interface, which is essential for evaluating the load transfer during the post-crack stage of the composite, as already shown in the literature. For these reasons, the studies that provide indications on analytical or numerical modeling of the tensile behaviour of FRCM materials are still limited. This study presents the results of a series of FE numerical simulations, aimed at evaluating the tensile behaviour of FRCM composites. The elaborations are carried out through an appropriate definition of the sliding laws between the components (fibres and mortar) and a parametric analysis is performed by varying the type of fibre, the mechanical characteristics of the mortar and the interface bond law. The purpose of the study is to provide indications on the modeling of the tensile response of FRCMs, with particular regards to the evaluation of the fibrematrix interface behaviour. The numerical results are validated through comparison with some experimental data selected from the literature. The performed analyses allow evaluating the influence of the selected parameters and obtaining a qualitative comparison on the mechanical performances of different types of reinforcement in terms of maximum tensile strength and ultimate strain.