Nonlocal damage and interface modeling approach for the micro-scale analysis of FRCM

In this paper, the Fiber Reinforced Cementitious Matrix (FRCM) material is considered as a composite material obtained embedding a fiber grid into the mortar matrix. The mechanical response of the FRCM is, hence, derived through an homogenization procedure for periodic composite materials, considering the nonlinear behavior of the constituents. In particular, the mortar is modeled introducing a nonlocal damage constitutive law, characterized by two different damage parameters, in tension and in compression, and by a plastic response in compression. A linear response is considered for the fiber grid, while the possible decohesion of the fiber from the matrix is accounted for introducing suitable interfaces. The numerical procedure is detailed and implemented in a finite element code. Several numerical applications are presented, investigating the tensile and shear response of the FRCM. For the tensile test, a comparison with experimental evidences is illustrated; moreover, a sensitivity analysis is performed investigating the influence of the nonlocal radius, the fracture energy and the fiber stiffness on the overall tensile response of the FRCM. Then, the shear response is reproduced, remarking the importance of the damage and plasticity in compression. Finally, the effect of the confinement on the shear response of the FRCM is also investigated