Fracture modeling of fiber reinforced concrete in a multiscale approach

Abstract

This paper proposes numerical models for the study of fracture of fiber reinforced concrete. The composite material behavior is described at the macroscale and at the mesoscale. The macroscale model considers homogeneous equivalent continuum properties taken from experimental curves of the composite. In order to reproduce the effect of the random distribution of steel fibers within the cementitious matrix, random values of equivalent elasticity modulus and equivalent tensile strength are assigned to solid and cohesive elements, respectively. The mesoscale model represents the fiber explicitly inside the concrete matrix through cohesive interface elements with steel properties. In this case, fibers are located and oriented randomly in the matrix. In addition, to allow matrix fracture, cohesive elements with softening constitutive behavior are placed at the edges of the solid elements in the meso and macroscale models. The numerical models were applied to the simulation of a direct tensile laboratory test for a steel fiber reinforced concrete. The macroscale model uses probability functions to define the mechanical properties for each element. The predicted fracture paths and load capacity present satisfactory results when compared to those obtained experimentally. In the mesoscale model, distinct mechanical properties are applied for the steel fibers and for the cementitious matrix. The results from the mesoscale approach reinforce the concept that fiber dispersion and orientation affect the structural load capacity and matrix brittleness. In addition, cohesive interface elements proved to be an attractive approach to predict fracture propagation in the composite material.