Fracture of fiber-reinforced cement composites: effects of fiber dispersion

Abstract

Short-fiber reinforcement is commonly used to improve various properties of cement-based materials, including their resistance to shrinkage cracking, post-cracking strength, and toughness. The spatial distribution of fibers within a structural component exhibits local variations that depend on many factors, including the methods of production. Local measures of fiber volume fraction can be much lower than the global average and such regions can act as flaws within the composite material. In addition, fiber orientation is restricted by any near surfaces of the structural component. Such non-uniformities of the fiber distribution can significantly affect fracture behavior and complicate the interpretation of fracture test results. This paper concerns the computational modeling of fiber- reinforced cement composites (FRCC), with attention to the effects of non-uniform fiber distributions. The simulations utilize lattice models of the matrix phase of the composite, based on the Voronoi tessellation of irregularly positioned nodes within the structural domain. A crack band approach provides energy-conserving, mesh-insensitive descriptions of fracture through the irregular lattice. Each fiber is explicitly modeled within the lattice framework. The fiber distributions are synthetically constructed within the structural domain, although experimentally determined fiber positions could be used. Models of simple tensile tests demonstrate a dependence of post-cracking strength and toughness on the spatial distributions of the fibers.