Abstract :
Irregular lattice models are developed to
simulate fracture of multiphase particulate materials,
such as concrete. The models are composed of rigidbody-
spring elements that break according to simple
rules. A salient feature of the models is the use of Voronoi
diagrams to define the lattice structure and assign
the elastic and fracture properties of the elements. The
material is discretized as a three-phase composite consisting
of a matrix phase, coarse inclusions, and the
matrix-inclusion interfacial zones. Aggregates are randomly
positioned in the domain according to a target
granulometric distribution. A procedure is outlined for
the explicit representation of the surfaces of such heterogeneous
features, including control over the thickness
of thematrix-aggregate interfacial zones. Fracture simulations
are conducted for notched, three-point bend
specimens of concrete, where each phase is assigned locally
brittle fracture properties. The simulation resultsshow both pre- and post-peak behavior that agrees with
experimental findings, at least in a qualitative sense. In
particular, toughening mechanisms form through interaction
of developing cracks with the evolving material
structure. However, the post-peak toughness is largely
underestimated due, in part, to the coarse discretization
of the material and the lack of frictional effects
in the model. For comparison, the same specimen is
analyzed using a homogeneous material model and a
cohesive crack approach, which lumps the various energy
dissipation mechanisms active at finer scales into
a cohesive traction versus separation law.
