Time-dependent effective behavior of jointed materials

Resumo

Inspections carried out on materials used in engineering often reveal the presence of discontinuities in
different shapes and scales. Discontinuities are one of the main forms of physical-mechanical degradation of the
material’s properties. More specifically, joints are a particular type of discontinuity whose geometry is plane and
have the mechanical capacity to transfer efforts along their opposite faces. Most works that aim to determine the
properties of jointed materials tend to neglect differed deformation components, which are fundamental in several
engineering fields. In this context, this work aims to propose a constitutive law that describes the effective behavior
of viscoelastic jointed materials, without disregard aging effects. Backed by laboratory tests, the joints are modeled
as interfaces whose mechanical behavior relates the stress vector to the displacement jumps on the joint’s faces.
Coupling the viscoelastic behavior of the constituents (solid matrix and joints) to micromechanical relationships,
the homogenized creep tensor was analytically formulated, being written as the creep tensor of the solid matrix
added to a fourth-order tensor related to the joints’ properties. Classic cases of rock mechanics are derived, which
show that particular distributions of joints families can cause anisotropy in the effective behavior of the material.