  A micromechanically motivated phase-field damage model is proposed to
investigate the fracture behaviour in crosslinked polyurethane adhesive. The
crosslinked polyurethane adhesive typically show viscoelastic behaviour with
geometric nonlinearity. The finite-strain viscoelastic behaviour is modelled
using a micromechanical network model considering shorter and longer chain
length distribution. The micromechanical viscoelastic network model also
consider the softening due to breakage/debonding of the short chains with
increase in deformation. The micromechanical model is coupled with the
phase-field damage model to investigate the crack initiation and propagation.
Critical energy release rate is needed as a material property to solve
phase-field equation. The energy release rate is formulated based on the
polymer chain network. The numerical investigation is performed using finite
element method. The force-displacement curves from the numerical analysis and
experiments are compared to validate the proposed material model.
