  Progressive damage, which eventually leads to failure, is ubiquitous in
biological and synthetic polymers. The simplest case to consider is that of
elastomeric materials, which can undergo large reversible deformations with
negligible rate dependence. In this paper, we develop a theory for modeling
progressive damage and rupture of such materials. We extend the phase-field
method, which is widely used to describe the damage and fracture of brittle
materials, to elastomeric materials undergoing large deformations. A central
feature of our theory is the recognition that the free energy of elastomers is
not entirely entropic in nature---there is also an energetic contribution from
the deformation of the bonds in the chains. It is the energetic part in the
free energy which is the driving force for progressive damage and fracture.
