  Soft materials including elastomers and gels are pervasive in biological
systems and technological applications. Whereas it is known that intrinsic
fracture energies of soft materials are relatively low, how the intrinsic
fracture energy cooperates with mechanical dissipation in process zone to give
high fracture toughness of soft materials is not well understood. In addition,
it is still challenging to predict fracture energies and crack-tip strain
fields of soft tough materials. Here, we report a scaling theory that accounts
for synergistic effects of intrinsic fracture energies and dissipation on the
toughening of soft materials. We then develop a coupled cohesive-zone and
Mullins-effect model capable of quantitatively predicting fracture energies of
soft tough materials and strain fields around crack tips in soft materials
under large deformation. The theory and model are quantitatively validated by
experiments on fracture of soft tough materials under large deformations. We
further provide a general toughening diagram that can guide the design of new
soft tough materials.
