  The mechanical behaviour of many materials, including polymers or natural
materials, significantly depends on the rate of deformation. As a consequence,
a rate-dependent ductile-to-brittle fracture transition may be observed. For
toffee-like caramel, this effect is particularly pronounced. At room
temperature, this confectionery may be extensively deformed at low strain
rates, while it can behave highly brittle when the rate of deformation is
raised. Likewise, the material behaviour does significantly depend on
temperature, and even a slight cooling may cause a significant embrittlement.
  In this work, a thorough experimental investigation of the rate-dependent
deformation and fracture behaviour is presented. In addition, the influence of
temperature on the material response is studied. The experimental results form
the basis for a phase-field modelling of fracture. In order to derive the
governing equations of the model, an incremental variational principle is
introduced. By means of the validated model, an analysis of the experimentally
observed ductile-to-brittle fracture transition is performed. In particular,
the coupling between the highly dissipative deformation behaviour of the bulk
material and the rate-dependent fracture resistance is discussed.
