3.2. Modeling
In this section, a phenomenological constitutive model for polytetrafluoroethylene in tensile loading is introduced. The proposed mathematical model is divided into two parts: the first part is defined by a true strain range varying from 0 to ɛ∗, while the second one is taken for true strain value larger than ɛ∗.
In order to find an adequate expression to model the mechanical behavior of PTFE under tensile loading performed at different strain rates, the following mathematical model is proposed,