Fracture mechanics concepts applied to PVDF polymeric material exhibiting porosity, time and temperature dependency

摘要

The Polyvinylidene fluoride (PVDF) under study is a semi-crystalline polymer that exhibits significant initial porosity and sensitivity on mechanical properties to both strain rate and temperature. A comprehensive experimental database was built in order to analyze the fracture behavior in the ductile to brittle transition domain. Experimental data on smooth and notched specimens were produced at temperature ranging from -50°C to 20°C. They were used to determine temperature dependent material parameters by using the mechanics of porous media. The obtained set of parameters was validated on two kinds of pre-cracked specimens, by using the local approach of fracture mechanics. With the help of a finite element code, both global and local approaches of fracture mechanics were shown to complement one another: whereas classical formulae of J-integral fail to characterize crack initiation for this PVDF, the present methodology allowed the plot of J_(1C) values with respect to temperature.