Visco- and plasto-elastic fracture of nano-porous polymer sheets

TL;DR

This study investigates the fracture surface energy dependence on pulling velocity in nano-porous polypropylene sheets, identifying static and dynamic components as plastoelastic and viscoelastic, suggesting a universal fracture mechanism for porous polymers.

Contribution

It introduces a unified interpretation of fracture energy components in nano-porous polymers, extending previous findings from polyethylene to polypropylene.

Findings

Identified static and dynamic components of fracture energy.

Proposed a universal physical mechanism for porous polymer fracture.

Discussed the equivalence of Griffith's energy balance to a stress criterion.

Abstract

We study the dependence of the fracture surface energy on the pulling velocity for nano-porous polypropylene (PP) sheets to find two components: the static and dynamic ones. We show that these terms can be interpreted respectively as plastoelastic and viscoelastic components, as has been shown for soft polyethylene (PE) foams in a previous work. Considering significant differences in the pore size, volume fraction and Young's modulus of the present PP and previous PE sheets, the present results suggest a universal physical mechanism for fracture of porous polymer sheets. The simple physical interpretation emerging from the mechanism could be useful for developing tough polymers. Equivalence of Griffith's energy balance in fracture mechanics to a stress criterion is also discussed and demonstrated using the present experimental data.