# Velocity jump in the crack propagation induced on a semi-crystalline polymer sheet by constant-speed stretching

## TL;DR

This study reports the observation of velocity jumps in crack propagation in semi-crystalline polymer sheets under constant-speed stretching, extending knowledge beyond elastomers and providing physical insights based on recent theories.

## Contribution

It is the first to document velocity jumps in crack propagation in semi-crystalline polymers without a rubbery plateau, using a novel constant-speed stretching test.

## Key findings

- Velocity jumps observed in semi-crystalline polymers.
- Advantages of constant-speed stretching for crack testing.
- Physical interpretation aligns with recent crack velocity theories.

## Abstract

It has long been known for elastomers that the velocity of crack propagation jumps as a function of strain. On the other hand, such a jump has not been reported in the literature for polymers which do not exhibit a rubbery plateau in the storage-modulus plot. Here, we report observation of jumps in crack propagation for semi-crystalline polymer sheets without the rubbery plateau, as a result of pulling the sheets at a constant speed. We discuss the advantages of this crack-propagation test under constant-speed stretching and provide physical interpretation of the velocity jump observed for non-elastomer sheets on the basis of a recently proposed theory for the velocity jump in crack propagation.