Fracture of a biopolymer gel as a viscoplastic disentanglement process

TL;DR

This study investigates the slow crack propagation in gelatin gels, confirming a model where fracture occurs via viscoplastic chain pull-out rather than chain scission, highlighting differences from chemically cross-linked gels.

Contribution

The paper extends the viscoplastic disentanglement model for fracture in physical hydrogels, supported by extensive experimental data on gelatin gels.

Findings

Fracture involves viscoplastic pull-out of chains, not chain scission.

Gel stiffness sensitivity confirms the model.

Reversible gels fracture without breaking chains.

Abstract

We present an extensive experimental study of mode-I, steady, slow crack dynamics in gelatin gels. Taking advantage of the sensitivity of the elastic stiffness to gel composition and history we confirm and extend the model for fracture of physical hydrogels which we proposed in a previous paper (Nature Materials, doi:10.1038/nmat1666 (2006)), which attributes decohesion to the viscoplastic pull-out of the network-constituting chains. So, we propose that, in contrast with chemically cross-linked ones, reversible gels fracture without chain scission.