Fracture characterization of hyperelastic polyacrylamide hydrogels

This work aims at investigating the fracture behaviour of polyacrylamide hydrogels, which have been chosen for their ideal hyperelastic response and their widespread engineering and biomedical applications. The applicability of the energy separation principle to this class of hydrogels is analysed. This principle allows identifying the fracture initiation without visual monitoring of the specimen and to calibrate the geometry factor required to estimate the fracture toughness. Such innovative approach is compared to established methods: (i) single specimen methods, based on the determination of the energy release rate, for the calculation of fracture toughness; (ii) a multi-specimen methodology for the calibration of the geometry factor. Results show that the energy separation principle is valid for this class of hydrogels, and it can provide a toughness parameter corresponding to a small crack advancement.