Assessment of the viscoelasticity effects on the fracture resistance of polyacrylamide-alginate hydrogels

• Fracture parameters of polyacrylamide-alginate hydrogels were determined using VEFM. • Poroelastic relaxation time was much higher than the duration of fracture tests. • Fracture behaviour from mechanical relaxation response without poroelastic response. • Linear relationship between J-integral and CTOD in reference elastic body. • Cohesive stress similar to tensile strength. Hydrogels are conditioned by viscoelasticity and poroelasticity. This work aims to assess the viscoelastic dissipation on the fracture parameters of polyacrylamide-alginate hydrogels applying the Viscoelastic Fracture Mechanics approach. The viscoelastic and poroelastic contributions were separated and quantified and the analysis of the characteristic times revealed that the poroelastic contribution could be disregarded. The fracture behaviour was obtained using the viscoelastic response once the poroelastic contribution was discounted from the mechanical relaxation response. The viscoelastic dissipation on the fracture parameters was not pronounced, with better fracture resistance the higher the alginate content. A linear relation has been observed between the J-integral and Crack Tip Opening Displacement through a cohesive stress with values similar to the tensile strength.