Dynamic fracture and catastrophic crack branching in highly entangled hydrogels.

Dynamic fracture toughness in highly entangled hydrogels can be significantly lower than static toughness, with cracks reaching near shear-wave speeds and exhibiting unconventional branching.

• Why it matters: Understanding how soft materials fail under dynamic conditions is crucial for designing more durable devices and structures, yet the mechanisms of crack propagation and energy dissipation remain poorly understood.
• What they did: The study systematically varied network and loading parameters in highly entangled polymer hydrogels, developing a shear-lag model to analyze viscous dissipation and fracture behavior at different strain rates and solvent viscosities.
• The result: Localized viscous dissipation at the crack tip governs fracture dynamics, with the fracture energy inversely related to a Weissenberg-like number, offering insights for enhancing failure resistance in soft, elastic materials.