Multiscale Mechanics of Softs Solids – Fracture of biopolymer hydrogels

 

Hydrogels, composed essentially of solvent, are soft elastic materials in which the propagation of a fracture requireslarge deformations: the crack head is very blunt. It is therefore particularly easy to visualize its propagation.

Caption: Open crack growing from right to left in a gelatin gel.

Crack propagation in mixed mode

A crack subjected to mechanical loading containing simultaneously opening (mode I) and shear (mode II) deformationsleads to the deflection of the fracture. The prediction of the path followed by a crack under these conditions remains an open problem in fracture mechanics. We quantitatively study the evolution of the deformation field during fracture propagation in soft hydrogels.

 

Mechanical properties of hybrid gels

Hydrogels are naturally not very resistant to fracture. A reinforcement strategy consists in cross-linking the polymerchains in a thermo-reversible (dissipative sacrificial bonds) and covalent (brittle bonds but ensuring a distribution of the mechanical load) manner. With gelatin, we have a model system allowing to optimize the fraction of covalent bonds (obtained by enzymatic way). We study the mechanical properties of your hybrid gels up to rupture.

 

Main collaboration

• CY Hui : Department of Engineeering, Cornell University (USA)

 

Publications

• H. Souguir, O. Ronsin, C. Caroli, Tristan Baumberger. Two-step build-up of a thermoreversible polymer network: From early local to late collective dynamics. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, American Physical Society, 2015, 91 (4), pp.042305. https://hal.archives-ouvertes.fr/hal-01239400
• I. Naassaoui, O. Ronsin and T. Baumberger. A poroelastic signature of the dry/wet state of a crack tip propagating steadily in a physical hydrogel, Extreme Mechanics Letters, 2018, 22, 8. https://www.sciencedirect.com/science/article/pii/S2352431618300403
• O. Ronsin, I. Naassaoui, A. Marcellan, T. Baumberger. Environmental Nanoparticle-Induced Toughening and Pinning of a Growing Crack in a Biopolymer Hydrogel. Physical Review Letters, American Physical Society, 2019, 123 (15), pp.158002. https://hal.sorbonne-universite.fr/hal-02498100v1
• T. Baumberger, & O. Ronsin (2020). Environmental control of crack propagation in polymer hydrogels. Mechanics of Soft Materials, 2020, 2(1), 1-38. https://link.springer.com/article/10.1007/s42558-020-00027-2