- Role of Normal Stress in the Creep Dynamics and Failure of a Biopolymer Gel doi link

Auteur(s): Pommella A., Cipelletti L., Ramos L.(Corresp.)

(Article) Publié: Physical Review Letters, vol. 125 p.268006 (2020)
Texte intégral en Openaccess : arxiv

Ref HAL: hal-03139495_v1
DOI: 10.1103/PhysRevLett.125.268006
WoS: WOS:000604249900023
Exporter : BibTex | endNote

We investigate the delayed rupture of biopolymer gels under a constant shear load by simultaneous dynamic light scattering and rheology measurements. We unveil the crucial role of normal stresses built up during gelation: All samples that eventually fracture self-weaken during the gelation process, as revealed by a partial relaxation of the normal stress concomitant to a burst of microscopic plastic rearrangements.Upon applying a shear stress, weakened gels exhibit in the creep regime distinctive signatures in their microscopic dynamics, which anticipate macroscopic fracture by up to thousands of seconds. The dynamics in fracturing gels are faster than those of nonfracturing gels and exhibit large spatiotemporal fluctuations. A spatially localized region with significant plasticity eventually nucleates, expands progressively, and finally invades the whole sample, triggering macroscopic failure.