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SUMMARY:Science in food: rheology\, yielding and strain stiffening in enta
 ngled assemblies of chains - from spaghetti to polymers  - Mehdi Habibi - 
 Laboratory of Physics and Physical Chemistry of Foods\, Wageningen Univers
 ity\, The Netherlands
DTSTART:20251112T154500Z
DTEND:20251112T164500Z
UID:TALK240277@talks.cam.ac.uk
CONTACT:Ian Wilson
DESCRIPTION:Macroscale chains have been proposed to provide insight into t
 he physics of molecular polymer systems and have been suggested as a parad
 igm for understanding physics at the molecular scale. Nevertheless\, under
 standing the rheological response of systems composed of quasi-one-dimensi
 onal semiflexible materials\, such as spaghetti\, remains a significant ch
 allenge. We study the nonlinear rheology of random assemblies of macroscal
 e chains\, including steel bead chains and cooked spaghetti\, under oscill
 atory shear. We show that a universal transition from localized to wide sh
 ear zones occurs upon increasing the strain amplitude\, across a wide rang
 e of lengths\, flexibilities\, and other structural parameters of the cons
 tituent elements. The critical strain amplitude coincides with the onset o
 f strain stiffening in the system. We derive scaling laws for transition s
 harpness\, shear-zone width\, and stiffness enhancement as functions of ch
 ain length. Our findings suggest that the entanglements between the consti
 tuent elements strengthen when approaching the critical strain amplitude a
 nd rapidly become long-range\, even spanning the entire finite system for 
 sufficiently long chains. We demonstrate that the nonlinear rheological re
 sponse is governed by the interplay between increasing stored elastic forc
 es due to entanglements and the increasing contribution of dissipation wit
 h shear rate and interlocking between chains. Our results highlight both t
 he differences and similarities between the physics of macroscale chains a
 nd molecular polymer systems.
LOCATION:Lecture Theatre 1\, Department of Chemical Engineering and Biotec
 hnology\, West Cambridge Site
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