Administration Nationale: Elu/nommé au comité national CNRS

Domaines de Recherche:  Physique/Physique/Dynamique des Fluides
 Physique/Matière Condensée/Matière Molle
 Physique/Mécanique/Mécanique des fluides
 Physique/Mécanique/Mécanique des matériaux
 Sciences de l'ingénieur/Matériaux
 Sciences de l'ingénieur/Mécanique/Mécanique des fluides
 Sciences du Vivant/Sciences agricoles/Agronomie
 Sciences du Vivant/Sciences agricoles/Sciences et techniques de l'agriculture
 Sciences de l'ingénieur/Milieux fluides et réactifs
 Sciences de l'ingénieur/Mécanique
 Chimie/Matériaux
 Physique/Matière Condensée/Science des matériaux
 Sciences de l'ingénieur/Mécanique/Mécanique des matériaux
 Chimie/Polymères
 Physique
 Physique/Matière Condensée/Autre

Dernieres productions scientifiques :


Viscoelasticity and elastocapillarity effects in the impact of drops on a repellent surface
Auteur(s): Charles C.A., Louhichi A., Ramos L., Ligoure C.
(Article) Publié:
Soft Matter, vol. 17 p.5829 (2021)
Texte intégral en Openaccess :
Ref HAL: hal03254324_v1
Ref Arxiv: 2105.09244
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: We investigate freely expanding viscoelastic sheets. The sheets are produced by the impact of drops on a quartz plate covered with a thin layer of liquid nitrogen that suppresses shear viscous dissipation as a result of the cold Leidenfrost effect. The time evolution of the sheet is simultaneously recorded from top and side views using highspeed cameras. The investigated viscoelastic fluids are Maxwell fluids, which are characterized by low elastic moduli, and relaxation times that vary over almost two orders of magnitude, thus giving access to a large spectrum of viscoelastic and elastocapillary effects. For the purposes of comparison, Newtonian fluids, with viscosity varying over three orders of magnitude, are also investigated. In this study, $d_{\mathrm{max}}$, the maximal expansion of the sheets, and $t_{\mathrm{max}}$ the time to reach this maximal expansion from the time at impact, are measured as a function of the impact velocity. By using a generalized damped harmonic oscillator model, we rationalize the role of capillarity, bulk elasticity and viscous dissipation in the expansion dynamics of all investigated samples. In the model, the spring constant is a combination of the surface tension and the bulk dynamic elastic modulus. The timevarying damping coefficient is associated to biaxial extensional viscous dissipation and is proportional to the dynamic loss modulus. For all samples, we find that the model reproduces accurately the experimental data for $d_{\mathrm{max}}$ and $t_{\mathrm{max}}$.



Spinning elastic beads: a route for simultaneous measurements of the shear modulus and the interfacial energy of soft materials
Auteur(s): Carbonaro A., ChaguaEncarnacion KennedyNexon, Charles C.A., Phou T., Ligoure C., Mora S., Truzzolillo D.
(Article) Publié:
Soft Matter, vol. 16 p.8412  8421 (2020)
Texte intégral en Openaccess :
Ref HAL: hal02947316_v1
DOI: 10.1039/d0sm01024c
Exporter : BibTex  endNote
Résumé: Large deformations of soft elastic beads spinning at high angular velocity in a denser background fluid are investigated theoretically, numerically, and experimentally using millimetersize polyacrylamide hydrogel particles introduced in a spinning drop tensiometer. We determine the equilibrium shapes of the beads from the competition between the centrifugal force and the restoring elastic and surface forces. Considering the beads as neoHookean up to large deformations, we show that their elastic modulus and surface energy constant can be simultaneously deduced from their equilibrium shape. Also, our results provide further support to the scenario in which surface energy and surface tension coincide for amorphous polymer gels.



Biaxial extensional viscous dissipation in sheets expansion formed by impact of drops of Newtonian and nonNewtonian fluids
Auteur(s): Louhichi A., Charles C.A., Phou T., Vlassopoulos Dimitris, Ramos L., Ligoure C.
(Article) Publié:
Physical Review Fluids, vol. 5 p.053602 (2020)
Texte intégral en Openaccess :
Ref HAL: hal02884674_v1
Ref Arxiv: 2004.04825
DOI: 10.1103/PhysRevFluids.5.053602
WoS: WOS:000530638500002
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: We investigate freely expanding liquid sheets made of either simple Newtonian fluids or solutions of high molecular watersoluble polymer chains. A sheet is produced by the impact of a drop on a quartz plate covered with a thin layer of liquid nitrogen that suppresses shear viscous dissipation thanks to an inverse Leidenfrost effect. The sheet expands radially until reaching a maximum diameter and subsequently recedes. Experiments indicate the presence of two expansion regimes: the capillary regime, where the maximum expansion is controlled by surface tension forces and does not depend on the viscosity, and the viscous regime, where the expansion is reduced with increasing viscosity. In the viscous regime, the sheet expansion for polymeric samples is strongly enhanced as compared to that of Newtonian samples with comparable zeroshear viscosity. We show that data for Newtonian and nonNewtonian fluids collapse on a unique master curve where the maximum expansion factor is plotted against the relevant effective \textit{biaxial extensional} Ohnesorge number that depends on fluid density, surface tension and the biaxial extensional viscosity. For Newtonian fluids, this biaxial extensional viscosity is six times the shear viscosity. By contrast, for the nonNewtonian fluids, a characteristic \textit{Weissenberg number}dependent biaxial extensional viscosity is identified, which is in quantitative agreement with experimental and theoretical results reported in the literature for biaxial extensional flows of polymeric liquids.



Impact of elastic beads and liquid drops on repellent surface :a unified description
Auteur(s): Arora S., Fromental J.M., Mora S., Phou T., Ramos L., Ligoure C.
Conference: Liquids@nterface (Bordeaux, FR, 20181022)
Ref HAL: hal01938934_v1
Exporter : BibTex  endNote
Résumé: We investigate freely expanding sheets formed by ultrasoft gel beads, and liquid and viscoelastic drops, produced by the impact of the bead or drop on a silicon wafer covered with a thin layer of liquid nitrogen that suppresses viscous dissipation thanks to an inverse Leidenfrost effect. Our experiments show a unified behavior for the impact dynamics that holds for solids, liquids, and viscoelastic fluids and that we rationalize by properly taking into account elastocapillary effects. In this framework, the classical impact dynamics of solids and liquids, as far as viscous dissipation is negligible, appears as the asymptotic limits of a universal theoretical description. A novel materialdependent characteristic velocity that includes both capillary and bulk elasticity emerges from this unified description of the physics of impact.



Keynote lecture: Fracture propagation in polymeric transient networks
Auteur(s): Ligoure C.
Conférence invité: Annual European Rheology Conference (AERC) 2018 (Sorrente, IT, 20180417)
Ref HAL: hal01779573_v1
Exporter : BibTex  endNote
Résumé: We investigate the fracture nucleation and propagation of reversible double transient networks, constituted of water solutions of entangled surfactant wormlike micelles reversibly linked by various amounts of telechelic polymers thus producing transient double
networks when the micelles are sufficiently long and entangled. Two different geometries of fracture are considered: (i) For a filament stretching geometry, we provide a state diagram that delineates the regime of fracture without necking of the filament from the regime where no fracture or breakup has been observed. We show that filaments fracture when stretched at a rate larger than the inverse of the slowest relaxation time of the networks. We quantitatively demonstrate that dissipation processes are not relevant in our experimental conditions and that, depending on the density of nodes in the networks, fracture occurs in the linear viscoelastic regime or in a nonlinear regime. In addition, analysis of the crack opening profiles indicates deviations from a parabolic shape close to the crack tip for weakly connected networks. We demonstrate a direct correlation between the amplitude of the deviation from the parabolic shape and the amount of nonlinear viscoelasticity [1].(ii) For a HeleShaw cell geometry based on the injection of a low viscosity fluid into the viscoelastic material confined between two plates, we show
that cracks nucleate when the sample deformation rate involved is
comparable to the inverse of the shortest relaxation time scale of the networks. For a double network, significant rearrangements of the micelles occur as a crack nucleates and propagates. We show that birefringence develops at the crack tip over a finite length, ξ, which corresponds to the length scale over which micelle alignment occurs. We find that ξ is larger for slower cracks, suggesting an increase of ductility.

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