Paper Number
PO87 

Session
Poster Session

Title
Modeling interactions in carbon nanotube suspensions: Transient flows

Presentation Date and Time
October 8, 2014 (Wednesday) 6:05

Track / Room
Poster Session / Poster

Authors (Click on name to view author profile)

1. Natale, Giovanniantonio (École Polytechnique de Montréal, Chemical Engineering)
2. Ferec, Julien (Université de Bretagne du Sud, Mechanical Engineering)
3. Ausias, Gilles (Université de Bretagne du Sud, Mechanical Engineering)
4. Heuzey, Marie-Claude (École Polytechnique de Montréal, Chemical Engineering)
5. Carreau, Pierre J. (École Polytechnique de Montréal, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Giovanniantonio Natale¹, Julien Ferec², Gilles Ausias², Marie-Claude Heuzey¹, and Pierre J. Carreau^1
1Chemical Engineering, École Polytechnique de Montréal, Montréal, Québec, Canada; ²Mechanical Engineering, Université de Bretagne du Sud, Lorient, France

Speaker / Presenter 
Natale, Giovanniantonio

Text of Abstract
Transient flow data of untreated CNTs dispersed in a Newtonian epoxy matrix have been analyzed. A sequence of shearing and rest steps was applied to characterize the transient responses of the suspensions. Stress overshoots appeared at very small deformations during forward and reverse flow measurements, and their intensity increased with rest time between two consecutive flows, during which the suspensions structure was reconstructed. The transient behavior of the CNT suspensions is explained with the help of a recently proposed model¹. The CNTs are described as rigid rods dispersed in a Newtonian matrix and the evolution of the system is controlled by hydrodynamic, rod-rod interactions and Brownian motion. Flexibility is here neglected since the interactions are assumed to play a more important role for these concentrated suspensions. The force due to the interactions is modelled as a non-linear lubrication force, which is a function of the relative velocity at the contact point, and is weighted according to the contact probability. The total stress tensor is evaluated calculating the well-known fourth order orientation tensor and a new fourth order interaction tensor. The Fokker-Planck equation is numerically solved for simple shear flows using a finite volume method avoiding the need of closure approximations. The model predictions show that the overshoots are mainly due to interactions between rods and for the first time, the effect of shear rate is directly accounted by the model.

1. Natale G, Heuzey MC, Carreau PJ, Ausias G, Férec J. Rheological modeling of carbon nanotube suspensions with rod–rod interactions. AIChE Journal. 2014;60(4):1476-1487.