1st Place, 86th Annual Meeting, Oct 2014, Philadelphia - Giovanniantonio Natale
1st Place, 86th Annual Meeting, Oct 2014, Philadelphia
Modeling interactions in carbon nanotube suspensions: Transient flows Giovanniantonio Natale1, Julien Ferec2, Gilles Ausias2, Marie-Claude Heuzey1, and Pierre J. Carreau1
1Chemical Engineering, École Polytechnique de Montréal, Montréal, Québec, Canada; 2Mechanical Engineering, Université de Bretagne du Sud, Lorient, France
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)
Author and Affiliation Lines (in printed abstract book)
Giovanniantonio Natale1, Julien Ferec2, Gilles Ausias2, Marie-Claude Heuzey1, and Pierre J. Carreau1
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.