Leader : Peters François
External Collaborators : Ausias Gilles (Laboratoire d’Ingénierie des MATériaux de Bretagne (LITMATB))
PhD students/Post-doctoral fellows : Bounoua Nahed Sihem
Soutiens financiers : Soon available...
Technological platforms : Center for Micro & Nanorheometry
Due to their high shape anisotropy, fibres have been found to considerably increase the mechanical properties of various composite materials such as fibre-reinforced plastics or carbon nanotube composites. The enhancement of the mechanical properties is very sensitive to the fibre orientation distribution. Thus to improve plastic composite processing, it is highly desirable to predict both the rheological behaviour of the involved suspension and the fibre orientation. These problems are complex since there exists a strong coupling between the flow, the fibre orientation and the interactions between fibres. Only few experimental results are reported on the orientation distribution of fibres in concentrated regimes and they suffer from numerous sources of uncertainty. Furthermore, the viscosity of fibre suspensions is difficult to measure through macroscopic rheometric experiments since several artefacts such as shear-induced migration or strong edge effects are expected to take place.
We carry out experiments to obtain accurate and reliable information on viscosity, normal stresses and the microstructure of a concentrated suspension of fibres. In particular shear reversal experiments provide important information about the coupling between fibre orientation and viscosity. Indeed,when the shear flow is reversed, the viscosity of a suspension of fibres increases to a maximum where the fibres would be oriented with an angle of 45° relative to the velocity direction, then, it decreases to the value it had before the inversion of the direction of flow. The other experiments consist in measuring more precisely than what is done in conventional rheometry the normal stress differences and the particle normal stresses (see project Suspension rheology and shear-induced migration).
At last, we aim to measure directly the fibre orientation using a device that has been developed in order to measure the microstructure in non-Brownian concentrated suspensions (see project Local rheology of concentrated suspensions).
Fluides & Matériaux Complexes, Rhéologie des Suspensions
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