3D real time and in situ observation of the fibre orientation during the plane strain flow of concentrated fibre suspensions
Résumé
Short-fibre reinforced polymer composites are increasingly used as structural or functional components in many engineering fields. To obtain high-performance composite materials, the polymer matrices are reinforced with high fibre contents (>20–50 wt%). Hence, during their forming, the composites behave as concentrated fibre suspensions that exhibit a non-Newtonian rheology. In addition, their end-use properties depend on the fibre orientation which drastically evolves during the forming operations. Within this context, it is crucial to analyse the induced microstructure changes in flowing concentrated fibre suspensions. For that purpose, 3D in situ compression experiments were performed on model non-Newtonian concentrated fibre suspensions that were imaged using fast X-ray synchrotron microtomography. At the fibre scale, large fluctuations in the translation and rotation of the fibres were observed during compression. These fluctuations were shown to be on the same order of magnitude than the mean fields. They can be attributed to long-range hydrodynamic interactions between neighbouring fibres as well as to short-range interactions induced by the numerous fibre-fibre contacts which practically follow trends predicted by the tube model. Surprisingly, in spite of the chaotic kinematics of the fibres, the macroscopic deformation of the suspension was homogeneous and the flow-induced evolution of fibre orientation was found to be well described by the averaged Jeffery's equation (related to the second order orientation tensor).
Origine | Fichiers produits par l'(les) auteur(s) |
---|