In situ experimental investigation of fiber orientation kinetics during uniaxial extensional flow of polymer composites

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The demand for fiber-filled polymers has witnessed a significant upswing in recent years. A comprehensive understanding of the local fiber orientation is imperative to accurately predict the mechanical properties of fiber-filled products. In this study, we experimentally investigated the fiber orientation kinetics in uniaxial extensional flows. For this, we equipped a rheometer with a Sentmanat extensional measurement device and with an optical train that allows us to measure the fiber orientation in situ during uniaxial extension using small angle light scattering. We investigated an experimental system with glass fibers for the suspended phase ( L / D = 8 − 15 ), and for the matrix either low density polyethylene, which shows strain hardening in extension, or linear low density polyethylene, which shows no strain hardening. For these two polymer matrices, the fiber orientation kinetics were investigated as a function of fiber volume fraction ( ϕ = 1 % , 5%, and 10%) and Weissenberg number (by varying the Hencky strain rate, ϵ ˙ H = 0.01 − 1 s − 1 ). We found that all these parameters did not influence the fiber orientation kinetics in uniaxial extension and that these kinetics can be described by a multiparticle model, based on Jeffery’s equation for single particles. Our results show that, in uniaxial extension, fiber orientation is solely determined by the applied strain and that, up to the concentrated regime ( ϕ ≈ D / L ), fiber-fiber interactions do not influence the fiber orientation. The extensional stress growth coefficient of these composites, which is measured simultaneously with the orientation, shows high agreement with Batchelor’s equation for rodlike suspensions.

Originele taal-2Engels
Pagina's (van-tot)171-185
Aantal pagina's15
TijdschriftJournal of Rheology
Nummer van het tijdschrift2
StatusGepubliceerd - 1 mrt. 2024

Bibliografische nota

Publisher Copyright:
© 2024 Author(s).


This research forms part of the research programme of the Dutch Polymer Institute (DPI), Project No. 840, Engineering the rheology ANd processinG-induced structural anisotropy of poLymEr composites with non-Brownian fibrous particles (ANGLE). The authors thank Nippon Electric Glass NL for supplying the short glass fibers, and Rafael Sablong of PTG Eindhoven for the GPC measurements.

Nippon Electric Glass NL
Dutch Polymer Institute (DPI)840


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