A model long-discontinuous-fiber filled thermoplastic melt in extensional flow |
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| Affiliation: | 1. Laboratory of Thermodynamics of Solutions of Non-electrolytes and Biologically Active Substances, Krestov Institute of Solution Chemistry, Russian Academy of Sciences, 1 Akademicheskaya Str., 153045 Ivanovo, Russian Federation;2. United Physicochemical Center of Solution, Krestov Institute of Solution Chemistry, Russian Academy of Sciences, 1 Akademicheskaya Str., 153045 Ivanovo, Russian Federation;3. Department of Inorganic Chemistry, Ivanovo State University of Chemistry and Technology, 7 Sheremetevsky Ave., 153000 Ivanovo, Russian Federation;1. Department of Bioproducts and Biosystems, Aalto University School of Chemical Engineering, P.O. Box 16300, 00076 Aalto, Finland;2. Product Design and Perception, Research Institutes of Sweden, P.O. Box 5401, 40229 Gothenburg, Sweden;3. Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, 00076 Aalto, Finland;1. School of Textile and Material Engineering, Dalian Polytechnic University, Dalian 116034, PR China;2. Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI 53715, USA;3. State Key Laboratory of Structural Analysis of Industrial Equipment, Dalian University of Technology, Dalian, Liaoning 116023, PR China;4. Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA;1. State Key Laboratory of Fluid Power and Mechatronic System, School of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China;2. Key Laboratory of Advanced Manufacturing Technology of Zhejiang Province, School of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China |
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| Abstract: | The shear cell model works for dilute fiber filled systems in extensional flow. This research investigates the suitability of the idea for highly aligned fibers in a concentrated suspension. A model fiber-filled polymer system made from nylon fibers in low-density polyethylene provided a means of controlling the material parameters. Two systems, with fiber aspect ratios of 20 and 100, containing 50% 0.5 mm fibers by volume are investigated. The thickness of the polymer layer, i.e. with fibers this size, allows bulk viscosity data to be compared with the data from the filled fluid. A weaving process created the discontinuous fiber/polyethylene preforms with high alignment of the fibers and with control of the fiber to fiber overlap. Testing the polyethylene in simple shear and extending the nylon/polyethylene provided the data needed to check the micro mechanics. A cone and plate rheometer and a capillary instrument produced the viscosity/strain rate data that characterized the specific polyethylene used in the composite. A furnace inset placed in an Instron hydraulic test machine allowed extension of the filled system at strain rates from 0.002 to 0.4 s−1. The shear experiments show that the low-density polyethylene is a simple shear-thinning melt that provides a good model fluid. The extension of the filled systems shows an increase of the apparent extensional viscosity from that of neat polyethylene. Apparent viscosity rises two to three orders of magnitude for the systems investigated. The micromechanics allowed the conversion of the extensional data from the two filled systems to the shear viscosity of the polymer surrounding the fibers. The calculated polyethylene viscosity compares well with the data from the standard rheometers. The shear cell approach may be applied to highly aligned, high fiber-volume-fraction suspensions when the viscosity of the polymer is known at the scale of the film surrounding each fiber. |
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