Kinetik der scherinduzierten und elektrisch induzierten Perkolation in Carbon Nanotubes gefüllten Kunststoffen
Final Report Abstract
Fiber-level simulations together with a resistor network algorithm were used to create microstructures and predict the electrical conductivities of CNT/polymer suspensions. The effects of fiber shape, flexibility, orientation and imposed shear flow on the composite conductivity could be successfully studied with this method. Tunneling resistance of the insulating matrix film between nanotubes was also considered in the simulations. In sheared suspensions, percolation threshold was observed at lower volume fractions than randomly oriented and homogenously distributed suspensions. Increasing aspect ratio and using more curved nanotubes favor the formation of extended aggregates in sheared suspensions which result in conductive network formation and decrease in percolation threshold. Increasing shear rates cause destruction of the connected nanotube network and alignment of the nanotubes in the flow direction. But, at low and moderate shear rates, because of the dominance of nanotube aggregation mechanisms and very little orientation, higher conductivities can be achieved than for the case of high shear rates. These behaviors are also qualitatively consistent with the previous experimental studies. We showed that for a specific shear rate, independent of the previous shear rate, a reproducible electrical conductivity and nanotube orientation, as well as a simitar microstructure can be achieved. Simulations show that in order to produce a conductive light-weight material with reduced cost and using low CNT amounts, nanotubes with aspect ratio of at least of the order of 100 should be used.
Publications
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"Effects of Shear Forces on the Conductive Network Formation in Multiwalled Carbon Nanotube/Epoxy Composites", 81st Annual Meeting of Society of Rheology in Madison, USA, 2009
A. E. Eken, J. Kovacs, C. Schulz, W. Bauhofer
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"Shear-controlled Electrical Conductivity of Carbon Nanotubes Networks Suspended in Low and High Molecular Weight Liquids", Polymer 51. 5024-5027 (2010)
W. Bauhofer, S. C. Schulz, A. E. Eken, T. Skipa, D. Leilinger, I. Alig, E.J. Tozzi, D. J. Klingenberg
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"Simulations of Carbon Nanotube/Polymer Composites", 2010 Material Research Society (MRS) Meeting Boston, USA, 2010
A. E. Eken, E. J. Tozzi, D. J. Klingenberg, W. Bauhofer
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"A Simulation Study on the Combined Effects of Nanotube Shape and Shear Flow on the Electrical Percolation Thresholds of Carbon Nanotube/Polymer Composites" Journal of Applied Physics 109, 084342 (2011)
A. E. Eken, E. J. Tozzi, D. J. Klingenberg, W. Bauhofer
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"A Simulation Study On The Effects Of Nanotube Anisotropy And Non-Straightness On The Electrical Properties Of Carbon Nanotube/Polymer Composites", The Nineteenth Annual International Conference on Composites/Nano Engineering, Shanghai, China, 2011
A. E. Eken, E. J. Tozzi, D. J. Klingenberg, W. Bauhofer
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"A simulation study on the effects of shear flow and ,nanotube shape on the electrical conductivity of carbon nanotube/polymer composites". 83rd Annual Meeting of Society of Rheology in Cleveland, USA, 2011
A. E. Eken, E. J. Tozzi, D. J. Klingenberg, W. Bauhofer
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"A Simulation Study on the Effects of Shear Flow and Nanotube Shape on the Microstructure and Electrical Properties of Carbon Nanotube/Polymer Composites", NT11 International Conference on the Science and Applications of Nanotubes-Nanocarbon Composites Symposia in Cambridge, UK, 2011
A. E. Eken, E. J. Tozzi, D. J. Klingenberg, W. Bauhofer
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"A Simulation Study on the Effects of Shear Flow on the Microstructure and Electrical Properties of Carbon Nanotube/Polymer Composites", Polymer 52, 5178-5185 (2011)
A. E. Eken, E. J. Tozzi, D. J. Klingenberg, W. Bauhofer
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"Combined Effects of Nanotube Aspect Ratio and Shear Rate on the Carbon Nanotube/Polymer Composites", Polymer 53,4493-4500 (2012)
A. E. Eken, E. J. Tozzi, D. J. Klingenberg, W. Bauhofer
