A constitutive model for characterization of shear and extensional rheology and flow induced orientation of carbon nanofiber/polystyrene melt composites

We characterize the transient shear and uniaxial extensional rheology of melt phase polystyrene/carbon nanofiber composites and measure orientation development during each flow type. Experimental measurements show an increase in the viscosity of the composite with increasing carbon nanofiber concentration under both types of flow. We present a microstructurally based constitutive model to predict the experimentally observed rheological behavior and evolution of nanofiber orientation. Experimental measurements were performed to determine the average orientation of the carbon nanofibers at various points in time during shear and extensional flows. We demonstrate that the constitutive model predicts the transient shear and extensional viscosities of polystyrene/carbon nanofiber composites and the orientation evolution of nanofibers during flow. (C) 2011 The Society of Rheology. [DOI: 10.1122/1.3579160]