IMPROVEMENT OF A CONSTITUTIVE MODEL FOR PREDICTING FLOW BEHAVIOR OF NANOCOMPOSITES
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Date
2013-08
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The Ohio State University
Abstract
This research project focuses on the development of a constitutive model to predict the flow properties of polymer/nanoparticle composites (nanocomposites). Nanocomposites have gained much interest due to the ability of the nanoparticle to improve properties of the pure polymer such as electrical and thermal conductivities and mechanical strength. The high surface area/volume ratio of the nanosize particles gives these improved properties at small loading levels compared to larger conventional particles. Predicting the flow behavior is important when using the nanocomposite in processes such as spraying, extruding and molding. Two types of experiments were performed. Shear flows at a constant shear rate and small amplitude oscillatory shear flows. These flows were induced on the pure polymer or nanocomposite and the stress recorded as a function of time. Steady shear flows were studied both in the forward and reverse directions with varying rest periods between flow reversals. A constitutive model is used for predicting nanoparticle orientation and flow behavior. There are several parameters in the model that need to be fit to experimental data to accurately predict flow properties of the nanocomposite. Two model parameters were fit to experimental data to give the most accurate prediction of flow behavior. These optimized parameters allow the model to give more accurate predictions of shear viscosity. The model was also expanded to be able to make stress predictions for small amplitude oscillatory shear flows. The predictions from this model can be used to develop and optimize large scale nanocomposite manufacturing processes.
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Rheology, nanocomposites, modeling, carbon nanofibers