Effect of fiber length distribution on rheology of fiber suspension.

摘要

To manufacture composite materials effectively one needs to predict fiber orientation in final product and rheological properties of fiber suspended polymer melt accurately. One of the factors that affect the rheological properties as well as fiber orientation is the aspect ratio of the suspended particles, defined as the ratio of the length to the diameter.;From the experimental result, it is found that among the conventional averaging techniques weight averaging technique consistently outperforms z-averaging and number averaging technique for a series of experiments. The proposed new model based averaging technique can predict single mode suspension viscosity well.;Numerical results show that fiber-fiber interaction coefficient has different values in different regions, namely, Newtonian plateau, transition region and shear thinning region due to change in fiber orientation. With increase in aspect ratio hydrodynamic interaction coefficient value increases. In general fiber-polymer coupling factor decreases with increase in aspect ratio.;In this study a combination of experimental measurement and numerical modeling is used to investigate the effect of the aspect-ratio distribution on the rheological properties of polymer-fiber suspensions. Different conventional averaging techniques such as number average, weight average and z-average are evaluated. A new averaging technique based on the model used to calculate the contribution of fiber in suspension viscosity is proposed. The results of the experiments are compared with the predictions of a mathematical model based on a modified FENE-P constitutive equation to describe the behavior of the polymer solution and a fiber model where orientation distribution of fibers is described in terms of second and fourth order tensors of fiber orientations.