Mechanistic models for fiber flow

This dissertation presents a study on the behavior of polymer composites in molding processes. The initial part of the dissertation is devoted to the development of analytical tools that provide a better understanding of the underlying phenomena taking place when a polymer composite is molded. By applying tools like dimensional analysis and Newton's equations of motion in simplified molding scenarios it is possible to characterize the parameters playing a role in the molding process. Using this framework, a mechanistic model that uses dimensional analysis to predict fiber-matrix separation in ribbed sections of compression molded parts is presented. The model combines a mechanical analysis of compression molding with some experimentally measured variables.;The second part of this dissertation is focused on modeling the processing of fiber reinforced polymer composites by using computer simulation. The flow of fiber suspension in a polymer matrix is modeled by using a mechanistic algorithm based on a Molecular Dynamics (MD) approach. Fibers are modeled as chains or rigid beads connected by springs. Parameters such as fiber concentration, fiber length and stiffness can be modified to match specific processing conditions. Simulation results include final fiber orientations and fiber distributions within a molded part. Specific applications for these types of simulations are the calculation of fiber orientation and the prediction of fiber-jamming and fiber-matrix separation in the compression molding of Sheet Molding Compound (SMC) and consequently are presented in the final part of this work.