Modeling short fiber deformation in dilute suspension: Fiber deposition process

Abstract

A new process to align short fibers into a preform for composite applications has been developed. The short fibers are dispersed in a fluid at a high dilution ratio. During fluid extraction, the fibers decelerate with respect to the fluid velocity and are subjected to significant forces that provide the mechanism to align the fibers. In this study, a model that describes the motion and deformation of a flexible elastic fiber in low Reynolds number flow is formulated. The governing equations are described and forces acting on the fiber are estimated. The numerical implementation of the model is described, and its numerical performance is evaluated. Several validation checks are performed to determine if the model is capturing the experimentally observed phenomena and if the estimated parameters provide reasonable quantitative agreement with experimental observations. The model is then applied to several simple examples such as the evaluation of bending stress (moment) and the associated fiber deformation (buckling behavior) versus the results observed in the process. The effect of fiber boundary condition is demonstrated. It is shown that the model can describe the buckling-like slow folding of the misaligned fiber. Finally, the model utility is demonstrated by a simple parametric study which explores the influence of process parameters on the fiber alignment process.