Modeling of resin flow in natural fiber reinforcement for liquid composite molding processes

A model for the resin flow in natural fiber preform is developed and validated by experimental measurements. During the resin flow in natural fiber reinforcement, the fiber diameter increases as the liquid resin is absorbed into the natural fiber. It has been well known that the fiber swell leads to a time-dependent change of reinforcement permeability. Moreover, the increase of fiber diameter and the liquid resin absorption affect the resin flow velocity by changing the volumes of fiber and resin, which has been ignored in the conventional modeling approaches. We propose a new resin flow model considering the volumetric changes of resin and of fiber as well as the permeability change because of the fiber swell. A new experimental method is employed to obtain the liquid absorption characteristics of fiber immersed in liquid resin. The validities of several models in the literature and of the present model were evaluated by comparisons with experimental data of mold filling process. The conventional model approaches show significant discrepancy with the experimental results, in the case of high fiber volume fraction, whereas the current model predictions always show good agreements.