Permeability characterization and microvoid prediction during impregnation of fiber tows in dual-scale fabrics.

摘要

Accurate characterization of the permeability of fabrics used as reinforcement materials in liquid composite molding (LCM) processes is necessary to realistically model the flow through these porous preforms. When dual-scale preforms are employed, not just the macro permeability values are of interest; the micro-scale permeability of the fiber tows inherent to the fabric must additionally be determined. These permeability values can then be used in LCM simulations in which standard two- or three-dimensional (2D or 3D) mesh elements are combined with one-dimensional (1D) elements. The 1D elements are attached at each node and represent the fiber tows in preforms that exhibit dual scale porosity. This implementation allows for the interactions between the macro and micro flow, and can predict the saturation of the fiber tows, along with the movement of the macroscopic resin flow front. Consequently, the time it will take to fill the mold and saturate all regions can be accurately predicted and any void formation sites can be forecasted.; A methodology is proposed, which can determine the macro permeability along with a simulation fitting parameter that is closely associated to the micro permeability. (Abstract shortened by UMI.)