A gas flow method for determination of in‐plane permeability of fiber preforms

Abstract

Resin flow plays a crucial role in many composite manufacturing processes. The most important parameters used in modeling and designing mold filling are the permeability of the fibrous preform, which is a kind of flow conductance and a property of the reinforcement, and the viscosity of the resin. The extent of chemical reaction, or degree of cure, is also important and causes change of resin viscosity during mold filling. To determine the permeability of fiber preforms, many researchers have been using liquid flow analysis. In this study, a new scheme for determining permeability using gas flow is proposed. In conventional liquid flow methods, radial propagation of the polymer into a porous medium is measured and used to determine permeability, whereas in the gas flow method, the flow rate for several different preform geometries is measured and used. The effectiveness of the gas flow method was verified by comparing it with conventional methods.

Characterization of local preform defects in resin transfer molding by the gas flow method and statistical analysis

“…This in turn relates to a variance in the local permeability which can be detected as a deviation in the flow rate/pressure gradient relationship as given by Eq. (2). More specifically, the permeability can be thought of as the proportionality constant for a given material under specified conditions, i.e., given fiber volume ratio.…”

“…After the polymer completely saturates the preform, it is allowed to cure. The impregnation of the fluid into the preform is defined by the permeability of the reinforcement, which is the ability of a Newtonian fluid to permeate a porous medium with a sufficiently low Reynolds number, as given by Darcy's law [1][2][3][4].…”

“…Um et al [2] and Kim et al [12] have introduced methods for two-dimensional in-plane permeability determination of orthotropic and isotropic preforms utilizing gas flow. Kim et al [13,14] have also recently proposed a gas flow method for preform defect detection based on the inverse estimation of space-varying permeability and an additional technique which statistically analyzes normalized pressure deviations between measured and computed values.…”

Gas Flow Method for Detecting Local Preform Defects by Inverse Estimation of Space-Varying Permeability

“…They demonstrated the feasibility of the gas flow method by trying to correlate gas permeability and liquid permeability. Um et al introduced another method for the determination of in-plane permeability of an orthotropic preform utilizing gas flow [8]. Kim et al further improved the gas flow method for permeability determination by making the solution more robust and simplifying the experimental procedure [9].…”

A Finite Element-based Heuristic Estimation of Local Preform Permeability for Resin Transfer Molding

“…Starr and Hablutzel (1998) also worked on the permeability of cloth layup preforms by gas transport via pressure-driven permeation. Ding et al (2003), Um et al (2001), and Kim et al (2003a,b) established a method using gas flow and pressure field to measure the local preform permeability variation in the closed mold. These proposed gas flow methods were verified by comparing calculated permeability values with measured values or by comparing results with those obtained by the conventional liquid flow methods.…”