In-situ Monitoring of Fiber Preform Permeability Variations for Resin Transfer Molding Process

摘要

The quality control of final parts of resin transfer molding (RTM) processes depends significantly on the uniformity of the fiber preform. Conventional permeability measurement methods only measure the averaged preform permeability and they cannot be conducted in-situ due to the concern of fiber pollution. This paper introduces an innovative permeability characterization method that uses gas flow to not only qualitatively detect preform variations but also measure its permeability distribution quantitatively in a closed mold assembly before actual resin injection. This in-situ characterization strategy is made possible by two recent research findings: (1) resin permeability is highly correlated with gas permeability for the same fiber preform with well-controlled gas flow, and (2) the whole-field gas permeability distribution of a preform can be obtained through measuring the pressure field of gas flow. In this study, the gas-assisted, in-situ permeability measurement technique was validated first. The effectiveness of the technique was further demonstrated by its ability to qualitatively detecting non-uniformities and permeability variations in pre-arranged fiber performs. Finally, a two-dimensional, finite difference flow model, based on the Darcy's law, was developed to quantitatively estimate the whole-field preform permeability profile using predetermined pressure distribution. The efficacy of the new method was illustrated favorably by experimental results.