A new measurement set-up for the identification of fibre reinforcement permeabilities of composite materials

In today's market an increasing demand for high-quality fibre reinforced polymers (FRP's) can be noticed. Applications range from automobile, sports, marine, heavy-duty machinery to household applications. The interest for the RTM production technique has risen significantly over the past few years because of higher demands on finish quality, production volumes, cycle times and last but not least, environmental implications. RTM can comply with all of these demands. One disadvantage of the RTM-technique is that the moulds used are often a relatively high cost-factor in the process and thus mould design has gained an increasing interest. Mould manufacturers are encouraged to perform flow front simulations in order to avoid mould filling problems and to optimise processing parameters. Almost all of these flow front simulation programs are based on Darcy's law. This law describes the relation between the flow-front speed and the applied pressure gradient for the saturated flow of an incompressible, Newtonian fluid in a porous medium. The program hence requires the input of processing parameters like viscosity, fibre volume fraction, etc. The dynamic viscosity of the resin can be measured relatively easily by means of special viscometers. The permeability however is linked to the porosity of the reinforcement that in turn is a function of the applied closing pressure of the mould. A good knowledge of the permeability is necessary to make good predictions using the flow front simulation software. Performing good permeability measurements is a tedious task that requires a great deal of skill and experience of the experimenter. The test set-up that will be discussed in this paper proposes new, user-friendlier permeability measurement equipment that relies much less on the operator capabilities.