PERMEABILITY MODEL FOR A WOVEN FABRIC

The resin transfer molding (RTM) method is used to manufacture composi te parts. The reinforcing fibers are placed in a mold cavity and the r esin is injected to fill up the empty spaces. After the resin cures, t he mold is opened and the part ejected. To predict necessary pressures and filling times and the proper locations for the inlet ports for re sin injection and vents for air ejection it is necessary to model the resin infiltration process. A key to this modeling is permeability whi ch characterizes the resistance of fibers to the flow of infiltrating resin. A simplified model for in-plane permeability of fabric reinforc ement (preform) is developed here. This model uses lubrication theory for modeling the flow through open pores and Darcy's law for the trans verse flow through the reinforcement. Scaling analysis is provided to justify the simplification and to estimate the range of validity for r esulting expressions. Extension of the model to cover multi-layered pr eforms is derived. Boundary conditions and the data necessary to speci fy the problem geometry are discussed. A numerical experiment is condu cted to estimate the influence of the transverse permeability of the p reform on the solution. A calculation is provided for the permeability of a plain weave fabric.