NUMERICAL-ANALYSIS OF THE RESIN TRANSFER MOLDING PROCESS BY THE FINITE-ELEMENT METHOD

As large components of fiber reinforced composite materials are being more frequently produced by Resin Transfer Molding (RTM), a computer simulation of the injection process can help the mold designer to accomplish three important tasks: (1) to ensure a complete filling of the mold through adequate positioning of the injection ports and of the air vents; (2) to verify the integrity of the mold during the filling process through knowledge of the pressure distribution; and (3) to optimize the production cycle using information about the filling time. The resin impregnation is usually modeled as a flow through a porous medium. It is governed by Darcy's law, which states that the flow rate is proportional to the pressure gradient. In our model, Darcy equation is solved at each time step inside the saturated part of the mold using nonconforming finite elements. This method was chosen because the approximated flow rates, contrary to conforming finite elements, satisfy locally the important physical condition of resin conservation across inter-element boundaries. This permits simplification of the numerical procedure. It is no longer necessary to resort to a control volume approach to move the flow front forward. The resin pressure distribution and the resin front positions are obtained by the computer simulation and calculated results for selected mold geometries are compared with experimental observations. Molds with inserts, multiple injection ports, and the case of anisotropic preforms can be analyzed by the computer program. (C) 1993 John Wiley & Sons, Inc.