Simulation and experimental validation of mould tooling forces in RTM and CRTM for nonplanar components

Abstract

To date, simulation of the forces exerted on mould tools during RTM and Compression RTM (CRTM) has focused on planar cases. While a flat plate case has some limited validity in practical applications, the majority of applications are for nonplanar geometry components. Such components present a more challenging case to simulate, as the nonplanar geometry introduces an additional out-of-plane shear component to the local tooling stresses as well as effects due to the geometry itself (such as race-tracking in corners). This article presents the first thorough study of mould tooling forces for a nonplanar geometry. A number of RTM and CRTM experiments were undertaken using a truncated-pyramid mould with an acrylic top platen to allow flow front visualization to be undertaken. Repeatability studies showed variations in fill time and peak tooling forces observed during RTM and CRTM cases which could not be accounted for by variation in the sample mass or fluid viscosity alone. This demonstrated that the processes were influenced by the spatial variability in the areal mass of the preforms. The experimental results were also compared to numerical simulations of the processes. Good agreement between experiment and simulation was observed for both RTM and CRTM cases in terms of flow front evolution. Peak forces were also well predicted, within the variability observed in the experimental results; this was partly due to the out-of-plane shear component of the tooling force being well predicted, in combination with the normal component. In addition to the velocity-controlled mould closure cases, force-controlled mould closure was also investigated for CRTM. Good agreement with simulation was also achieved for this complex situation. The range of processes and conditions investigated here show that the simulation package is providing good agreement to experiment for both flow evolution and tooling forces and stresses.