Modeling and evaluation of the filling stage of injection/compression moulding

Abstract

Resin Transfer Moulding (RTM) and Injection/Compression Moulding (I/CM) are closed mould polymer composite manufacturing processes. Analytical solutions to simple flow geometries have been utilised to explore the potential benefits of I/CM relative to RTM. A series of parametric studies are presented, considering the effects of process parameters on mould filling times, and internal tooling forces. Two modes of compression flow are considered, constant speed, and constant force. While significant reductions in fill time can be achieved, these gains are balanced by increased clamping force, or increased internal stress applied to the mould. Constant force compression is shown to minimise fill times, using the full capacity of the clamping device. An experimental study was completed to verify the applied models. Comparisons to predicted fluid pressure histories are very good, verifying the applied pressure governing equations. Total clamping force predictions have shown important qualitative differences, which have been related to the use of elastic preform deformation models. Significant viscoelastic stress response was exhibited by the reinforcement studied, in the absence of any resin. Due to the similar time scales of I/CM filling and preform stress relaxation behaviour, viscoelastic deformation models are required to improve filling simulations.