Advances in the development of the resin injection moulding techniques has meant large scale automated production of high-quality composites is a realistic option. New resin systems in combination with techniques such as Resin Transfer Moulding (RTM) enable a large degree of automation and relatively short process time for large parts. A typical RTM process involves the impregnation of a fibre structure. After impregnation the resin forms a gel (rubber-like material) and then vitrifies to the glassy state. These transformations are accompanied by significant changes in the viscoelastic properties of the resin system that are related to the formation of a crosslinked molecular structure. In this work the physical changes in the resin system are detected using a parallel plate rheometer for Dynamic Mechanical Analysis (DMA). Analysis of resin cure using rheometry or other laboratory techniques provides the basis for characterisation of epoxy resins. However one or a combination of several factors, including permeability of fibre, geometry of part, pressure, part thickness, variations in temperature etc. mean that a complimentary process monitoring technique should be employed to monitor resin cure in the mould. Dynamic mechanical material characterisation in the mould itself is possible using an ultrasonic through transmission technique. The intention is to apply this technique to monitor and document the curing process for composite parts, thereby providing a large improvement on present process and quality control techniques. In this presentation a detailed characterisation of the epoxy resin will be employed in order to aid the interpretation of the ultrasonic sound velocity and attenuation results. This information is crucial to the industrial implementation of this technique.
展开▼
