Application of ultrasonics for the process control of Resin Transfer Moulding (RTM)

The Resin Transfer Moulding (RTM) process is a manufacturing technology to produce three-dimensional, complex and large composite parts with a high potential for automation. To realise optimum part quality, the processing of RTM parts needs a lot of experience and good skills. Current methods to optimise the RTM process are focused on RTM equipment, e.g. mould design and automated injection, and simulation programs to predict the injection and curing behaviour of the resin during the RTM process. However, on-line process control with in-mould sensors is not often used in industrial manufacturing of RTM parts. The article deals with the application of ultrasonic techniques to realise on-line monitoring and control of the RTM process. A prototype mould was manufactured to investigate the ultrasonic technique in comparison to pressure transducers and dielectric sensors. The main goal was to localise the flow front during injection and to monitor the curing behaviour of the resin. It is shown that, based on the data generated from the ultrasonic sensors, an optimisation of the RTM process and the part quality is possible to reduce cycle time and to avoid dry spots in the laminate. (c) 2004 Elsevier Ltd. All rights reserved.