JEC COMPOSITES MAGAZINE - Issue #47 - March/April 2009 - 106

KNOW-HOW Process monitoring …/… Process monitoring using ultrasound measurement technology Fig. 4: Influence of the mould temperature on sound velocity. Fig. 6: Influence of a delayed process start on sound velocity. process at the very beginning. Figure 5 compares the sound velocity of a cycle where the compression process started immediately after placing the SMC in the mould and another cycle where the compression process started after 60 seconds. During these 60 seconds, the material heats up and the curing reaction initiates the increase in sound velocity approximately 15 seconds earlier. If the curing reaction takes place before the cavity is completely filled, it can negatively affect the material flow. Therefore, the sensors should be placed in critical areas to monitor the curing reaction. the amplitude, no influence of sound velocity on the compression force is detected. The curves show equal trends for the three compression forces. This example demonstrates that it is necessary to observe both the sound velocity and the amplitude to gain as much information as possible. Conclusion The presented application shows the potential of ultrasound measurement technology in SMC compression moulding. This technology enables SMC parts manufacturers to control the quality of the unprocessed material while monitoring the influence of process parameters such as temperature and internal pressure. In particular, controlling the curing reaction could result in shorter cycle times. More information: www.ikv-aachen.de Contact: kremer@ikv.rwth-aachen.de Bibliography [1] Stauber R.: Kunststoffe im Automobilbau – Technische Lösungen und Trends. Automobiltechnische Zeitschrift ATZ 03 (2007), pp. 202-209. [2] Stark W., Bartusch J., Bräuning R., Döring J., Goering H., Götz J., Kürten C., McHugh J.: Unsaturated polyester resins, BMC and SMC – Characterisation from maturisation to curing. 8. Internationale AVK-TV Tagung, 2005, Baden-Baden. Fig. 5: Influence of a delayed process start on sound velocity. Another parameter that can be observed is the internal pressure. Figure 6 shows relative amplitude graphs at moulding forces of 1,000 kN, 1,200 kN and 1,400 kN. Here, the internal pressure is quantified simultaneously to the ultrasound measurements. The different compression forces result in a 20 bar pressure increase. In the liquid state, the differences in compression forces have negligible influence on the ultrasound amplitude. After the reaction is initiated, increasing differences in amplitude can be seen in the measured amplitudes. A constant offset is reached after 110 seconds. The growing amplitude at higher moulding forces can be explained by the better coupling between the material and the mould at the boundary surfaces. Contrary to the observed influence of the compression force on [3] Rath M.: Online Ultraschalluntersuchungen an duroplastischen Formmassen zur Prozeßkontrolle. TU Berlin, Dissertation, 2000. [4] Schmachtenberg E., Schulte zur Heide J., Töpker J.: Application of ultrasonic for the process control of Resin Transfer Moulding (RTM). Polymer Testing, 24 (2005), pp. 330-338. [5] Stark W., Bartusch J., Döring J., McHugh J.: Making cure visible: monitoring the cross-linking process using integrated ultrasound sensors. JEC Composites Magazine, 45 (2008), No. 38, pp. 64-66. [6] Töpker J.: Ultrasonic Measurement Technique for Online Control and Analysis of the Impregnation and Curing Process by Resin Transfer Moulding. Institute of Plastics Processing, RWTH Aachen, Dissertation, 2002, ISBN: 3-89653-982-5. Acknowledgement The research project (No. 14985N) of the research association Plastics Processing was funded within the program for the sponsorship of the “Industrielle Gemeinschaftsforschung” of the Federal Ministry of Economics and Technology by the AiF, to whom we extend our thanks. 106 jec composites magazine / No47 March-April 2009

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JEC COMPOSITES MAGAZINE - Issue #47 - March/April 2009

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