JEC COMPOSITES MAGAZINE - Issue #57 - May 2010 - 32

FEATURE

“Automation”

Automatic process monitoring and control for composite production
In composite materials production, there is an urgent need for non-intrusive process monitoring and control systems that would automatically optimize and tune production in real time. Previous research has shown that the dielectric monitoring technology can be used to monitor the processing of thermoset [1] and thermoplastic [2] matrices for composite materials production. So, by combining electrical and temperature measurements with material models, resin viscosity and degree-of-cure can be calculated in real time in the mould or die. These models can be used either offline to provide the optimal process cycle, or online to provide optimal, real-time process control [3]. This is the target of the iREMO project (www.iremo.eu), an EC-funded collaborative European project that involves CEMCAT, Sora Composites Group and Atoutveille (Fr), NTUA and Synthesites (Gr), Inasmet and Acciona (S), BIBA (D), UNewcastle (UK) and Karnic (Cy).
although no significant progress in monitoring the complete composite processing cycle has been made known until recently. Synthesites recently presented a new DC-based process monitoring system with a clear focus on industrial applications for composite materials. The new system measures the material’s resistivity and temperature using durable sensors and suitable electronic systems capable of in-situ monitoring the full transformation of a thermoset resin; i.e. from very low viscosities at high temperatures to fully cured resins where the measured resistance varies from 106 ohms up to 1014 ohms. Comparisons between DC

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(1) NIKOS G. PANTELELIS, SCHOOL OF MECHANICAL ENGINEERING, NATIONAL TECHNICAL UNIVERSITY OF ATHENS (2) MARC-PHILIPPE TOITGANS, CEMCAT (3) JOËL LEVEQUE, ATOUTVEILLE, (4) EFTHYMIOS BISTEKOS, SYNTHESITES

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n the iREMO project, the electrical resistance of the resin is measured directly using a steady-state (DC) electrical excitation instead of a range of sinusoidal excitations (AC). This gives a context similar to dielectric cure monitoring, but with improved performance. Although several sensors and DC amplifiers have been proposed in the past [4,5], the first commercial system was only recently made available for use in lab and industrial-scale applications.

Process monitoring
In dielectric cure monitoring, a frequency range of sinusoidal voltage or current excitations are applied to a pair of electrodes, which are in contact with the material being investigated so that the post-processed feedback provides information about the material state. The use of DC conductivity for process monitoring purposes is even older,

Fig. 1: Simultaneous measurements of imaginary impedance max (Z’’ max) and electrical resistance on the black right axis and temperature (left axis) together with the theoretical degree-of-cure (green right axis) during the mid-temp curing of an epoxy system

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jec composites magazine / No57 May 2010
http://www.iremo.eu
JEC COMPOSITES MAGAZINE - Issue #57 - May 2010

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #57 - May 2010
