The development of a dielectric system for the on-line cure monitoring of the resin transfer moulding process

The aerospace industry has identified the need for an on-line cure monitoring system for the resin transfer moulding (RTM) process which can determine the through-thickness cure state of a composite, without affecting the integrity of the finished component. Several techniques have been extensively investigated but dielectric analysis (DEA) appears to offer the greatest potential. The parallel plate sensor configuration is appropriate for through-thickness measurements. Using a laboratory dielectric instrument, dielectric properties in fibre (conductive and non-conductive) reinforced composite samples have been measured during a simulated RTM cure cycle. Particular parameters derived from dielectric measurements have been shown to be useful in terms of monitoring and optimising the RTM cure cycle. These parameters can be used to identify the key stages in the curing process and to estimate the values of the resin properties at these stages. Correlation of key dielectric events with other thermal data has been shown. Sensors currently are being developed with a view to incorporation into the RTM mould. The ultimate aim of this work is the development of an on-line cure monitoring system for the RTM process in collaboration with Bombardier Shorts.