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Flow Front and Cure Monitoring for Resin Transfer Molding Using Ultrasonic Guided Waves in Cylindrical Wires

The mechanical properties and quality of the RTM resin products depends highly on the complete filling and curing of resins in the mold. Hence, a method for monitoring the filling and curing of resins in mold has been a challenging problem in the field of RTM fabrication for a long time, particularly for thick components. In this paper, we describe a promising online method to monitor the flow and curing of RTM resins using ultrasonic guided waves in cylindrical wires. The reflection of the ultrasonic torsional guided waves at a boundary where a free cylindrical waveguide enters an embedded wire was investigated. An image processing algorithm was also developed for suppressing the unwanted signals from the kinks and other stationary signals. The time-of-flight of the reflected wave was used to determine the flow of resin and the amplitude of the reflected wave is used to measure the shear properties such as the viscosity of resin. From the viscosity changes, the curing of the resin can be monitored. The reflection of the lowest order torsional mode was considered as they are more sensitive to shear properties of the resin. Moreover, they are least attenuated and non dispersive in air providing an opportunity to place the sensor far away from the mold.