Laser Ultrasonic Array System for Real-Time Cure Monitoring of Polymer-Matrix Composites

Abstract

A laser ultrasonic system for real-time cure monitoring of a graphite-epoxy composite is proposed. The system contains an array of fiberized laser ultrasonic sources, and an embedded fiber optic Sagnac ultrasonic sensor, and is integrated with a Resin Transfer Molding machine. The use of an optical switch allows ultrasonic generation at several locations of the composite part. Ultrasound generated by the laser source is transmitted into the composite and is detected by the embedded sensor. The cure state is inferred from measurements of ultrasonic velocity. The results of ultrasonic measurements during manufacturing of a composite specimen are presented. The laser ultrasonic cure monitoring system described in this paper has the ability tooperate in a high temperature and high pressure environment; is small enough to be incorporated into molds; and measures the cure state at several locations within the composite part.