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24 July 2001 Distributed photoacoustic system for cure monitoring of composites
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In this paper we describe a laser ultrasonic system for real-time monitoring of the degree of cure of a graphite-epoxy composite part during manufacturing. The system is integrated with a Resin-Transfer Molding (RTM) machine, and contains (i) a fiberized laser ultrasonic source, and (ii) an embedded ultrasonic sensor based on an intrinsic fiber optic Sagnac interferometer. Bulk ultrasonic waves generated by the laser source are transmitted into the composite structure and are subsequently detected by the embedded ultrasonic sensor. The degree of cure can be obtained from measurements of ultrasonic velocity and attenuation in the composite part. The use of an optical switch in the fiber optic delivery system of the laser ultrasonic source allows ultrasonic generation at several locations of the composite part. In this paper we discuss the design of the laser ultrasonic source and the sensor optimized for cure monitoring applications, and their integration with the RTM mold. The results of ultrasonic measurements during manufacturing of a composite specimen are presented. Our results show that laser ultrasonics offer distinct advantages for manufacturing of modern composite structures including the ability to operate in a high temperature and high pressure environment and provide distributed sensing that can cover critical areas of a component.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Pavel A. Fomitchov, Yeong K. Kim, Alexei K. Kromine, Sridhar Krishnaswamy, Jan D. Achenbach, and Isaac M. Daniel "Distributed photoacoustic system for cure monitoring of composites", Proc. SPIE 4335, Advanced Nondestructive Evaluation for Structural and Biological Health Monitoring, (24 July 2001);

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