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Acoustic fibers are potential candidates for developing sensors used in nondestructive evaluation (NDE) and process monitoring of composite materials. Acoustic fibers, like optical fibers, are easily embedded into polymeric composite materials. Because of the mechanical nature of the acoustic wave, acoustic fibers have direct sensing abilities on the variation of mechanical properties of their surrounding materials. Two experimental fiber acoustic sensors are developed. One is applied to detect the changes of properties of cured RHO-C rubber with temperature. Another is used to monitor the curing process of epoxy. Test results show the feasibility of applying the fiber acoustic sensors to NDE and process monitoring for polymeric materials.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper presents a discussion of multimode optical fibers used for acoustic wave (2–10 MHz) propagation. The optical fiber acts as a connecting rod between two piezoelectric transducers (PZT) that are attached at each end (dumbbell arrangement). This device is then completed by encapsulation of a solid epoxy or a strengthened composite. One piezoceramic is excited and generates an elastic wave to propagate along the optical fiber and into the other piezoceramic. An alteration of the steady‐state signal thus is indicative of an impact and/or random pressure disturbances upon the composite. Additionally, environmental temperature changes are also detectable. Experimental measurement and related theories are demonstrated.