This paper demonstrates acoustic speed measurements in anisotropic composite materials using a fiber-optic extrinsic Fabry-Perot interferometric sensor (EFPI). Acousto-ultrasound technique is used to generate unidirectional surface acoustic waves in a multilayered composite specimen. The principle of operation and the fabrication of the EFPI sensor are explained. The composite specimen is interrogated by a piezoelectric transducer driven by 1.2 MHz signal pulses from an rf generator. The acoustic speed is calculated by noting the difference in the arrival times of the acoustic signal detected by the sensor for different locations of the piezoelectric source separated by a known distance. The possible variation of the acoustic signal speed with respect to the direction of the fibers is studied. This study could be used in determining the dispersion curves of materials and impact locating detection in composite materials.
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