20 April 1995 Optical fiber sensors embedded in composite panels for impact detection
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Abstract
This paper mainly describes a methodology of finding appropriate optical fiber sensors and associated potential demodulation techniques that have the capability to measure impact induced high-strain rate events in graphite/epoxy panels. The capacity of the sensor's dynamic range has to accommodate the average failure strain of about 9,000 (mu) (epsilon) and center frequency of about 40 Hz for a typical low velocity impact event for [902/04/OF(0)/04/902] and [(45/-45)3/OF(0)/(-45/45)3] layups. Three potential demodulators are investigated. These include the synthetic heterodyne with differential-cross-multiplier, single channel phase tracker, and sin((phi) )/cos((phi) ) based analog phase tracker all using a 10 KHz sinusoidal modulation. The maximum sensor lengths for different sensor types have been calculated based on the Fourier spectrum of a typical impact event and maximum detectable phase vs. frequency of these demodulators. As a result, a localized and reflective version of a In-Line Fiber Etalon sensor with a maximum cavity length of 73 micrometers for 1.3 micrometers wave-length of a light source is selected for impact testing. The strain responses from three different demodulators are comparable to that of a surface mounted resistance strain gage.
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Chia-Chen Chang, Chia-Chen Chang, James S. Sirkis, James S. Sirkis, } "Optical fiber sensors embedded in composite panels for impact detection", Proc. SPIE 2444, Smart Structures and Materials 1995: Smart Sensing, Processing, and Instrumentation, (20 April 1995); doi: 10.1117/12.207700; https://doi.org/10.1117/12.207700
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