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12 June 2000 Detection of transverse cracks in composites by using embedded FBG sensors
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In the present research, fiber Bragg grating (FBG) sensors were applied for the detection of transverse cracks, which cause strain distribution within the gage length, in carbon fiber reinforced plastic (CFRP) cross-ply laminates. An uncoated FBG sensor was embedded in 0° ply on the border of 90° ply in a CFRP cross-ply laminate. The reflection spectra from the FBG sensor were measured at various tensile stresses. As a result, the reflection spectrum became broad and had some peaks with increase of the transverse crack density in the 90° ply. After the crack density was saturated, the spectrum became narrow and had one large peak again. For confirming that the change in the spectrum form was caused by transverse cracks, the spectra were calculated theoretically. The calculated result reproduced the change in the measured spectrum form very well. These results show that the occurrence of transverse cracks can be detected from the change in the form of the reflection spectrum, and the spectrum width at the half-maximum is a good indicator for the quantitative evaluation of the transverse crack density on real-time.
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Yoji Okabe, Shigeki Yashiro, Tatsuro Kosaka, and Nobuo Takeda "Detection of transverse cracks in composites by using embedded FBG sensors", Proc. SPIE 3986, Smart Structures and Materials 2000: Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials, (12 June 2000);

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