Detection of microscopic damages in composite laminates with embedded small-diameter fiber Bragg grating sensors

• Published in: Composites science and technology Vol. 62; no. 7-8; pp. 951 - 958
• Main Authors: OKABE, Yoji, MIZUTANI, Tadahito, YASHIRO, Shigeki, TAKEDA, Nobuo
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier 01.06.2002
• Subjects: Applied sciences; Exact sciences and technology; Forms of application and semi-finished materials; Laminates; Polymer industry, paints, wood; Technology of polymers; Laminate; Fiber reinforced material; Mechanical properties; Epoxy resin; Bragg grating; Tensile property; Experimental study; Composite material; Fiber optic sensors; Reflection spectrum; Transverse crack; Embedded transducer; Measurement method; Computing method; Damaging; Carbon fiber
• ISSN: 0266-3538; 1879-1050
• DOI: 10.1016/S0266-3538(02)00009-X

Small-diameter fiber Bragg grating (FBG) sensors, of outside diameter 52 mu m, have been developed by the authors and Hitachi Cable Ltd. for embedding inside a laminate without deterioration of the mechanical properties of the composite laminate. In this research, the small-diameter FBG sensor was embedded in the 0 deg ply of a CFRP cross-ply laminate for the detection of transverse cracks in the 90 deg ply. The reflection spectra from the FBG sensor were obtained at various tensile stresses. As a result of damage, the spectrum became broad and had some peaks with increase in the transverse crack density. Furthermore, theoretical calculation reproduced the change in the spectrum very well. These results show that small-diameter FBG sensors have the potential to detect the occurrence of transverse cracks through the change in the form of the spectrum, and to evaluate the transverse crack density quantitatively by the spectrum width. (Material noted: T800H/3631.)