On the feasibility of optical fibre sensors for strain monitoring in thermoplastic composites under fatigue loading conditions

• Published in: Optics and lasers in engineering Vol. 47; no. 3; pp. 403 - 411
• Main Authors: De Baere, I., Luyckx, G., Voet, E., Van Paepegem, W., Degrieck, J.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2009; Elsevier
• Subjects: Blades; Exact sciences and technology; Extensometers; Fatigue; Fatigue (materials); Fiber optics; Fibre; Fibre Bragg grating; Fundamental areas of phenomenology (including applications); General equipment and techniques; Gratings; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Optical elements, devices, and systems; Optical fibers; Optics; Other fiber-optical devices; Physics; Polymer matrix composites; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Sensors, gyros; Strain; Thermoplastic composites; Thermoplastic resins; Fibre Bragg grating; Thermoplastic composites; Fatigue; Optical fibers; Fatigue testing; Thermoplastics; Data acquisition; Measuring methods; Diffraction gratings; Grating in fiber; Fiber optic sensors; Bragg gratings; Carbon fibers; Composite materials; Strains; Optical method; Manufacturing; Optical sensors
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2008.01.001

This study investigates the possibility of using optical fibres with Bragg gratings for measurements in thermoplastic composites under fatigue loading conditions. Two setups are considered: (i) the fibre is embedded in the composite and (ii) the grating is bonded externally. Detailed information is given on the principle of optical fibre measurements and the data acquisition for both setups. To verify the strain derived from the optical fibre, the strain is compared with extensometer measurements. A special design of the blades of the extensometer is presented, since the standard blades suffer from a loss of grip on the surface of the specimen. The material used for this study was a carbon fibre-reinforced polyphenylene sulphide. It can be concluded for both setups that the optical fibre survives over half a million loading cycles, without de-bonding of the fibre. The advantage of the external fibre over the embedded one is that it can be mounted after manufacturing of the plate, but it has a higher risk of being damaged during working conditions of the component.