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

Abstract

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.

Effect of Embedded Strain Gage on the Mechanical Behavior of Composite Structures

“…Currently, the insert of smart parts by integrating sensor networks in the composite become possible. These networks record different physical signals [10,11] and can even work as active components. The good use of composite materials requires understanding of the mechanical responses and monitoring of the performance of each component in the composite under mechanical loads and external environmental.…”

Fatigue testing and online inspection of carbon textile composites for aeronautical applications

“…They can withstand high strain levels and have been found to be suitable for embedding in thermoplastic composites (De Baere et al, 2007;De Baere, Luyckx, Voet, Van Paepegem, & Degrieck, 2009). They can withstand high strain levels and have been found to be suitable for embedding in thermoplastic composites (De Baere et al, 2007;De Baere, Luyckx, Voet, Van Paepegem, & Degrieck, 2009).…”

Embedded Sensor Networks for Textile‐Reinforced Thermoplastics: Sensor Network Design and Mechanical Composite Performance

“…For example, various sensors embedded in composite structures are used to measure strains or to detect, localize, and quantify damages . Networks involving sensors and actuators open new fields of application.…”