Embedded flexible photonic sensors for cure monitoring and assessment of structural performance
Topic(s) : Multifunctional and smart composites
Co-authors :
Micheal GODFREY , Shahrzad ZAHERTAR (UNITED KINGDOM), Charles GODFREY , Bruno MOOG , Timothy LEE , Tom BRADLEY , Martynas BERESNA , Richard DAY , Janice M. DULIEU-BARTON (UNITED KINGDOM), Christopher HOLMESAbstract :
Flexible photonics are planar optical substrates that contain optical waveguides, often referred to as Planar Lightwave Circuits or Photonic Integrated Circuits. These are compatible with regular optical fibre and offer new optical multifunctionality when embedded into composite materials. A well-established approach for introducing sensing capability into material is the embedding of optical fibre sensors, e.g. [1]. These can be seamlessly embedded into the composite material at the manufacturing stage so that the sensors become an integral part of the composite structure, enabling an inbuilt means for continuous and reliable monitoring.
A new type of flexible sensor is proposed which unlike standard optical fibre in planar in its construction. The concept has been demonstrated in laminated composite structures with a sensor constructed by depositing doped silica upon silicon wafers using a flame hydrolysis deposition process [2]. The 50 μm thick flexible sensor was mounted between the plies of a laminated carbon fibre structure. The findings presented a compelling avenue for further research, particularly in the realms of in-process monitoring of polymer cure and in service through life assessment of composite structures. A key issue was scalability with length scales confined to that of the silica wafer, typically of around of 200 cm. Hence planar flexible photonic sensors created by tower drawing using ‘stack and draw’ techniques, with the potential to produce 10s of metres of fibre or more, are explored in the paper.
The construction of the flat optical fibre sensors is described. The sensors are embedded into carbon fibre panel and used to monitor a standard autoclave curing process (see Figure 1). Figure 2 demonstrates that the sensors can identify the different stages of the curing process in terms of both temperature and pressure. The process is validate against standard optical fibres and by locating the flexible photonic sensors inside the autoclave but outside of the composite stack. It is also demonstrated that post curing, the inclusion of the sensors in the composite has little effect on structural performance. It is discussed how ultimately then sensor could offer a new ‘smarter’ sensing capability as well as distribution of information through a composite structure using optical circuitry.
[1] M. Ramakrishnan, G. Rajan, Y. Semenova, and G. Farrell, “Overview of fiber optic sensor technologies for strain/temperature sensing applications in composite materials,” Sensors 2016, Vol. 16, Page 99, vol. 16, no. 1, p. 99, Jan. 2016, doi: 10.3390/S16010099.
[2]C. Holmes, M. Godfrey, D. J. Bull, and J. M. Dulieu-Barton, “Real-time through-thickness and in-plane strain measurement in carbon fibre reinforced polymer composites using planar optical Bragg gratings,” Opt Lasers Eng, vol. 133, no. 106111, 2020, doi: 10.1016/j.optlaseng.2020.106111.
A new type of flexible sensor is proposed which unlike standard optical fibre in planar in its construction. The concept has been demonstrated in laminated composite structures with a sensor constructed by depositing doped silica upon silicon wafers using a flame hydrolysis deposition process [2]. The 50 μm thick flexible sensor was mounted between the plies of a laminated carbon fibre structure. The findings presented a compelling avenue for further research, particularly in the realms of in-process monitoring of polymer cure and in service through life assessment of composite structures. A key issue was scalability with length scales confined to that of the silica wafer, typically of around of 200 cm. Hence planar flexible photonic sensors created by tower drawing using ‘stack and draw’ techniques, with the potential to produce 10s of metres of fibre or more, are explored in the paper.
The construction of the flat optical fibre sensors is described. The sensors are embedded into carbon fibre panel and used to monitor a standard autoclave curing process (see Figure 1). Figure 2 demonstrates that the sensors can identify the different stages of the curing process in terms of both temperature and pressure. The process is validate against standard optical fibres and by locating the flexible photonic sensors inside the autoclave but outside of the composite stack. It is also demonstrated that post curing, the inclusion of the sensors in the composite has little effect on structural performance. It is discussed how ultimately then sensor could offer a new ‘smarter’ sensing capability as well as distribution of information through a composite structure using optical circuitry.
[1] M. Ramakrishnan, G. Rajan, Y. Semenova, and G. Farrell, “Overview of fiber optic sensor technologies for strain/temperature sensing applications in composite materials,” Sensors 2016, Vol. 16, Page 99, vol. 16, no. 1, p. 99, Jan. 2016, doi: 10.3390/S16010099.
[2]C. Holmes, M. Godfrey, D. J. Bull, and J. M. Dulieu-Barton, “Real-time through-thickness and in-plane strain measurement in carbon fibre reinforced polymer composites using planar optical Bragg gratings,” Opt Lasers Eng, vol. 133, no. 106111, 2020, doi: 10.1016/j.optlaseng.2020.106111.