Waveguide based optical sensors for airframe monitoring

Problem statement

Composite materials are used in a wide array of application markets such as aviation, automotive, biomedical implants, construction materials, etc. by virtue of their strength, stiffness and lightness. A major part of these structures do not allow for traditional - electrical - sensing systems. Because of this lack of structural health monitoring systems, many composite structures are replaced today purely for precautionary reasons at one hand or after failure of the construction on the other hand. Adding optical sensing intelligence to these structures not only prolongs their lifetime but also significantly decreases the environmental impact through a reduced use of raw materials and energy savings.
We are therefore investigating the use of optical waveguides with integrated sensing structures based on wavelength-selective mirrors. Different optical fabrication technologies are available within the research lab CMST (department Elis), http://www.cmst.be. One of these technologies is the fabrication of polymer optical waveguides which can be made mechanically flexible and combined with integrated optoelectronics (lasers and detectors) to read out the sensors.

Figure: (left) Composite materials such as fiber reinforced plastcis (FRPs) comprise more than 20% of the Airbus 380's airframe, (right) Polymer flexible waveguide fabricated at CMST.

Goals of the master thesis

A variety of methods for fabricating polymer optical waveguides is available at Cmst. The goal of this master thesis is to investigate different possibilities for implementing sensing structures in these optical waveguides.

The first step is mechanical and/or optical simulation of the sensing principle, the surrounding light guiding medium and the composite host material. Secondly, the sensing system itself will be designed and fabricated using the CMST cleanroom capabilities. Later in the development cycle, these newly developed sensors can be integrated in an optical sensing/interrogation system and combined with composite host materials. This will be done in close collaboration with the research lab Mechanics of Materials and Structures (MMS, http://www.composites.ugent.be).

The work is divided in the following parts:

- Design/modeling/simulation of the sensing structures and the interaction with the sensing medium.
- Fabricating and validating the new sensing concepts and work towards a sensing system.
- Testing the full sensing system in a real composite environment.

Together with the master student, the focus of the master thesis can be slightly shifted towards one of the specified parts.

Figure: (left) Single mode polymer waveguides of different size which can be used as a starting point for the optical sensors, (right) Typical optical mode profile in such a waveguide (arbitrary units).


polymer waveguide, grating,composite material, modeling, fabrication, field tests


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