| Summary: | Due to the degradation of most civil engineering infrastructures, there is an urgent need for the development of non-destructive evaluation techniques of structures. In view of this increasing demand, fibre optic sensors are one of the most promising alternatives, because they are very small, extremely reliable and durable, and can take absolute measurements and transmit them over long distances. Among the instruments examined, both fibre Bragg grating sensors and Fabry-Pérot sensors were privileged in this study for their unequalled properties. In the case of structures strengthened with composite materials, these detectors can even be integrated to the strengthening material. However, it is recognised that fibre optic sensors embedded in composites disturb the strain state of the host material. In addition, fibre Bragg gratings are well known for their large sensitivity to transverse strains. These effects must be well understood otherwise Bragg sensors measurements could lead to erroneous interpretations. The primary objective of this thesis was to develop a precise measurement method of the strains in composite materials, that would take into account the presence of the detector. Here, Bragg sensors integrated to composite laminates were subjected to an exhaustive series of strain conditions in order to study their behaviour. The originality of this study comes first from the realisation of a testing program combining a unique concept of cruciform specimen to an innovative instrumentation technique; secondly, from the programming or the execution of two complex mathematical models in the aim of confronting them, for the first time, to experimental results. The last part of the thesis reviews three cases of structural rehabilitation which have been monitored with fibre optic sensors. These continuous evaluations confirmed the reliability and the durability of Fabry-Pérot sensors.
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