Optimisation du procédé de tomographie X appliqué à la détection des défauts dans les matériaux composites.

Abstract : The carbon-fiber-reinforced-polymer (CFRP) materials display excellent properties considering their weight. However, they also can display defects that can significantly decrease their properties. In order to verify the internal structure of the composite materials, non destructive control is required. In this document, the X-ray computed tomography is used. Nevertheless, the distinction of the defects is difficult because of the chemical proximity between the carbon and the resin. In order to improve the detection of the defects, this document proposes to study the different physical phenomena happening during the tomography process such as the study of the acquisition parameters and the phenomena that decrease the image quality. In order to help to understand the different phenomena, the simulation tool is used. It allows to study the different phenomena independently to the others. After the presentation of the composite materials and the x-ray computed tomography in the first part, the features of the used acquisition system are presented in the second part. The features of the simulation of the acquisition system are also presented. The third part propose a study of the different phenomena contributing to the image. The comparison of the results between the simulation and the experimental allows to highlight a backscattering phenomenon happening inside the detector. A protocol allowing to determine these phenomena experimentally and to add it on the computed projections is presented. Furthermore, the simulation does not take the noise on the projection into account. Another protocol is presented, allowing to determine it experimentally. The fourth part displays the study of the optimization of the image quality using the simulation. The choice of the accelerating voltage is studied as well as the influence of the object scatter radiation. The fifth part proposes an experimental validation of the results. Especially, a correction of the backscattering is presented and applied to the composites objects.
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  • HAL Id : tel-01469390, version 2

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Cyril Uhry. Optimisation du procédé de tomographie X appliqué à la détection des défauts dans les matériaux composites.. Traitement du signal et de l'image [eess.SP]. Université de Lyon, 2016. Français. ⟨NNT : 2016LYSEI083⟩. ⟨tel-01469390v2⟩

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