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Durabilité d'un système composite biosourcé (matrice époxy-fibres de lin) pour applications de renforcement structural : approches expérimentale et fiabiliste

Abstract : In France, the built heritage of civil engineering and building structures is vast and ageing. Recent reports prepared by experts highlight this alarming situation and point out the need to significantly increase the resources allocated to the rehabilitation of this heritage. In this context, structural reinforcement by externally bonded composites has become an attractive solution for the rehabilitation of structures and the extension of their lifespan. This thesis, funded by the French Research Agency (ANR), aims to develop a new composite reinforcement system with a reduced environmental footprint, on one hand, and to build an original reliability approach to estimate the lifetime of reinforcement systems and their failure probability at any time, on the other hand. In this manuscript, the main phases of development of the bio-based system are first recalled. In particular, it is recalled that the formulation of the bio-sourced epoxy matrix was based upon the specifications and characteristics of the Foreva® TFC matrix, and the criteria that guided the choice of the unidirectional flax fibre reinforcement fabric are also presented. The second part of the manuscript presents all the experimental results obtained within the framework of the durability study on the bio-based strengthening system. This test campaign relies on a Design of Experiment optimized by Hoke’s matrix. Laminated composite plates and concrete slabs reinforced with these composites were subjected to accelerated ageing under hygrothermal conditions, and to natural ageing on an outdoor exposure site in Lyon as well, for a total duration of 24 months. In a first step, the results of various physico-chemical characterizations that were periodically conducted on the bio-based composites, highlighted the relative contributions of mechanisms involved in microstructural evolutions and degradation phenomena of both the polymer matrix and fiber/matrix interfaces. In a second step, the changes in the main performance indicators related to the composite and the concrete-composite interface subjected to the various ageing environments, are presented and interpreted in the light of the previous physico-chemical characterizations. In a third step, a comparison is made between the bio-based composite system and a traditional carbon fibre strengthening system. The last part of the manuscript is devoted to the implementation of the reliability approach, relying on the experimental database previously collected for the bio-based system. A statistical analysis by the ANOVA method is first carried out on all experimental data. Two degradation models were then developed to describe the evolutions of performance indicators over time for any hygrothermal ageing condition: an analytical model with explicit terms related to quadratic effects and coupling between temperature and relative humidity, and a physical model based on Eyring's law.In a next step, these models were used to estimate the lifetime of the bio-based strengthening system under accelerated ageing conditions. End-of-life criteria were first defined based on specifications proposed by different design guidelines, in particular by ACI and AFGC reports.In order to evaluate the lifetime under actual service conditions, a specific procedure was then proposed to apply the analytical model in the case of natural ageing. Finally, a probabilization of the analytical model is carried out in order to determine the probability of failure of the bio-based strengthening system at any time during its lifetime
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Submitted on : Thursday, July 9, 2020 - 10:19:12 AM
Last modification on : Friday, October 23, 2020 - 4:38:26 PM


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  • HAL Id : tel-02894653, version 1



Robert Chlela. Durabilité d'un système composite biosourcé (matrice époxy-fibres de lin) pour applications de renforcement structural : approches expérimentale et fiabiliste. Matériaux et structures en mécanique [physics.class-ph]. Université Paris-Est, 2019. Français. ⟨NNT : 2019PESC2076⟩. ⟨tel-02894653⟩



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