Abstract EN:

The automotive infrastructure in France is extensive but often aged. In particular, many French bridges (30 %) have defects that need to be repaired in a more or less short term period to prevent the rapid development of structural disorders, and 7 % of them have a risk of collapse in short term. Critical failures in large infrastructures, beyond the risk of human-life losses, can cause huge economic issues and, for sure, the loss of services. For those aged or potentially damaged infrastructures, the complete demolition and reconstruction is not conceivable just because of the inherent waste of resources. Yet, in order to still guarantee a safe usage of these constructions, certain reinforcement strategies can be adopted to extend the service life of damaged buildings, and to recover the requirements of bearing capacity and safe use. This would be undoubtedly a better deal.For that purpose, fiber-reinforced thermosetting composites have received a lot of attention. They are usually bonded on the surface to protect the infrastructure from the inner stress and external erosion or to limit crack growth. Up now, the composites are mainly based on glass or carbon fibers and cold-curing epoxy resin made from fossil resources. As environmental problems worsen, as oil resources diminish, the advantages of environmentally friendly renewable resources become more prominent. The production and recycling process of natural fibers has little impact on the environment. Besides, due to photosynthesis, the cultivation of natural fibers can reduce the greenhouse effect by increasing the oxygen content and reducing the amount of carbon dioxide in the atmosphere. Compared to traditional synthetics, natural fibers present certain engineering advantages like lightness, recyclability, abrasiveness with interesting specific properties and they are relatively cheap as well as abundant. Also, as partly made from environmentally renewable resources, thermosetting bio-epoxy resins are alternatives to conventional resins in the field of civil engineering renovation. For building fixings, the composites patches act as a structural component, whose mechanical properties are directly in relation to the reinforcement type. The viscoelastic matrix properties, and reinforcement/matrix interactions dependent on the curing state. The moisture content is also a significant element to be taken into account due to the natural origin of the fibers. This aspect can imply specific sensitivity to damage or early ageing for the patches. Therefore, they must be tailored and monitored to ensure long-term structural performance. This could be achieved through the application of an in-situ embedded sensor for continuous (in real-time) monitoring for the precise follow-up of the curing state as well as of their structural integrity (moisture ageing, damage extent). Such an embedded sensing system can also help the supervision of self-repairing constituent. This other aspect of added features to composite materials will enable the patch to slow down damage growth before catastrophic failure occurs. Moreover, the external bonding reinforcement effect, or enhancing efficiency, mainly depends on whether the component interface can effectively transfer stress. The bonding interface between the composite reinforcement sheet and the infrastructure is the weak link of the entire reinforced component. Interfacial peeling is a brittle failure that occurs suddenly without obvious warning signs so far.In this study, a novel composite patch was manufactured with flax fiber and bio-epoxy resin for the purpose of enhancing those aged or potentially damaged civil infrastructures. To obtain a comprehensive and profound acknowledgment about this research, the curing mechanism of epoxy resin, the mechanical performance of flax fiber-reinforced epoxy resin composite (FFRC), the durability behaviors of FFRC, and the shear-lap test between FFRC and concrete were the exploration priorities.