6533b82efe1ef96bd12924d1

RESEARCH PRODUCT

Thermal and hydrothermal ageing of bio-based composite/metal hybrid materials. Application to the development of ultra-light and durable street furniture

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In the perspectives of the future city, the progressive use of autonomous vehicles seems to become unavoidable. The preparation of an adequate framework for the deployment of this future mobility represents an important issue. This requires revisiting the urban infrastructures of cities from the choice of material to the design, and to propose solutions based on mobile street furniture. Faced with this challenge, hybrid materials such fibre metal laminates (FML) present interesting characteristics. FML made of plant fibre composites are of particular interest to minimize their environmental impact. Thus, the objective of this thesis is to design and manufacture plant-fibre metal laminates and assess their mechanical performance and durability in view of their use for street furniture.Two families of hybrid materials are studied, namely steel/flax-epoxy and steel/flax-polypropylene. For the steel/flax-epoxy hybrid material, the influence of some aspects such as the composite/metal assembly method, the lamination of the composite layers, and the structuring of the hybrid was evaluated on the mechanical performances using three-point bending and impact tests. The structuring of the hybrid is the most influential parameter on the measured properties. The results also show that the developed hybrid solutions have superior properties when compared to most of the mono-material solutions generally used for street furniture.Hybrid steel/flax-polypropylene and flax/polypropylene composites were subjected to accelerated hydrothermal and thermal ageing. Hydrothermal ageing leads to a drop in the flexural and impact properties of the composite, as well as a degradation of the latter. For the hybrid, a real drop was only observed in the flexural properties. The composite of the hybrid also degrades, but the phenomenon is attenuated by the presence of the metallic layers. Thermal ageing leads to yellowing and embrittlement of the composite by thermo-oxidation. This results in a significant drop in the bending properties and impact of the composite over the long term. At the hybrid level, the interface is severely affected by aging; the metal is delaminated after less than two days of aging.