Fanny Pelisson's thesis (since November 2022)
supervised by Vincent Placet, Pauline Butaud and Morvan Ouisse
This thesis aims to optimize the damping of sustainable structures as plant fiber composites through a detailed understanding of their dynamic properties. The loss factor of plant fiber composites is about ten times higher than that of conventional composites based on glass or carbon fibers. Compared to the modulus of rigidity, which responds to a mixing law, the loss factor is more difficult to apprehend. For now, the use of plant fibers is thus mainly limited to non-structural applications. To design plant fiber composite structures that offer high stiffness and high damping, understanding the role of the various constituents, in particular the fibers and the fiber-matrix interface, in damping performance is of crucial importance. For now, there is no characterization method capable of providing this information. In this thesis, innovative experimental methods at the microscale will be developed to access novel measurements of the dynamic properties of plant fibers. The fiber/matrix interface will be characterized through dynamic mapping at the microscale. These mechanical properties will enable the optimization of the dynamic behavior of plant fiber-based composites to achieve a balance between rigidity, damping, and environmental impact.
Tsilat Shiferaw's thesis (since October 2023)
supervised by Morvan Ouisse, Pauline Butaud and Vincent Placet
Contributions to the understanding of dissipation phenomena in bio-based composites
This thesis aims to optimize the damping of sustainable structures as plant fiber composites through a detailed understanding of their dynamic properties. The loss factor of plant fiber composites is about ten times higher than that of conventional composites based on glass or carbon fibers. Compared to the modulus of rigidity, which responds to a mixing law, the loss factor is more difficult to apprehend. For now, the use of plant fibers is thus mainly limited to non-structural applications. To design plant fiber composite structures that offer high stiffness and high damping, understanding the role of the various constituents, in particular the fibers and the fiber-matrix interface, in damping performance is of crucial importance. In this thesis, innovative multi-scale modeling methods, based on finite element analysis of a representative elementary volume, will be developed to identify the influencing parameters. To ensure the reliability of the results, dynamic tests will be carried out at the composite scale, and a calculations-tests correlation will be performed. Multi-objective optimization procedures will be implemented to determine key parameters (morphology, spatial distribution, fiber volume fraction) for the conception of a composite rigid, damped and with low environmental impact.