• Ziapkoff, Mathias

Abstract

The objective of this thesis is to model the damping properties of a layer (epoxy/flax fibers) in order to predict the damping behavior of biosourced composite structures. Three rheological models are considered in order to establish representative laws for the viscoelastic behaviour of a layer. At the composite scale, this leads to the solution of a non-linear complex eigenvalue vibration problem. We then use numerical techniques of homotopy and perturbation to transform the non- linear problem into a series of linear recurrent problems. The finite element method is used for the spatial description. In parallel, experimental tests are carried out to characterize the elastic and vibratory properties of the flax fiber composite and the carbon fiber composite used as a reference. These results allow us to identify the parameters of the layer constitutive laws using the Nelder-Mead simplex algorithm with a multi-modal approach. These identifications are then validated by considering two multilayered structures. The natural character of flax fibers implies a certain influence of temperature, UV radiation or ageing in marine environment on the damping behaviour of the composite. For this reason, we are conducting three experimental campaigns to characterize the mechanical properties of a biosourced composite structure subjected to these environmental factors.

Topics

• impedance spectroscopy
• Carbon
• composite
• aging