The objective of the project is to contribute to the optimization of the damping of sustainable lightweight structures made of plant fibers composites through a detailed understanding of their dynamic properties. The loss factor of polymer composites reinforced with plant fibers is about one decade higher than that of more traditional composites based on glass or carbon fibers. Contrary to the modulus of rigidity which responds to a law of mixture, the loss factor is more difficult to predict. The use of plant fibers composites is mainly limited for the moment to non-structural applications. To design plant fibers composite structures that combine high stiffness and high damping, the understanding of the role of each component, in particular that of the fibers and the fiber-matrix interface in damping performance, is of crucial importance. To date, there is no characterization method that can provide this information. MIDIFIC proposes to develop innovative experimental methods at the micro-scale to access novel measurements of the dynamic properties. Scientific and technological challenges are numerous due to the complex experimental environment and because of the complexity of the considered plant fibers. The viscoelastic properties of the fiber/matrix interface will be characterized through dynamic micro-scale mapping. The information obtained at micro-scale will feed multi-scale model capable of predicting the dissipative behavior at higher scales. All these tools will be used to advance the knowledge and to develop innovative methods in structural mechanics. Through a wide range of scientific approaches, experimental and modeling, MIDIFIC aims to improve the mechanical properties of composite structures. It is a unique project on the national territory and it is this strong originality that will allow the scientific coordinator to deploy her research strategy and to increase her national and international influence.