CE10 - Usine du futur : Homme, organisation, technologies

Towards a predictive modelling of the damping of bio-based composites – Bio-Damping

Bio-Damping: Towards predictive modelling of bio-sourced composites damping

Thanks to their natural properties, biosourced fibers are attracting increasing interest from industrial actors. Indeed, their intrinsic damping and lightness capacities make them suitable for transport -applications (naval, nautical, air, rail, or automotive) to improve user comfort. The objective of the Bio-Damping project is to propose a viscoelastic constitutive law for a flax/matrix ply to develop biosourced composites, in order to be able to simulate the vibratory behaviour of structures.

Characterization, modelling of the constitutive law of a flax/matrix ply to study the damping of bio-based composite structures and the variability.

The objective of this project is to model the damping properties of a ply (flax fiber/matrix) to predict the damping of biosourced composite structures. This will increase their use in industry, particularly in marine engineering. Due to the natural character of fibers, it is assumed that temperature, hygrometry, UV and ageing in a marine environment will have some influence on the behaviour of the composite structure. Therefore, in order to achieve the objective of this project, it is necessary to study the vibratory behaviour of natural fiber-reinforced composite structures according to the orientation of the fibers and the parameters mentioned above. The first challenge will be the identification of the most representative viscoelastic model of the fiber/matrix ply and the determination of the parameters of the law. The second challenge will be the simulation of the vibratory behaviour of a natural fiber-reinforced composite structure. It will be necessary to use specific numerical methods to solve the nonlinear problem induced by the viscoelastic model. Once the viscoelastic modelling of a ply has been established and the simulation of the vibration behaviour of a natural fiber composite structure has been validated, it will be necessary to take into account the variability due to the natural character of flax fibers. Indeed, the uncertainties related to natural fibers properties are probably more important than those related to synthetic fibers, with an evolution according to the climatic and storage conditions. The variability of the vibratory behaviour of the composite structure, considering uncertain material and physical properties, is the third challenge of this project.

The static and dynamic experimental study will be carried out at LEM3 in Metz. On the one hand, the mechanical characteristics will be identified by determining the Young's modulus using tensile tests (Zwick Roell) at temperature. On the other hand, experimental investigations on the dynamics of the structures will be carried out on the Vibration platform. The dynamic characterization of different plates by vibration tests will permit to understand the influence of temperature, hygrometry, UV, frequency and orientation of the fibers on the damping properties of the plant fiber composite. Given the large number of experimental tests planned in this study and the industrial production conditions, the manufacture of the specimens (plates and beams) will be subcontracted to companies in the Lorient region. The objective of the modelling part is to develop viscoelastic constitutive laws of a ply, easy to implement in calculation codes. To do this, various identification methods will be implemented using experimental data.

The constitutive models of the flax fiber/matrix ply will be complex, with frequency and temperature dependence. Conventional methods of solving vibration problems will not be applicable. Therefore, it will be necessary to determine the most relevant methods for solving nonlinear vibration problems, forced or not, of flax fiber-reinforced composite structures. These methods will be based on homotopy and perturbation techniques, or on the Numerical Asymptotic Method (NAM). The uncertainties associated with flax fiber-reinforced composites require that the variability of the influential parameters of the composite, in particular the material properties, be taken into account in the deterministic model. The non-deterministic simulation aims to better control the uncertainties in order to improve the predictivity of the numerical model. The propagation of uncertainties through the model will be carried out by a probabilistic approach in order to obtain an assessment of the variability of the model outputs. A Monte-Carlo approach combined with the modal stability assumption will be used to significantly reduce the computation time. An error indicator will also be used to limit the number of random samples and therefore the number of simulations.

All of this work will result in a predictive tool that will allow the development of the industrial use of flax fibers. Industrialists will be able, on the one hand, to optimize their structures, such as by choosing the best orientations for the fibers in the stacking of the structure's plies, and on the other hand, to predict their modal characteristics (frequencies and damping) without carrying out expensive experimental tests. The predictive tool established will make it possible to choose the laminated structure to be made in order to reduce certain vibrations while ensuring sound comfort and safety. It will also permit to predict the evolution of structure's behaviour according to the variability of material parameters and ageing. A natural fiber-reinforced structure, which is lighter and more damping than a conventional fiber-reinforced structure, will also reduce energy consumption during its implementation, thanks to the proximity of the raw material, and during its use, by reducing oil-ressources consumption.

The «Bio-damping« project proposes a model of the damping properties of a ply (flax fibers/matrix) to predict the damping of biosourced composite structures by taking into account the variability of certain parameters. It is part of a problematic of dimensioning structures taking into account of the environment of the structure (T°, humidity rate, UV). Many fields of application are directly impacted by structural vibration problems. Passive damping is a direct lever for this problem.
In the south of Brittany, the nautical companies of the Sailing Valley aim to integrate flax fibers in the realization of parts of their ships and boats, in particular foils, rudders and masts. The use of these appendages causes vibrations that can be uncomfortable for sailors but can also destabilize the boat during maneuvers. The results of the project will allow us to propose to these companies an architecture for their composite structure (choice of fibre orientation) according to the frequencies to be damped.
With nearly one third of the world's textile flax surface area, France is the leader in the production of this plant, which is grown only in the Hauts-de-France and Normandy regions, thanks to the unique combination of a naturally humid oceanic climate, low thermal density, generous soils and the know-how of flax growers. The Bio-Damping project will also enable the development of applications for flax fiber composites.
Today, as a metallurgy basin, the Lorraine region is opening up to future sectors of activity. Renewable energy or, more precisely, the contribution of natural fiber in composites would bring innovation to industrialists in the sector, such as small and medium-sized composite companies for the manufacture of hulls for civil aviation. The project is part of a wider dimension to boost the socio-economic fabric through research towards ecological production through the proof of concept of a bio-structured composite and its damping capacities.

A publication is in preparation. No patent.

Thanks to their numerous natural advantages, bio-sourced fibers are of increasing interest to industrialists. Indeed, bio-sourced fibers are closely linked to the fields of maritime-, air-, railway- and road-transportation, due to their intrinsic lightweight and damping capacities to improve the comfort of passengers and users. In an eco-design approach, manufacturers, especially those dealing in sailing with parts such as foils, masts, rudders and steering-gears are questioning the interest of incorporating bio-sourced fibers in all or part of a structure made of composite materials. Nowadays, incorporating bio-sourced fibers in composite materials still generates difficulty in dealing with production, mechanical characterization, modelling and simulation.
The aim of the Bio-Damping project is to provide a solution to the last three locks. Based on an experimental test campaign, the project will enable to model the damping properties of the bio-sourced composite layer to be incorporated in a specific structure calculation code.
For this purpose, two companies renowned for their ability and expertise to implement composite structures will produce test-specimens. The manufacturing process management will enable to keep control of the risks regarding the use of fibers of homogenous origin, resins of constant quality, reproducible manufacturing processes and controlled environments.
The test-specimens produced thereby will make it possible to identify, define and characterize the supposed constitutive law (Maxwell, Zener, ...) of a fiber/matrix layer. This will take the fiber-orientation along with the specific parameters related to temperature, hygrometry, aging due to UV radiations, salty environment, into account. The influence of the manufacturing process will be studied by comparing the mechanical properties of the test-specimens from two different processes, i.e. the infusion process of prepregs and the method of placing fibers by a robot.
The behavior model will be incorporated into a specific structure calculation code developed within the IRDL. This code is dedicated to solving non-linear problems. It provides efficient and robust resolution algorithms so as to determine the response of vibration (eigenmodes, structural damping) of a composite structure. Based on methods associating high order perturbation and continuation technique, the calculation code enables to carry out parametric studies. Thus, a sensitivity study of the response of vibration, related to the variability of the physical and mechanical characteristics of bio-sourced fibers and the environmental conditions will be carried out.
At the end of the Bio-Damping project, a methodology dedicated to designing and sizing of composite structures based on bio-sourced fibers, will have been designed. Associated with an eco-design approach, the solutions gained during the project will enable an industrialist interested in these bio-sourced composites with uncertain properties, to substitute the current production for bio-sourced composite parts: they will be able to choose the relevant fiber-orientation in their multi-ply composite depending on the requested damping capacity. Specific parameters related to environmental and climatic conditions, such as temperature, hygrometry, aging due to UV radiations, salty environment – may also be taken into account.

Project coordination

Laëtitia DUIGOU (IRDL)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


LEM3 Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux
Laboratoire Roberval. Unité de recherche en mécanique acoustique et matériaux.

Help of the ANR 298,795 euros
Beginning and duration of the scientific project: January 2020 - 42 Months

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