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ESR5: Periodic inclusions in PU foams PhD Position at Université de Franche-Comté, Besançon, France
Ecole Centrale de Lyon, Ecully
LTDS
Engineering 
Full Description:

Objectives

In this work we will address the development of design tools for locally resonant sonic crystals with porous matrix. The whole problem will be investigated numerically and experimentally validated. The numerical tools which will be developed will include:
1- a Biot-Allard description of the foam behaviour, in order to include both acoustic dissipation from the fluid phase and skeleton viscoelasticity to correctly handle vibrations and dissipation of the elastic phase;
2- a possibility to consider complex geometric shapes through the use of 3D finite elements;
3- the shift-cell operator approach which allows description of the propagation of all existing waves from the description of the unit cell through the resolution of a quadratic eigenvalue problem which can handle any frequency-dependency of parameters. Up to that day, to the partner’s knowledge, this type of model has never been implemented to handle 3D Biot-Allard model with periodic inclusions.
This will be possible in a short time period through the combination of existing tools in the partners’ numerical toolboxes. This combination, by itself, will constitute the first important novelty of the work. This will render possible to overcome the limits of existing approaches, by designing more specifically the inclusions in the system. The various way to improve the vibroacoustic properties of the media that will be investigated will be the size and the shape of the inclusions, which will be potentially constituted by 2 phases, and exhibiting a resonant character. Inclusions with more than 1 resonance in the frequency band of interest will be considered. A particular attention will be paid to overcome the limitation of the efficiency of the resonant concept, which can be observed on these systems like on the well-known tuned mass dampers. The design of the sound package will combine all physical phenomenon (Bragg effect, dissipation in the material, resonance effects in inclusions, coupling with fluid and solid phases of the foam, grading) in order to obtain to obtain a device whose frequency efficiency outperforms existing designs. Practical implementation of the designed concept will be realized at the lab scale for first tests in impedance tube, and then a 4 square-meter panel will be manufactured with the help of AST. Inclusions in the porous layer will be realized by 3D printing and included by hand, the automation of the process being out of the range of the project. This panel will be realized with materials classically used in the aerospace industry to check the feasibility of the concept in this field. In the very last part of the PhD work, functional inclusions like anisotropy effects, nonlinearities, or multi-physics couplings (thermal, electro-active, magnetic) will be investigated and manufactured in scaled prototypes. This functionalization will either improve again the device performance in terms of broadband absorption, or provide new properties (flexibility, tunability, shock absorption...).

 

Expected Results: Numerical design tools for periodic inclusions design in poroelastic materials. Optimisation and testing of different inclusions.



Posted on: 30 May 2016Deadline to apply: 01 September 2016Start Date: 01 October 2016 Duration: 36 months
The Fund category is Mixed Funding and the salary is 35-40k€ annual gross
Doctoral School is Doctoral program in physical and engineering sciences in the Rhône-Alpes Region.

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