Master thesis intership : Multilayered structures models with complex interfaces

Context

Generally, poroelastic materials are inserted along the path of noise propagation to mitigate and dissipate the propagation of sound waves. More and more sophisticated material architectures are developed integrating solid inclusions, anisotropic materials, heterogeneous materials, damping systems, stiffeners... However, for this type of nonhomogeneous solutions, conventional modeling and characterization tools are generally difficult to implement and finite element solutions are often used. These solutions are very expensive in terms of resources and computation time and unknowns remain as the boundary conditions and interface conditions to be considered between the different layers. Reduced and condensed models, mainly analytical, are thus necessary to better understand and optimize the vibratory and damping behaviour of these structures.
Scientific objectives and description of the study
If analytical equivalent models of multilayered structures with "ideal" conditions of continuity at interfaces (conditions of continuity of constraints or "canonical" displacements) exists and are commonly used by the community [1-4], scientific obstacles remain when it comes to model easily structures where several homogenized layers are coupled together in an "unconventional" manner. For example conditions of partial sliding between the layers (which tends to increase dissipation for a bending stress) or the presence of detachment and local heterogeneities (which can create an additional phenomenon requiring a multi-scale description of vibrational phenomena) or non-linear couplings, may not be currently modelled.
In this context, the master thesis internship proposed in collaboration LTDS/LVA aims at modelling multilayer assemblies with complex architecture taking into account the interface conditions. The principal objective is to provide the theoretical formalism necessary for the description of these local phenomena, and thus to answer to the problems commonly encountered with this type of structure, in industry in particular. The master will begin with one simple « unconventional » interface condition (for example a partial sliding condition on a three-layer plate with poro-elastic core) and complexity will be integrated step by step depending on the progress of the work
The optimization of the vibro-acoustic behavior of these multilayered structures in view of local dynamics will be also investigated. Ultimately, the resulting structural functionalization would then allow the treatment of acoustic and vibration problems in a more robust manner.

Industrial applications – Experimental comparisons

Depending on the progress of the master internship and in order to validate the theoretical methodology proposed, applications case study representative of problems encountered in the industry (sandwich structures with complex interface conditions) will be tested experimentally and compared to the equivalent model. Matelys will provide the representative sampling material, used in building, automotive and aerospace industry.