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Smart skins

Self-tunable and integrated systems for vibroacoustics and health monitoring

This program aims mainly at developing new distributed devices for structural control.
The concept is based on a network of passive and/or active cells distributed on a surface that constitutes a “smart skin”, which is able to measure control the mechanical properties of the structure.

The objective is to demonstrate the integration of adaptive and energetically autonomous cells that can produce internal coupling mechanisms to program functionalities of interest, namely the structure’s reliability (Structural Health Monitoring of composite structures) and/or environmental perturbations control (control of acoustic radiation, vibration damping, wave trapping…).

Among others, this program will find applications in structural weight reduction for aeronautics, aerospace or automotive, by integrating reconfigurable functionalities in non-planar composite structures, using either integrated transducers/electronics or light/flexible nonintrusive skin.

A particular focus on energy management is also studied: low power or autonomous systems are indeed required to have a chance to be deployed at large scale.


Integrated structural health monitoring and residual life prediction of composites

Real-time health monitoring of composite structures using acoustic emissions

Development of Surface acoustic wave (SAW)-based technology for the health monitoring of composite containers (transportation of granulated or pulverized goods and materials).
Partners: Eurovrac Spitzer, Freq|n|Sys, SENSeOr, UHA

Conformable CMUTS for acoustic waves control

Our long-term objective is to create a flexible skin which could be bonded to a structure at the boundary of an acoustic domain to be controlled. As energy converters from electrical to mechanical domain and vice versa, the CMUTs (Capacitive Micromachined Ultrasound Transducer) will play the role of loudspeakers realizing an impedance synthesis by a semi-distributed control strategy preventing the propagation of acoustic waves in a specific direction.

Prognostics and health management

The NASA’s Prognostics Center of Excellence and the Labex ACTION has published together a review paper about the state-of-the-art research methods used in the prognostics and health management of turbofan engines.
A focus is particularly made on data-driven methods which rely on multidimensional time-series and include advanced statistical analysis and machine learning techniques as well as the representation, quantification and propagation of uncertainty for reliable and robust in-service monitoring.
Performance Benchmarking and Analysis of Prognostic Methods for CMAPSS Datasets, Int. Journal of Prognostics and Health Management (jan. 2015).

Metamaterials and metasurfaces for vibroacoustics

Semi-active distributed and tunable system for vibroacoustic control

The distributed active system is reconfigurable through the tuning of a single resistance in the shunt circuit and provides 2 configurations:
- A vibration barrier which confines the energy on a specific part of the structure,
- A damping configuration inducing huge reduction of the vibration levels on the whole structure (5 to 15dB on 250Hz-4000Hz range).

Smart skin for acoustic control in nacelles

- Coupling of local and distributed strategies for acoustic control
- Use of dedicated loudspeakers provided
- Prototype design & manufacturing (structure, electronics, control) @FEMTO-ST
- Fully reconfigurable control thanks to dedicated electronics
Partners: Safran/Aircelle, EPFL

Acoustic comfort and sound insulation using acoustic metamaterials

The concept consists in creating reflector or absorber acoustic  screens by integrating several miniaturised cells. Experimental results achieved with a metamaterial-based panel have shown an attenuation exceeding 40dB !
Degrees of freedom:
- Adaptability in terms of choice of solid material wood, glass, metal, polymers…(no need to use a inherently absorbing or dense material)
- Possibility of air circulation or heat exchange
- ” scalability ” in terms of frequency
- Decrease space requirements

Energy harvesting and integration

Smart composite skins with integrated transducers networks

The aim of this project is to demonstrate the feasability of integrating transducers in lightened complex structures in order to provide them with new functionalities (SHM) without compromising their robutness.
Promising results were achieved with the fabrication of a glass fiber based composite prototype (an automotive spoiler) which integrates a network of 50 piezoelectric patches. Each transducer is electrically independent and can be separately actuated. The useful frequency range of these elements is compatible with the use in aeronautics and car industry.
The next challenges are the full integration of the microcontroller-based devices and electronic circuits into the structure.
Partners: MyOCCS, Freq|n|Sys, IRTES-M3M (UTBM), Espera SBARRO design school (UTBM)


Smart Skins for SHM of composites using acoustic emission


Active vibro-acoustic control

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