• Ichchou, Mohamed
• Ohayon, Roger
• Ouisse, Morvan
• Collet, Manuel

Abstract

Research activities in smart materials and structures are very important today and represent a significant potential for technological innovation in mechanics and aerospace. In order to implement new vibroacoustic functionalities inside complex coupled fluid/structure system, new technologies are now available which allow integration of dense and distributed set of smart materials, electronics, chip sets and power supply systems for implementing distributed control strategies. It is also possible to develop the next generation of smart "composite" structures also called adaptive metacomposite. By using such an integrated distributed set of electromechanical transducers, one can imagine to attain new desired acoustic dispersion and scattering that can allow the control of mechanical or acoustic flow in a large frequency band. Tailoring the dynamical behavior of wave-guide structures can provide an efficient and physically elegant approach for optimizing mechanical components with regards to vibration and acoustic criteria, among others. However, achieving this objective may lead to different outcomes depending on the context of the optimization. In the preliminary stages of a product's development, one mainly needs optimization tools capable of rapidly providing global design directions. Such optimization will also depend on the frequency range of interest. Thus, piezoelectric materials and other adaptive and smart systems are employed to improve the vibroacoustic quality of structural components, especially in the Low Frequency range even if distributed transducers are used. Recently, much effort has been spent on developing new multi-functional structures integrating electro-mechanical systems in order to optimize their vibroacoustic behavior over a larger frequency band of interest. For medium and high Frequency band, metacomposite concept also appears as a very efficient way for reaching optimal vibroacoustic functionalities. This concept couples two different aspects in vibration control. The first concept is connected to periodic structures theories usually connected to metamaterial developments. In this case, it is well known that the dynamic behavior is fully connected to periodicity ratios and existing pass bands and blocked bands can be of real use in vibration control. The second concept is associated to vibration control through piezoelectric and smart materials. Specifically, shunted piezoelectric smart materials are employed for the metacomposite achievement by integrating into the metamaterial electronics and numerical components allowing implementation of adaptive and controlled behavior. We also tend to extend the notion of programmable matter to vibroacoustic programming composite. First application of these concepts has been already done for controlling mechanical energy power flow or by processing acoustic radiation effect. In this paper, we present an integrated methodology for optimizing vibroacoustic energy flow in interaction between an adaptive metacomposite made of periodically distributed shunted piezoelectric material glued onto passive plate and open acoustic domain. Extension of shifted cell operator methodology to fluid-structure interaction is presented. The computation of interacting Floquet-Block propagators is also used to optimize vibroacoustic indicators as noise absorption and emission. The main purpose of this work is first to propose the numerical methodology to compute the fluid-structure multi-modal wave dispersions. In a second step optimization of electric circuit is used to control the acoustic power flow. After recalling the Floquet-Bloch theorems, we introduce a new numerical formulation for computing the multi-modal damped wave numbers dispersion in the whole first Brillouin domain of a periodical smart structure made of periodically distributed shunted piezoelectric patches. Based on this wave modeling, optimization of the electrical impedance of the shunted circuit is made in order to decrease group velocity of flexural waves. The obtained optimal impedance is also tested in controlling the response in a large frequency band of a semi-distributed system. Different kinds of composite architectures are tested for underlining control efficiency as function of design options. We also show that piezoelectric patches have to be located directly into the fluid/structure interface to increase controllability and also the systems efficiency.

Topics

• impedance spectroscopy
• dispersion
• composite
• positron annihilation lifetime spectroscopy
• Photoacoustic spectroscopy
• metamaterial
• piezoelectric material