VIPER is a European Joint Doctorate on Vibroacoustics. VIPER aims at consolidating academic research dealing with VIbroacoustics of PERiodic media. Structural periodic design is a powerful strategy for lightweight structures achievements while remaining a convenient solution for manufacturing guidelines aspects. Including vibroacoustic design rules at early stage of products development is one of the main research targets. Periodic media exhibit proper dynamic filtering effects that can be smartly used for vibroacoustic design. The question addressed then is simple: how periodic concepts can improve the broadband vibroacoustic signatures and performances? Most of vibroacoustic treatments are frequency band limited. Indeed, on the one hand, viscoelastic materials (for instance) can be used for low frequency passive vibration control. On the other hand, poroelastic blankets are efficient for high and mid frequency absorption of acoustic disturbance. Newly and extensively employed lightweight structures present a strong dynamical overlapping between low, mid and high frequency bands that needs to be dealt with.
The VIPER project’s main goal is to develop and to validate tools for the design of global vibroacoustic treatments based on periodic patterns allowing passive control of vibration and acoustic paths in layered concepts. This will be achieved by addressing in-depth structural periodicity stiffness as well as absorption attributes. The proposed concepts would ensure a significant improvement of vibroacoustic performances in a wide frequency range. Dealing with large scale periodic structural-acoustic concepts involves a multi-scale aspect that needs specific numerical tools. A two scale strategy will be pursued in most of the achievements to handle periodicity effects: the meso-scale is related to the elementary cell or the span, while the macroscale relates to the full-size structure. Each scale will be characterized by its own efficiency indicators: effective parameters (mechanical and acoustical equivalent material properties, dispersion characteristics…) at the meso-scale, and vibroacoustic indicators (structural damping, acoustic absorption, transmission loss…) at the macro-scale.
Bridging the cell scale behaviour and the vibroacoustic indicator is a challenging issue that will significantly improve the macro-scale structural design. The cell topology and constitutive materials effects are important and still open questions. The VIPER project will consider the combination of different materials and structural arrangements allowing maximization of energy dissipation while maintaining both structural stiffness and a reduced mass. Viscoelastic, poroelastic, auxetic materials will play a major role in the problems that will be addressed. In order to achieve the expected efficiency, numerical tools and virtual design will be deeply used. Small and large-scale manufacturing aspects of the production of periodic media made from foams and composites will be also evaluated. The issue of reduced modeling of the periodic media vibroacoustics is also a key aspect in the project. Such reduced models will allow easy optimization of the proposed concepts. Experimental evidences of the concepts will be exhibited through the tests that will be performed on manufactured structures. Finally, the VIPER project will also bring up questions about “uncertainty”, due to the lack of perfect periodicity either desired or not. This issue is quite important, in view of the manufacturing aspects of engineering applications of periodic media. The project will consider these aspects in view of robustness analysis involving periodicity-based concepts.
VIPER has a multi-disciplinary character, coupling expertise from material science, vibration and acoustics as well as applied mathematics. VIPER beneficiaries are high ranking representatives of their field of expertise and they will put together all the necessary competences to make this project a success. Finally, VIPER can offer different applications in the transportation sector (aeronautics and space, automobile) as well as energy and civil engineering sectors, where vibroacoustic integrity and comfort are crucial points.