Search

In G. Pernigotti, F. Patuzzi, A. Prada, V. Corrado & A. Gasparella (Eds.), Building Simulation Applications BSA 2022 (pp. 473–478).

International audience; The characterisation of fibrous materials is an important part of the process for the development of NVH packages in the automotive industry. In particular, fibrous materials for acoustical applications have been extensively studied over the past years and a considerable number of experimental tests have been carried out as a function of fiber geometrical characteristics (for example, overall density, fiber diameter and density, open porosity, etc.) in order to determine analytical formulations for the prediction of physical parameters. Due to the random nature of the mix of individual fibres, which can include different densities and thicknesses, predictive models normally do not take into account the individual fibres but instead deal with the mixture as a whole. This paper examines an ongoing study into the experimental characterisation of individual fibres (in terms of airflow resistivity, open porosity, tortuosity, characteristic lengths and static thermal permeability) and the validation of new analytical models (as a function of open porosity and fiber radius) that will help in the determination of overall acoustic performance.

Nowadays, several analytical and numerical approaches are available for analysing the performance of materials used in noise and vibration control applications. All these methodologies require knowledge of a set of input parameters which, in the case of viscoelastic materials, could exhibit strong dependence on frequency in the entire audible range. The aim of this paper is to present a simplified transfer matrix approach for the determination of the complex modulus for longitudinal waves of isotropic viscoelastic materials as a function of frequency. To that effect, the tested material is excited by an electromagnetic shaker and longitudinal waves are investigated. Using a frequency sweep as an excitation signal, the time domain response is measured downstream and upstream of the sample itself. A velocity transfer function is measured and, by using a transfer matrix model of the experimental setup, the complex wave number for longitudinal waves and, consequently, the complex modulus can be determined once the Poisson’s ratio is known in advance. The results are presented and discussed for different materials and compared with well-established quasi-static and dynamic techniques.

Proceedings of the ICA 2019 and EAA Euroregio : 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019 : 9-13 September 2019, Aachen, Germany / proceedings editor: Martin Ochmann, Michael Vorländer, Janina Fels 23rd International Congress on Acoustics, integrating 4th EAA Euroregio 2019, ICA 2019, Aachen, Germany, 9 Sep 2019 - 13 Sep 2019; Aachen (2019)., Published by Aachen

ispartof: http://www.euronoise2018.eu/ ispartof: Euronoise 2018 location:Crete date:27 May - 31 May 2018 status: Published online