Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption

Airborne sound absorption in porous materials is a complex process that involves multiple working mechanisms of converting mechanical acoustic energy into heat, including thermal effect due to the dynamic heat conduction forced by the rarefaction and the densification of the air, viscous effect caus...

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Main Author: Ayman Mahmod Mohamed Khalil Shahin
Other Authors: Wang Junling
Format: Thesis-Doctor of Philosophy
Language:English
Published: Nanyang Technological University 2020
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Online Access:https://hdl.handle.net/10356/137057
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Institution: Nanyang Technological University
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spelling sg-ntu-dr.10356-1370572023-03-04T16:45:30Z Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption Ayman Mahmod Mohamed Khalil Shahin Wang Junling Yao Kui School of Materials Science & Engineering Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR) aymanmah001@ntu.edu.sg Engineering::Materials Airborne sound absorption in porous materials is a complex process that involves multiple working mechanisms of converting mechanical acoustic energy into heat, including thermal effect due to the dynamic heat conduction forced by the rarefaction and the densification of the air, viscous effect caused by the adherence of the fluid at the interface with the solid, and structure’s damping effect with mechanical energy dissipation when the sound wave impacts on the solid. Electromechanically active coupling effect, particularly piezoelectric effect, has so far been studied mainly for structural vibration damping but not for airborne sound absorption. This thesis examines contributions of the electromechanical conversion mechanism to the airborne sound absorption effect, particularly local piezoelectric effect in porous polar materials. The study on the local piezoelectric effect on airborne sound absorption properties tested in a standard impedance acoustic tube was carried out in three sections. Firstly, open-cell poly(vinylidene fluoride) (PVDF) homopolymer foams were prepared and used in order to obtain porous samples with comparable morphology and structure, but with and without substantial piezoelectric property, for providing an example showing the local piezoelectric property effect on sound absorption. Secondly, composite foams comprising piezoelectric poly(vinylidene fluoride-co trifluoroethylene) (P(VDF-TrFE)) matrix and multi-walled carbon nanotubes (MWCNTs) were fabricated and tested, with the experimental results and theoretical analyses showing how an optimal conductivity of the piezoelectric composite foams improved sound absorption coefficient. Thirdly, composite foams comprising PVDF matrix and inorganic piezoelectric potassium sodium niobate (K0.5Na0.5) NbO3 (KNN) nanofibers were produced and tested, with the investigation results showed that introducing the piezoelectric KNN nanofibers in the foams improved sound absorption coefficient. The experimental results and theoretical analyses indicate that the introduction of piezoelectric property with mechanical-into-electrical energy conversion effect in porous polymer materials can substantially enhance the airborne sound absorption performance, which is valuable to be explored for noise mitigation applications. Doctor of Philosophy 2020-02-17T08:49:14Z 2020-02-17T08:49:14Z 2019 Thesis-Doctor of Philosophy Ayman Mahmod Mohamed Khalil Shahin. (2019). Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/137057 10.32657/10356/137057 en This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0). application/pdf Nanyang Technological University
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Materials
spellingShingle Engineering::Materials
Ayman Mahmod Mohamed Khalil Shahin
Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption
description Airborne sound absorption in porous materials is a complex process that involves multiple working mechanisms of converting mechanical acoustic energy into heat, including thermal effect due to the dynamic heat conduction forced by the rarefaction and the densification of the air, viscous effect caused by the adherence of the fluid at the interface with the solid, and structure’s damping effect with mechanical energy dissipation when the sound wave impacts on the solid. Electromechanically active coupling effect, particularly piezoelectric effect, has so far been studied mainly for structural vibration damping but not for airborne sound absorption. This thesis examines contributions of the electromechanical conversion mechanism to the airborne sound absorption effect, particularly local piezoelectric effect in porous polar materials. The study on the local piezoelectric effect on airborne sound absorption properties tested in a standard impedance acoustic tube was carried out in three sections. Firstly, open-cell poly(vinylidene fluoride) (PVDF) homopolymer foams were prepared and used in order to obtain porous samples with comparable morphology and structure, but with and without substantial piezoelectric property, for providing an example showing the local piezoelectric property effect on sound absorption. Secondly, composite foams comprising piezoelectric poly(vinylidene fluoride-co trifluoroethylene) (P(VDF-TrFE)) matrix and multi-walled carbon nanotubes (MWCNTs) were fabricated and tested, with the experimental results and theoretical analyses showing how an optimal conductivity of the piezoelectric composite foams improved sound absorption coefficient. Thirdly, composite foams comprising PVDF matrix and inorganic piezoelectric potassium sodium niobate (K0.5Na0.5) NbO3 (KNN) nanofibers were produced and tested, with the investigation results showed that introducing the piezoelectric KNN nanofibers in the foams improved sound absorption coefficient. The experimental results and theoretical analyses indicate that the introduction of piezoelectric property with mechanical-into-electrical energy conversion effect in porous polymer materials can substantially enhance the airborne sound absorption performance, which is valuable to be explored for noise mitigation applications.
author2 Wang Junling
author_facet Wang Junling
Ayman Mahmod Mohamed Khalil Shahin
format Thesis-Doctor of Philosophy
author Ayman Mahmod Mohamed Khalil Shahin
author_sort Ayman Mahmod Mohamed Khalil Shahin
title Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption
title_short Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption
title_full Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption
title_fullStr Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption
title_full_unstemmed Energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption
title_sort energy conversion through local piezoelectric effect in polymer foams for enhancing sound absorption
publisher Nanyang Technological University
publishDate 2020
url https://hdl.handle.net/10356/137057
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