Manufacturing, structure and properties of magnetorheological elastomers

Stefan Awietjan

Abstract

The subject of this work were magnetorheological elastomers (MREs) – analogues of magnetorheological fluids. MREs change their rheological properties under an external magnetic field and are considered to be “smart materials”, which are used as actuators and in active vibration damping systems. The fields of their applications include automobile and aviation industry where they can be used for dampers. The aim of this work was to develop original elastomers capable of changing their rheological properties in an external magnetic field, which are based on ferromagnetic particles – carbonyl iron with different sizes of particles dispersed in soft polyurethane and urea-urethane elastomers. The conducted research programme included optimising composition and manufacturing conditions to obtain desirable properties of the MREs. It has been found that the volume fracture of ferromagnetic particles has a significant effect on their arrangement into aligned structures under external magnetic field. For small volume fractions Fe particles arrange easily into chain-like structures. When the amount of particles is high spatial network of particles is observed. It was also found that the viscosity of the matrix has a significant effect on the arrangement of particles under an applied magnetic field. In the case of high viscosity matrices, higher strength fields are required. The microstructure of the MREs was correlated with magnetic properties, parallel and perpendicular to the particle orientation. It has been found that the change of MRE properties under the influence of an external magnetic field strongly depends on the microstructure shaped during curing of the elastomeric matrix under magnetic field. The magnetorheological material response to the applied magnetic field was measured, using a specially designed set-up. The results confirmed that the displacement of the MREs in the external magnetic field depends on the number of particles and their arrangement. The results of the compression tests showed that under an external magnetic field the composites exhibit high compressive strengths. The increase in stiffness is greater with a higher density of ferromagnetic particles. The results also show that rheological properties of the obtained MRE samples depend on the microstructure, which in turn depends on the amount of ferromagnetic particles and their arrangement. It has been shown that the storage modulus of the MRE composites 8 increases significantly under applied magnetic field. The elastic modulus increases with increasing angular frequency and strength of the applied magnetic field. The MREs fabricated in this thesis were found to change their elastic properties rapidly and reversibly under the influence of an external magnetic field. Samples with anisotropic, aligned microstructures were shown to have much better magnetorheological properties than isotropic microstructure. The behaviours of the MRE composites investigated in the present work indicate that such composites could be applied as intelligent dampers and actuators.
Diploma typeDoctor of Philosophy
Author Stefan Awietjan (FMSE)
Stefan Awietjan,,
- Faculty of Materials Science and Engineering
Title in EnglishManufacturing, structure and properties of magnetorheological elastomers
Languageen angielski
Certifying UnitFaculty of Materials Science and Engineering (FMSE)
Disciplinematerial sciences and engineering / (technology domain) / (technological sciences)
Defense Date24-09-2010
Supervisor Krzyszof Kurzydłowski (FMSE)
Krzyszof Kurzydłowski,,
- Faculty of Materials Science and Engineering

Internal reviewers Marcin Leonowicz (FMSE / DCFM)
Marcin Leonowicz,,
- Division of Construction and Functional Materials
External reviewers Jerzy Kaleta, prof. - [Wroclaw University of Science and Technology (PWr)]
Jerzy Kaleta, prof.,,
-
- Politechnika Wrocławska
Pages136
Keywords in Englishxxx
Abstract in EnglishThe subject of this work were magnetorheological elastomers (MREs) – analogues of magnetorheological fluids. MREs change their rheological properties under an external magnetic field and are considered to be “smart materials”, which are used as actuators and in active vibration damping systems. The fields of their applications include automobile and aviation industry where they can be used for dampers. The aim of this work was to develop original elastomers capable of changing their rheological properties in an external magnetic field, which are based on ferromagnetic particles – carbonyl iron with different sizes of particles dispersed in soft polyurethane and urea-urethane elastomers. The conducted research programme included optimising composition and manufacturing conditions to obtain desirable properties of the MREs. It has been found that the volume fracture of ferromagnetic particles has a significant effect on their arrangement into aligned structures under external magnetic field. For small volume fractions Fe particles arrange easily into chain-like structures. When the amount of particles is high spatial network of particles is observed. It was also found that the viscosity of the matrix has a significant effect on the arrangement of particles under an applied magnetic field. In the case of high viscosity matrices, higher strength fields are required. The microstructure of the MREs was correlated with magnetic properties, parallel and perpendicular to the particle orientation. It has been found that the change of MRE properties under the influence of an external magnetic field strongly depends on the microstructure shaped during curing of the elastomeric matrix under magnetic field. The magnetorheological material response to the applied magnetic field was measured, using a specially designed set-up. The results confirmed that the displacement of the MREs in the external magnetic field depends on the number of particles and their arrangement. The results of the compression tests showed that under an external magnetic field the composites exhibit high compressive strengths. The increase in stiffness is greater with a higher density of ferromagnetic particles. The results also show that rheological properties of the obtained MRE samples depend on the microstructure, which in turn depends on the amount of ferromagnetic particles and their arrangement. It has been shown that the storage modulus of the MRE composites 8 increases significantly under applied magnetic field. The elastic modulus increases with increasing angular frequency and strength of the applied magnetic field. The MREs fabricated in this thesis were found to change their elastic properties rapidly and reversibly under the influence of an external magnetic field. Samples with anisotropic, aligned microstructures were shown to have much better magnetorheological properties than isotropic microstructure. The behaviours of the MRE composites investigated in the present work indicate that such composites could be applied as intelligent dampers and actuators.
Thesis file
Awietjan.pdf 13.36 MB

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