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Performance of Magnetorheological Rubber Materials
KTH, Superseded Departments, Fibre and Polymer Technology.
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Magnetorheological (MR) rubber materials are the solid analogue of magnetorheological fluids; i.e. their rheological properties can be controlled continously, rapidly, and reversibly by an applied magnetic field. They consist of magnetically polarisable particles in an elastomer matrix and they can be made to respond to changes in their environment; hence, they are considered as "smart" materials. Examples of potential applications for these materials are adaptive tuned vibration absorbers, stiffness-tuneable mounts and suspensions, and automotive bushings.

The purpose of this work was to increase the knowledge relating to magnetorheological materials for damping applications. The materials should exhibit a large response to an applied magnetic field, and have good mechanical and long-term properties.

MR rubber materials were made from nitrile, natural and silicone rubber, with irregularly shaped iron particles several micrometres in size. The particles were not aligned by a magnetic field prior to the vulcanisation; hence, the materials can be considered to be isotropic. These materials show a large MR effect, i.e. an increase in the shear modulus when a magnetic field is applied, although the particles are not aligned within the material. This is explained by the low critical particle volume concentration (CPVC) of such particles. Similar behaviour can be obtained with materials containing carbonyl iron, if the particles are aggregated so that they behave like large irregular particles. The iron particle concentration must be very close to the CPVC in order to obtain a large MR effect without alignment of the particles.

The absolute MR effect (MPa) in an isotropic MR rubber material with large irregular iron particles is independent of the matrix material, and the relative MR effect (%) can thus be increased by the addition of plasticisers. However, the obtainable effect is limited by the reinforcement of the particles and by friction between the particles. Therefore, it is very difficult, if not impossible, to achieve an MR effect larger than 60%.

Other ways of increasing the MR effect are to increase the strength of the magnetic field, although the materials saturate magnetically at high field strengths, or to use small strain amplitudes. The strong strain amplitude dependence of the MR effect suggests that MR rubber materials are most suitable for low amplitude applications, such as sound and vibration insulation. Measurements at frequencies within the audible frequency range show that this is a promising application for MR rubber materials.

The incorporation of large amounts of iron into the rubber matrix decreases the oxidative stability dramatically. This is probably due to iron oxides on the surface of the particles, and to the fact that the oxidation rate is enhanced by iron ions, which are able to diffuse into the matrix. Standard antioxidants do not provide sufficient stabilisation for MR rubbers. Thus, proper stabilisation systems have to be found in order for these materials to be successful in applications.

Place, publisher, year, edition, pages
Stockholm: Fiber- och polymerteknologi , 2004.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2004:32
Keyword [en]
Materials science, magnetorheological rubber
Keyword [sv]
Materialvetenskap
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-31ISBN: 91-7283-856-6 (print)OAI: oai:DiVA.org:kth-31DiVA: diva2:8859
Public defence
2004-10-01, K2, KTH, Teknikringen 28, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2012-03-22
List of papers
1. Performance of Isotropic Magnetorheological Rubber Materials
Open this publication in new window or tab >>Performance of Isotropic Magnetorheological Rubber Materials
2003 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 22, no 3, 245-251 p.Article in journal (Refereed) Published
Abstract [en]

Magnetorheological (MR) rubber materials are the solid analog of magnetorheological fluids; hence, their theological properties can be controlled by an applied magnetic field. If the particles embedded in the matrix are carbonyl iron, they have to be aligned by a magnetic field before the curing of the rubber, in order to achieve a substantial MR effect. However, the use of a crosslinked matrix allows larger particles to be used. We show that MR rubber materials with large irregular particles have a large MR effect although the particles are not aligned within the material. This is explained by the low critical particle volume concentration of such particles. A similar effect can be obtained for materials with carbonyl iron, if the particles are badly dispersed and thereby behaving like larger irregular particles. Besides the achieved level of dispersion, the theological properties of the matrix material do not influence the MR effect.

Keyword
magnetorheology, rubber, NBR, iron, critical particle volume concentration
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5333 (URN)10.1016/S0142-9418(02)00043-0 (DOI)000180951300002 ()
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2017-12-01Bibliographically approved
2. Structure-borne sound properties of isotropic magneto-rheological rubber
Open this publication in new window or tab >>Structure-borne sound properties of isotropic magneto-rheological rubber
2002 (English)In: Kautschuk und Gummi, Kunststoffe, ISSN 0022-9520, Vol. 55, no 12, 669-673 p.Article in journal (Refereed) Published
Abstract [en]

The dynamic properties of isotropic magneto-rheological rubber are examined through experiments within an audible frequency range covering 100 to 1250 Hz while applying an external magnetic field of 0 to 0.8 T. The shear modulus for this manufacturer convenient material, consisting of dispersed irregular, micrometer sized iron particles in a nitrile rubber matrix, is found to depend strongly on both frequency and magnetic field, while the loss factor is almost independent of those factors. Magneto-rheological rubbers applied to vibration isolators promise to have more functionality than conventional isolators while rapidly and reversibly change rigid body and stiffness peak frequencies.

Keyword
magneto-rheology, isotropy, iron particle, shear modulus, loss factor, magnetic field
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-5334 (URN)000179899900007 ()
Note
NR 20140805Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2017-12-01Bibliographically approved
3. Improving the magnetorheological effect in isotropic magnetorheological rubber materials
Open this publication in new window or tab >>Improving the magnetorheological effect in isotropic magnetorheological rubber materials
2003 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 22, no 6, 677-680 p.Article in journal (Refereed) Published
Abstract [en]

Magnetorheological (MR) rubber materials are the solid analogue of magnetorheological fluids; i.e. their theological properties can be controlled by an applied magnetic field. However, the use of a crosslinked matrix allows larger particles to be used than in fluid matrices, and when large irregular particles are used alignment of the particles is not necessary for obtaining a substantial MR effect. We show that the absolute MR effect of isotropic MR rubber materials with large irregular iron particles is independent of the matrix material, and that the relative MR effect can be increased by the addition of plasticisers. Other ways of increasing the MR effect are to increase the magnetic field, although the materials saturate magnetically at high fields, or to use small amplitude strains. Finally, we show that the damping of isotropic MR rubbers is to some extent increased by an applied magnetic field, but that the increase is too small to be of any practical importance.

Keyword
magnetorheology, rubber, iron, plasticiser
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5335 (URN)10.1016/S0142-9418(02)00175-7 (DOI)000183686500011 ()
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2017-12-01Bibliographically approved
4. Oxidation of Natural Rubber based Magnetorheological Elastomers
Open this publication in new window or tab >>Oxidation of Natural Rubber based Magnetorheological Elastomers
2004 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 86, no 3, 467-471 p.Article in journal (Refereed) Published
Abstract [en]

The Theological properties of magnetorheological (MR) materials can be changed continuously, rapidly and reversibly by an applied magnetic field. Solid MR materials consist of magnetically polarisable particles, generally iron, in an elastomer matrix. The high iron concentrations required (about 30% by volume) in order to get a substantial magnetorheological effect should influence the long-term stability of the materials. In this paper, the oxidative stability of natural rubber-based magnetorheological elastomers has been studied by chemiluminescence and oven ageing. The results show that the oxidative stability of natural rubber decreases dramatically when large amounts of iron particles are incorporated in the matrix. This is probably due to the large amounts of oxygen on the surface of the particles. Conventional antioxidants can be used to prolong the lifetime of magnetorheological elastomers, but in order to get acceptable lifetime of the materials a careful selection of the antioxidant system has to be made.

Keyword
Iron, Magnetorheology, Natural rubber, Oxidation
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5336 (URN)10.1016/j.polymdegradstab.2004.05.019 (DOI)000225547600010 ()2-s2.0-5644268085 (Scopus ID)
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2017-12-01Bibliographically approved
5. Magnetorheological Rubber Materials: The role of Reinforcement and Friction
Open this publication in new window or tab >>Magnetorheological Rubber Materials: The role of Reinforcement and Friction
(English)Manuscript (Other academic)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5337 (URN)
Note
QC 20110214Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2011-02-14Bibliographically approved

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