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Improving the magnetorheological effect in isotropic magnetorheological rubber materials
KTH, Superseded Departments, Fibre and Polymer Technology.
KTH, Superseded Departments, Fibre and Polymer Technology.
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.

Place, publisher, year, edition, pages
2003. Vol. 22, no 6, 677-680 p.
Keyword [en]
magnetorheology, rubber, iron, plasticiser
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-5335DOI: 10.1016/S0142-9418(02)00175-7ISI: 000183686500011OAI: oai:DiVA.org:kth-5335DiVA: diva2:8856
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2017-12-01Bibliographically approved
In thesis
1. Performance of Magnetorheological Rubber Materials
Open this publication in new window or tab >>Performance of Magnetorheological Rubber Materials
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
Materials science, magnetorheological rubber, Materialvetenskap
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-31 (URN)91-7283-856-6 (ISBN)
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

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