Open Access
Matrix dependence of the linear viscoelastic region in magnetorheological elastomers
(SAGE, 2015-04-21) Agirre Olabide, Iker; Elejabarrieta, María Jesús; Bou-Ali, M. Mounir; Ingeniería; Ingeniaritza
The aim of this work is to study the linear viscoelastic region limit of isotropic magnetorheological elastomers at different compositions and working conditions. Regarding the synthesis process, the matrix and the particle content are analysed. The analysed matrixes are a natural rubber, a silicone rubber and ELASTOSIL® silicone, and three particle contents are synthesised. The influence of the characterisation variables on the linear viscoelastic limit, that is, frequency, external magnetic field and temperature, is also analysed. Strain sweep tests are used to determine the dynamic complex modulus. The loss factor and the storage modulus are analysed to define the linear viscoelastic limit of each isotropic magnetorheological elastomer sample in all the working conditions. The results show that the linear viscoelastic region of the magnetorheological elastomers is defined by the loss factor. Moreover, the volumetric particle content reduces and frequency increases the linear viscoelastic region of all the matrixes, whereas the external magnetic field and the temperature influences are matrix dependent.
Open Access
Maximum attenuation variability of isotropic magnetosensitive elastomers
(Elsevier, 2016-07-14) Agirre Olabide, Iker; Elejabarrieta, María Jesús; Ingeniería; Ingeniaritza
Magnetosensitive elastomers (MSE) are innovative high-tech materials that exhibit changed dynamic properties when an external magnetic field is applied. In this work, the influence of particle content, frequency, temperature and magnetic field on the maximum attenuation of isotropic MSEs was studied. Six particle content types were synthesised using carbonyl iron powder particles embedded in a room-temperature vulcanizing silicone rubber matrix. The characterization of the MSE samples was performed with a Physica MCR 501 rheometer from the Anton Paar Company that is equipped with a magnetorheological cell. All samples were characterized using frequency sweep tests within the lineal viscoelastic region. In addition, a four-parameter fractional derivative model was used and extended over a wide frequency range. The influence of temperature was modelled using the Arrhenius model, coupled with the fractional derivative model. The maximum attenuation is increased with frequency and magnetic field and is independent of temperature.
Open Access
Compression and torsion testing for elastic moduli and Poisson's ratio characterization in silicone rubber samples with varying shape factors
(Elsevier, 2025-05-19) Cortazar-Noguerol, Julen; Cortés, Fernando; Agirre Olabide, Iker; Elejabarrieta, María Jesús; Ingeniería; Ingeniaritza
Elastomeric materials, such as silicone rubber, are widely used in engineering applications due to their high deformability and viscoelastic properties. Under quasistatic regime and small deformations their behavior can be considered purely elastic and can be characterized by the elastic modulus, shear modulus, and Poisson's ratio, which are interrelated in isotropic materials. Although standard methodologies exist for determining these properties, experimental measurements are known to be affected by the geometry of the tested samples. The influence of sample geometry on compressive modulus measurements is well understood, however, its effect on shear modulus measurements is less explored. This study investigates how the dimensions of cylindrical samples influence the experimental determination of both the compressive and shear moduli and, consequently, Poisson's ratio. Compression and torsion tests are performed on silicone rubber samples of varying diameters and lengths using a dynamic mechanical analyzer and a rheometer respectively. The results confirm that both the compressive and shear moduli are affected by sample geometry, leading to unrealistic values of Poisson's ratio. To account for these effects, a correction model is proposed for shear modulus measurements, complementing existing corrections for compressive tests. The model successfully describes experimental trends and provides a more reliable estimation of Poisson's ratio, aligning with theoretical expectations for nearly incompressible elastomers. These findings emphasize the importance of considering geometric effects in compressive and torsion tests and provide a framework for improving the accuracy of mechanical characterization in elastomeric materials.
Open Access
Characterization of the linear viscoelastic region of magnetorheological elastomers
(SAGE, 2014-01-13) Agirre Olabide, Iker; Berasategui, Joanes; Elejabarrieta, María Jesús; Bou-Ali, M. Mounir; Ingeniería; Ingeniaritza
The linear viscoelastic behaviour of magnetorheological elastomers is analysed in this work according to their formulation and working conditions. This study comprised both the synthesis of different magnetorheological elastomers and the strain and frequency sweep characterization under different magnetic fields and temperatures. The characterization was performed by a Physica MCR 501 rheometer from Anton Paar, equipped with a magnetorheologic cell 70/1T MRD. In the synthesis with a given elastomeric matrix, samples with different magnetic particle content are studied with two types of curing conditions: under the action of a magnetic field (anisotropic magnetorheological elastomers) and without a magnetic field (isotropic magnetorheological elastomers). The working conditions are excitation frequency, temperature and the applied external magnetic field. In this work, a new procedure to determine the linear viscoelastic behaviour is proposed; the loss factor is analysed in addition to analysing the storage modulus to determine the linear viscoelastic region of each sample. The results show that high temperatures and magnetorheological elastomers with higher volume fraction of magnetic particles restrict the linear viscoelastic behaviour of magnetorheological elastomers.

Agirre Olabide, Iker

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