RESUMO

The aim of this article was to investigate the mechanical performance of magnetorheological polyurethane elastomers reinforced with different concentrations of carbonyl iron microparticles (CIPs) in which stress softening, energy dissipation, residual strains, microparticles orientation, and magnetic flux density effects will be considered. Other aspects, such as the determination of the dissipated energy during cyclic loading and unloading, were investigated by considering a pseudo-elastic network model that takes into account residual strains, magnetic field intensity, and the isotropic and anisotropic material behavior. Theoretical predictions confirmed that the material shear modulus becomes sensitive not only for higher concentrations of CIPs added into the elastomer material matrix, but also to the magnetic flux intensity that induces attractive forces between CIPs and to the strong bonds between these and the elastomer matrix. It was also found that the addition of CIPs when embedded into the polymer matrix with a predefined orientation enhances the material shear modulus as well as its capacity to dissipate energy when subjected to magnetic flux density in loading and unloading directions.

Assuntos

RESUMO

This article focuses on evaluating the influence that the addition of carbonyl iron micro-particles (CIPs) and its alignment have on the mechanical and rheological properties for magnetorheological elastomers (MREs) fabricated using polydimethylsiloxane (PDMS) elastomer, and 24 wt % of silicone oil (SO). A solenoid device was designed and built to fabricate the corresponding composite magnetorheological material and to perform uniaxial cyclic tests under uniform magnetic flux density. Furthermore, a constitutive material model that considers both elastic and magnetic effects was introduced to predict stress-softening and permanent set effects experienced by the MRE samples during cyclic loading tests. Moreover, experimental characterizations via Fourier transform infrared (FTIR), X-ray diffraction (XRD), tensile mechanical testing, and rheological tests were performed on the produced MRE samples in order to assess mechanical and rheological material properties such as mechanical strength, material stiffness, Mullins and permanent set effects, damping ratio, stiffness magnetorheological effect (SMR), and relative magnetorheological storage and loss moduli effects. Experimental results and theoretical predictions confirmed that for a CIPs concentration of 70 wt %, the material samples exhibit the highest shear modulus, stress-softening effects, and engineering stress values when the samples are subject to a maximum stretch value of 1.64 and a uniform magnetic flux density of 52.2 mT.