An Optimum Specimen Geometry for Equibiaxial Experimental Tests of Reinforced Magnetorheological Elastomers with Iron Micro- and Nanoparticles

Abstract

The aim of this paper focused on obtaining the optimum cruciform geometry of reinforced magnetorheological elastomers (MRE) to perform homogeneous equibiaxial deformation tests, by using optimization algorithms and Finite Element Method (FEM) simulations. To validate the proposed specimen geometry, a digital image correlation (DIC) system was used to compare experimental result measurements with respect to those of FEM simulations. Moreover, and based on the optimum cruciform geometry, specimens produced from MRE reinforced with carbonyl-iron microparticles or iron nanoparticles were subjected to equibiaxial loading and unloading cycles to examine their Mullin’s effect and their residual strain deformations.

Development, Fabrication, and Characterization of Composite Polycaprolactone Membranes Reinforced with TiO2 Nanoparticles

“…The strain field values on the sample surface were measured using a digital image correlation (DIC) system, Aramis V8. The measurements were performed at room temperature using a cruciform sample geometry [14]. The corresponding experimental tests were carried out by considering three loading and unloading cycles with specified displacement of 1, 2, and 3 mm.…”

Basic studies in biaxial tensile tests

“…This can be performed either by finite element simulations, where a constitutive model has to be assumed, or by experimental testing (or a combination of both). Shape optimization using finite elements might either be done by trial and error contour definitions, or by applying numerical tools from optimization …”

“…Shape optimization using finite elements might either be done by trial and error contour definitions, [27,30,34] or by applying numerical tools from optimization. [20,36,37] Since we are interested in talking about homogeneity of the strain distribution in a certain region, we have to introduce a measure. Thus, we define the region length L 0 , which is clear for the specimens in Figures 2A and 4A; thinnest region in the center of the specimen, and determine the mean value within the central region of L m = 0.2L 0 using the data of the DIC system.…”

“…In Hannon and Tiernan the literature review about planar biaxial tests and possible geometry of thin steel sheet specimens is provided. The proposed geometries range from the ones with constant thickness, where the shape and the radius of the 4 corners at the intersection of the arms vary or some slots are realized, as well, to the ones with a reduction of the center section of the specimen . Further proposals of biaxial testing machines and methods for the optimal design of laminates and fiber composite specimens can be found .…”

“…Further studies on shape optimization and biaxial validation tests of polymeric elastomers can be found in Chen etal and Seibert et al, where different geometries of a one‐layer specimen have been tested. In this respect, we refer to Palacios‐Pineda et al as well, where shape optimization is applied to obtain a minimum equivalent strain difference at two points in the center of the specimen. In this respect see Makris et al also.…”