Study of mechanical behavior of elastomeric nanocomposites under large cyclic shear deformations

Abstract

The paper presents the results of experimental studies of viscoelastic properties of elastomeric nanocomposites based on styrene-butadiene rubber and various nanofillers: carbon black, detonation nanodiamonds, graphene nanoplates and single-walled graphene nanotubes. Corresponding tests were also carried out for pure unfilled rubber (as a basis for comparison and analysis of results). Non-standard samples and equipment specially designed for testing at finite shear strains (deformation by hundreds of percent) were used. In order to reveal the specific features of the viscoelastic behavior of the materials under consideration, test programs with complex loading trajectories were carried out —  symmetric cyclic shear deformation with increasing amplitude and stops for relaxation when the direction of the tensile machine grips movement is changed. In addition, to evaluate the strength properties of these nanocomposites, they were all subjected to standard uniaxial tensile to rupture tests at a constant strain rate. The analysis of the obtained experimental data is carried out. It was found that the greatest enhancement effect is provided by the input of carbon nanotubes — several times in comparison with other samples. In this case, the largest increase in the hysteresis loop (i.e. dissipative loss) is also observed. This circumstance is very important when using such materials as damping elements. According to the authors, the effect of mechanical enhancement at large shear strains depends on the shape of the nanofiller particles. Nanotubes, due to their huge (compared to the transverse dimensions) length and flexibility, have a much stronger effect on the rearrangement of the composite microstructure compared to other types of fillers, thereby increasing dissipative losses.