Experimental analysis of the effect of carbon nanoparticles with different geometry on the appearance of anisotropy of mechanical properties in elastomeric composites

The paper presents studies of the properties of elastomeric materials based on the solution-polymerized styrene-butadiene rubber (S-SBR) filled with nanoparticles of different geometry – grainy (nanodiamonds), layered (graphene nanoplates) and fibrous (nanotubes). Despite the introduction of a small amount of fillers, the significant strengthening of the matrix is exhibited. Of particular interest is the behavior of the nanodiamond-filled elastomer composite, for which a double increase in rupture stress with an increase in rupture strain is observed at the filler volume fraction approximately equal to 2%. The structure of composites is investigated by optical and atomic force microscopy. In addition to standard mechanical testing, experiments of successive cyclic loading along each of two mutually perpendicular axes of plane elastomeric samples were conducted with use of a Zwick 4-vector test stand (biaxial testing machine). The phenomenon of induced anisotropy in materials is analyzed. A hypothesis to explain its manifestation is suggested.