Modeling of Structural Damage Evolution in Dispersion-Filled Elastomeric Nanocomposites with Regard for Interfacial Interaction

Abstract

Computer modeling of internal damage evolution in elastomeric nanocomposites with high structural phase inhomogeneity (hard dispersed filler and soft elastomeric matrix) has been carried out. The concentration of filler particles was chosen to be sufficiently high, so that their mutual interaction affected significantly the strength properties of the material. Dispersed inclusions were assumed to be absolutely rigid and durable. Only a finitely deform able incompressible matrix (the mechanical properties of which were set using the neo-Hookean elastic potential) could be damaged. The model takes into account the following specific features of the composite structure: a high stress concentration in the gaps between closely located inclusions, the presence of elastomeric layers with increased stiffness on the surface of filler particles, different interphase contact conditions (full adhesion or slip at the matrix–inclusion interface), and the possibility of anisotropic hardening during uniaxial stretching (due to the reorientation of molecular chains in the elongation direction). The latter factor made it possible to study theoretically the mechanism of formation of high-strength microstrands in the gaps between adjacent particles. The occurrence of such formations in filled elastomers, which was observed in numerous experiments, is a proven fact. A new (anisotropic) fracture criterion has been developed to describe it, because this phenomenon cannot be simulated within the generally accepted strength criteria. The calculations based on this new approach showed that local matrix discontinuities occur not in the gaps between particles (sites of highest stress concentration) but at a certain distance, forming a hollow ring (microstrand) around it. The link between neighboring inclusions is not violated, and the material retains its load-carrying capacity at the macrolevel. Thus, the presence of microstrands is a possible reason for hardening an elastomer when a hard dispersed filler is introduced into it.