Polyurea/Fused-silica interfacial decohesion induced by impinging tensile stress-waves

Abstract

All-atom non-equilibrium molecular-dynamics simulations are used to investigate the problems of polyurea-borne tensile-stress waves interacting with a polyurea/fused-silica interface and fused-silica tensile-stress waves interacting with a fused-silica/polyurea interface, and the potential for the accompanying interfacial decohesion. To predict the outcome of the interactions of stress-waves with the material-interfaces in question, at the continuum level, previously determined material constitutive relations for polyurea and fused-silica are used within an acoustic-impedance-matching procedure. These continuum-level predictions pertain solely to the stress-wave/interface interaction aspects resulting in the formation of transmitted and reflected stress- or release-waves, but do not contain any information regarding potential interfacial decohesion. Present direct molecular-level simulations confirmed some of these continuum-level predictions, but also provided direct evidence of the nature and the extent of interfacial decohesion. In the molecular-level simulations, reactive force-field potentials are utilized to properly model the initial state of interfacial cohesion and its degradation during stress-wave-loading. Examination of the molecular-level interfacial structure before the stress-wave has interacted with the given interface, revealed local changes in the bonding structure, suggesting the formation of an “interphase.” This interphase was subsequently found to greatly affect the polyurea/fused-silica decohesion strength and the likelihood for interfacial decohesion during the interaction of the stress-wave with the interface.