The purpose of this paper is to address the problems of interaction of tensile stress-waves with polyurea/fused-silica and fused-silica/polyurea interfaces, and the potential for the accompanying interfacial decohesion.
The problems are investigated using all-atom non-equilibrium molecular-dynamics methods and tools. Before these methods/tools are employed, previously determined material constitutive relations for polyurea and fused-silica are used, within an acoustic-impedance-matching procedure, to predict the outcome of the interactions of stress-waves with the material-interfaces in question. These 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. Direct molecular-level simulations confirmed some of these predictions, but also provided direct evidence of the nature and the extent of interfacial decohesion. To properly model the initial state of interfacial cohesion and its degradation during stress-wave-loading, reactive forcefield potentials are utilized.
Direct molecular-level simulations of the polyurea/fused-silica interfacial regions prior to loading 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.
To the authors’ knowledge, the present work is the first public-domain report of the use of the non-equilibrium molecular dynamics and reactive force-field potentials to study the problem of interfacial decohesion caused by the interaction of tensile waves with material interfaces.
The material presented in this paper is based on work supported by the Office of Naval Research (ONR) research contract entitled “Elastomeric Polymer-By-Design to Protect the Warfighter Against Traumatic Brain Injury by Diverting the Blast Induced Shock Waves from the Head”, Contract Number 4036-CU-ONR-1125 as funded through the Pennsylvania State University, and the Army Research Office (ARO) research contract entitled “Friction Stir Welding Behavior of Selected 2000-series and 5000-series Aluminum Alloys”, Contract Number W911NF-11-1-0207. The authors are indebted to Dr Ralph A. Anthenien Jr of ARO for his continuing support and interest in the present work.
Grujicic, M., Yavari, R., Snipes, J.S., Ramaswami, S. and Barsoum, R.S. (2014), "All-atom molecular-level computational analyses of polyurea/fused-silica interfacial decohesion caused by impinging tensile stress-waves", International Journal of Structural Integrity, Vol. 5 No. 4, pp. 339-367. https://doi.org/10.1108/IJSI-01-2014-0001
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