Kinetic concepts and local failure in the interfacial shear strength of epoxy-graphene nanocomposites

Interfacial shear strength (IFSS) is a key property in the design of composites and nanocomposites. Many simulation studies quantify the interfacial characteristics of sandwichlike specimens in terms of the IFSS and pullout force; a common feature of these studies is that they employ finite model systems and are therefore subject to strong finite size effects. We propose an alternative approach which is applicable to both aperiodic and periodic computational specimens. The interfaces are subjected to multiple shear deformation simulations over a wide range of temperatures (T) and shear stresses (σ_{zx}). From these simulations we collect the failure times (t_{f}); by analyzing them in the framework of an extended Boltzmann-Arrhenius-Zhurkov kinetic equation we derive the IFSS, the limiting stress for barrierless transitions, the activation energy, the activation volume for failure, the sliding velocities, and a local elastic shear modulus for the interface. We test our methodology on epoxy diglycidyl ether bisphenol F-diethyl toluene diamine interfaces in contact with (i) pristine graphene, (ii) graphene with single-atom vacancies, and (iii) graphene with hydroxyl-ΟΗ groups. Differences in the mechanism of interfacial failure among these three systems are discussed.