Multiscale modeling of organic-inorganic interface: From molecular dynamics simulation to finite element modeling
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Multiscale modeling of organic-inorganic interface: From molecular dynamics simulation to finite element modeling Authors:
Denvid Lau, Oral Büyüköztürk, Markus J. Buehler
Affiliation: Department of Civil and Environmental Engineering, MIT, Cambridge, MA, United States. ABSTRACT Bi-layer material systems are found in various engineering applications ranging from nanoscale components, such as thin films in circuit boards, to macroscale structures, such as adhesive bonding in aerospace and civil infrastructure. They are also found in many natural and biological materials such as nacre or bone. The structural integrity of a bi-layer system depends on properties of both the interface and the constitutive materials. In particular, interfacial delamination has been observed as a major integrity issue. Here we present a multiscale model, which can predict the macroscale structural behavior at the interface between organic and inorganic materials, based on a molecular dynamics (MD) simulation approach combined with the metadynamics method used to reconstruct the free energy surface (FES) between attached and detached states of the bonded system. We apply this technique to model an epoxy-silica system that primarily features non-bonded and non-directional van der Waals and Coulombic interactions. The reconstructed FES of the epoxy-silica system derived from the molecular level is used to quantify the traction-separation relation at epoxy-silica interface. In this paper, two different approaches in deriving the traction-separation relation based on the reconstructed FES are described. With the derived traction-separation relation, a finite element approach using cohesive zone model (CZM) can be implemented such that the structural behavior of epoxysilica interface at the macroscopic length scale can be predicted. The prediction from our multiscale model shows a good agreement with experimental data of the interfacial fracture toughness. The method used here provides a powerful new approach to link nano to macro for complex heterogeneous material systems. INTRODUCTION Organic-inorganic interface exists in many natural and synthetic material systems, such as mineral-protein interfaces seen in bone and epoxy-silica interfaces found in concrete buildings and bridges. The study of such interfaces has been the subject of interest in various research fields, including biomechanical engineering, electrical engineering, materials science and structural engineering because of its biological, scientific and technological significance. Prior research on interfacial properties of bonded systems has demonstrated that the structural and mechanical integrity of the interface is highly affected by the physical and/or chemical interactions between the interface and the surrounding region at the nanoscale [1-4]. With the development of molecular dynamics (MD) as a powerful method to describe the mechanics of interfaces through the observation of atomic and molecular motions, the integrity of the bonded material system can be studied from a fun
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