Characterization of the intrinsic strength between epoxy and silica using a multiscale approach
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ganic–inorganic interfaces exist in many natural or synthetic materials, such as mineral–protein interfaces found in bone and epoxy–silica interfaces found in concrete construction. Here, we report a model to predict the intrinsic strength between organic and inorganic materials, based on a molecular dynamics simulation approach combined with the metadynamics method, used to reconstruct the free energy surface between attached and detached states of the bonded system and scaled up to incorporate it into a continuum model. We apply this technique to model an epoxy–silica system that primarily features nonbonded and nondirectional van der Waals and Coulombic chemical interactions. The intrinsic strength between epoxy and silica derived from the molecular level is used to predict the structural behavior of epoxy–silica interface at the macroscopic length scale by invoking a finite element approach using a cohesive zone model which shows a good agreement with existing experimental results.
I. INTRODUCTION
Organic–inorganic interface exists in many material systems that can be found broadly in natural and synthetic materials, 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 investigations in various research fields, including biomechanical engineering, electrical engineering, materials science, and structural engineering because of its biological, scientific, and technological significance. Based on prior research on interfacial properties of bonded systems,1–4 it is known 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. With the development of molecular dynamics (MD) as a powerful method to describe the mechanics of interfaces from fundamental chemical principles upwards, information about the mechanical behavior of the interfacial region through the observation of atomic and molecular motions can be acquired.5,6 In particular, the integrity of the bonded material system can be studied from a fundamental perspective by monitoring the interactions and the deformation mechanism between two materials along the interfacial region at a molecular level. More recently, there are several examples where mechanical properties from molecular simulations match reasonably well with those measured experimentally at larger scales a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.96 J. Mater. Res., Vol. 27, No. 14, Jul 28, 2012
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(see, e.g., case studies discussed in Ref. 6). However, deformation mechanisms at the interface can be complicated and can change across different length scales. Besides the change of deformation mechanisms, the disparity in timescale and length scale also leads to the discrepancies between MD simulation and the experimental results. Hence, there is a need
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