Multiscale Modeling Approach for Glassy Polymer Using Molecular Dynamics Simulations and Micromorphic Theory
Year: 2020
Type: dissertation
Abstract: This thesis starts with an investigation on the strain rate discrepancy of tensile experiments and molecular dynamics (MD) simulations for glassy polymers. It is postulated that MD tensile simulations conducted under super-fast strain rates represent the nanoscale craze region in the macro tensile specimen. By comparing the ductile-brittle transition of glassy polymers at experiments and simulations, the postulation is validated resulting in a conclusion that to understand the constitutive relation of a glassy polymer by using the MD simulation, a multi-scale continuum approach must be employed which can incorporate MD results as the physics of the micro (or nano) scale. For this purpose, the two-scale micromorphic theory is adopted where tensile experimental results are applied to the macro-scale and MD results are applied to the micro-scale. With a proper choice of the length parameter of the micro-scale, the length scale of the continuum model became compatible with MD RUC. Finally, the multi-scale model exhibited the distinctive ductile and brittle plastic deformation when given with ductile and brittle MD s-s curves respectively. Since it also returns the dynamic response from the s-s curves, the time-scale and the strain rate of the MD simulations and the continuum model can be comparable by choosing proper model parameters. This multi-scale approach is expected to be an essential method for the scale bridging between the nanomechanics and the continuum mechanics.
Author: 박찬욱
Language: English
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3111794521