Multiscale modeling of carbon nanotube-reinforced polymer with coarse-grain molecular dynamics informed morphology

This article presents a molecular dynamics (MD)-aided multiscale modeling framework that accounts for the nanoscale deformation kinetics and morphological irregularities in polymer with randomly-dispersed carbon nanotubes (CNTs). First, a novel coarse-grain MD approach is developed to generate large-size simulation domains comprising realistic aspect ratio CNTs and crosslinked molecular network of the bulk thermoset polymer. The coarse-grain approach can simulate the CNT dispersion state and cluster formation resulting from molecular-level interactions during the polymer curing process, several orders of magnitude faster than traditional all-atom MD approaches. Next, CNTs are approximated as equivalent solid fibers at the continuum level, and their cluster morphology is geometrically reconstructed using the information obtained from coarse-grain simulations. The reconstructed CNTs are embedded within a host polymer finite element simulation domain for multiscale homogenization. The polymer is modeled using a recently developed damage model that accounts for bond breakage information obtained from all-atom simulations. Standardized test specimens are also fabricated and characterized to support model calibration and hypotheses. The model predictions for effective properties correlated well with in-house and literature test results for different CNT weight fractions. The model also revealed critical mechanisms attributed to improved mechanical properties with increasing CNT aspect ratios.