Dynamic Mechanical Behaviors of Nacre-Inspired Graphene-Polymer Nanocomposites Depending on Internal Nanostructures*

Nacre, a natural nanocomposite with a brick-and-mortar structure existing in the inner layer of mollusk shells, has been shown to optimize strength and toughness along the laminae (in-plane) direction. However, dynamic responses and deformation mechanisms of layered structures under impact load in the out-of-plane direction, which is the dominant loading from predators, have been much less analyzed. This study investigates the dynamic mechanical behaviors of nacre-inspired layered nanocomposite films using a model system that comprises alternating multi-layer graphene (MLG) and polymethyl methacrylate (PMMA) phases. With a validated coarse-grained molecular dynamics simulation approach, we systematically study the mechanical properties and impact resistance of the MLG-PMMA nanocomposite films with different internal nanostructures, which are characterized by the layer thickness and number of repetitions while keeping the total volume constant. We first use tensile and free vibration tests to characterize the elastic moduli of nanocomposite films depending on nanostructures and illustrate the nanoconfinement effect in the layered structures. We then use ballistic impact simulations to explore the dynamic responses of nanocomposite films. We find that the impact resistance and dynamic failure mechanisms of the films depend on the internal nanostructures. Our study provides insights into the effect of nanostructures on the dynamic mechanical behaviors of layered nanocomposites, which can lead to effective design strategies for impact-resistant films.