Superior impact resistance conferred by hierarchical nacre-inspired nanocomposites: A molecular dynamics study

Innovations in impact-resistant materials design inspired by nacre's hierarchical “brick and mortar” structure have ushered a new era of lightweight biomimetics with exceptional strength and toughness. However, the role of microstructure, notably the effect of hierarchy, is hitherto poorly understood. Here, we investigate the impact resistance of graphene-polyethylene nanocomposites that are modeled after nacre's microstructure, capturing the behavior of the stiff (graphene) and soft (polyethylene) phases. Besides the dependence of the impact resistance on the graphene grain size and grafting between the phases, we show that it is the hierarchy that plays the most important role in drastically enhancing impact resistance, with the hierarchical nanocomposite showing up to a three-fold improvement in the ballistic limit without grafting, and a seven-fold increase in the presence of grafting. This research also sheds light on the detailed molecular mechanisms behind these enhancements that can be leveraged for the development of advanced biomimetic materials.