The central goal of this project is to establish a paradigm shift in material design by combining theory, modeling, and experimentation in a multiscale and synergistic manner to maximize the strength and toughness of nanocomposite materials that emulate the performance of natural nacre using graphene oxide. It is expected that graphene oxide sheets with optimal overlap geometry, bonded together by tunable chemistry, will mimic nacre. Specifically, this research will lead to characterization of the deformation mechanisms of multilayer nanocomposite systems through studies of the strength and stiffness of both the individual atomically thin sheets as well as their crosslinking elements. This project aims to develop a fundamental understanding of the roles that van der Waals interactions, hydrogen bonds, and chemical crosslinking, conformation, and geometrical assembly play in modulating the mechanical behavior of nanocomposite materials based on graphene oxide. The mechanical performance of functionalized graphene sheets and macroscopic oxidized-graphene materials will be optimized through a series of iterative synthesis-assembly-modeling cycles.
Novel nanoscale mechanical testing methods based on MEMS technologies and AFM will be applied to measure the mechanical behavior of few-layer graphene oxide materials with "brick-and-mortar" like hierarchical structures. New crosslinking chemistries, such as thiol-amines, will be explored to impart significant improvements in controlling shear interactions through covalent bond breaking and reformation. Varying geometrical overlap between layers and conformations of the sheets will be explored. In-situ electron microscopy mechanical testing, to yield atomic and micro-scale characteristics on multiple length scales, coupled with computational modeling using ab initio and semi-empirical methods, will quantify the interface strength and deformation governing load-transfer mechanisms. The developed insight will then be used to guide the synthesis of a macroscopic nanocomposite material that takes advantage of the strength of graphene and the hierarchically assembled structures inspired by Nature.
It is expected that the development of criteria for predicting and tailoring the mechanical properties of graphene oxide-based nanocomposite materials will be transferable to a wide range of nanocomposites and will optimize the design process of materials with hierarchical structure that incorporate stiff building blocks and ductile crosslinking elements. These next-generation synthetic materials are essential for advances in the aerospace, satellite, automotive, military, and healthcare industries. The research also will serve as an excellent training platform for graduate students and postdoctoral fellows in the critical frontier of structure-based material design and in the art of interdisciplinary scientific research in the areas of synthesis, modeling, and hierarchical measurements.
