Date of Award
Master of Science (MS)
Graphene possesses remarkable electrical, thermal, and mechanical properties and has been utilized in many advanced applications in either independent form or nanocomposites as nanofillers. In particular, multilayer graphene nanosheets (MLGSs) have been applied as nano-reinforcements in different types of matrices. One of the most promising material systems is graphene reinforced polymer nanocomposites. Many experimental, computational, and analytical studies have been conducted to investigate the physical and functional properties of such nanocomposites. It has been shown that molecular-, nano-, and micro-structures all play significant roles in nanocomposites’ final properties.The thesis focuses on the mechanics and viscoelastic properties of graphene reinforced polymer nanocomposites depending on two specific structural features that have been largely overlooked in recent studies. The first is the wrinkles formed in MLGSs within polymer nanocomposites. The second is the polymer chain structure, particularly the side group’s size in polymer chains. Building upon previously developed coarse-grained models of both MLGSs and polymethyl methacrylate coupled with molecular dynamics (MD) simulations, I have systematically investigated nanocomposites depending on wrinkle configurations of MLGSs and polymer chain structures. I find that both factors significantly impact the mechanical and viscoelastic properties of nanocomposites through non-equilibrium MD simulations by applying different mechanical tests on representative nanocomposite systems. Interlayer sliding within MLGSs happen in specific wrinkle configurations of MLGSs under global shear deformation, which significantly influences the viscoelastic properties of nanocomposites. In addition, the size of the side group in polymer chains affects the interfacial interactions between polymer chains and graphene sheets. With these interactions being altered, the reinforcement effect of MLGSs and the dynamic moduli of the nanocomposite systems are subsequently changed. As a result, both wrinkles formed in MLGSs and side group size of polymer chains have a non-trivial effect on the mechanics and viscoelastic properties of studied nanocomposites. The studies presented in the thesis illustrate the critical dependence of graphene reinforced polymer nanocomposites on graphene configuration and polymer chain structures and provide essential insights into experimental characterization and optimized design of such composites for structural applications.
Wang, Yitao, "Mechanics and Viscoelastic Properties of Graphene Reinforced Polymer Nanocomposites Through Coarse-Grained Molecular Dynamics Simulations" (2021). All Theses. 3492.