Collaborative Research: Experimental and Computational Nanomechanics of the Load Transfer Mechanisms at the Graphene Polymer Interface

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Polymer nanocomposites show substantial property enhancements at much lower filler component weight as compared to conventional polymer composites. Graphene has been considered an ideal candidate for reinforcing additives in polymers due to its high stiffness and strength. However, there is a lack of fundamental understanding of strength properties of graphene-polymer interfaces. This collaborative research award supports fundamental research to provide mechanistic understanding of the stress-transfer processes across interfaces between selected polymers and graphene. These processes ultimately control the stiffness, strength, and toughness of graphene polymer nanocomposite. This research will contribute towards achieving light, strong, and tough polymer nanocomposite materials. Such advanced materials would impact the aerospace and automotive industries. The research crosses the disciplines of manufacturing, mechanics, materials science, and nanotechnology. Results from this multi-disciplinary research will be incorporated into existing undergraduate courses at both universities. The research results will also form the basis of a new lecture series for K-12 summer camp students introducing these poetntail future engineers to the topic of polymer nanocomposites as next generation aerospace materials. The strength characteristics of graphene-polymer interfaces play critical roles in the bulk mechanical response of graphene-based nanocomposites. Yet, the complex nanoscale phenomena occurring during shear deformation associated with the pull-out of graphene from the polymer matrix are not well understood. This collaborative research award supports investigations of deformation, load transfer and failure of graphene-polymer interfaces at the nanoscale. A combination of complementary experimental and computational methods is employed. The research team will perform pull-out tests on individual graphene sheets embedded within polymer matrixes using an unique in-situ nanomechanical characterization technique. The nanomechanical pull-out experiments will provide direct and quantitative measurements of the interfacial strength properties. These experiments represent a significant advancement over prior macroscopic measurements of the bulk composite properties where the graphene-polymer interfacial properties can only be inferred indirectly and qualitatively. In parallel, molecular dynamics simulations of the pull-out tests will be conducted at size-scales relevant to the experiments. This complementary approach facilitates comparison between the results of experiments and simulations. The simulations will provide insights into the fine graphene-polymer interfacial details not accessible by experiments, and will guide further experiments. This complementary experimental and computational effort will provide mechanistic understanding of the nanoscale interfacial strengthening processes, and decipher the roles of the size and morphology of the embedded graphene on the mechanical strength of graphene-polymer interfaces.