Session: 04-28-02: Modeling and Experiments in Nanomechanics and Nanomaterials

Paper Number: 113779

113779 - Crystal Plasticity Modeling for the Strengthening Effect of Multilayered Copper-Graphene Nanocomposites 

The work investigates plastic deformation mechanisms in metal-graphene nanocomposite to demonstrate the strengthening effect of materials through a crystal plasticity finite element (CPFE) model comparing published experimental results. The existing experimental research identified that the two-dimensional shape of graphene, which can effectively control dislocation motion, can significantly strengthen metals. Considering the nature of dislocation motions in hundreds of nano-meter length scales, nanopillar compression tests were simulated by using the physics-based CP model that incorporated surface nucleation and single-arm source dislocation mechanisms. The crystal plasticity models have the configuration of a nanolayered composite with layers of copper grains and monolayer graphene sandwiched between them, with repeat layer spacings of 200 nm, 125 nm, and 70 nm, respectively. The present study quantified the accumulation of dislocations at the graphene interfaces, leading to the ultra-high strength of the copper-graphene composite. Furthermore, a Hall-Petch-like correlation was established between yield strength and the number of embedded graphene layers.

This study presents the plastic deformation configurations of copper-graphene composites and copper polycrystals, as well as the evaluation of the mechanical properties of copper-graphene nanolayered composites. The simulation results showed that the deformation of the copper polycrystal was uniform, whereas the nanolayered composite system demonstrated a complex deformation pattern. The simulation results, as determined from the true stress-true strain curves, confirmed the existence of a Hall-Petch-like hardening effect, which is dependent on the governing length scale. The respective slopes of the log-log plots were in close agreement with the Hall-Petch exponent, suggesting a high level of dislocation accumulation at the interface, conforming with experiments on copper-graphene nanolayered composites (Kim et al., 2013).

The study aims to understand the high strength and strain-hardening behavior of Cu-graphene nanopillars by analyzing the dislocation mechanisms of CuGr200 and CuGr125 using CP simulations. The simulation results for the CuGr200 composite show a concentration of high dislocation densities in the top copper layer and low densities in the bottom copper layer, with the majority of gliding dislocations nucleated in the upper copper grain effectively blocked by the graphene layer. The findings on dislocation density distributions are presented through three-dimensional mappings and statistical analysis, indicating a complex distribution of dislocations in the upper layer of copper and a dense concentration near the interface in the lower layer. Computational simulations were also performed for CuGr125 to study its high strength. The simulation results also indicated a direct correlation between the dislocation distributions and Hall-Petch-like effects, with dislocation starvation not observed in any layer of CuGr125 due to the increased dislocation densities with reduced opportunities for dislocations to escape. The distributions of GNDs and SSDs for CuGr125 are depicted in three-dimensional visualizations and boxplots, demonstrating the direct correlation between Hall-Petch-like effects and the accumulation of SSDs.

Presenting Author: George Z Voyiadjis Louisiana State University

Presenting Author Biography: George Z. Voyiadjis is the Boyd Professor at the Louisiana State University, in the Department of Civil and Environmental Engineering. This is the highest professorial rank awarded by the Louisiana State University System. He is also the holder of the Freeport-MacMoRan Endowed Chair in Engineering. He joined the faculty of Louisiana State University in 1980. He is currently the Chair of the Department of Civil and Environmental Engineering. He holds this position since February of 2001. He also served from 1992 to 1994 as the Acting Associate Dean of the Graduate School. He currently also serves since 2012 as the Director of the Louisiana State University Center for GeoInformatics (LSU C4G).
Voyiadjis is a Foreign Member of the Academia Europaea (Physics & Engineering Sciences), the European Academy of Sciences, and the European Academy of Sciences and Arts (Technical and Environmental Sciences). He is also a Foreign Member of both the Polish Academy of Sciences, Division IV (Technical Sciences) and the National Academy of Engineering of Korea. He is the recipient of the 2008 Nathan M. Newmark Medal of the American Society of Civil Engineers and the 2012 Khan International Medal for outstanding life-long Contribution to the field of Plasticity. He was also the recipient of the of the ICDM2 Lifetime Achievement Medal for his significant contribution to Continuum Damage Mechanics, presented to him during the Second International Conference on Damage Mechanics (ICDM2), Troyes, France July 8-11, 2015. This is sponsored by the International Journal of Damage Mechanics and is held every three years. In 2022 he was the recipient of the American Society of Mechanical Engineers, ASME, Nadai Medal, of the Materials Division.

Authors:

George Z Voyiadjis Louisiana State University