Tailoring flake size and chemistry to improve impact resistance of graphene oxide thin films

HL White and A Giuntoli and M Fermen-Coker and S Keten, CARBON, 215, 118382 (2023).

DOI: 10.1016/j.carbon.2023.118382

Multilayered graphene oxide (MLGO) possesses high elastic modulus and strength, as well as enhanced resistance to inter-layer sliding from functional groups. This makes it a promising candidate for impact- resistant thin films and nanocomposites. However, the effects functionalization and flake size on the physics of MLGO failure under high-strain rate impact remains to be fully understood. While laser induced projectile impact tests (LIPIT) have enabled microballistic characterization of MLGO, the dynamics of interlayer sliding processes cannot be accurately studied in physical experiments due to resolution challenges of existing techniques. Here we utilize systematically coarse-grained molecular dynamics to simulate MLGO under high-rate microballistic impact, explicitly accounting for functional group distributions while approaching micron-size specimen dimensions. In doing so, we evaluate the effects of oxidation level on the thin films' ability to dissipate ballistic energy. We additionally explore effects of varying flake size on these systems, improving on studies that only consider infinite flake dimensions. The primary failure mechanism of these thin films (consisting of relatively small flakes) is found to be sliding of the GO flakes as no bonds were broken. We discover that elevated levels of oxidation increase the amount of energy required to penetrate the film, as do larger GO flake sizes as they increase energy dissipation via friction between sliding flakes. These findings illustrate the potential for MLGO films to be tailored for maximum ballistic energy dissipation, providing a starting point to design impact-resistant GO materials for diverse applications.

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