Scale Effects on the Ballistic Penetration of Graphene Sheets

TL;DR

This study combines numerical and analytical models to understand how the number of layers in graphene sheets affects their ballistic penetration energy, resolving discrepancies between previous experiments and simulations.

Contribution

It introduces a scaling law linking layer number to penetration energy, clarifying the impact of scale effects on graphene's ballistic protection properties.

Findings

Penetration energy decreases with more layers, from ~25 MJ/kg for single-layer to ~0.26 MJ/kg for many layers.

Scaling law accurately predicts experimental and simulation results across different layer counts.

Scale effects explain previous discrepancies between experimental and numerical data.

Abstract

Carbon nanostructures are promising ballistic protection materials, due to their low density and excellent mechanical properties. Recent experimental and computational investigations on the behavior of graphene under impact conditions revealed exceptional energy absorption properties as well. However, the reported numerical and experimental values differ by an order of magnitude. In this work, we combined numerical and analytical modeling to address this issue. In the numerical part, we employed reactive molecular dynamics to carry out ballistic tests on single and double-layered graphene sheets. We used velocity values within the range tested in experiments. Our numerical and the experimental results were used to determine parameters for a scaling law, which is in good agreement with all experimental and simulation results. We find that the specific penetration energy decreases as the number of layers (N) increases, from ~25 MJ/kg for N=1 to ~0.26 MJ/kg as N goes to infinity. These scale effects explain the apparent discrepancy between simulations and experiments.