Impact energy absorption behavior of graphene aerogels prepared by different drying methods

The experimental investigation of the dynamic mechanical behavior of graphene aerogel is still lacking due to its low impendence. The present work, therefore, reports on the preliminary experimental characterization of the energy absorption characteristics of graphene aerogel by using the split Hopkinson pressure bar emphasis on the influence of the drying method. The graphene aerogels were synthesized by the sol-gel method and dried, either by supercritical CO₂ drying (SD) or by freeze-drying methods (FD). It was observed that under dynamic uniaxial compression, the SD samples exhibited a negative Poisson's ratio throughout gradual compression. However, FD samples failed by radial shattering without this auxetic behavior. The energy dissipation ratios of SD samples increased from 41% to 73% as expected with the specimen thickness increasing from 3 mm to 12 mm, being overall higher in comparison with FD samples which rises from 35% to 43%. SD graphene aerogels have a large number of random pores (∼50 nm), which is beneficial for absorbing the kinetic energy through plastic deformation and pore walls’ collapse. By contrast, the FD graphene aerogels’ pore walls buckle readily under the impact, and fail due to their ordered porous structure at the micron scale (∼1μm), which impairs their energy absorption capability.