Surface-topology-controlled mechanical characteristics of triply periodic carbon Schwarzite foams

Abstract

Bulky sp²-carbon Schwarzites with negative Gaussian curvature are promising structures for practical applications due to their unique properties such as high surface area, large porosity, and stability against graphitization. Herein, a comprehensive study on the tension, compression and shear mechanical characteristics of seven triply periodic carbon Schwarzite foams with distinct topologies is performed using reactive molecular dynamics (MD) simulations. All carbon Schwarzites exhibit unique thermal and mechanical properties that are markedly dictated by the topology. One of the structures presents a negative thermal expansion coefficient. Under uniaxial tension, the temperature is able to play a positive or negative role in the tensile stiffness, and there is no apparent positive relationship between tensile strength and mass density. Subjected to compression and shear loads, carbon Schwarzites can fail due to brittle fracture, and uniform and stepwise structural instabilities. Both compression- and tension-negative Poisson's ratios are revealed to originate from a curvature-flattening deformation mechanism. Analysis of the crush force efficiency, the stroke efficiency and the energy-absorption demonstrates that carbon Schwarzites are effective energy-absorbers. This study provides a fundamental understanding of the relationship between the topology and mechanical properties of carbon Schwarzites for designing 3D graphitic nanostructures with good mechanical performances.