  In the current study, mechanical characteristics of graphene oxide (GO) as a
promising substitute of graphene are systematically studied through molecular
dynamics simulation. For this purpose, several GO samples having different
concentrations of epoxide and hydroxyl functional groups are considered. The
results reveal that increasing the epoxide coverage causes a noticeable
deterioration in the mechanical characteristics of GO systems. This change is
correlated with the increase of the formation of ripples in the structure upon
increasing the epoxide coverage. Moreover, investigating the bond lengths in
the system, it is concluded that the higher epoxide percentage leads to an
increase in the length of single and hybrid resonance bonds leading to an
overall deterioration of the mechanical properties of GO samples. Additionally,
our results demonstrate that high concentration of functional groups can lead
to a negative Poisson ratio. Increasing the amount of hydroxyl groups shows the
same declining effect on the Young modulus. In a graphene system containing
both epoxide and hydroxyl groups, it is deduced that a higher percentage of the
former can result in a higher residual strain because of the formation of more
ripples within the system.
