  Graphene is the stiffest material known so far but, due to its one-atom
thickness, it is also very bendable. Consequently, free-standing graphene
exhibit ripples that has major effects on its elastic properties. Here we will
summarize three experiments where the influence of rippling is essential to
address the results. Firstly, we observed that atomic vacancies lessen the
negative thermal expansion coefficient of free-standing graphene. We also
observed an increase of the Young's modulus with global applied strain and with
the introduction of small density defects that we attributed to the decrease of
rippling. Here, we will focus on a surprising feature observed in the data: the
experiments consistently indicate that only the rippling with wavelengths
between 5-10nm influences the mechanics of graphene. The rippling responsible
of the negative TEC and anomalous elasticity is thought to be dynamic, i.e.
flexural phonons. However, flexural phonons with these wavelengths should have
minor effects on the mechanics of graphene, therefore other mechanisms must be
considered to address our observations. We propose static ripples as one of the
key elements to correctly understand the thermomechanics of graphene and
suggest that rippling arises naturally due to a competition of symmetry
breaking and anharmonic fluctuations.
