  In the present study the stress transfer mechanism in graphene-polymer
systems under tension is examined experimentally using the technique of laser
Raman microscopy. We discuss in detail the effect of graphene edge geometry,
lateral size and thickness which need to be taken under consideration when
using graphene as a protective layer. The systems examined comprised of
graphene flakes with large length (over ~50 microns) and thickness of one to
three layers simply deposited onto PMMA substrates which were then loaded to
tension up to ca. 1.60% strain. The stress transfer profiles were found to be
linear while the results show that large lateral sizes of over twenty microns
are needed in order to provide effective reinforcement at levels of strain
higher than 1%. Moreover, the stress-built up has been found to be quite
sensitive to both edge shape and geometry of the loaded flake. Finally, the
transfer lengths were found to increase with the increase of graphene layers.
The outcomes of the present study provide crucial insight on the issue of
stress transfer from polymer to nano-inclusions as a function of edge geometry,
lateral size and thickness in a number of applications.
