  We experimentally implement a virtual geometric periodicity in an elastic
metamaterial. First, unwanted boundary reflections at the domain ends are
cancelled through the iterative injection of the polarity reversed, reflected
wavefield. The resulting boundless experimental state allows for a much better
analysis of the metamaterials influence on the propagating wavefield.
Subsequently, the propagating wavefield exiting on one end of the structure is
reintroduced at the opposite end, creating a virtual geometric periodicity. We
find that the experimentally observed band gap converges to the analytical
solution through the introduction of the virtual periodicity. The established
workflow introduces a novel approach to the experimental investigation and
validation of metamaterial prototypes in the presence of strongly dispersive
wave propagation and internal scattering. The fully data driven, ad-hoc
treatment of boundary conditions in metamaterial experimentation with arbitrary
mechanical properties enables reflection suppression, virtual periodicity, and
the introduction of more general fictitious boundaries.
