  In this paper we show that an enriched continuum model of the micromorphic
type (Relaxed Micromorphic Model) can be safely used to model metamaterials'
response in view of their use for meta-structural design. We focus on the fact
that the reduced model's structure, coupled with the introduction of well-posed
interface conditions, allows us to easily test different combinations of
metamaterials' and classical-materials bricks, so that we can eventually end-up
with the conception of a meta-structure acting as a mechanical diode for
low/medium frequencies and as a total screen for higher frequencies. Thanks to
the reduced model's structure, we are also able to optimize this meta-structure
so that the diode-behaviour is enhanced for both "pressure" and "shear"
incident waves and for all possible angles of incidence.
