  In this paper we show that an enriched continuum model of the micromorphic
type (Relaxed Micromorphic Model) can be 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.
