  Advances in manufacturing techniques may now realize virtually any imaginable
microstructures, paving the way for architected materials with properties
beyond those found in nature. This has lead to a quest for closing gaps in
property-space by carefully designed metamaterials. Development of mechanical
metamaterials has gone from open truss lattice structures to closed plate
lattice structures with stiffness close to theoretical bounds. However, the
quest for optimally stiff and strong materials is complex. Plate lattice
structures have higher stiffness and (yield) strength but are prone to buckling
at low volume fractions. Hence here, truss lattice structures may still be
optimal. To make things more complicated, hollow trusses or structural
hierarchy bring closed-walled microstructures back in the competition. Based on
analytical and numerical studies of common microstructures from the literature,
we provide higher order interpolation schemes for their effective stiffness and
(buckling) strength. Furthermore, we provide a case study based on
multi-property Ashby charts for weight-optimal porous beams under bending, that
demonstrates the intricate interplay between structure and microarchitecture
that plays the key role in the design of ultimate load carrying structures. The
provided interpolation schemes may also be used to account for microstructural
yield and buckling in multiscale design optimization schemes.
