  Optimized topology of bi-material acoustic metamaterial lattice plates is
studied for maximized locally resonant bandgap of flexural guided waves.
Optimized layout of the two relatively stiff and compliant material phases in
the design domain is explored, free from any restrictions on the topology and
shape of the relevant domains. Multiobjective optimization is performed through
which maximized effective stiffness or minimized overall mass of the bandgap
topology is additionally ensured. Extreme and selected intermediate optimized
topologies of Pareto fronts are presented and their bandgap efficiencies and
effective stiffness are compared. The bi-material constitution of selected
topologies are further altered and modal band structure of resultant
multilateral and porous designs are evaluated. Novel, core-shell like, locally
resonant bandgaps are introduced. It is shown that how the bandgap efficiency
and structural mass and/or stiffness can be optimized through optimized
microstructural design of the matrix and the resonating core domains.
