Stiff, strong, zero thermal expansion lattices via material hierarchy

For engineering applications where tight dimensional tolerances are required, or for applications where materials are subjected to a wide range of temperatures it becomes desirable to reduce a material's coefficient of thermal expansion. By carefully designing lattice microstructures, zero thermal expansion can be achieved. This work describes lattice microstructures that achieve zero expansion by utilizing either the Poisson effect to negate thermal expansion, or a curved, bi-material rib morphology. Previously described microstructures were composed of solid material constituents. The lattices presented here have structural hierarchy in which lattice ribs contain oriented porosity. This gives rise to improved strength and modulus, and provides additional design freedom associated with anisotropy. (C) 2013 Elsevier Ltd. All rights reserved.