Architected cellular materials (i.e., single or multi-phase periodic cellular materials with unit cell topology optimized for one or more functionalities) have been extensively investigated over the past two decades, for their potential to achieve combinations of properties unavailable in any existing monolithic material. Historically, the difficulty in manufacturing such materials (except for the simplest, large-scale topologies) have limited investigation and application of architected materials with complex microstructures. More recently, extraordinary advances in additive manufacturing technologies have enabled fabrication of macro-scale architected materials of unprecedented topological complexity and structural hierarchy, allowing a whole new level of mechanical and multifunctional performance, and opening the field of mechanical metamaterials. These manufacturing advances have catalyzed enormous research interest in two areas: (i) the hierarchical design and fabrication of macro-scale architected material with microscale – or even nanoscale – features, which enables translation of beneficial size effects on mechanical properties that only exist at small scale (e.g., strengthening of metals and toughening of ceramics) to a macroscopic material; (ii) the development of novel topology optimization tools that enable architected materials design that take full advantage of the new additive manufacturing capabilities, resulting in multi-phase designs, highly hierarchical designs, designs that circumvent additive manufacturing limitations (e.g., the need for external supports), and designs with non-linear objectives and constraints.
In this talk, I will review recent progress in both areas, with specific focus on the fabrication and optimization of micro/nano-lattices with exceptional specific strength and topologically complex architectures that enable non-linear effective mechanical response from linear elastic constituents.