Mechanical Characterization of Irregular Architected Two-Phase Materials

Architected materials offer a wide range of mechanical properties through the choice of their constitutive materials and the design of their structure. Periodic architected materials are the most widely studied and used in practical applications, as their repeating unit cells are easy to design, fabricate, and analytically model, but these materials are only a small subset of the possible design space. Irregular architected materials, which are aperiodic but not necessarily stochastic, offer a way to achieve a wider design space of mechanical properties. In this thesis, we explore the design space of irregular architected materials and relate structural irregularity to the mechanical properties using measures of topology and geometry. We show that these measures of irregularity can be used to spatially and temporally control the mechanical response across linear and non-linear regimes, including fracture and dynamic impact, and we show that irregularity leads to improved mechanical properties when compared with periodic equivalents. To generate the irregular architected materials, we use a virtual growth algorithm, which imitates the stochastic growth process of biological structures by assembling a finite set of building blocks according to local connectivity rules. By varying the building blocks and connectivity rules, we show how to achieve a wide range of structures with varying degrees of irregularity all the way up to fully periodic structures. This thesis primarily focuses on the fabrication and characterization of additively manufactured two-phase polymer composites, but the design methods and irregular structure characterizations are material-agnostic, opening up a wide design space for future architected materials which use irregularity to achieve excellent mechanical performances.