Investigation of Mechanical Performance of Composites Based on ‘Hat’ Aperiodic Monotile Structures

Disordered structures, as oftentimes found in nature, have the potential to have unique behaviors and higher mechanical performance in terms of stiffness, strength, and toughness compared to ordered structures. However, such a disordered structure increases the complexity of design and fabrication process, which can be resolved if the infinite plane can be aperiodically covered with a single unit cell (i.e. aperiodic monotile). With the long efforts of the mathematics community, a hat-shaped aperiodic monotile structure was recently discovered. This study proposes new composite designs using an aperiodic monotile structure and investigates mechanical performance and mechanisms. For tensile loading, aperiodic monotile composites consisting of stiffer material for core areas and softer material for boundaries are considered varying volume fractions of each phase. On the other hand, for compressive loading, the composites composed of stiffer material forming boundaries and softer material as filling are examined with different size of unit cells. The specimens are fabricated using multimaterial polyjet additive manufacturing processes. To probe further into the mechanisms, phase field modeling based fracture simulations are conducted for tensile loading cases and explicit dynamic fracture simulations are conducted for compressive loading cases. Simulations show that aperiodic monotile structure enables high strength and toughness compared to a honeycomb structure under tensile loading. In addition, the aperiodicity of the aperiodic monotile structure allows superior performance under compression compared to the periodic structure. This study shows that the aperiodic monotile composite structure can be next generation of composite structure showing superiority to other conventional composite structures in terms of stiffness, strength, and toughness.