Stiffness, strength, energy dissipation and reusability in heterogeneous architected polycrystals

We design, fabricate and test heterogeneous architected polycrystals, composed of hard plastomers and soft elastomers, which thus show mechanical resilience and energy dissipation simultaneously. Grain boundaries (GBs) that separate randomly oriented single crystalline grains are carefully designed, enabling coherent connectivity and strength in the GB regions throughout the polycrystalline network. By combining experiments and numerical simulations on three-dimensional (3D)-printed prototypes, we show that the interplay between grain interiors (GIs) and GBs is responsible for the grain-size effects on elastic stiffness and inelastic strength; furthermore, we demonstrate, when damaged, the engineered GBs are crucial for reusability and energy dissipation capability in these architected materials by impeding the propagation of local failures. Direct visualization of inter- and intra-grain deformation and failure mechanisms at the macroscopic scale also reveals that crystallographic texture throughout the architected polycrystalline aggregates plays a fundamental role in the key mechanical features. Our results show that the engineered GBs and crystallographic textures not only modify the highly resilient yet dissipative global responses but also critically influence reusability in this new class of heterogeneous architected materials.