On the crack resistance and damage tolerance of 3D-printed nature-inspired hierarchical composite architecture

Abstract

Materials scientists have taken a learn-from-nature approach to study the structure-property relationships of natural materials. Here we introduce a new type of nature-inspired composite architecture showing a hierarchical assembly of granular-like building blocks with specific topological textures. The structural complexity of the resulting architecture was advanced by applying the concept of ‘grain orientation’ internally to each building block to induce a tailored crack resistance. Hexagonal grain-shaped building blocks were filled with parallel-oriented filament bundles, and these functioned as stiff-blocks with high anisotropy due to the embedded fiber reinforcements. Process-induced interfacial voids provided preferential crack paths, were strategically integrated with cracks to improve fracture toughness at the macroscopic scale. The resultant characteristic cracking behaviors were inherently induced by the synergistic crack-void interactions and the obstacle effects of aligned fibers. This study discusses the structural effects of the local/global orientations, stacking sequences, feature sizes, and gradient assemblies of granular blocks on crack tolerance behavior. Our approach to applying crystallographic concepts to complex composite architectures provides an alternative method for gaining insight into natural toughening mechanisms at the meso- and macro-scale and may inspire for new models of fracture mechanics.