Amplifying Strength, Toughness, and Auxeticity via Wavy Sutural Tessellation in Plant Seedcoats

Protective armors are widespread in nature and often consist of periodic arrays of tile-like building blocks that articulate with each other through undulating interfaces. To investigate the mechanical consequences of these wavy tessellations, especially in instances where the amplitude of the undulations is near the scale of the constituent tiles as is found in the seedcoats of many plant species, an approach that integrates parametric modeling and finite element simulations with direct mechanical testing on their 3D-printed multi-material structural analogues is presented. Results from these studies demonstrate that these tiled arrays of largely isotropic star-like unit cells exhibit an unusual combination of mechanical properties including auxeticity and mutually amplified strength and toughness which can be systematically tuned by varying the waviness of the sutural tessellation.