Tunability and enhancement of mechanical behavior with additively manufactured bio-inspired hierarchical suture interfaces

In nature, biological structures often exhibit complex geometries that serve a wide range of specific mechanical functions. One such example are the ammonites, a large group of extinct mollusks, which produced elaborate, fractal-like hierarchical suture interface patterns. This report experimentally explores the influence of hierarchical suture interface designs on mechanical behavior by taking advantage of additive manufacturing and its ability to fabricate complex geometries. In addition, structure/property relationships of additively manufactured multi-material prototypes are investigated. It is shown that increasing the order of hierarchy amplifies stiffness by more than an order of magnitude. Tensile strength can also be tailored by changing the order of hierarchy, which alters the normal to shear stress ratio of the interfacial layer. The addition of failure mechanisms with increased order of hierarchy also significantly increases the toughness. Therefore, hierarchical suture interfaces can be used to diversify the mechanical behavior of additively manufactured materials.