Tunability and enhancement of mechanical behavior with additively manufactured bio-inspired hierarchical suture interfac
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Yaning Li Department of Mechanical Engineering, University of New Hampshire, Durham, NH 03824, USA
James C. Weaver Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138, USA
Christine Ortiz Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Mary C. Boycea) Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; and School of Engineering and Applied Sciences, Columbia University, New York, NY 10027, USA (Received 8 April 2014; accepted 20 June 2014)
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.
I. INTRODUCTION
Additive manufacturing, with its ability to rapidly fabricate complex geometries, has emerged as a useful approach for prototyping and understanding the mechanical behavior of new material designs.1–4 Materials in nature often possess complex geometries that are critical for their mechanical performance,5–7 and therefore the use of additive manufacturing for prototyping bio-inspired materials designs is a particularly powerful experimental research platform. These complex geometries are often hierarchical, both across8,9 and within10,11 length scales. Hierarchical designs within a given length scale consist of intricate, fractal-like patterns with repeating self-similar geometries, and have been shown to contribute significantly to the mechanical properties of natural materials.12,13 One particularly fascinating example of hierarchical design in nature is suture interfaces, which consist of a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.175 J. Mater. Res., Vol. 29, No. 17, Sep 14, 2014
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interdigitating stiffer components, or teeth, joined by a compliant interfacial layer.11,12,14–17 Suture interface geometries vary significantly both across species, ranging from the triangular waveform of the three-spined stickleback 18 to the intricat
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