Staggered Fibrils and Damageable Interfaces Lead Concurrently and

Dec 19, 2016 - The high toughness and work to fracture of hierarchical composites, like antler bone, involve structural mechanisms at the molecular, n...
1 downloads 8 Views 2MB Size
Subscriber access provided by University of Newcastle, Australia

Article

Staggered fibrils and damageable interfaces lead concurrently and independently to hysteretic energy absorption and inhomogeneous strain fields in cyclically loaded antler bone Paolino De Falco, Ettore Barbieri, Nicola M. Pugno, and Himadri S. Gupta ACS Biomater. Sci. Eng., Just Accepted Manuscript • DOI: 10.1021/acsbiomaterials.6b00637 • Publication Date (Web): 19 Dec 2016 Downloaded from http://pubs.acs.org on December 19, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Biomaterials Science & Engineering is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Biomaterials Science & Engineering

1

Staggered fibrils and damageable interfaces lead concurrently and

2

independently to hysteretic energy absorption and inhomogeneous

3

strain fields in cyclically loaded antler bone a

4

a

P. De Falco , E. Barbieri , N. Pugno

a,b,c

a*

and H. S. Gupta

5

a

6

b

7

Mechanical Engineering, University of Trento, Trento, Italy

8

c

Center for Materials and Microsystems, Fondazione Bruno Kessler, Povo (Trento), Italy

9

*

Corresponding author: Himadri S. Gupta ([email protected])

Queen Mary University of London, School of Engineering and Material Science, London, E1 4NS, UK

Laboratory of Bio-Inspired and Graphene Nanomechanics, Department of Civil, Environmental and

10

Keywords

11

Antler bone, interface, nanoscale, cohesive behaviors, heterogeneity, hysteresis

12

Abstract

13

The high toughness and work to fracture of hierarchical composites, like antler bone, involve structural

14

mechanisms at the molecular, nano- and micro scales, which are not completely explored. A key

15

characteristic of the high energy absorption of such materials is the large hysteresis during cyclic loading, but

16

its origin remains unknown. In situ synchrotron X-ray diffraction tests during tensile loading of antler bone

17

showed heterogeneous fibrillar deformation and hysteresis. To explain the origin of these mechanisms from

18

the nanostructure of antler bone, here we develop a class of finite-element fibril models whose predictions

19

are compared to experimental data across a range of potential composite architectures. We demonstrate

20

that the key structural motif enabling a match to experimental data is an axially staggered arrangement of

21

stiff mineralized collagen fibrils coupled with weak, damageable interfibrillar interfaces.

22 23

1 INTRODUCTION

24

Natural structural materials exhibit mechanical properties through complex hierarchical

25

architectures and load-absorbing mechanisms. These architectures evolved naturally from

26

basic building blocks thanks to a ‘self-organization’ strategy during growth1. In fact,

27

biological structures adapt, change function during growth, renew their material and build

28

hierarchies2. The macroscopic behaviour of these materials depends on the interaction 1 ACS Paragon Plus Environment

ACS Biomaterials Science & Engineering

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

29

between structural properties at different scales3. Bio-composites, such as bone, shells

30

and nacre, represent an excellent example of how the design at lower hierarchical scales

31

confers higher mechanical properties than the single constituents4. Although the stiffness

32

of these biocomposites is comparable to that of the basic constituent at the nanoscale,

33

their toughness results hugely increased. For instance, in bone and shell, the toughness of

34

the mineral constituents is