4.5 Article

Nanofibril-mediated fracture resistance of bone

期刊

BIOINSPIRATION & BIOMIMETICS
卷 16, 期 3, 页码 -

出版社

IOP Publishing Ltd
DOI: 10.1088/1748-3190/abdd9d

关键词

fracture; bone; toughening mechanisms; fatigue; micro-nanoscale mechanics

资金

  1. National Science Foundation through the Graduate Research Fellowship Program (NSF GFRP)
  2. US Department of Basic Energy Sciences [DE-SC0006599]
  3. U.S. Department of Energy (DOE) [DE-SC0006599] Funding Source: U.S. Department of Energy (DOE)

向作者/读者索取更多资源

Natural hard composites like human bone possess excellent strength and toughness due to their complex hierarchical structure spanning multiple length scales. A new experimental methodology allows for quantifying nano-scale toughening mechanisms and crack behavior, providing insights for designing biomimetic composites.
Natural hard composites like human bone possess a combination of strength and toughness that exceeds that of their constituents and of many engineered composites. This augmentation is attributed to their complex hierarchical structure, spanning multiple length scales; in bone, characteristic dimensions range from nanoscale fibrils to microscale lamellae to mesoscale osteons and macroscale organs. The mechanical properties of bone have been studied, with the understanding that the isolated microstructure at micro- and nano-scales gives rise to superior strength compared to that of whole tissue, and the tissue possesses an amplified toughness relative to that of its nanoscale constituents. Nanoscale toughening mechanisms of bone are not adequately understood at sample dimensions that allow for isolating salient microstructural features, because of the challenge of performing fracture experiments on small-sized samples. We developed an in situ three-point bend experimental methodology that probes site-specific fracture behavior of micron-sized specimens of hard material. Using this, we quantify crack initiation and growth toughness of human trabecular bone with sharp fatigue pre-cracks and blunt notches. Our findings indicate that bone with fatigue cracks is two times tougher than that with blunt cracks. In situ data-correlated electron microscopy videos reveal this behavior arises from crack-bridging by nanoscale fibril structure. The results reveal a transition between fibril-bridging (similar to 1 mu m) and crack deflection/twist (similar to 500 mu m) as a function of length-scale, and quantitatively demonstrate hierarchy-induced toughening in a complex material. This versatile approach enables quantifying the relationship between toughness and microstructure in various complex material systems and provides direct insight for designing biomimetic composites.

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