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Hypothesis: bones toughness arises from the suppression of elastic waves.

Davies B, King A, Newman P, Minett A, Dunstan CR, Zreiqat H - Sci Rep (2014)

Bottom Line: Bone's toughness is a result of numerous extrinsic and intrinsic toughening mechanisms that operate synergistically at multiple length scales to produce a tough material.At the system level however no theory or organizational principle exists to explain how so many individual toughening mechanisms can work together.In turn, the heterogeneous, hierarchal, and multiscale structure of bone (which is generic to biological materials such as bone and nacre) can be rationalized because of the unique ability of such a structure to localize phonons of all wavelengths.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Aerospace, Mechanical and Mechatronic Engineering, Faculty of Engineering and Information Technologies, University of Sydney, NSW. 2006, Australia [2] Laboratory for Sustainable Technology, School of Chemical and Biomolecular Engineering, University of Sydney, NSW. 2006.

ABSTRACT
Bone and other natural material exhibit a combination of strength and toughness that far exceeds that of synthetic structural materials. Bone's toughness is a result of numerous extrinsic and intrinsic toughening mechanisms that operate synergistically at multiple length scales to produce a tough material. At the system level however no theory or organizational principle exists to explain how so many individual toughening mechanisms can work together. In this paper, we utilize the concept of phonon localization to explain, at the system level, the role of hierarchy, material heterogeneity, and the nanoscale dimensions of biological materials in producing tough composites. We show that phonon localization and attenuation, using a simple energy balance, dynamically arrests crack growth, prevents the cooperative growth of cracks, and allows for multiple toughening mechanisms to work simultaneously in heterogeneous materials. In turn, the heterogeneous, hierarchal, and multiscale structure of bone (which is generic to biological materials such as bone and nacre) can be rationalized because of the unique ability of such a structure to localize phonons of all wavelengths.

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Multiscale Phonon Confinement and Localization in Bone.
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f3: Multiscale Phonon Confinement and Localization in Bone.

Mentions: What evidence is there that bone actually suppresses phonon propagation? Bone exhibits the generic microstructure required to localize a broad wavelength of phonons: a large reflectance between collagen and hydroxyapatite (Reflectance = .83, S3) and a hierarchical structure capable of localizing multiple phonon wavelengths simultaneously51718 (See Figure 3). We have estimated the propagating elastic energy by calculating the transmission of a wave through 3 and 5 consecutive interfaces with the same reflectance as collagen and hydroxyapatite (Reflectance = .83, S3) being .5% and .014% respectively. This corresponds to Ψ = .995 and .99986; for a single wavelength over a distance of 3 and 5 wavelengths respectively. We note that a collagen matrix when hydrated is visco-elastic, leading to the adsorption of elastic waves. Though not included in the above analysis for simplicity, this property would only serve to increase phonon attenuation because elastic energy is dissipated by the viscous component of the collagen matrix.


Hypothesis: bones toughness arises from the suppression of elastic waves.

Davies B, King A, Newman P, Minett A, Dunstan CR, Zreiqat H - Sci Rep (2014)

Multiscale Phonon Confinement and Localization in Bone.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4269876&req=5

f3: Multiscale Phonon Confinement and Localization in Bone.
Mentions: What evidence is there that bone actually suppresses phonon propagation? Bone exhibits the generic microstructure required to localize a broad wavelength of phonons: a large reflectance between collagen and hydroxyapatite (Reflectance = .83, S3) and a hierarchical structure capable of localizing multiple phonon wavelengths simultaneously51718 (See Figure 3). We have estimated the propagating elastic energy by calculating the transmission of a wave through 3 and 5 consecutive interfaces with the same reflectance as collagen and hydroxyapatite (Reflectance = .83, S3) being .5% and .014% respectively. This corresponds to Ψ = .995 and .99986; for a single wavelength over a distance of 3 and 5 wavelengths respectively. We note that a collagen matrix when hydrated is visco-elastic, leading to the adsorption of elastic waves. Though not included in the above analysis for simplicity, this property would only serve to increase phonon attenuation because elastic energy is dissipated by the viscous component of the collagen matrix.

Bottom Line: Bone's toughness is a result of numerous extrinsic and intrinsic toughening mechanisms that operate synergistically at multiple length scales to produce a tough material.At the system level however no theory or organizational principle exists to explain how so many individual toughening mechanisms can work together.In turn, the heterogeneous, hierarchal, and multiscale structure of bone (which is generic to biological materials such as bone and nacre) can be rationalized because of the unique ability of such a structure to localize phonons of all wavelengths.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Aerospace, Mechanical and Mechatronic Engineering, Faculty of Engineering and Information Technologies, University of Sydney, NSW. 2006, Australia [2] Laboratory for Sustainable Technology, School of Chemical and Biomolecular Engineering, University of Sydney, NSW. 2006.

ABSTRACT
Bone and other natural material exhibit a combination of strength and toughness that far exceeds that of synthetic structural materials. Bone's toughness is a result of numerous extrinsic and intrinsic toughening mechanisms that operate synergistically at multiple length scales to produce a tough material. At the system level however no theory or organizational principle exists to explain how so many individual toughening mechanisms can work together. In this paper, we utilize the concept of phonon localization to explain, at the system level, the role of hierarchy, material heterogeneity, and the nanoscale dimensions of biological materials in producing tough composites. We show that phonon localization and attenuation, using a simple energy balance, dynamically arrests crack growth, prevents the cooperative growth of cracks, and allows for multiple toughening mechanisms to work simultaneously in heterogeneous materials. In turn, the heterogeneous, hierarchal, and multiscale structure of bone (which is generic to biological materials such as bone and nacre) can be rationalized because of the unique ability of such a structure to localize phonons of all wavelengths.

Show MeSH
Related in: MedlinePlus