Determination of the Elastic Properties of Horn Keratin

Warburton, F. L.

doi:10.1080/19447014808663158

Cited by 20 publications

(8 citation statements)

References 7 publications

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“…Therefore, two cases will be considered: an isotropic case and an anisotropic case using an arbitrary transverse stiffness of 2.25 GPa which is half the longitudinal stiffness. Warburton (1948) measured a Poisson ratio of 0.23 for sheep horn using an ultrasonic method. Kitchener (1985) measured repeatedly a Poisson ratio of about 0.4 for gemsbok horn using orthogonal strain gauges.…”

Section: Critical Stress Intensity Factorsmentioning

confidence: 99%

Fracture toughness of horns and a reinterpretation of the horning behaviour of bovids

Kitchener

1987

Journal of Zoology

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The keratinous horns of bovids are used in intraspecific combat to gain access to females in oestrus. Horn sheath keratin is a composite material consisting of stiff protein fibres and a pliant protein matrix. Unlike antlers, horns are permanent structures which are likely to accumulate damage during fighting. Therefore, horn sheath keratin should be resistant to fracture (tough) and insensitive to surface defects (scratches and cracks) which may weaken horns by acting as stress concentrators. The effect of water on the toughness and notch‐sensitivity of horn sheath keratin was investigated in three‐point bending and tensile tests. Several measures of toughness were made on dry (0% water content), fresh (20%) and wet (40%) horn keratin, including total work of fracture, Gurney & Hunt work of fracture, critical strain energy release rate and critical stress intensity factor. The mean total work of fracture of fresh horn is about 40 kJ/m2 which is relatively much greater than most biological and synthetic materials. Most of the work of fracture is due to plastic yielding of the matrix (50–75%); the rest is due to crack‐tip specific fracture mechanisms such as fibre pull‐out and Cook Gordon crack‐stopping. Dehydration reduces the total work of fracture of horn keratin by preventing the yielding of the matrix. The strength of fresh and wet horn is insensitive to notches, but dry horn is very notch‐sensitive. Therefore, bovids must avoid dehydration of their horns due to the desiccating effect of the environment. The ‘horning’ behaviour of bovids may be a maintenance activity which ensures that the horn sheath is adequately hydrated to remain tough and notch‐insensitive.

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Section: Critical Stress Intensity Factorsmentioning

confidence: 99%

Fracture toughness of horns and a reinterpretation of the horning behaviour of bovids

Kitchener

1987

Journal of Zoology

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“…This dependence is similar to other horns studied. An earlier study reported that [190] the moisture in a sheep horn severely decreased its elastic modulus. The oryx horns showed that both the elastic and shear modulus decreased significantly with an increase in the moisture content [125].…”

Section: Hornsmentioning

confidence: 99%

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Wang

Yang

McKittrick

et al. 2016

Progress in Materials Science

658

474

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a b s t r a c tA ubiquitous biological material, keratin represents a group of insoluble, usually high-sulfur content and filament-forming proteins, constituting the bulk of epidermal appendages such as hair, nails, claws, turtle scutes, horns, whale baleen, beaks, and feathers. These keratinous materials are formed by cells filled with keratin and are considered 'dead tissues'. Nevertheless, they are among the toughest biological materials, serving as a wide variety of interesting functions, e.g. scales to armor body, horns to combat aggressors, hagfish slime as defense against predators, nails and claws to increase prehension, hair and fur to protect against the environment. The vivid inspiring examples can offer useful solutions to design new structural and functional materials.Keratins can be classified as a-and b-types. Both show a characteristic filament-matrix structure: 7 nm diameter intermediate filaments for a-keratin, and 3 nm diameter filaments for b-keratin.Both are embedded in an amorphous keratin matrix. The molecular unit of intermediate filaments is a coiled-coil heterodimer and that of b-keratin filament is a pleated sheet. The mechanical response of a-keratin has been extensively studied and shows linear Hookean, yield and post-yield regions, and in some cases, a high reversible elastic deformation. Thus, they can be also be considered 'biopolymers'. On the other hand, b-keratin has not been investigated as comprehensively. Keratinous materials are strain-rate sensitive, and the effect of hydration is significant.Keratinous materials exhibit a complex hierarchical structure: polypeptide chains and filament-matrix structures at the nanoscale, Progress in Materials Science 76 (2016) 229-318 Contents lists available at ScienceDirect Progress in Materials Sciencej o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p m a t s c i organization of keratinized cells into lamellar, tubular-intertubular, fiber or layered structures at the microscale, and solid, compact sheaths over porous core, sandwich or threads at the macroscale. These produce a wide range of mechanical properties: the Young's modulus ranges from 10 MPa in stratum corneum to about 2.5 GPa in feathers, and the tensile strength varies from 2 MPa in stratum corneum to 530 MPa in dry hagfish slime threads. Therefore, they are able to serve various functions including diffusion barrier, buffering external attack, energy-absorption, impact-resistance, piercing opponents, withstanding repeated stress and aerodynamic forces, and resisting buckling and penetration.A fascinating part of the new frontier of materials study is the development of bioinspired materials and designs. A comprehensive understanding of the biochemistry, structure and mechanical properties of keratins and keratinous materials is of great importance for keratin-based bioinspired materials and designs. Current bioinspired efforts including the manufacturing of quill-inspired aluminum composites, animal horn-inspired SiC composites, and feather-i...

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“…Figure shows the nanoindentation properties of the mouthparts in “dry” and “fresh” conditions. The maximum load for indentation was 10 mN, the load rate was 0.33 mN/s, and holding time was 30 s. A value of 0.3 for Poisson's ratio was used according to the literatures [0.25 for sheep horn (Warburton, ); 0.3 for rostrum of insect (Singh et al, ); 0.3 for elytra (Dai & Yang, )]. The Young's modulus and hardness were observed to be constant with respect to depth (plateau region) between ∼500 and 1000 nm (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Morphology and nanoindentation properties of mouthparts in Cyrtotrachelus longimanus (Coleoptera: curculionidae)

Guo

et al. 2017

Microscopy Res & Technique

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Microstructure and nanoindentation properties of the mouthparts for the skillful driller Cyrtotrachelus longimanus are presented. The composition and morphological examinations are made using light, fluorescent, scanning electron microscopy, and Energy Disperse Spectroscopy, respectively. Nanoindentation was carried out to measure the elastic modulus and the hardness of mouthparts. The hardness and modulus for "dry" samples is 0.202 ± 0.065 and 8.604 ± 0.838 GPa, respectively, and the values of "fresh" ones is 0.126 ± 0.0196 and 6.951 ± 0.065 GPa, respectively. These results are critical for analyze the drilling mechanism of the weevil and provide a biological template to inspire the biomimetic design.

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Determination of the Elastic Properties of Horn Keratin

Cited by 20 publications

References 7 publications

Fracture toughness of horns and a reinterpretation of the horning behaviour of bovids

Fracture toughness of horns and a reinterpretation of the horning behaviour of bovids

Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration

Morphology and nanoindentation properties of mouthparts in Cyrtotrachelus longimanus (Coleoptera: curculionidae)

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