Mechanical properties of nacre and highly mineralized bone

Currey, John D.; Zioupos, Peter; Peter, Davies; Casinos, Adriá

doi:10.1098/rspb.2000.1337

Cited by 103 publications

(74 citation statements)

References 18 publications

(16 reference statements)

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“…Currey et al, 2001;Barthelat et al, 2007). This may also be true for limpet shell material as regards the propagation of through-thickness cracks, which generate very rough fracture surfaces (see Fig.…”

Section: Impact Fatiguementioning

confidence: 99%

Impact damage and repair in shells of the limpet Patella vulgata

Taylor

2016

Journal of Experimental Biology

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Experiments and observations were carried out to investigate the response of the Patella vulgata limpet shell to impact. Dropped-weight impact tests created damage that usually took the form of a hole in the shell's apex. Similar damage was found to occur naturally, presumably as a result of stones propelled by the sea during storms. Apex holes were usually fatal, but small holes were sometimes repaired, and the repaired shell was as strong as the original, undamaged shell. The impact strength (energy to failure) of shells tested in situ was found to be 3.4-times higher than that of empty shells found on the beach. Surprisingly, strength was not affected by removing the shell from its home location, or by removing the limpet from the shell and allowing the shell to dry out. Sand abrasion, which removes material from the apex, was found to have a strong effect. Shells were also subjected to repeated impacts, which caused failure after 2-120 repetitions. In situ shells performed poorly in this test. It is proposed that the apex acts as a kind of sacrificial feature, which confers increased resistance but only for a small number of impacts. Microscopy showed that damage initiates internally as delamination cracks on low-energy interfaces, leading to loss of material by spalling. This mode of failure is a consequence of the layered structure of the shell, which makes it vulnerable to the tensile and shear stresses in the impact shock wave.

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Section: Impact Fatiguementioning

confidence: 99%

Impact damage and repair in shells of the limpet Patella vulgata

Taylor

2016

Journal of Experimental Biology

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“…Loading between flat metal plates, as carried out by other workers [5,7] creates high local stresses at the contact points. To Table 1 Typical values of Fracture Toughness K c and Young's Modulus E for Various Materials Data from [27] except the following: mussel shells [28]; nacre [17]; bone [18]; temporomandibular joint disc [29]; cartilage [30]; stratum corneum [31]. prevent this we used hemispherical cups (actually wooden egg cups) and placed a layer of low-stiffness foam between the egg and the cup to redistribute the contact forces over a large area.…”

Section: Methodsmentioning

confidence: 99%

“…The remarkable toughness values of these materials have been the subject of much research in recent times (e.g. [9,16,17]). Structure at the micro and nano scale can give rise to toughening mechanisms, hindering crack growth.…”

Section: Failure Mechanisms In Eggshell and Other Calcite/aragonite-bmentioning

confidence: 99%

The fracture toughness of eggshell

et al. 2016

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a b s t r a c tThe shells of avian eggs are very brittle, but how brittle? Fracture toughness, K c is a standard measure used widely to characterise engineering materials. We devised a novel way to measure K c and applied it to commercial hens' eggs, obtaining a value of 0.3 MPa p m. This value is much lower than previous published values, which we argue are incorrect and misleading. We discuss how this exceptionally low toughness value (in comparison to that of other natural materials made from calcium carbonate) has been achieved by prevention of toughening mechanisms. Eggshell has an unusual combination of mechanical properties (low fracture toughness combined with high Young's modulus), making it ideally suited as a container for the developing chick, which must be stiff and rigid but also brittle enough to be broken when required. Further testing and analysis using the Theory of Critical Distances and Weibull probability theory allowed us to describe the effects of defects of various types: cracks, holes and notches, on the strength of whole eggs. These results are of commercial importance because many eggs break prematurely as a result of microscopic defects. Statement of SignificanceThis paper presents the first accurate measurements of the fracture toughness of eggshell. These results are important because eggshell is a brittle material which fails from microscopic defects, so knowledge of the fracture toughness is essential to understand its mechanical performance. The toughness value obtained is discussed in the context of other mechanical properties, of eggshell and other natural materials. This is useful for understanding how eggshell's stiffness and toughness make it ideally suited to its purpose, and the mechanisms by which toughness is achieved. The paper also contains analysis of the effect of defect type, including cracks, notches and holes, to provide a fuller picture of defect tolerance which will be useful in the egg producing industry.

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“…This brings us back to the idea of durophagy, and what potential prey items may have been causing these coarse scratches. Plenty of marine invertebrates have hard body parts, and the complex structure of nacre may allow it to reach the hardness of enamel (Ashby et al, 1995;Currey, 1980;Currey et al, 2001;Jackson et al, 1988;Katti et al, 2005;Meyers et al, 2008). Schulp (2005) evaluated a variety of (extant) potential prey items using a reconstructed jaw model, which allowed to bracket the potential prey items of Carinodens to (the Cretaceous equivalents of) small oysters, gastropods, arthropods and echinoderms (see also , for a re-evaluation).…”

Section: Abrasivesmentioning

confidence: 99%

Dental macro- and microwear in Carinodens belgicus, a small mosasaur from the type Maastrichtian

Holwerda

Beatty

Schulp

2013

Netherlands Journal of Geosciences

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Teeth of the small durophagous mosasaur Carinodens belgicus are known from Maastrichtian Atlantic-Tethyan deposits worldwide. The peculiar dentition of Carinodens inspired debate and speculation on its dietary niche ever since its first description. In this contribution, we describe the macro- and microwear pattern in five well-preserved isolated teeth, allowing further and independent evaluation of aspects of feeding behaviour and diet. Macroscopically, wear is concentrated on the apex and mesiodistal sides. Microwear was mapped using Scanning Electron Microscopy at several magnifications and can be characterised as scratches and pits. Coarse scratches were found to be the most common and pits were found to be the least common feature. Scratch orientation is primarily along the mesiodistal plane or in the labiolingual plane with an angle of ~130°. These microwear features can be explained either by oral processing or passive abrasion by sediments or food. As scratch width only indicates the minimum width of the abrading particle, the material causing the wear here could have ranged from silica-based silts to larger abrasives. However, in this case, abrasion by sediments might not explain this wear because of the biocalcarenitic nature of the type Maastrichtian sediments; siliciclastics are virtually absent. Therefore it is more likely that hard food particles, such as benthic organisms with hard exoskeletons, caused the wear on the enamel of Carinodens, or Carinodens ventured out to more sandy areas to forage as well. The mesiodistal and labiolingual direction of the microwear scratches might suggest that Carinodens showed more complexity in the use of its teeth than simple grasping, and that a gripping and pulling motion during feeding similar to that employed by modern varanids may have been the cause.

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Mechanical properties of nacre and highly mineralized bone

Cited by 103 publications

References 18 publications

Impact damage and repair in shells of the limpet Patella vulgata

Impact damage and repair in shells of the limpet Patella vulgata

The fracture toughness of eggshell

Dental macro- and microwear in Carinodens belgicus, a small mosasaur from the type Maastrichtian

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