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The fracture toughness of eggshell

Paper ID Volume ID Publish Year Pages File Format Full-Text
108 10 2016 7 PDF Available
Title
The fracture toughness of eggshell
Abstract

The shells of avian eggs are very brittle, but how brittle? Fracture toughness, Kc is a standard measure used widely to characterise engineering materials. We devised a novel way to measure Kc and applied it to commercial hens’ eggs, obtaining a value of 0.3 MPa√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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Keywords
Egg; Shell; Eggshell; Toughness; Fracture; Defect
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The fracture toughness of eggshell
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Publisher
Database: Elsevier - ScienceDirect
Journal: Acta Biomaterialia - Volume 37, June 2016, Pages 21–27
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us