ENGRI1110_Lect29_Nov6_posted - Umbach Office Hours: Friday:...

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Umbach Office Hours: Friday: reschedule to 1:30-2:30
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Nacre of abalone shell An oriented coating composed of alternating layers of aragonite (CaCO 3 ) and a biopolymer. Its laminated structure simultaneously provides strength, hardness and toughness Containing about 1 vol. % polymer, nacre is twice as hard and 1,000 times as tough as its constituent phases
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E. DiMasi, J. L. Jordan-Sweet (BNL), and M. Sarikaya (U. Washington, Seattle); http://www.solids.bnl.gov/~dimasi/bones/abalone/index.html
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Hierarchy of the abalone structure Bhushan B Phil. Trans. R. Soc. A 2009;367:1445-1486
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ABALONE SHELL 95wt% inorganic - site specific calcite platelet oriented growth 5wt% β -sheet protein organic structure directing matrix Organic-inorganic nanocomposite 1000x fracture toughness of bulk calcite
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a, Scanning electron micrograph of a freshly cleaved abalone shell showing adhesive ligaments formed between consecutive abalone nacre tablets on exertion of mechanical stress. The tablets are approx 400 nm thick. b, Transmission electron micrograph of another cleaved abalone shell, showing the adhesive ligaments between nacre tablets. The space between the tablets is approx 600 nm. Thus the ligaments can lengthen to many times the original spacing between the tablets, which is of the order of 30 nm.
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Force–extension curves for three different kinds of molecules. A short molecule resists pulling up to a high force before it breaks at small extensions. A long molecule behaves like an entropic spring and yields to the pulling force up to large extensions. The energy to break the long molecule is larger than that for the small molecule, but the forces at low extensions are small. But a long molecule that is compacted into domains that are held together with
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ENGRI1110_Lect29_Nov6_posted - Umbach Office Hours: Friday:...

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