Tablet-level origin of toughening in abalone shells and translation to synthetic composite materials

Espinosa, Horacio D.; Juster, Allison; Latourte, Félix; Loh, Owen Y.; Grégoire, David; Zavattieri, Pablo

doi:10.1038/ncomms1172

Cited by 344 publications

(237 citation statements)

References 48 publications

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“…In contrast, the (LDH92/PSS) n /LDH92 coatings strain harden, an effect which can be attributed to in9plane sliding of the well9arranged LDH platelets and subsequent progressive platelet interlocking. This strain hardening phenomenon of (LDH92/PSS) n /LDH92 coatings is similar to that of natural nacre, 47 although the exact mechanism of platelet interlocking is unclear; in natural systems, wedging, 55,56 asperities, 15,57 mineral bridges, 58,59 nanograin rotation 3 and negative Poisson's ratio 60 have been proposed.…”

supporting

confidence: 53%

Nacre-nanomimetics: Strong, Stiff, and Plastic

Luca¹,

Menzel²,

Blaker³

et al. 2015

ACS Appl. Mater. Interfaces

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*Address correspondence to m.shaffer@imperial.ac.uk , The bricks and mortar in the classic structure of nacre have characteristic geometry, aspect ratios and relative proportions; these key parameters can be retained whilst scaling down the absolute length scale by more than one order of magnitude. The results shed light on fundamental scaling behavior and provide new opportunities for high performance, yet ductile, lightweight nanocomposites. Reproducing the toughening mechanisms of nacre at smaller length scales allows a greater volume of interface per unit volume whilst simultaneously increasing the intrinsic properties of the inorganic constituents. Layer9by9Layer (LbL) assembly of poly (sodium 49styrene sulfonate) (PSS) polyelectrolyte and well9defined [Mg 2 Al(OH) 6 ]CO 3 .nH 2 O layered double hydroxide (LDH) platelets produces a dense, oriented, high inorganic content (~90 wt%) nanostructure resembling natural nacre, but at a shorter length scale. The smaller building blocks enable the (self9) assembly of a higher quality nanostructure than conventional mimics, leading to improved mechanical properties, approaching those of natural nacre, whilst allowing for substantial plastic deformation. Both strain hardening and crack deflection mechanisms were observed by scanning electron microscopy (SEM) during nanoindentation. The best properties emerge from an ordered nanostructure, generated using regular platelets, with narrow size dispersion.Like many natural composites, the structure of nacre, found in the inner part of some mollusk shells, is a complex hierarchical structure organized over multiple hierarchical levels leading to coupled toughening mechanisms. 196 In particular, its characteristic "brick9and9mortar" structure 7 is understood to play the key role in developing a high resistance to defects; it consists of 95 % brittle inorganic aragonite (CaCO 3 ) building blocks, around 2009900 nm thick and 59 8 Jm wide (aspect ratio from 7915), 8 "glued" together by a soft chitin9containing organic framework. This organic layer is around 209 30 nm thick 9 and makes up the remaining 5 % of the structure. The combination of a small fraction of organic phase along with this specific three9 dimensional architecture leads to exceptional mechanical properties, including high toughness (≈ 1.24 kJ.m 92 ), strength (≈ 140 MPa) and stiffness (E ≈ 60 GPa). 10,11 When loaded, the "bricks" have the ability to slide over one another within the organic phase and eventually interlock 12,13 via a range of possible mechanisms, 14 leading to strain hardening. 14,15 In addition, when a crack initiates from a defect within the nacre structure, multiple crack 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 deflections occur at the building block interfaces. 16 According to the Griffith criterion, the fracture strength of pure aragonite platelets can...

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supporting

confidence: 53%

Nacre-nanomimetics: Strong, Stiff, and Plastic

Luca¹,

Menzel²,

Blaker³

et al. 2015

ACS Appl. Mater. Interfaces

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“…Sequential combination of hard and soft phase has previously been proven to reinforce toughness and strength of both nature and engineering materials (Espinosa et al, 2011;Naraghi et al). Similar structures, combining soft deformable materials with hard and rigid ones, can also be found in civil engineering structures.…”

Section: Discussionmentioning

confidence: 99%

Load-bearing in cortical bone microstructure: Selective stiffening and heterogeneous strain distribution at the lamellar level

Katsamenis

Chong

Andriotis

et al. 2013

Journal of the Mechanical Behavior of Biomedical Materials

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An improved understanding of bone mechanics is vital in the development of evaluation strategies for patients at risk of bone fracture. The current evaluation approach based on bone mineral density (BMD) measurements lacks sensitivity, and it has become clear that as well as bone mass, bone quality should also be evaluated.The latter includes, among other parameters, the bone matrix material properties, which in turn depend on the hierarchical structural features that make up bone as well as their composition. Optimal load transfer, energy dissipation and toughening mechanisms have, to some extent, been uncovered in bone. Yet, the origin of these properties and their dependence upon the hierarchical structure and composition of bone are largely unknown. Here we investigate load transfer in the osteonal and subosteonal levels and the mechanical behaviour of osteonal lamellae and interlamellar areas during loading. Using cantilever-based nanoindentation, in situ microtensile testing during atomic force microscopy (AFM) and digital image correlation (DIC), we report evidence for a previously unknown mechanism. This mechanism transfers load and movement in a manner analogous to the engineered "elastomeric bearing pads" used in large engineering structures. ȝ-RAMAN microscopy investigations 2 showed compositional differences between lamellae and interlamellar areas. The latter have lower collagen content but an increased concentration of noncollagenous proteins (NCPs). Hence, NCPs enriched areas on the microscale might be similarly important for bone failure as on the nanoscale. Finally, we managed to capture stable crack propagation within the interlamellar areas in a time-lapsed fashion, proving their significant contribution towards fracture toughness.

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“…9a for the example case of abalone) [67,[93][94][95]. These shells forfeit all flexibility in favor of high (a) Cross-section of the abalone shell displaying the calcitic and aragonitic (nacre) layers; (b) the brick-and-mortar structure of nacre displaying calcium carbonate plates with mortar-like chitin layers; (c) crack deflection toughening mechanism that causes a more tortuous crack path; (d) microbuckling toughening mechanism in compression of the calcium carbonate plates that creates significant additional surface area.…”

Section: Mollusk Shellsmentioning

confidence: 99%