Failure mode transition in nacre and bone-like materials

Rabiei, Reza; Bekah, Sacheen; Barthelat, François

doi:10.1016/j.actbio.2010.04.008

Cited by 144 publications

(124 citation statements)

References 20 publications

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“…However, it should be noted that aspect ratios that are higher than 12.0 do not result in an increase in the tensile toughness. Rabiei et al [61] have also shown that the pen shell has low fracture toughness due to its high platelets' aspect ratio [61]. Figure 7b suggests that an aspect ratio around 12.0 is an optimal ratio for the design of these multilayered materials with nanoscale features.…”

Section: Toughening Mechanism and The Role Of The Componentsmentioning

confidence: 97%

Toughening mechanisms in bioinspired multilayered materials

Askarinejad

Rahbar

2015

J. R. Soc. Interface.

129

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Outstanding mechanical properties of biological multilayered materials are strongly influenced by nanoscale features in their structure. In this study, mechanical behaviour and toughening mechanisms of abalone nacre-inspired multilayered materials are explored. In nacre's structure, the organic matrix, pillars and the roughness of the aragonite platelets play important roles in its overall mechanical performance. A micromechanical model for multilayered biological materials is proposed to simulate their mechanical deformation and toughening mechanisms. The fundamental hypothesis of the model is the inclusion of nanoscale pillars with near theoretical strength (s th E/30). It is also assumed that pillars and asperities confine the organic matrix to the proximity of the platelets, and, hence, increase their stiffness, since it has been previously shown that the organic matrix behaves more stiffly in the proximity of mineral platelets. The modelling results are in excellent agreement with the available experimental data for abalone nacre. The results demonstrate that the aragonite platelets, pillars and organic matrix synergistically affect the stiffness of nacre, and the pillars significantly contribute to the mechanical performance of nacre. It is also shown that the roughness induced interactions between the organic matrix and aragonite platelet, represented in the model by asperity elements, play a key role in strength and toughness of abalone nacre. The highly nonlinear behaviour of the proposed multilayered material is the result of distributed deformation in the nacre-like structure due to the existence of nano-asperities and nanopillars with near theoretical strength. Finally, tensile toughness is studied as a function of the components in the microstructure of nacre.

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Section: Toughening Mechanism and The Role Of The Componentsmentioning

confidence: 97%

Toughening mechanisms in bioinspired multilayered materials

Askarinejad

Rahbar

2015

J. R. Soc. Interface.

129

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“…S20), the mechanical properties of the synthetic nacre are still not as good as that of natural nacre (35,36) (Fig. 4, B and C).…”

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confidence: 99%

Great apes anticipate that other individuals will act according to false beliefs

Krupenye

Kano

Call

et al. 2016

Science

619

414

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( fig. S20), the mechanical properties of the synthetic nacre are still not as good as that of natural nacre (35,36) (Fig. 4, B and C). Due to the larger aspect ratio of the aragonite platelets in the synthetic nacre, the platelets exhibit a "partly pullout" behavior, which leads to lower crack-resistance capability.Because the precipitation of the second phase onto the matrix relies on electrostatic force, CaCO 3 and chitin can be substituted by other precursors with opposite charges to make superior composites such as engineering ceramics (21-24) (figs. S21 and S22). Besides, as the dependence of properties of the composite materials on the characteristic length of their periodic microstructure (37), the mechanical performance of these materials can be optimized by adjusting the properties of the original matrix (38), which affect both the amount of electrostatically absorbed precipitates and the density of the nucleation sites. The fabrication of the laminated synthetic nacre is not a special case; there are other techniques, such as programmable 3D printing, for constructing predesigned macroscopic matrices that can be readily incorporated with our strategy to produce composite materials. Moreover, this strategy is also adaptable for fabricating robust bulk materials with brittle and heat-labile components ( fig. S21B). Given the importance of nano-and microscopic structures for the materials performance, we thus anticipate that our method can be extended to produce various composite materials with unique properties. Humans operate with a "theory of mind" with which they are able to understand that others' actions are driven not by reality but by beliefs about reality, even when those beliefs are false. Although great apes share with humans many social-cognitive skills, they have repeatedly failed experimental tests of such false-belief understanding. We use an anticipatory looking test (originally developed for human infants) to show that three species of great apes reliably look in anticipation of an agent acting on a location where he falsely believes an object to be, even though the apes themselves know that the object is no longer there. Our results suggest that great apes also operate, at least on an implicit level, with an understanding of false beliefs.C entral to everything that makes us humanincluding our distinctive modes of communication, cooperation, and culture-is our theory of mind (TOM). TOM is the ability to impute unobservable mental states, such as desires and beliefs, to others (1, 2). For nearly four decades, a cardinal question in psychology has concerned whether nonhuman animals, such as great apes, also possess this cognitive skill (1, 3). A variety of nonverbal behavioral experiments have provided converging evidence that apes can predict others' behavior, not simply based on external cues but rather on an understanding of others' goals, perception, and knowledge (3, 4). However, it remains unclear whether apes can comprehend reality-incongruent mental states (e.g., false beliefs) (3...

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“…In addition, the delamination process is retarded bythe infiltrated silk fibroin binding layers and thus further dissipates energy ( ( fig. 820), the mechanical properties of the syn thetic nacre are still not as good as that of natural nacre (35,36) (Fig. 4, B and C).…”

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confidence: 99%

Synthetic nacre by predesigned matrix-directed mineralization

Mao

Gao

Yao

et al. 2016

Science

799

547

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Although biomimetic designs are expected to play a key role in exploring future structural materials, facile fabrication of bulk biomimetic materials under ambient conditions remains a major challenge. Here, we describe a mesoscale "assembly-and-mineralization" approach inspired by the natural process in mollusks to fabricate bulk synthetic nacre that highly resembles both the chemical composition and the hierarchical structure of natural nacre. The milfimeter·thick synthetic nacre consists of alternating organic layers and aragonite platelet layers (91 weight percent) and exhibits good ultimate strength and fracture toughness. This predesigned matrix-directed mineralization method represents a rational strategy for the preparation of robust composite materials with hierarchically ordered structures, where various constituents are adaptable, including brittle and heat-labile materials. Biological materials are built from limited components, but their mechanical perfor mances, such as strength and toughness, are far beyond their artificial counterparts. The secret of success is their hierarchically ordered structure at multiscale levels (1 4). The most studied model among these biological rna terials is the nacreous part in some mollusk shells that oonsists of about 95 weight% (wt %) of brittle aragonitic Ca00 3 and 5 wt% of organic materials (5). Mollusks produce nacre by first generating several layers of insoluble 13 chitin matrix filled with silk fibroin gel (6). Then aragonite cores form on the surface of the matrix at the nuclea tion sites (7), followed by lateral growth in the confined space of adjacent organic layers, which finally leads to a V<.ronoi ~ (5). These arago nite platelets, despite their single crystal diffraction pattern, are not perfett single crystals but essen tially cmsist of nanograins with the same aystal lographic orientation (mesocrystals), whereby the platelets are not as fragile as perfect single crys ta1s (8). The mature nacre bas a "brick and mortar" microstructure where aragonite platelet layers are bound by an organic matrix (3). Through a number of such structural designs and toughening mech anisms at muhiscale levels (2, 9, 10), nacre ream ciles its toughness and strength, which are mutually exclusive in most artificial materials (11).In contrast to biological materials, the evolu tion of synthetic structural materials bas been achieved predominately by developing new syn thetic compounds rather than optimizing the micro/nanostructures of existing materials. (Fig. 1, A and B, and fig. Sl), a chitosan matrix with predesigned laminated structure is fubricated ( fig. S2, A, B, D, and E). Then the matrix is acetylated (Fig.lC) and transformed to 13 chitin to avoid unwanted swelling or dissolution ( fig. S2, C and E, and table Sl). The acetylated matrix is mineralized in a peristaltic pump driven circula tory system via the decomposition of Ca(H00 3 )z in the presence of polyacrylic acid (P AA) and M~· (Flg. lD). Then the final material is obtained by silk fibroin infiltration and...

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Failure mode transition in nacre and bone-like materials

Cited by 144 publications

References 20 publications

Toughening mechanisms in bioinspired multilayered materials

Toughening mechanisms in bioinspired multilayered materials

Great apes anticipate that other individuals will act according to false beliefs

Synthetic nacre by predesigned matrix-directed mineralization

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