A mechanism for the control of crack propagation in all-brittle systems

Cook, J. W.; Gordon, Jeff

doi:10.1098/rspa.1964.0248

Cited by 611 publications

(44 citation statements)

References 4 publications

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“…Cracks were observed to stop or be deflected at the plate\disc interface (figure 8). Such crack deflection will significantly increase the toughness of this part, due to blunting of the crack tip and an increased energy of fracture (Cook & Gordon 1964). The use of layered structures to increase toughness is quite common in synthetic ceramic composites and has also been observed in biological materials such as the nacreous layer of mollusc shells (Currey 1977 ;Jackson et al 1988).…”

Section: (B) Laminated Ceramic Composite-the Plates/discs Complexmentioning

confidence: 99%

Design strategies of sea urchin teeth: structure, composition and micromechanical relations to function

Wang

Addadi

Weiner

1997

Phil. Trans. R. Soc. Lond. B

170

177

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SUMMARYThe teeth of sea urchins comprise a variety of different structural entities, all of which are composed of magnesium-bearing calcite together with a small amount of organic material. The teeth are worn down continuously, but in such a way that they remain sharp and functional. Here we describe aspects of the structural, compositional and micromechanical properties of the teeth of Paracentrotus li idus using scanning electron microscopy, infrared spectrometry, atomic absorption, X-ray diffraction and microindentation. The S-shaped single crystalline calcitic fibres are one of the main structural elements of the tooth. They extend from the stone part to the keel. The diameter of the fibres increases gradually from less than 1 µm at the stone tip to about 20 µm at the keel end, while their MgCO $ contents decrease from about 13 mol % to about 4.5 mol %. Each fibre is coated by a thin organic sheath and surrounded by polycrystalline calcitic discs containing as much as 35 mol % MgCO $ . This structure constitutes a unique kind of gradient fibre-reinforced ceramic matrix composite, whose microhardness and toughness decrease gradually from the stone part to the keel. Primary plates are also important structural elements of the tooth. Each primary plate has a very unusual sandwich-like structure with a calcitic envelope surrounding a thin apparently amorphous CaCO $ layer. This central layer, together with the primary plate\disc interface, improves the toughness of this zone by stopping and blunting cracks. The selfsharpening function of the teeth is believed to result from the combination of the geometrical shape of the main structural elements and their spatial arrangement, the interfacial strength between structural elements, and the hardness gradient extending from the working stone part to the surrounding zones. The sea urchin tooth structure possesses an array of interesting functional design features, some of which may possibly be applicable to materials science.

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Section: (B) Laminated Ceramic Composite-the Plates/discs Complexmentioning

confidence: 99%

Design strategies of sea urchin teeth: structure, composition and micromechanical relations to function

Wang

Addadi

Weiner

1997

Phil. Trans. R. Soc. Lond. B

170

177

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“…At the nano/microscopic level (B0.5-10 mm), the interlocking cross-sections of the fibrous building blocks lead to crack deflection along the interfaces between them, which acts as a toughening mechanism operating at crack tips. This process follows the well-known Cook-Gordon mechanism for crack deflection with the presence of weak interfaces ahead of the crack tip 39 . Moreover, unlike most metal and ceramic engineering polycrystalline materials with pseudo-hexagonal grains, the crosssections in C. pyramidata have triple junction grain angles close to 90°(as compared with B120°in engineering materials) and concave boundaries (the inner angles are 4180°).…”

Section: Articlementioning

confidence: 99%

Hierarchical structural design for fracture resistance in the shell of the pteropod Clio pyramidata

Weaver²,

Ortiz

2015

Nat Commun

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The thecosomes are a group of planktonic pteropods with thin, 1 mm-sized aragonitic shells, which are known to possess a unique helical microstructure consisting of interlocking nanofibres. Here we investigate the detailed hierarchical structural and mechanical design of the pteropod Clio pyramidata. We quantify and elucidate the macroscopic distribution of the helical structure over the entire shell (B1 mm), the structural characteristics of the helical assembly (B10-100 mm), the anisotropic cross-sectional geometry of the fibrous building blocks (B0.5-10 mm) and the heterogeneous distribution of intracrystalline organic inclusions within individual fibres (o0.5 mm). A global fibre-like crystallographic texture is observed with local in-plane rotations. Microindentation and electron microscopy studies reveal that the helical organization of the fibrous building blocks effectively constrains mechanical damages through tortuous crack propagation. Uniaxial micropillar compression and cross-sectional transmission electron microscopy directly reveal that the interlocking fibrous building blocks further retard crack propagation at the nanometre scale.

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“…[35] the author indicates plastic deformation as an additional factor influencing the toughening process. However, since the NiAl-Al 2 O 3 interface is weak, the crack propagates mainly through the interface, just like in the case of the CookGordon mechanism [36]. The toughening effect is predominantly caused by crack deflection and/or crack bridging.…”

Section: Metal-ceramic Functionally Graded Materials -Manufacturing mentioning

confidence: 99%

Metal-ceramic functionally graded materials – manufacturing, characterization, application

Chmielewski¹,

Pietrzak²

2016

Bulletin of the Polish Academy of Sciences Technical Sciences

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Abstract. Functionally graded materials (FGMs) belong to a new, continuously developing group of materials, finding application in various branches of industry. The idea of freely designing their construction profile, restricted only by the available manufacturing techniques, enables obtaining materials with composition and structure gradients having unprecedented properties. In this paper, selected results of works carried out by the authors and relating to the application of the developed metal-ceramic composites were presented in order to manufacture functionally graded materials for target purposes. Gradient structures with various construction profiles that can play different roles were produced on the basis on the following material pairs: Cr-Al2O3, NiAl-Al2O3 and Cu-AlN. Manufacturing conditions, microstructure characteristics and selected properties, crucial from the point of view of future applications, were presented.

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A mechanism for the control of crack propagation in all-brittle systems

Cited by 611 publications

References 4 publications

Design strategies of sea urchin teeth: structure, composition and micromechanical relations to function

Design strategies of sea urchin teeth: structure, composition and micromechanical relations to function

Hierarchical structural design for fracture resistance in the shell of the pteropod Clio pyramidata

Metal-ceramic functionally graded materials – manufacturing, characterization, application

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