Hindered Crack Propagation in Materials with Periodically Varying Young's Modulus—Lessons from Biological Materials

Fratzl, Peter; Gupta, Himadri S.; Fischer, Franz Dieter; Kolednik, O.

doi:10.1002/adma.200602394

Cited by 243 publications

(192 citation statements)

References 37 publications

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“…This observation also correlates well with the observations Fratzl et al made, where the difference in elastic modulus between the alternating layers determines the increase in toughness [29]. In cases where the ratio between the elastic moduli is at least five, toughening is observed.…”

Section: Investigated Voxel Edge Lengths and Their Influence On Impacsupporting

confidence: 79%

Bioinspired engineering polymers by voxel-based 3D-printing

et al. 2016

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Additive manufacturing (AM) has become an important tool in the product development process as it offers the possibility to produce parts of good geometrical quality within a short period of time, allowing geometrical validations and the visualisation of ideas. Yet the application of AM is often limited due to the poor mechanical properties of AM parts. In the automotive sector for example, there is a high demand for tough AM parts which have an impact strength comparable to industrially moulded thermoplasts. This paper explores the possibility to increase the impact strength of AM parts by combining a stiff, hard and brittle component (VeroWhite Plus in this instance) with a soft, elastomer-like component (TangoBlack Plus) and arranging these on a micro-scale level in form of alternating, chess-pattern voxels. While one material was responsible for maintaining a sufficient stiffness and strength of the resulting composite structure, the other material acted as an obstacle for crack propagation. Varying the edge length of the voxels, it was possible to investigate the influence of the microscopic voxel geometry on the part's macroscopic impact strength. It was shown that the Charpy impact strength could be raised by a factor of eight (from 10.9 kJ/m 2 to values between 80 kJ/m 2 and 86.1 kJ/m 2 ) compared to the single material. Above a certain voxel edge length the impact strength decreases again. The critical voxel edge length at which this decrease begins was determined. However, the increase in impact strength is accompanied by a decrease in the glass transition temperature.

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Section: Investigated Voxel Edge Lengths and Their Influence On Impacsupporting

confidence: 79%

Bioinspired engineering polymers by voxel-based 3D-printing

et al. 2016

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“…The mechanical strength of multilayered materials such as bivalve shells is inversely related to the thickness of each layer (Anderson and Li, 1995;He et al, 1997). Thinner layers more frequently deflect cracks, hence forcing a more treacherous path and more interactions of the cracks with elastic organic material (Fratzl et al, 2007;Zhang et al, 2010). Using oyster juveniles, Beniash et al (Beniash et al, 2010) showed that calcitic laths were significantly thicker in the shell deposited under low pH or low  calcite conditions compared with that of oysters exposed to normocapnia.…”

Section: G H Dickinson and Othersmentioning

confidence: 99%

Interactive effects of salinity and elevated CO2 levels on juvenile eastern oysters,Crassostrea virginica

Dickinson

Ivanina

Matoo

et al. 2012

Journal of Experimental Biology

233

145

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SUMMARYRising levels of atmospheric CO 2 lead to acidification of the ocean and alter seawater carbonate chemistry, which can negatively impact calcifying organisms, including mollusks. In estuaries, exposure to elevated CO 2 levels often co-occurs with other stressors, such as reduced salinity, which enhances the acidification trend, affects ion and acid-base regulation of estuarine calcifiers and modifies their response to ocean acidification. We studied the interactive effects of salinity and partial pressure of CO 2 (P CO2 ) on biomineralization and energy homeostasis in juveniles of the eastern oyster, Crassostrea virginica, a common estuarine bivalve. Juveniles were exposed for 11weeks to one of two environmentally relevant salinities (30 or 15PSU) either at current atmospheric P CO2 (~400atm, normocapnia) or P CO2 projected by moderate IPCC scenarios for the year 2100 (~700-800atm, hypercapnia). Exposure of the juvenile oysters to elevated P CO2 and/or low salinity led to a significant increase in mortality, reduction of tissue energy stores (glycogen and lipid) and negative soft tissue growth, indicating energy deficiency. Interestingly, tissue ATP levels were not affected by exposure to changing salinity and P CO2, suggesting that juvenile oysters maintain their cellular energy status at the expense of lipid and glycogen stores. At the same time, no compensatory upregulation of carbonic anhydrase activity was found under the conditions of low salinity and high P CO2 . Metabolic profiling using magnetic resonance spectroscopy revealed altered metabolite status following low salinity exposure; specifically, acetate levels were lower in hypercapnic than in normocapnic individuals at low salinity. Combined exposure to hypercapnia and low salinity negatively affected mechanical properties of shells of the juveniles, resulting in reduced hardness and fracture resistance. Thus, our data suggest that the combined effects of elevated P CO2 and fluctuating salinity may jeopardize the survival of eastern oysters because of weakening of their shells and increased energy consumption.

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“…[3] The periodic nature of hard and soft interfaces, in this case between alpha-chitin fibrils and hydroxyapatite crystals, results in a crack-tip shielding effect that changes the crack driving force and thereby arresting crack propagation. [35,36] He and Hutchinson discussed the role of elastic mismatch on the strain energy release rate of a crack, which determines if the crack gets deflected at an interface or penetrates through to the other solid. [34] Submitted to 9 However, unlike a simple 90° crack deflection, cracks within this structure are twisting and thus increase toughening.…”

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confidence: 99%

A Sinusoidally Architected Helicoidal Biocomposite

et al. 2016

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A fibrous herringbone-modified helicoidal architecture is identified within the exocuticle of an impact-resistant crustacean appendage. This previously unreported composite microstructure, which features highly textured apatite mineral templated by an alpha-chitin matrix, provides enhanced stress redistribution and energy absorption over the traditional helicoidal design under compressive loading. Nanoscale toughening mechanisms are also identified using high load nanoindentation and in-situ TEM picoindentation. A Sinusoidally-Architected Helicoidal BiocompositeBy Nicholas A. Yaraghi, Nicolás Guarín-Zapata, Lessa K. Grunenfelder, Eric Hintsala, Sanjit Bhowmick, Jon M. Hiller, Mark Betts, Edward L. Principe, Jae-Young Jung, Leigh Sheppard, Richard Wuhrer, Joanna McKittrick, Pablo D. Zavattieri Keywords: (Composites, Toughness, Impact, Biomineral, Ultrastructure) Submitted to 3 Biologically mineralized composites offer inspiration for the design of next generation structural materials due to their low density, high strength and toughness currently unmatched by engineering technologies. [1][2][3][4][5][6][7][8][9] Such properties are based on the ability for the organism to utilize structural organics and acidic proteins to guide and control the mineralization process to yield hierarchical architectures with well-defined compositional gradients.One notable example is the highly developed raptorial appendage, or dactyl, of the stomatopods, a group of aggressive marine crustaceans that use these structures for feeding upon hard-shelled and soft-bodied prey. [10][11][12][13][14] The dactyls of the "smashers", those that feed primarily on hard-shelled prey, (see Figure 1A) takes the form of a bulbous club ( Figure 1B), which is used to smash through mollusk shells, crab exoskeletons, and other tough mineralized structures with tremendous force and speed. [11][12][13][14][15][16] Achieving accelerations over 10,000g and reaching speeds of 23 m/s from rest, the dactyl strike is recognized as one of the fastest and most powerful impacting events observed in Nature. [11,12] The club is capable of delivering and subsequently enduring repetitive impact forces up to 1500 N and cavitation stresses without catastrophically failing, demonstrating its utility as an exceptionally damage-tolerant natural material.The origins of such a mechanical response lie in the structural design. Previous work identified the club as a multi-regional composite material containing an organic matrix composed of alpha-chitin fibers mineralized by amorphous forms of calcium carbonate and calcium phosphate as well as crystalline apatite. [17,18] These investigations revealed mechanisms responsible for providing damage-tolerance and impact-resistance to the club, which were largely attributed to the interior of the club (periodic region), identified as the primary energy-absorbing layer. [17,18] The combination of soft polymeric nanofibers and stiffer mineral provides a periodic modulus mismatch leading to crack deflection, which in co...

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Hindered Crack Propagation in Materials with Periodically Varying Young's Modulus—Lessons from Biological Materials

Cited by 243 publications

References 37 publications

Bioinspired engineering polymers by voxel-based 3D-printing

Bioinspired engineering polymers by voxel-based 3D-printing

Interactive effects of salinity and elevated CO2 levels on juvenile eastern oysters,Crassostrea virginica

A Sinusoidally Architected Helicoidal Biocomposite

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