The Utility of <i>R</i>‐Curves for Understanding Fracture Toughness‐Strength Relations in Bridging Ceramics

Kruzic, Jamie J.; Satet, R.L.; Hoffmann, Michael J.; Cannon, R. M.; Ritchie, Robert O.

doi:10.1111/j.1551-2916.2008.02380.x

Cited by 80 publications

(78 citation statements)

References 58 publications

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“…According to tangency criterion, rising R-curve materials fracturing from the propagation of "short" cracks are not able to develop the whole toughening capability, and fracture at effective toughness levels (K eff ) lower than the intrinsic fracture toughness measured for long cracks [21,22,32,35,36]. Furthermore, Rcurve materials also exhibit stable subcritical crack growth extension before catastrophic failure.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Strength and reliability of WC-Co cemented carbides: Understanding microstructural effects on the basis of R-curve behavior and fractography

Tarragó

Coureaux

Torres

et al. 2018

International Journal of Refractory Metals and Hard Materials

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Strength and reliability of WC-Co cemented carbides (hardmetals) are dependent on effective fracture toughness as well as on nature, size and distribution of processing flaws. Regarding toughness, they exhibit a crack growth resistance (R-curve) behavior, derived from the development of a multiligament bridging zone at the crack wake. Accordingly, successful implementation of fracture mechanics requires consideration of tangency criterion, between applied stress intensity factor and R-curve, in addition to fractographic inspection. It is the aim of this study to evaluate the strength behavior of a series of experimental WC-Co grades on the basis of R-curve failure criteria. Results indicate that microstructural effects on the strength of hardmetals may be satisfactorily rationalized following the referred criterion.The analysis includes consideration of nature and distribution of fracture origins, found to be more diverse and wider respectively for the harder fine-grained grades. This experimental evidence, together with the fact that these hardmetals exhibit steeper rising R-curves than tougher coarse-grained ones, leads to lower reliability for the former. This investigation documents and validates the great relevance of R-curve behavior for optimizing the mechanical performance of WC-Co cemented carbides on the basis of microstructural design.

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Section: Accepted Manuscriptmentioning

confidence: 99%

Strength and reliability of WC-Co cemented carbides: Understanding microstructural effects on the basis of R-curve behavior and fractography

Tarragó

Coureaux

Torres

et al. 2018

International Journal of Refractory Metals and Hard Materials

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“…the fracture stress, σF, can be deduced from the R-curve with a knowledge of the prevalent flaw sizes, a. As discussed in detail elsewhere, [8] in addition to the peak toughness, it is the early proportion of the R-curve (over the first hundred micrometers or so of crack extension) that is also very important for ceramics as this governs their fracture strength at realistic flaw sizes. Consequently, the resulting strengths depend markedly on the details of the R-curve and of course the initial flaw sizes, such that optimizing strength vs. toughness can once again involve different choices of microstructures.…”

Section: Ceramic Materialsmentioning

confidence: 99%

On the Fracture Toughness of Advanced Materials

2009

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Few engineering materials are limited by their strength; rather they are limited by their resistance to fracture or fracture toughness. It is not by accident that most critical structures, such as bridges, ships, nuclear pressure vessels and so forth, are manufactured from materials that are comparatively low in strength but high in toughness. Indeed, in many classes of materials, strength and toughness are almost mutually exclusive. In the first instance, such resistance to fracture is a function of bonding and crystal structure (or lack thereof), but can be developed through the design of appropriate nano/microstructures. However, the creation of tough microstructures in structural materials, i.e., metals, polymers, ceramics and their composites, is invariably a compromise between resistance to intrinsic damage mechanisms ahead of the tip of a crack (intrinsic toughening) and the formation of crack-tip shielding mechanisms which principally act behind the tip to reduce the effective "crack-driving force" (extrinsic toughening).Intrinsic toughening is essentially an inherent property of a specific microstructure; it is the dominant form of toughening in ductile (e.g., metallic) materials. However, for most brittle (e.g., ceramic) solids, and this includes many biological materials, it is largely ineffective and toughening conversely must be developed extrinsically, by such shielding mechanisms as crack bridging. From a fracture mechanics perspective, this results in toughening in the form of rising resistance-curve behavior where the fracture resistance actually increases with crack extension. The implication of this is that in many biological and high-strength advanced materials, toughness is developed primarily during crack growth and not for crack initiation. This is an important realization yet is still rarely reflected in the way that toughness is measured, which is invariably involves the use of single-value (crack-initiation) parameters such as the fracture toughness KIc.

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“…5) (35). This form of toughening is particularly potent and the prime source of the fracture resistance of most monolithic structural ceramics with engineered grain boundaries, i.e., course-grained Al 2 O 3 , Si 3 N 4 and SiC (36)(37)(38)(39)(40)(41)(42)(43). However, the contribution from bridging alone does not account for the fact that the observed toughness of the best brick-and-mortar 80% alumina structure (J c ~ 8000 J/m 2 ) is over 300 times higher in terms of energy than the toughness of its main constituent, Al 2 O 3 (J c ~ 26 J/m 2 ).…”

mentioning

confidence: 99%

Tough, Bio-Inspired Hybrid Materials

Munch

Launey

Alsem

et al. 2008

Science

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1,607

1,238

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The notion of mimicking natural structures in the synthesis of new structural materials has generated enormous interest but has yielded few practical advances. Natural composites achieve strength and toughness through complex hierarchical designs extremely difficult to replicate synthetically. Here we emulate Nature's toughening mechanisms through the combination of two ordinary compounds, aluminum oxide and polymethylmethacrylate, into ice-templated structures whose toughness can be over 300 times (in energy terms) that of their constituents. The final product is a bulk hybrid ceramic material whose high yield strength and fracture toughness (~200 MPa and ~30 MPa√m) provide specific properties comparable to aluminum alloys. These model materials can be used to identify the key microstructural features that should guide the synthesis of bio-inspired ceramic-based composites with unique strength and toughness.With the quest for more efficient energy-related technologies, there is an imperative to develop lightweight, high-performance structural materials that possess both exceptional strength and toughness. Unfortunately, these two properties tend to be mutually exclusive and the attainment of optimal mechanical performance is invariably a compromise often achieved through the empirical design of microstructures. Nature has long developed the ability to combine brittle minerals and organic molecules into hybrid composites with exceptional fracture resistance and structural capabilities (1-3); indeed, many natural materials like bone, wood and nacre (abalone shell) have highly sophisticated structures with complex hierarchical designs whose properties are far in excess what could be expected from a simple mixture of their components (2,4). Biological mineralized composites, in particular bone, dentin and nacre (5-7), can generate fracture toughness (i.e., resistance to the initiation and growth of a crack) primarily by extrinsic toughening mechanisms (8) that "shield" any crack from the applied loads. These mechanisms, which are quite different to those that toughen metals for

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The Utility of R‐Curves for Understanding Fracture Toughness‐Strength Relations in Bridging Ceramics

Cited by 80 publications

References 58 publications

Strength and reliability of WC-Co cemented carbides: Understanding microstructural effects on the basis of R-curve behavior and fractography

Strength and reliability of WC-Co cemented carbides: Understanding microstructural effects on the basis of R-curve behavior and fractography

On the Fracture Toughness of Advanced Materials

Tough, Bio-Inspired Hybrid Materials

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