Computer-Controlled Stable Crack Growth as a Reliable and Fast Method to Determine Subcritical Crack Growth

Özcoban, Hüseyin; Fett, T.; Schneider, Gerold A.

doi:10.1520/jte104191

Cited by 6 publications

(4 citation statements)

References 18 publications

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“…The fracture toughness and work of fracture were measured in four‐point bending, a test that is commonly used for brittle materials. A custom‐made mechanical testing device was used, with automated control of stable crack growth using the Single‐Edge‐V‐Notched‐Beam method . A full description of the device can be found elsewhere .…”

Section: Methodsmentioning

confidence: 99%

Tough Alumina/Polymer Layered Composites with High Ceramic Content

et al. 2014

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Ceramic composites found in nature, such as bone, nacre, and sponge spicule, often provide an effective resolution to a wellknown conflict between materials' strength and toughness. This arises, on the one hand, from their high ceramic content that ensures high strength of the material. On the other hand, various pathways are provided for stress dissipation, and thus toughness, due to their intricate hierarchical architectures. Such pathways include crack bridging, crack deflection, and delamination in the case of layered structures. On the basis of these inspiring ideas, we attempted here to create simultaneously strong and tough laminated alumina composite with high ceramic content. Composites were prepared from highgrade commercial alumina with spin-coated interlayers of ductile polymers (PMMA and PVA). The specimens' ultimate properties (strength, fracture toughness, and work of fracture) were measured by a four-point bending method. In some cases, fracture toughness of the composites was increased by up to an order of magnitude, reminiscent of the natural layered composites. It is proposed that this increase may be attributed to an interlocking mechanism, often encountered in biological composites. The significance of sample architecture and the role of the interfacial and bulk properties of the interlayer material are discussed. J ournalspicule. The structural architecture and interlayer adhesion will be viewed as variable parameters, the optimized values of which will hopefully lead to a tough and strong composite with high ceramic content. Emphasis is put here on the use of simple, affordable materials and techniques so as to demonstrate the universality and applicability of bioinspired toughening mechanisms. Supporting InformationAdditional Supporting Information may be found in the online version of this article:

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Section: Methodsmentioning

confidence: 99%

Tough Alumina/Polymer Layered Composites with High Ceramic Content

et al. 2014

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“…1. Inducing crack formation in compression as recommended in DIN EN 14425-3 [15] 2. slow loading rates However, while an appropriate pre-cracking step significantly enhances the rate of valid test results, the use of slow load rates leads to a significant influence of subcritical crack growth effects, which result in lower measured K IC values [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

On the feasibility of the Chevron Notch Beam method to measure fracture toughness of fine-grained zirconia ceramics

Kailer

Stephan

2016

Dental Materials

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“…For testing, samples were loaded in three-point-bending with a support span of 20 mm and with the attachment being located on the tensile side of the sample (Figure b). All tests were displacement-controlled with loading rates around 10 μm/min and performed in the custom-made bending device that has also been used by Jelitto et al, Özcoban et al, and Livanov et al − This device features an automated unloading algorithm upon crack advancement that allows for incremental, stable crack propagation through the adhesive zone.…”

Section: Methods and Experimental Proceduresmentioning

confidence: 99%

Shear Strength and Interfacial Toughness Characterization of Sapphire–Epoxy Interfaces for Nacre-Inspired Composites

Behr

Jungblut

Swain

et al. 2016

ACS Appl. Mater. Interfaces

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The common tensile lap-shear test for adhesive joints is inappropriate for brittle substrates such as glasses or ceramics where stress intensifications due to clamping and additional bending moments invalidate results. Nevertheless, bonding of glasses and ceramics is still important in display applications for electronics, in safety glass and ballistic armor, for dental braces and restoratives, or in recently developed bioinspired composites. To mechanically characterize adhesive bondings in these fields nonetheless, a novel approach based on the so-called Schwickerath test for dental sintered joints is used. This new method not only matches data from conventional analysis but also uniquely combines the accurate determination of interfacial shear strength and toughness in one simple test. The approach is verified for sapphire-epoxy joints that are of interest for bioinspired composites. For these, the procedure not only provides quantitative interfacial properties for the first time, it also exemplarily suggests annealing of sapphire at 1000 °C for 10 h for mechanically and economically effective improvements of the interfacial bond strength and toughness. With increases of strength and toughness from approximately 8 to 29 MPa and from 2.6 to 35 J/m, respectively, this thermal modification drastically enhances the properties of unmodified sapphire-epoxy interfaces. At the same time, it is much more convenient than wet-chemical approaches such as silanization. Hence, besides the introduction of a new testing procedure for adhesive joints of brittle or expensive substrates, a new and facile annealing process for improvements of the adhesive properties of sapphire is suggested and quantitative data for the mechanical properties of sapphire-epoxy interfaces that are common in synthetic nacre-inspired composites are provided for the first time.

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Computer-Controlled Stable Crack Growth as a Reliable and Fast Method to Determine Subcritical Crack Growth

Cited by 6 publications

References 18 publications

Tough Alumina/Polymer Layered Composites with High Ceramic Content

Tough Alumina/Polymer Layered Composites with High Ceramic Content

On the feasibility of the Chevron Notch Beam method to measure fracture toughness of fine-grained zirconia ceramics

Shear Strength and Interfacial Toughness Characterization of Sapphire–Epoxy Interfaces for Nacre-Inspired Composites

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