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Special Issue "The Failure Micromechanics and Toughening Mechanisms of Materials"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (28 February 2017)

Special Issue Editor

Guest Editor
Prof. Dr. It-Meng (Jim) Low

Department of Applied Physics, Curtin University, GPO Box U1987, Perth WA 6845, Australia
Website | E-Mail

Special Issue Information

Dear Colleagues,

Engineering materials are central to the successful evolution and prosperity of human societies in the 21st century and beyond. Many metals, alloys, ceramics, polymers and their composites are being used in structures, such as bridges, ships, aeroplanes, buildings, and so on. In addition to strength, the toughness of a material is just as critical in its ultimate use in a particular structure. Toughness is an intrinsic property of a material and it is the ability of a material to dissipate deformation energy without propagation of a crack. Not all materials (e.g., ceramics, glassy polymers) are inherently tough, which render them susceptible to brittle failure and of limited use. To circumvent this limitation, several strategies have been developed to improve the fracture toughness of these materials. However, the design of tough microstructures in structural materials demands 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 act behind the tip to reduce the effective “crack-tip driving force” (extrinsic toughening). In the former, improved toughness is obtained by increasing the microstructural resistance to suppress damage in the form of microcracking or microvoid formation ahead of the crack tip. In the latter, toughness is developed primarily during crack growth and not for crack initiation. In essence, fracture arises from a mutual competition between intrinsic damage mechanisms ahead of the crack tip that promote cracking and extrinsic shielding mechanisms mainly behind the tip trying to impede it.

Toughening mechanisms and the concomitant failure micromechanics are very much material-dependent. In metals, toughness arises primarily from crack-tip plasticity and involves highly mobile dislocations. In brittle materials, such as ceramics and glassy polymers, toughening must be achieved extrinsically, i.e., through the use of microstructures which can promote crack-tip shielding mechanisms such as crack deflection, in situ phase transformations, constrained microcracking and crack bridging. Understanding of these toughening and failure processes is vital for the design and use of new-generation materials for challenging engineering applications.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews that cover all aspects of toughening and failure in various materials (i.e., metals, alloys, ceramics, polymers, composites, etc.) are all welcome.

Prof. Jim Low
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Fracture toughness
  • Toughening mechanism
  • Failure micromechanics
  • Intrinsic toughening
  • Extrinsic toughening
  • Crack-bridging
  • Crack-tip shielding
  • Plastic deformation

Published Papers (7 papers)

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Research

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Open AccessArticle Influence of Texture on Impact Toughness of Ferritic Fe-20Cr-5Al Oxide Dispersion Strengthened Steel
Materials 2017, 10(7), 745; doi:10.3390/ma10070745
Received: 28 April 2017 / Revised: 16 June 2017 / Accepted: 26 June 2017 / Published: 3 July 2017
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Abstract
Fe-based oxide dispersion strengthened (ODS) steels are oriented to applications where high operating temperatures and good corrosion resistance is paramount. However, their use is compromised by their fracture toughness, which is lower than other competing ferritic-martenstic steels. In addition, the route required in
[...] Read more.
Fe-based oxide dispersion strengthened (ODS) steels are oriented to applications where high operating temperatures and good corrosion resistance is paramount. However, their use is compromised by their fracture toughness, which is lower than other competing ferritic-martenstic steels. In addition, the route required in manufacturing these alloys generates texture in the material, which induces a strong anisotropy in properties. The V-notched Charpy tests carried out on these alloys, to evaluate their impact toughness, reveal that delaminations do not follow the path that would be expected. There are many hypotheses about what triggers these delaminations, but the most accepted is that the joint action of particles in the grain boundaries, texture induced in the manufacturing process, and the actual microstructure of these alloys are responsible. In this paper we focused on the actual role of crystallographic texture on impact toughness in these materials. A finite elements simulation is carried out to solely analyze the role of texture and eliminate other factors, such as grain boundaries and the dispersed particles. The work allows us to conclude that crystallographic texture plays an important role in the distribution of stresses in the Charpy specimens. The observed delaminations might be explained on the basis that the crack in the grain, causing the delamination, is directly related to the shear stresses τ12 on both sides of the grain boundary, while the main crack propagation is a consequence of the normal stress to the crack. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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Open AccessArticle Fracture Analysis of MWCNT/Epoxy Nanocomposite Film Deposited on Aluminum Substrate
Materials 2017, 10(4), 408; doi:10.3390/ma10040408
Received: 23 February 2017 / Revised: 9 April 2017 / Accepted: 11 April 2017 / Published: 13 April 2017
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Abstract
Multi-walled carbon nanotube (MWCNT) reinforced epoxy films were deposited on an aluminum substrate by a hot-pressing process. Three-point bending tests were performed to determine the Young’s modulus of MWCNT reinforced nanocomposite films. Compared to the neat epoxy film, nanocomposite film with 1 wt
[...] Read more.
Multi-walled carbon nanotube (MWCNT) reinforced epoxy films were deposited on an aluminum substrate by a hot-pressing process. Three-point bending tests were performed to determine the Young’s modulus of MWCNT reinforced nanocomposite films. Compared to the neat epoxy film, nanocomposite film with 1 wt % of MWCNT exhibits an increase of 21% in the Young’s modulus. Four-point-bending tests were conducted to investigate the fracture toughness of the MWCNT/epoxy nanocomposite film deposited on an aluminum substrate with interfacial cracks. Based on the Euler-Bernoulli beam theory, the strain energy in a film/substrate composite beam is derived. The difference of strain energy before and after the propagation of the interfacial crack are calculated, leading to the determination of the strain energy release rate. Experimental test results show that the fracture toughness of the nanocomposite film deposited on the aluminum substrate increases with the increase in the MWCNT content. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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Open AccessFeature PaperArticle Improvement of Fracture Toughness in Epoxy Nanocomposites through Chemical Hybridization of Carbon Nanotubes and Alumina
Materials 2017, 10(3), 301; doi:10.3390/ma10030301
Received: 31 January 2017 / Revised: 22 February 2017 / Accepted: 14 March 2017 / Published: 16 March 2017
Cited by 2 | PDF Full-text (6244 KB) | HTML Full-text | XML Full-text
Abstract
The current study investigated the effect of adding a carbon nanotube–alumina (CNT–Al2O3) hybrid on the fracture toughness of epoxy nanocomposites. The CNT–Al2O3 hybrid was synthesised by growing CNTs on Al2O3 particles via the
[...] Read more.
The current study investigated the effect of adding a carbon nanotube–alumina (CNT–Al2O3) hybrid on the fracture toughness of epoxy nanocomposites. The CNT–Al2O3 hybrid was synthesised by growing CNTs on Al2O3 particles via the chemical vapour deposition method. The CNTs were strongly attached onto the Al2O3 particles, which served to transport and disperse the CNTs homogenously, and to prevent agglomeration in the CNTs. The experimental results demonstrated that the CNT–Al2O3 hybrid-filled epoxy nanocomposites showed improvement in terms of the fracture toughness, as indicated by an increase of up to 26% in the critical stress intensity factor, K1C, compared to neat epoxy. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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Open AccessArticle ZrB2-CNTs Nanocomposites Fabricated by Spark Plasma Sintering
Materials 2016, 9(12), 967; doi:10.3390/ma9120967
Received: 16 October 2016 / Revised: 18 November 2016 / Accepted: 22 November 2016 / Published: 29 November 2016
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Abstract
ZrB2-based nanocomposites with and without carbon nanotubes (CNTs) as reinforcement were prepared at 1600 °C by spark plasma sintering. The effects of CNTs on the microstructure and mechanical properties of nano-ZrB2 matrix composites were studied. The results indicated that adding
[...] Read more.
ZrB2-based nanocomposites with and without carbon nanotubes (CNTs) as reinforcement were prepared at 1600 °C by spark plasma sintering. The effects of CNTs on the microstructure and mechanical properties of nano-ZrB2 matrix composites were studied. The results indicated that adding CNTs can inhibit the abnormal grain growth of ZrB2 grains and improve the fracture toughness of the composites. The toughness mechanisms were crack deflection, crack bridging, debonding, and pull-out of CNTs. The experimental results of the nanograined ZrB2-CNTs composites were compared with those of the micro-grained ZrB2-CNTs composites. Due to the small size and surface effects, the nanograined ZrB2-CNTs composites exhibited stronger mechanical properties: the hardness, flexural strength and fracture toughness were 18.7 ± 0.2 GPa, 1016 ± 75 MPa, and 8.5 ± 0.4 MPa·m1/2, respectively. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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Open AccessArticle Rolling Contact Fatigue Performances of Carburized and High-C Nanostructured Bainitic Steels
Materials 2016, 9(12), 960; doi:10.3390/ma9120960
Received: 26 October 2016 / Revised: 22 November 2016 / Accepted: 22 November 2016 / Published: 25 November 2016
Cited by 2 | PDF Full-text (8004 KB) | HTML Full-text | XML Full-text
Abstract
In the present work, the nanostructured bainitic microstructures were obtained at the surfaces of a carburized steel and a high-C steel. The rolling contact fatigue (RCF) performances of the two alloy steels with the same volume fraction of undissolved carbide were studied under
[...] Read more.
In the present work, the nanostructured bainitic microstructures were obtained at the surfaces of a carburized steel and a high-C steel. The rolling contact fatigue (RCF) performances of the two alloy steels with the same volume fraction of undissolved carbide were studied under lubrication. Results show that the RCF life of the carburized nanostructured bainitic steel is superior to that of the high-C nanostructured bainitic steel in spite of the chemical composition, phase constituent, plate thickness of bainitic ferrite, hardness, and residual compressive stress value of the contact surfaces of the two steels under roughly similar conditions. The excellent RCF performance of the carburized nanostructured bainitic steel is mainly attributed to the following reasons: finer carbide dispersion distribution in the top surface, the higher residual compressive stress values in the carburized layer, the deeper residual compressive stress layer, the higher work hardening ability, the larger amount of retained austenite transforming into martensite at the surface and the more stable untransformed retained austenite left in the top surface of the steel. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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Open AccessArticle Preparation of Cement Composites with Ordered Microstructures via Doping with Graphene Oxide Nanosheets and an Investigation of Their Strength and Durability
Materials 2016, 9(11), 924; doi:10.3390/ma9110924
Received: 9 October 2016 / Revised: 4 November 2016 / Accepted: 8 November 2016 / Published: 14 November 2016
Cited by 1 | PDF Full-text (8968 KB) | HTML Full-text | XML Full-text
Abstract
The main problem with cement composites is that they have structural defects, including cracks, holes, and a disordered morphology, which significantly affects their strength and durability. Therefore, the construction of cement composites with defect-free structures and high strength and long durability is an
[...] Read more.
The main problem with cement composites is that they have structural defects, including cracks, holes, and a disordered morphology, which significantly affects their strength and durability. Therefore, the construction of cement composites with defect-free structures and high strength and long durability is an important research topic. Here, by controlling the size and chemical groups of graphene oxide nanosheets (GONs) used for doping, we were able to control the entire cement matrix to form an ordered microstructure consisting of polyhedron-like crystals and exhibit flower-like patterns. The cracks and holes in the cement matrix just about vanished. The compressive and flexural strengths as well as the parameters for the durability assessment of the corresponding cement composites obviously improved compared with the control samples. Thus, the formation mechanism of the cement matrix with the ordered microstructure is proposed, and a proper explanation is given to regulation action. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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Review

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Open AccessReview Toughening Mechanisms in Nanolayered MAX Phase Ceramics—A Review
Materials 2017, 10(4), 366; doi:10.3390/ma10040366
Received: 23 February 2017 / Revised: 21 March 2017 / Accepted: 23 March 2017 / Published: 30 March 2017
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Abstract
Advanced engineering and functional ceramics are sensitive to damage cracks, which delay the wide applications of these materials in various fields. Ceramic composites with enhanced fracture toughness may trigger a paradigm for design and application of the brittle components. This paper reviews the
[...] Read more.
Advanced engineering and functional ceramics are sensitive to damage cracks, which delay the wide applications of these materials in various fields. Ceramic composites with enhanced fracture toughness may trigger a paradigm for design and application of the brittle components. This paper reviews the toughening mechanisms for the nanolayered MAX phase ceramics. The main toughening mechanisms for these ternary compounds were controlled by particle toughening, phase-transformation toughening and fiber-reinforced toughening, as well as texture toughening. Based on the various toughening mechanisms in MAX phase, models of SiC particles and fibers toughening Ti3SiC2 are established to predict and explain the toughening mechanisms. The modeling work provides insights and guidance to fabricate MAX phase-related composites with optimized microstructures in order to achieve the desired mechanical properties required for harsh application environments. Full article
(This article belongs to the Special Issue The Failure Micromechanics and Toughening Mechanisms of Materials)
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