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fracture toughness

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https://www.readbyqxmd.com/read/28645511/lamellae-spatial-distribution-modulates-fracture-behavior-and-toughness-of-african-pangolin-scales
#1
Michael J Chon, Matthew Daly, Bin Wang, Xianghui Xiao, Alireza Zaheri, Marc A Meyers, Horacio D Espinosa
Pangolin scales form a durable armor whose hierarchical structure offers an avenue towards high performance bio-inspired materials design. In this study, the fracture resistance of African pangolin scales is examined using single edge crack three-point bend fracture testing in order to understand toughening mechanisms arising from the structures of natural mammalian armors. In these mechanical tests, the influence of material orientation and hydration level are examined. The fracture experiments reveal an exceptional fracture resistance due to crack deflection induced by the internal spatial orientation of lamellae...
June 10, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28642921/fracture-behavior-of-single-structure-fiber-reinforced-composite-restorations
#2
Kohji Nagata, Sufyan K Garoushi, Pekka K Vallittu, Noriyuki Wakabayashi, Hidekazu Takahashi, Lippo V J Lassila
Objective: The applications of single-structure fiber-reinforced composite (FRC) in restorative dentistry have not been well reported. This study aimed to clarify the static mechanical properties of anterior crown restorations prepared using two types of single-structure FRC. Materials and methods: An experimental crown restoration was designed for an upper anterior incisor. The restorations were made from IPS Empress CAD for CEREC (Emp), IPS e.max(®) CAD (eMx), experimental single-structure all-FRC (a-FRC), Filtek™ Supreme XTE (XTE), and commercially available single-structure short-FRC (everX Posterior™) (n = 8 for each material) (s-FRC)...
December 2016: Acta Biomaterialia Odontologica Scandinavica
https://www.readbyqxmd.com/read/28639437/ultrasound-assisted-green-economic-synthesis-of-hydroxyapatite-nanoparticles-using-eggshell-bio-waste-and-study-of-mechanical-and-biological-properties-for-orthopaedic-applications
#3
Vijay H Ingole, Kamal Hany Hussein, Anil A Kashale, Kalyani Ghule, Tomaž Vuherer, Vanja Kokol, Jia-Yaw Chang, Yong-Chien Ling, Aruna Vinchurkar, Hom N Dhakal, Anil V Ghule
Nanostructured hydroxyapatite (HAp) is most favorable candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. Herein, we report for the first time ultrasound assisted facile and economic approach for the synthesis of nanocrystalline hydroxyapatite (Ca10 (PO4 )6 (OH)2 ) using recycled eggshell bio-waste referred as EHAp. The process involves the reaction of eggshell bio-waste as a source of calcium and ammonium dihydrogen orthophosphate as a phosphate source...
June 22, 2017: Journal of Biomedical Materials Research. Part A
https://www.readbyqxmd.com/read/28638146/outstanding-compressive-creep-strength-in-cr-ir-codoped-mo0-85nb0-15-si2-crystals-with-the-unique-cross-lamellar-microstructure
#4
Koji Hagihara, Takaaki Ikenishi, Haruka Araki, Takayoshi Nakano
A (Mo0.85Nb0.15)Si2 crystal with an oriented, lamellar, C40/C11b two-phase microstructure is a promising ultrahigh-temperature (UHT) structural material, but its low room-temperature fracture toughness and low high-temperature strength prevent its practical application. As a possibility to overcome these problems, we first found a development of unique "cross-lamellar microstructure", by the cooping of Cr and Ir. The cross-lamellar microstructure consists of a rod-like C11b-phase grains that extend along a direction perpendicular to the lamellar interface in addition to the C40/C11b fine lamellae...
June 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28628168/fracture-toughness-of-wet-and-dry-particulate-materials-comprised-of-colloidal-sized-particles-role-of-plastic-deformation
#5
Mitchell L Sesso, George V Franks
This work demonstrates a method of measuring the fracture toughness of particulate materials comprised of colloidal sized particles over a wide range of saturation. Diametral compression of cylinders containing flaws of controlled length was used to measure the mode I fracture toughness. The effect of degree of saturation on the fracture toughness of slip cast ceramic grade alumina (d50 = 0.7 μm) was investigated. Dry powder compacts have significantly lower fracture toughness than when the powder compact is nearly fully saturated...
June 19, 2017: Soft Matter
https://www.readbyqxmd.com/read/28618481/crack-propagation-through-disordered-materials-as-a-depinning-transition-a-critical-test-of-the-theory
#6
Laurent Ponson, Nadjime Pindra
The dynamics of a planar crack propagating within a brittle disordered material is investigated numerically. The fracture front evolution is described as the depinning of an elastic line in a random field of toughness. The relevance of this approach is critically tested through the comparison of the roughness front properties, the statistics of avalanches, and the local crack velocity distribution with experimental results. Our simulations capture the main features of the fracture front evolution as measured experimentally...
May 2017: Physical Review. E
https://www.readbyqxmd.com/read/28607203/hydrogen-enhanced-cracking-revealed-by-in-situ-micro-cantilever-bending-test-inside-environmental-scanning-electron-microscope
#7
Yun Deng, Tarlan Hajilou, Afrooz Barnoush
To evaluate the hydrogen (H)-induced embrittlement in iron aluminium intermetallics, especially the one with stoichiometric composition of 50 at.% Al, a novel in situ micro-cantilever bending test was applied within an environmental scanning electron microscope (ESEM), which provides both a full process monitoring and a clean, in situ H-charging condition. Two sets of cantilevers were analysed in this work: one set of un-notched cantilevers, and the other set with focused ion beam-milled notch laying on two crystallographic planes: (010) and (110)...
July 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28602753/enhanced-toughening-of-the-crossed-lamellar-structure-revealed-by-nanoindentation
#8
Christopher L Salinas, Enrique Escobar de Obaldia, Chanhue Jeong, Jessica Hernandez, Pablo Zavattieri, David Kisailus
Gastropods shells have evolved to resist the threat of increasingly stronger predators that smash, peal, and crush their shells. Their shells are most commonly constructed from a crossed lamellar microstructure, which consists of an exquisitely architected arrangement of aragonitic mineral and organic encompassing at least four orders of hierarchy. It is this careful control of mineral and organic placement within the entire crossed lamellar structure that yields a four-order of magnitude increase in fracture toughness versus abiotic aragonite...
May 31, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28601650/tough-chitosan-hydrogel-based-on-purified-regeneration-and-alkaline-solvent-as-biomaterials-for-tissue-engineering-applications
#9
Shichao Bi, Zixian Bao, Xiaoyu Bai, Shihao Hu, Xiaojie Cheng, Xiguang Chen
The chitosan based on purified regeneration could be dissolved in 6wt% aqueous NaOH without freeze-thawing cycles and acetylation processing, and such a solution system was effective and different from other dissolving methods Upon heating, a tough hydrogel was constructed from the chitosan (purified regeneration) alkaline solution. The results of XRD, TEM, SEM and rheology analysis proved that chitosan easily aggregated in the solution and formed a nanofibers network to gelate at elevated temperature and concentration...
June 7, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28595102/a-comparative-study-of-progressive-wear-of-four-dental-monolithic-veneered-glass-ceramics
#10
Zhenzhen Zhang, Yuanping Yi, Xuesong Wang, Jiawen Guo, Ding Li, Lin He, Shaofeng Zhang
OBJECTIVES: This study evaluated the wear performance and wear mechanisms of four dental glass-ceramics, based on the microstructure and mechanical properties in the progressive wear process. METHODS: Bar (N = 40, n = 10) and disk (N = 32, n = 8) specimens were prepared from (A) lithium disilicate glass-ceramic (LD), (B) leucite reinforced glass-ceramic (LEU), (C) feldspathic glass-ceramic (FEL), and (D) fluorapatite glass-ceramic (FLU). The bar specimens were tested for three-point flexural strength, hardness, fracture toughness and elastic modulus...
May 30, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28594005/the-effect-of-stw-defects-on-the-mechanical-properties-and-fracture-toughness-of-pristine-and-hydrogenated-graphene
#11
Akarsh Verma, Avinash Parashar
Graphene is emerging as a versatile material with a diverse field of applications. Synthesis techniques for graphene introduce several topological defects such as vacancies, dislocations and Stone-Thrower-Wales (STW) defects. Among them STW defects are generated without deleting any atom from the lattice position, but are introduced by rotating single C-C bonds. In this article, molecular dynamics based simulations have been performed to study the effect of STW defects on the fracture toughness of pristine graphene as well as graphene with crack edges passivated with hydrogen atoms...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28577893/academy-of-dental-materials-guidance-resin-composites-part-i-mechanical-properties
#12
N Ilie, T J Hilton, S D Heintze, R Hickel, D C Watts, N Silikas, J W Stansbury, M Cadenaro, J L Ferracane
OBJECTIVE: The objective of this project, which was initiated from the Academy of Dental Materials, was to review and critically appraise methods to determine fracture, deformation and wear resistance of dental resin composites, in an attempt to provide guidance for investigators endeavoring to study these properties for these materials. METHODS: Test methods have been ranked in the priority of the specific property being tested, as well as of the specific test methods for evaluating that property...
May 31, 2017: Dental Materials: Official Publication of the Academy of Dental Materials
https://www.readbyqxmd.com/read/28573723/extruded-snacks-from-whole-wheat-supplemented-with-textured-soy-flour-effect-on-instrumental-and-sensory-textural-characteristics
#13
Arturo Rodríguez-Vidal, Héctor Eduardo Martínez-Flores, Eva González Jasso, Gonzalo Velázquez de la Cruz, Aurea K Ramírez-Jiménez, Eduardo Morales-Sánchez
The quality of extruded snacks can be affected not only by processing conditions, but also by some factors like the concentration and type of ingredients incorporated in their formulation and the working conditions used. Although the process conditions have been established with measurable textural properties, sensory qualities have not been correlated with these responses in expanded extruded snacks made with added functional ingredients. Therefore, in this study the effect of adding textured soy flour (TSF) and whole wheat flour (WWF) to refined wheat flour in the production of extruded snacks and expanded with hot air was evaluated...
June 2017: Journal of Texture Studies
https://www.readbyqxmd.com/read/28570023/strength-toughness-and-reliability-of-a-porous-glass-biopolymer-composite-scaffold
#14
Qiang Fu, Weitao Jia, Grace Y Lau, Antoni P Tomsia
Development of bioactive glass and ceramic scaffolds intended for the reconstruction of large segmental bone defects remains a challenge for materials science due to the complexities involved in clinical implantation, bone-implant reaction, implant degradation and the multiple loading modes the implants subjected to. A comprehensive evaluation of the mechanical properties of inorganic scaffolds and exploration of new ways to toughen brittle constructs are critical prior to their successful application in loaded sites...
June 1, 2017: Journal of Biomedical Materials Research. Part B, Applied Biomaterials
https://www.readbyqxmd.com/read/28560495/development-of-a-novel-method-for-the-strengthening-and-toughening-of-irradiation-sterilized-bone-allografts
#15
Tarik Attia, Mitchell Woodside, Gagan Minhas, Xing Ze Lu, David S Josey, Timothy Burrow, Marc Grynpas, Thomas L Willett
Reconstruction of large skeletal defects is a significant and challenging issue. Bone allografts are often used for such reconstructions. However, sterilizing bone allografts by using γ-irradiation, damages collagen and causes the bone to become weak, brittle and less fatigue resistant. In a previous study, we successfully protected the mechanical properties of human cortical bone by conducting a pre-treatment with ribose, a natural and biocompatible agent. This study focuses on examining possible mechanisms by which ribose might protect the bone...
May 30, 2017: Cell and Tissue Banking
https://www.readbyqxmd.com/read/28555697/double-network-hydrogels-with-highly-enhanced-toughness-based-on-a-modified-first-network
#16
Jun Liang, Guorong Shan, Pengju Pan
A novel double network (DN) hydrogel with highly enhanced toughness has been prepared using reversible addition-fragmentation transfer (RAFT)-modified poly(2-acrylamide-2-methylpropane sulfonic acid) (PAMPS) as the first network, and polyacrylamide (PAM) as the second network. The mechanical properties of the first-network-modified PAMPS/PAM DN hydrogels have been studied and the new DN hydrogel shows remarkably high fracture energy (3.3 MJ m(-3)) in tensile deformation, which is nearly 9 times larger than that of the unmodified PAMPS/PAM DN hydrogel...
June 7, 2017: Soft Matter
https://www.readbyqxmd.com/read/28552287/mechanical-properties-and-internal-fit-of-4-cad-cam-block-materials
#17
Alexis Goujat, Hazem Abouelleil, Pierre Colon, Christophe Jeannin, Nelly Pradelle, Dominique Seux, Brigitte Grosgogeat
STATEMENT OF PROBLEM: Recent polymer-based computer-assisted design and computer-assisted manufacturing (CAD-CAM) materials have been commercialized for inlay restorations, a polymer-infiltrated ceramic-network (PICN) and composite resin nanoceramics. Little independent evidence regarding their mechanical properties exists. Internal adaptation is an important factor for the clinical success and longevity of a restoration, and data concerning this parameter for inlays made with these blocks are scarce...
May 26, 2017: Journal of Prosthetic Dentistry
https://www.readbyqxmd.com/read/28550972/multiscale-structure-and-damage-tolerance-of-coconut-shells
#18
B Gludovatz, F Walsh, E A Zimmermann, S E Naleway, R O Ritchie, J J Kruzic
We investigated the endocarp of the fruit of Cocos nucifera (i.e., the inner coconut shell), examining the structure across multiple length scales through advanced characterization techniques and in situ testing of mechanical properties. Like many biological materials, the coconut shell possesses a hierarchical structure with distinct features at different length scales that depend on orientation and age. Aged coconut was found to have a significantly stronger (ultimate tensile strength, UTS = 48.5MPa), stiffer (Young's modulus, E = 1...
May 17, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28550764/mechanical-properties-of-crossed-lamellar-structures-in-biological-shells-a-review
#19
REVIEW
X W Li, H M Ji, W Yang, G P Zhang, D L Chen
The self-fabrication of materials in nature offers an alternate and powerful solution towards the grand challenge of designing advanced structural materials, where strength and toughness are always mutually exclusive. Crossed-lamellar structures are the most common microstructures in mollusks that are composed of aragonites and a small amount of organic materials. Such a distinctive composite structure has a fracture toughness being much higher than that of pure carbonate mineral. These structures exhibiting complex hierarchical microarchitectures that span several sub-level lamellae from microscale down to nanoscale, can be grouped into two types, i...
May 17, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28549214/griffith-criterion-for-nanoscale-stress-singularity-in-brittle-silicon
#20
Takashi Sumigawa, Takahiro Shimada, Shuuhei Tanaka, Hiroki Unno, Naoki Ozaki, Shinsaku Ashida, Takayuki Kitamura
Brittle materials such as silicon fail via the crack nucleation and propagation, which is characterized by the singular stress field formed near the crack tip according to Griffith or fracture mechanics theory. The applicability of these continuum-based theories is, however, uncertain and questionable in a nanoscale system due to its extremely small singular stress field of only a few nanometers. Here, we directly characterize the mechanical behavior of a nanocrack via the development of in situ nanomechanical testing using a transmission electron microscope and demonstrate that Griffith or fracture mechanics theory can be applied to even 4 nm stress singularity despite their continuum-based concept...
June 1, 2017: ACS Nano
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