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fracture toughness

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https://www.readbyqxmd.com/read/27935297/probing-the-soft-and-nanoductile-mechanical-nature-of-single-and-polycrystalline-organic-inorganic-hybrid-perovskites-for-flexible-functional-devices
#1
Jingui Yu, Mingchao Wang, Shangchao Lin
Although organic-inorganic hybrid perovskites have been extensively investigated for promising applications in energy-related devices, their mechanical properties, which restrict their practical deployment as flexible and wearable devices, have been largely unexplored at the atomistic level. Toward this level of understanding, we predict the elastic constant matrix and various elastic properties of CH3NH3PbI3 (MAPbI3) using atomistic simulations. We find that single-crystalline MAPbI3 is much stiffer and exhibits higher ultimate tensile strength than polycrystalline samples, but the latter exhibit unexpected, greatly enhanced nanoductility and fracture toughness, resulting from the extensive amorphization during the yielding process...
December 9, 2016: ACS Nano
https://www.readbyqxmd.com/read/27918708/patient-specific-hip-fracture-strength-assessment-with-microstructural-mr-imaging-based-finite-element-modeling
#2
Chamith S Rajapakse, Alexandra Hotca, Benjamin T Newman, Austin Ramme, Shaleen Vira, Elizabeth A Kobe, Rhiannon Miller, Stephen Honig, Gregory Chang
Purpose To describe a nonlinear finite element analysis method by using magnetic resonance (MR) images for the assessment of the mechanical competence of the hip and to demonstrate the reproducibility of the tool. Materials and Methods This prospective study received institutional review board approval and fully complied with HIPAA regulations for patient data. Written informed consent was obtained from all subjects. A nonlinear finite element analysis method was developed to estimate mechanical parameters that relate to hip fracture resistance by using MR images...
December 2, 2016: Radiology
https://www.readbyqxmd.com/read/27918290/nacre-mimetic-bulk-lamellar-composites-reinforced-with-high-aspect-ratio-glass-flakes
#3
Selen N Gurbuz Guner, Arcan F Dericioglu
Nacre-mimetic epoxy matrix composites reinforced with readily available micron-sized high aspect ratio C-glass flakes were fabricated by a relatively simple, single-step, scalable, time, cost and man-power effective processing strategy: hot-press assisted slip casting (HASC). HASC enables the fabrication of preferentially oriented two-dimensional inorganic reinforcement-polymer matrix bulk lamellar composites with a micro-scale structure resembling the brick-and-mortar architecture of nacre. By applying the micro-scale design guideline found in nacre and optimizing the relative volume fractions of the reinforcement and the matrix as well as by anchoring the brick-and-mortar architecture, and tailoring the interface between reinforcements and the matrix via silane coupling agents, strong, stiff and tough bio-inspired nacre-mimetic bulk composites were fabricated...
December 5, 2016: Bioinspiration & Biomimetics
https://www.readbyqxmd.com/read/27917901/fish-dna-modified-clays-towards-highly-flame-retardant-polymer-nanocomposite-with-improved-interfacial-and-mechanical-performance
#4
Omid Zabihi, Mojtaba Ahmadi, Hamid Khayyam, Minoo Naebe
Deoxyribonucleic Acid (DNA) has been recently found to be an efficient renewable and environmentally-friendly flame retardant. In this work, for the first time, we have used waste DNA from fishing industry to modify clay structure in order to increase the clay interactions with epoxy resin and take benefit of its additional thermal property effect on thermo-physical properties of epoxy-clay nanocomposites. Intercalation of DNA within the clay layers was accomplished in a one-step approach confirmed by FT-IR, XPS, TGA, and XRD analyses, indicating that d-space of clay layers was expanded from ~1...
December 5, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27916635/studies-on-the-effects-of-titanate-and-silane-coupling-agents-on-the-performance-of-poly-methyl-methacrylate-barium-titanate-denture-base-nanocomposites
#5
Nidal W Elshereksi, Mariyam J Ghazali, Andanastuti Muchtar, Che H Azhari
OBJECTIVES: This study aimed to fabricate and characterise silanated and titanated nanobarium titanate (NBT) filled poly(methyl methacrylate) (PMMA) denture base composites and to evaluate the behaviour of a titanate coupling agent (TCA) as an alternative coupling agent to silane. The effect of filler surface modification on fracture toughness was also studied. METHODS: Silanated, titanated and pure NBT at 5% were incorporated in PMMA matrix. Neat PMMA matrix served as a control...
December 1, 2016: Journal of Dentistry
https://www.readbyqxmd.com/read/27893169/reinforcement-in-removable-prosthodontics-a-literature-review
#6
REVIEW
Toshihito Takahashi, Tomoya Gonda, Yoko Mizuno, Yozo Fujinami, Yoshinobu Maeda
BACKGROUND: Removable prothodontics are often associated with mechanical troubles in daily use, such as fracture or deformation. These troubles render prostheses unusable and reduce wearers' QOL. Various reinforcements are used to prevent such problems, but consensus on reinforcement has not been reached. OBJECTIVE: This review aimed to summarize the effects of reinforcement, and to propose favorable reinforcement based on material, design, and position in the prostheses...
November 28, 2016: Journal of Oral Rehabilitation
https://www.readbyqxmd.com/read/27867109/towards-long-lasting-zirconia-based-composites-for-dental-implants-transformation-induced-plasticity-and-its-consequence-on-ceramic-reliability
#7
Helen Reveron, Marta Fornabaio, Paola Palmero, Tobias Fürderer, Erik Adolfsson, Vanni Lughi, Alois Bonifacio, Valter Sergo, Laura Montanaro, Jérôme Chevalier
: Zirconia-based composites were developed through an innovative processing route able to tune compositional and microstructural features very precisely. Fully-dense ceria-stabilized zirconia ceramics (84vol% Ce-TZP) containing equiaxed alumina (8vol%Al2O3) and elongated strontium hexa-aluminate (8vol% SrAl12O19) second phases were obtained by conventional sintering. This work deals with the effect of the zirconia stabilization degree (CeO2 in the range 10.0-11.5mol%) on the transformability and mechanical properties of Ce-TZP-Al2O3-SrAl12O19 materials...
November 17, 2016: Acta Biomaterialia
https://www.readbyqxmd.com/read/27836115/hollow-glass-fibers-in-reinforcing-glass-ionomer-cements
#8
Sufyan Garoushi, Pekka Vallittu, Lippo Lassila
OBJECTIVE: This study investigated the reinforcing effect of hollow and solid discontinuous glass fiber fillers with two different loading fractions on select mechanical properties of conventional and resin modified glass ionomer cements (GICs). METHODS: Experimental fiber reinforced GIC was prepared by adding discontinuous glass fiber (hollow/solid) of 0.5mm in length to the powder of commercial GICs (GC Fuji IX and II LC) with two different weight ratios (5 and 10wt%) using a high speed mixing machine...
November 8, 2016: Dental Materials: Official Publication of the Academy of Dental Materials
https://www.readbyqxmd.com/read/27805410/micro-scale-fracture-behavior-of-single-crystal-silicon-beams-at-elevated-temperatures
#9
Balila Nagamani Jaya, Jeffrey Martin Wheeler, Juri Wehrs, James P Best, Rafael Soler, Johann Michler, Christoph Kirchlechner, Gerhard Dehm
The micro-mechanical fracture behavior of single crystalline silicon was investigated as a function of temperature in situ in the scanning electron microscope equipped with a nanoindenter. A gradual but continuous increase in KC was observed with increasing temperature above 300 °C, in contrast to the sharp transitions observed in earlier works. No sharp brittle to ductile transition temperature (BDTT) could be identified, but a clear change in cracking mechanism occurs at ~300 °C with multiple load drops accompanying the deformation...
November 2, 2016: Nano Letters
https://www.readbyqxmd.com/read/27775026/size-effect-critical-resolved-shear-stress-stacking-fault-energy-and-solid-solution-strengthening-in-the-crmnfeconi-high-entropy-alloy
#10
Norihiko L Okamoto, Shu Fujimoto, Yuki Kambara, Marino Kawamura, Zhenghao M T Chen, Hirotaka Matsunoshita, Katsushi Tanaka, Haruyuki Inui, Easo P George
High-entropy alloys (HEAs) comprise a novel class of scientifically and technologically interesting materials. Among these, equatomic CrMnFeCoNi with the face-centered cubic (FCC) structure is noteworthy because its ductility and strength increase with decreasing temperature while maintaining outstanding fracture toughness at cryogenic temperatures. Here we report for the first time by single-crystal micropillar compression that its bulk room temperature critical resolved shear stress (CRSS) is ~33-43 MPa, ~10 times higher than that of pure nickel...
October 24, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27774538/enhanced-mechanical-properties-of-photo-clickable-thiol-ene-peg-hydrogels-through-repeated-photopolymerization-of-in-swollen-macromer
#11
C I Fiedler, E A Aisenbrey, J A Wahlquist, C M Heveran, V L Ferguson, S J Bryant, R R McLeod
Current hydrogels used for tissue engineering are limited to a single range of mechanical properties within the replicated tissue construct. We show that repeated in-swelling by a single hydrogel pre-cursor solution into an existing polymerized hydrogel followed by photo-exposure increases hydrogel mechanical properties. The process is demonstrated with a photo-clickable thiol-ene hydrogel using a biocompatible precursor solution of poly(ethylene glycol) dithiol and 8-arm poly(ethylene glycol) functionalized with norbornene...
October 24, 2016: Soft Matter
https://www.readbyqxmd.com/read/27771139/correlative-analysis-of-cement-dentin-interfaces-using-an-interfacial-fracture-toughness-and-micro-tensile-bond-strength-approach
#12
Evelise M Souza, Jan De Munck, Pong Pongprueksa, Annelies Van Ende, Bart Van Meerbeek
OBJECTIVES: To determine the interfacial fracture toughness (iFT) and micro-tensile strength (μTBS) of composite cements bonded to dentin. METHODS: Fifty feldspar ceramic blocks (Vita Mark II, Vita Zahnfabrik) were luted onto dentin using two self-adhesive (G-CEM LinkAce, GC; SpeedCEM, Ivoclar Vivadent), two self-etch (Multilink Primer & Multilink Automix, Ivoclar Vivadent; Scotchbond Universal & RelyX Ultimate, 3 M ESPE), and one etch-and-rinse (Excite F DSC & Variolink II, Ivoclar Vivadent) composite cement (n=10)...
December 2016: Dental Materials: Official Publication of the Academy of Dental Materials
https://www.readbyqxmd.com/read/27770920/crystallisation-of-hydroxyapatite-in-phosphorylated-poly-vinyl-alcohol-as-a-synthetic-route-to-tough-mechanical-hybrid-materials
#13
Akane Kusakabe, Ken Hirota, Tadashi Mizutani
Partially phosphorylated poly(vinyl alcohol) was prepared by treating poly(vinyl alcohol) with 100% phosphoric acid, and 5, 10 and 20% of the hydroxyl groups were converted to phosphoric acid ester. Addition of Ca(2+) to an aqueous solution of phosphorylated poly(vinyl alcohol) gave a transparent gel. Five cycles of alternate soaking of the gel in aqueous CaCl2 and aqueous (NH4)2HPO4 were carried out to crystallise hydroxyapatite (HAP) in the phosphorylated poly(vinyl alcohol) matrix. The X-ray diffraction peaks of HAP formed in 5% phosphorylated PVA were sharp, while those of HAP formed in 20% phosphorylated PVA were broad...
January 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/27770876/combined-effect-of-magnesia-and-zirconia-on-the-bioactivity-of-calcium-silicate-ceramics-at-c-s-ratio-less-than-unity
#14
Emad M M Ewais, Amira M M Amin, Yasser M Z Ahmed, Eman A Ashor, Ulrike Hess, Kurosch Rezwan
This paper describes the effect of magnesia in the presence of zirconia on the bioactivity, microstructure and physico-mechanical properties of calcium silicate composition adjusted at calcia/silica ratio(C/S) of 0.5. A mixture from calcium carbonate and silica was conducted at C/S of 0.5. 20wt.% of magnesia and 5-25wt.% of ZrO2 were added. Each mixture was mixed with ethanol in a planetary ball mill, dried, formed and fired at a temperature of 1325±5°C. Phase composition, FE-SEM, and physico-mechanical properties of the fired specimens were determined and explained...
January 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/27750002/superior-performance-of-polyurethane-based-on-natural-melanin-nanoparticles
#15
Yang Wang, Ting Li, Xuefei Wang, Piming Ma, Huiyu Bai, Weifu Dong, Yi Xie, Mingqing Chen
Melanin, a kind of well-known multifunctional biomacromolecules that are widely available in large quantities from a variety of natural sources. In this work, Polyurethane (PU) /melanin nanocomposites with enhanced tensile strength and toughness were successfully fabricated via in situ polymerization. It was found that the tensile strength (σ), elongation-at-break (εmax) and work to fracture (W) were increased from 5.6 MPa, 770% and 33 MJ/m3 for PU to 51.5 MPa, 1880% and 413 MJ/m3 for PU/melanin (2 wt %) nanocomposite, respectively...
October 17, 2016: Biomacromolecules
https://www.readbyqxmd.com/read/27749026/highly-stretchable-and-notch-insensitive-hydrogel-based-on-polyacrylamide-and-milk-protein
#16
Jinwoo Ma, Jaehun Lee, Sang Sub Han, Kyu Hwan Oh, Ki Tae Nam, Jeong-Yun Sun
Protein-based hydrogels have received attention for biomedical applications and tissue engineering because they are biocompatible and abundant. However, the poor mechanical properties of these hydrogels remain a hurdle for practical use. We have developed a highly stretchable and notch-insensitive hydrogel by integrating casein micelles into polyacrylamide (PAAm) networks. In the casein-PAAm hybrid gels, casein micelles and polyacrylamide chains synergistically enhance the mechanical properties. Casein-PAAm hybrid gels are highly stretchable, stretching to more than 35 times their initial length under uniaxial tension...
October 17, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27714361/fracture-toughness-of-hydrogels-measurement-and-interpretation
#17
Rong Long, Chung-Yuen Hui
The fracture mechanics of hydrogels, especially those with significantly enhanced toughness, has attracted extensive research interests. In this article we discuss the experimental measurement and theoretical interpretation of the fracture toughness for soft hydrogels. We first review the definition of fracture toughness for elastic materials, and the commonly used experimental configurations to measure it. In reality most gels are inelastic. For gels that are rate insensitive, we discuss how to interpret the fracture toughness associated with two distinct scenarios: crack initiation and steady-state crack propagation...
October 4, 2016: Soft Matter
https://www.readbyqxmd.com/read/27704183/autoimmune-arthritis-deteriorates-bone-quantity-and-quality-of-periarticular-bone-in-a-mouse-model-of-rheumatoid-arthritis
#18
T Shimizu, M Takahata, H Kimura-Suda, Y Kameda, K Endo, H Hamano, S Hiratsuka, M Ota, D Sato, T Ito, M Todoh, S Tadano, N Iwasaki
: This study showed that autoimmune arthritis induces especially severe osteoporosis in the periarticular region adjacent to inflamed joints, suggesting that arthritis increases the fragility fracture risk near inflamed joints, which is frequently observed in patients with RA. INTRODUCTION: Periarticular osteoporosis near inflamed joints is a hallmark of early rheumatoid arthritis (RA). Here we show that rheumatic inflammation deteriorates the bone quality and bone quantity of periarticular bone, thereby decreasing bone strength and toughness in a mouse model of RA...
October 4, 2016: Osteoporosis International
https://www.readbyqxmd.com/read/27698472/quantifying-yield-behaviour-in-metals-by-x-ray-nanotomography
#19
M Mostafavi, R Bradley, D E J Armstrong, T J Marrow
Nanoindentation of engineering materials is commonly used to study, at small length scales, the continuum mechanical properties of elastic modulus and yield strength. However, it is difficult to measure strain hardening via nanoindentation. Strain hardening, which describes the increase in strength with plastic deformation, affects fracture toughness and ductility, and is an important engineering material property. The problem is that the load-displacement data of a single nanoindentation do not provide a unique solution for the material's plastic properties, which can be described by its stress-strain behaviour...
October 4, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27697332/strength-toughness-and-aging-stability-of-highly-translucent-y-tzp-ceramics-for-dental-restorations
#20
Fei Zhang, Masanao Inokoshi, Maria Batuk, Joke Hadermann, Ignace Naert, Bart Van Meerbeek, Jef Vleugels
OBJECTIVE: The aim was to evaluate the optical properties, mechanical properties and aging stability of yttria-stabilized zirconia with different compositions, highlighting the influence of the alumina addition, Y2O3 content and La2O3 doping on the translucency. METHODS: Five different Y-TZP zirconia powders (3 commercially available and 2 experimentally modified) were sintered under the same conditions and characterized by X-ray diffraction with Rietveld analysis and scanning electron microscopy (SEM)...
December 2016: Dental Materials: Official Publication of the Academy of Dental Materials
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