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fracture toughness

Marianthi Topouzi, Eleana Kontonasaki, Dimitrios Bikiaris, Lambrini Papadopoulou, Konstantinos M Paraskevopoulos, Petros Koidis
PURPOSE: Fractures in long span provisional/interim restorations are a common complication. Adequate fracture toughness is necessary to resist occlusal forces and crack propagation, so these restorations should be constructed with materials of improved mechanical properties. The aim of this study was to investigate the possible reinforcement of neat silica nanoparticles and trietoxyvinylsilane-modified silica nanoparticles in a PMMA resin for fixed interim restorations. MATERIALS AND METHODS: Composite PMMA-Silica nanoparticles powders were mixed with PMMA liquid and compact bar shaped specimens were fabricated according to the British standard BS EN ISO 127337:2005...
January 9, 2017: Journal of the Mechanical Behavior of Biomedical Materials
B Karimi, B Ramezanzadeh
The reinforcement effect of graphene oxide nanosheets on the mechanical properties of an epoxy coating has been extensively studied. However, the effect of graphene oxide quantum dot (GOQD) as a new unique carbon based nanomaterial (with lateral dimension of 5-6nm and thickness of one carbon atom) on the mechanical properties of epoxy coating has not been reported and compared with GO yet. So this study aims at fabrication of a high-performance polymer composite with unique mechanical properties using GOQD nanosheets...
January 5, 2017: Journal of Colloid and Interface Science
Albin Thomas, Krishna C R Kolan, Ming C Leu, Gregory E Hilmas
Although implants made with bioactive glass have shown promising results for bone repair, their application in repairing load-bearing long bone is limited due to their poor mechanical properties in comparison to human bone. This work investigates the freeform extrusion fabrication of bioactive silicate 13-93 glass scaffolds reinforced with titanium (Ti) fibers. A composite paste prepared with 13-93 glass and Ti fibers (~16µm in diameter and lengths varying from ~200µm to ~2 mm) was extruded through a nozzle to fabricate scaffolds (0-90° filament orientation pattern) on a heated plate...
December 31, 2016: Journal of the Mechanical Behavior of Biomedical Materials
C J Hernandez, M C H van der Meulen
Increases in fracture risk beyond what are expected from bone mineral density (BMD) are often attributed to poor "bone quality" such as impaired bone tissue strength. Recent studies, however, have highlighted the importance of tissue material properties other than strength, such as fracture toughness. Here we review the concepts behind failure properties other than strength and the physical mechanisms through which they cause mechanical failure: strength describes failure from a single overload; fracture toughness describes failure from a modest load combined with a pre-existing flaw or damage; and fatigue strength describes failure from thousands to millions of cycles of small loads...
January 9, 2017: Journal of Bone and Mineral Research: the Official Journal of the American Society for Bone and Mineral Research
Peter Hess
A consistent set of 2D elastic and fracture properties of hexagonal boron nitride (h-BN) monolayers (boronitrene) and molybdenum disulfide (MoS2) nanosheets is derived. Reported literature values for Young's moduli and fracture strengths, based on experiments and DFT calculations, were used to estimate the line or edge energy with a local 2D bond-breaking model. Consistent information was obtained for intrinsic fracture properties. The basic mechanical properties of boronitrene are roughly 25% lower than the corresponding graphene values...
January 9, 2017: Nanotechnology
Kyudae Shim, Mohamed Abdellatif, Eunsoo Choi, Dongkyun Kim
The safety and effectiveness of antimicrobial ZnO films must be established for general applications. In this study, the antimicrobial activity, skin irritation, elution behavior, and mechanical properties of nanostructured ZnO films on stainless steel were evaluated. ZnO nanoparticle (NP) and ZnO nanowall (NW) structures were prepared with different surface roughnesses, wettability, and concentrations using an RF magnetron sputtering system. The thicknesses of ZnO NP and ZnO NW were approximately 300 and 620 nm, respectively, and ZnO NW had two diffraction directions of [0002] and [01-10] based on high-resolution transmission electron microscopy...
January 7, 2017: Applied Microbiology and Biotechnology
Huafeng Tian, Jiaan Yan, A Varada Rajulu, Aimin Xiang, Xiaogang Luo
In this work, starch/polyvinyl alcohol (PVA) blend films with different compositions were prepared by melt processing. The effect of the composition and relative humidity (RH) on the structure and properties of the resulting blends were investigated. OH groups on starch and PVA formed hydrogen bonding interactions, which could improve the compatibility of the two components. With the increase of starch, the degree of crystallinity of PVA component decreased. The fracture surface of the blend films exhibited rough surface, suggesting the tough fracture...
December 26, 2016: International Journal of Biological Macromolecules
Ning Zhang, Philippe Carrez, Rouzbeh Shahsavari
Nanoscale defects such as dislocations have a profound impact on physics of crystalline materials. Understanding and characterizing the motion of screw dislocation and its corresponding effects on mechanical properties of complex, low symmetry materials has long been a challenge. Herein, we focus on triclinic tobermorite, as a model system and a crystalline analog of layered hydrated cement, and report for the first time how the motion of screw dislocation can influence the strengthening-toughening relationship, imparting brittle-to-ductile transitions...
December 23, 2016: ACS Applied Materials & Interfaces
Carmine Maletta, Emanuele Sgambitterra, Fabrizio Niccoli
Temperature dependent fracture properties of NiTi-based Shape Memory Alloys (SMAs), within the pseudoelastic regime, were analyzed. In particular, the effective Stress Intensity Factor (SIF) was estimated, at different values of the testing temperature, by a fitting of the William's expansion series, based on Digital Image Correlation (DIC) measurements. It was found that temperature plays an important role on SIF and on critical fast fracture conditions. As a consequence, Linear Elastic Fracture Mechanics (LEFM) approaches are not suitable to predict fracture properties of SMAs, as they do not consider the effects of temperature...
December 2016: Scientific Reports
Siegward D Heintze, Nicoleta Ilie, Reinhard Hickel, Alessandra Reis, Alessandro Loguercio, Valentin Rousson
OBJECTIVE: To evaluate a range of mechanical parameters of composite resins and compare the data to the frequency of fractures and wear in clinical studies. METHODS: Based on a search of PubMed and SCOPUS, clinical studies on posterior composite restorations were investigated with regard to bias by two independent reviewers using Cochrane Collaboration's tool for assessing risk of bias in randomized trials. The target variables were chipping and/or fracture, loss of anatomical form (wear) and a combination of both (summary clinical index)...
December 16, 2016: Dental Materials: Official Publication of the Academy of Dental Materials
Amirhossein Kazemi, Majid Abdellahi, Armina Khajeh-Sharafabadi, Amirsalar Khandan, Neriman Ozada
In this study, diopside bioceramic was synthesized using a mechanical milling process and subsequent heat treatment. The simplicity of experiments and also the high energy available in ball milling lead to rapid synthesis of the products in comparison with other synthesis methods. Magnesium oxide (MgO), silicon dioxide (SiO2) and eggshell (as the calcium source) powders were weighted in stoichiometric conditions and milled to initial activation of the surface of the powder's mixture. Then a sintering process was conducted to complete formation of diopside nanopowder and also evaluates its thermal stability...
February 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Seung-Hei Oh, Jung-Hong Ha, Sang Won Kwak, Shin Wook Ahn, WooCheol Lee, Hyeon-Cheol Kim
INTRODUCTION: This study evaluated the effect of torsional preloading on the torsional resistance of nickel-titanium (NiTi) endodontic instruments. METHODS: WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) and ProTaper Universal F2 (Dentsply Maillefer) files were used. The ultimate torsional strength until fracture was determined for each instrument. In the phase 1 experiment, the ProTaper and WaveOne files were loaded to have a maximum load from 2...
January 2017: Journal of Endodontics
Diogo Longhini, Cibele Oliveira de Melo Rocha, Igor Studart Medeiros, Renata Garcia Fonseca, Gelson Luis Adabo
The aim of this study was to characterize a conventional and a pressed porcelain for zirconia core as to biaxial flexural strength (BFS), apparent fracture toughness (FT) and microstructure composition, and to investigate the effect of glaze cooling rate on the BFS of the zirconia/porcelain bilayers. Monolayers of conventional porcelain Vita VM9 and pressed porcelain Vita PM9 (n=15) (12 mm diameter x 1.2 mm thick) were prepared for the BFS test (MPa). Apparent fracture toughness (MPa.m1/2) was measured by indentation technique (n=15)...
September 2016: Brazilian Dental Journal
Ningxiao Yuan, Lu Xu, Hualiang Wang, Youpeng Fu, Zhe Zhang, Lan Liu, Cuiling Wang, Jianhao Zhao, Jianhua Rong
Double-network (DN) hydrogels with high strength and toughness have been developed as promising materials. Herein, we explored a dual physically cross-linked polyacrylamide/xanthan gum (PAM/XG) DN hydrogel. The nonchemically cross-linked PAM/XG DN hydrogels exhibited fracture stresses as high as 3.64 MPa (13 times higher than the pure PAM single network hydrogel) and compressive stresses at 99% strain of more than 50 MPa. The hydrogels could restore their original shapes after continuously loading-unloading tensile and compressive cyclic tests...
December 14, 2016: ACS Applied Materials & Interfaces
Thiago Porto, Renato Roperto, Anna Akkus, Ozan Akkus, Sizenando Porto-Neto, Sorin Teich, Lisa Lang, Edson Campos
BACKGROUND: This study compared two well-known computer-aided-design/computer-aided-manufactured (CAD/CAM) blocks (Paradigm MZ100 [3M ESPE] and Vitablocs Mark II [Vita] in terms of fracture toughness (Kic), index of brittleness (BI) and stress/strain distributions. MATERIAL AND METHODS: Three-point bending test was used to calculate the fracture toughness, and the relationship between the Kic and the Vickers hardness was used to calculate the index of brittleness...
December 2016: Journal of Clinical and Experimental Dentistry
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 27, 2016: ACS Nano
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
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
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
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...
January 2017: Journal of Dentistry
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