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fracture toughness

Akarsh Verma, Avinash Parashar
Aim of this article is to study the effects of functional groups such as hydroxyl, epoxide and carboxyl on the fracture toughness of graphene. These functional groups form the backbone of intrinsic atomic structure of graphene oxide (GO). Molecular dynamics based simulations were performed in conjunction with reactive force field parameters to capture the Mode-I fracture toughness of functionalised graphene. Simulations were performed in stages, to study the effect of these functional groups, individually as well as altogether on the fracture toughness of GO nanosheet...
January 18, 2018: Nanotechnology
Tapabrata Maity, Anushree Dutta, Parijat Pallab Jana, Konda Gokuldoss Prashanth, Jürgen Eckert, Jayanta Das
The present study demonstrates the evolution of eutectic microstructure in arc-melted (Zr0.76Fe0.24)100-xNbx (0 ≤ x ≤ 10 atom %) composites containing α-Zr//FeZr₂ nano-lamellae phases along with pro-eutectic Zr-rich intermetallic phase. The effects of Nb addition on the microstructural evolution and mechanical properties under compression, bulk hardness, elastic modulus, and indentation fracture toughness (IFT) were investigated. The Zr-Fe-(Nb) eutectic composites (ECs) exhibited excellent fracture strength up to ~1800 MPa...
January 11, 2018: Materials
Nesrin Sonmez, Pinar Gultekin, Volkan Turp, Gokhan Akgungor, Deniz Sen, Eitan Mijiritsky
BACKGROUND: Polymer infiltrated ceramics and nano-ceramic resins are the new restorative materials which have been developed in order to enhance the adverse properties of glass-matrix ceramics and resin composites. The aim of the present in vitro study was to evaluate the characteristics of various CAD/CAM materials through mechanical, microstructural, and SEM analysis. METHODS: Five test groups (n = 22) were formed by using the indicated CAD/CAM blocks: VITA Enamic (VITA Zahnfabrik), Lava Ultimate (3 M ESPE), IPS e...
January 8, 2018: BMC Oral Health
Kavya Mendu, Amrita Kataruka, Jasmine Puthuvelil, Ange-Therese Akono
Bone is a complex hierarchical material with five distinct levels of organization. Factors like aging and diseases like osteoporosis increase the fragility of bone, making it fracture-prone. Owing to the large socio-economic impact of bone fracture in our society, there is a need for novel ways to assess the mechanical performance of each hierarchical level of bone. Although stiffness and strength can be probed at all scales - nano-, micro-, meso-, and macroscopic - fracture assessment has so far been confined to macroscopic testing...
November 30, 2017: Journal of Visualized Experiments: JoVE
K Ravikumar, Debasish Sarkar, Bikramjit Basu
In view of the importance of the fracture resistance and wear properties on the performance and durability in a number of engineering applications, we have analysed such properties of sintered zirconia toughened alumina with varying zirconia content of 5 and 15 wt.%. Using micro-computed tomography, homogenous particulate distribution of zirconia is established through 3D volume rendering of the sintered pellet and by 2D orthoslice view. Depending on zirconia content and MgO addition (sintering additive), an interesting combination of strength and toughness properties was recorded with the investigated materials...
January 1, 2017: Journal of Biomaterials Applications
Sufyan Garoushi, Pekka K Vallittu, Lippo Lassila
This study aimed to evaluate and compare certain mechanical properties, Vickers-hardness, water sorption, fluoride-release, shrinkage-stress and wear of five commercial fluoride-releasing restorative materials (Dyract, CompGlass, BEAUTIFIL II, ACTIVARestorative, and GC Fuji II LC), in relation to their microstructural characteristics. Mechanical properties were determined for each material following ISO standards. A wear test was conducted with 15,000 chewing cycles using a dual-axis chewing simulator. Daily fluoride-release was measured during the first 10 days by using a fluoride ion selective electrode...
December 27, 2017: Dental Materials Journal
Débora Vilarinho, Antreas Theodosiou, Cátia Leitão, Arnaldo G Leal-Junior, Maria de Fátima Domingues, Kyriacos Kalli, Paulo André, Paulo Antunes, Carlos Marques
We propose a novel polymer optical fiber (POF) sensing system based on fiber Bragg gratings (FBGs) to measure foot plantar pressure. The plantar pressure signals are detected by five FBGs, in the same piece of cyclic transparent optical polymer (CYTOP) fiber, which are embedded in a cork insole for the dynamic monitoring of gait. The calibration and measurements performed with the suggested system are presented, and the results obtained demonstrate the accuracy and reliability of the sensing platform to monitor the foot plantar pressure distribution during gait motion and the application of pressure...
December 16, 2017: Sensors
Haiping Wu, Yue Cao, Haiping Su, Chao Wang
With high capacity, lithium (Li) metal is considered to enable at least two-times the energy density for lithium batteries. The growth of lithium dendrite and low columbic efficiency restrict the development of Li metal anode. Solid polymer electrolytes are expected to be promising candidates to solve the issue. But how to get polymer electrolyte which integrates high ionic conductivity and high mechanical strength is still challenging. Here, by introducing a double polymer network chemistry into electrolyte design to reshape, we have successfully developed a tough polymer electrolyte with high conductivity and further realized the stable operation of lithium metal anodes...
December 16, 2017: Angewandte Chemie
Chelsea S Davis, Kaitlyn E Hillgartner, Seung Hoon Han, Jonathan E Seppala
As more manufacturing processes and research institutions adopt customized manufacturing as a key element in their design strategies and finished products, the resulting mechanical properties of parts produced through additive manufacturing (AM) must be characterized and understood. In material extrusion (MatEx), the most recently extruded polymer filament must bond to the previously extruded filament via polymer diffusion to form a "weld". The strength of the weld limits the performance of the manufactured part and is controlled through processing conditions...
August 2017: Additive Manufacturing
Shaymaa E Elsaka
PURPOSE: To evaluate the optical and mechanical properties of newly introduced monolithic multilayer zirconia with two types of monolithic zirconia. MATERIALS AND METHODS: Three brands of monolithic zirconia were used in this study: Ceramill Zolid FX Multilayer (CZF), Prettau Anterior (PA), and Zenostar T (ZT). Translucency parameter (TP), contrast ratio (CR), flexural strength, fracture toughness, hardness, brittleness index, and microstructures were assessed. Data were analyzed using one-way ANOVA and Tukey's test...
December 14, 2017: Journal of Prosthodontics: Official Journal of the American College of Prosthodontists
Jingwei Liu, Chao Chen, Yuezhan Feng, Yonggui Liao, Yun-Sheng Ye, Xiaolin Xie, Yiu-Wing Mai
Understanding the chemistry and structure of interfaces within epoxy resins is important for studying the mechanical properties of nanofiller-filled nanocomposites as well as for developing high performance polymer nanocomposites. Despite intensive efforts to construct nanofillers/matrix interfaces, few studies have demonstrated both an enhanced stress transferring efficiency while avoiding unfavorable defor-mation, due to undesirable interface fractures. Here, we report an optimized method to prepare epoxy-based nanocomposites whose interfaces are chemically modulated by poly(glycidyl methacrylate)-block-poly(hexyl methacrylate) (PGMA-b-PHMA) functionalized multi-walled carbon nanotubes (bc@fMWNT) and also offer a fundamental explanation of crack growth behavior and the toughening mechanism of the resulting nanocomposites...
December 13, 2017: ACS Applied Materials & Interfaces
Grzegorz Ludwik Golewski
The paper presents the results of tests on the effect of the low calcium fly ash (LCFA) addition, in the amounts of: 0% (LCFA-00), 20% (LCFA-20) and 30% (LCFA-30) by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile), II (in-plane shear) and III (anti-plane shear) models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters...
December 6, 2017: Materials
Andreas Picker, Luc Nicoleau, Zaklina Burghard, Joachim Bill, Igor Zlotnikov, Christophe Labbez, André Nonat, Helmut Cölfen
Calcium silicate hydrate (C-S-H) is the binder in concrete, the most used synthetic material in the world. The main weakness of concrete is the lack of elasticity and poor flexural strength considerably limiting its potential, making reinforcing steel constructions necessary. Although the properties of C-S-H could be significantly improved in organic hybrids, the full potential of this approach could not be reached because of the random C-S-H nanoplatelet structure. Taking inspiration from a sea urchin spine with highly ordered nanoparticles in the biomineral mesocrystal, we report a bioinspired route toward a C-S-H mesocrystal with highly aligned C-S-H nanoplatelets interspaced with a polymeric binder...
November 2017: Science Advances
Joseph D Wood, Christopher M Harvey, Simon Wang
Interface adhesion toughness between multilayer graphene films and substrates is a major concern for their integration into functional devices. Results from the circular blister test, however, display seemingly anomalous behaviour as adhesion toughness depends on number of graphene layers. Here we show that interlayer shearing and sliding near the blister crack tip, caused by the transition from membrane stretching to combined bending, stretching and through-thickness shearing, decreases fracture mode mixity G II/G I, leading to lower adhesion toughness...
December 5, 2017: Nature Communications
Dayalan Subash, Krishnamma Shoba, Shibu Aman, Srinivasan Kumar Indu Bharkavi, Vijayan Nimmi, Radhakrishnan Abhilash
Introduction: The restoration of a severely damaged tooth usually needs a post and core as a part of treatment procedure to provide a corono - radicular stabilization. Biodentine is a class of dental material which possess high mechanical properties with excellent biocompatibility and bioactive behaviour. The sealing ability coupled with optimum physical properties could make Biodentine an excellent option as a core material. Aim: The aim of the study was to determine the fracture resistance of Biodentine as a core material in comparison with resin modified glass ionomer and composite resin...
September 2017: Journal of Clinical and Diagnostic Research: JCDR
Renan Belli, Michael Wendler, José I Zorzin, Ulrich Lohbauer
BACKGROUND: An important tool in materials research, development and characterization regarding mechanical performance is the testing of fracture toughness. A high level of accuracy in executing this sort of test is necessary, with strict requirements given in extensive testing standard documents. Proficiency in quality specimen fabrication and test requires practice and a solid theoretical background, oftentimes overlooked in the dental community. AIMS: In this review we go through some fundamentals of the fracture mechanics concepts that are relevant to the understanding of fracture toughness testing, and draw attention to critical aspects of practical nature that must be fulfilled for validity and accuracy in results...
December 1, 2017: Dental Materials: Official Publication of the Academy of Dental Materials
Rui Niu, Zhihui Qin, Feng Ji, Meng Xu, Xinlu Tian, Junjie Li, Fanglian Yao
The lack of sufficient mechanical properties restricts the application of polysaccharide-based hydrogels in the field of biomedicine, especially load-bearing tissue repair. Nowadays, double network (DN) hydrogels have aroused great interest through special cooperation between two contrasting networks. Inspired by this idea, here, we devised a new strategy to prepare a pectin-Fe3+/polyacrylamide hybrid DN hydrogel using a simple two-step method. The introduction of Fe3+ ions into a pectin network to produce strong reversible ionic complexation, results in excellent toughness...
December 4, 2017: Soft Matter
C Hare, T Bonakdar, M Ghadiri, J Strong
Tablets are the most common solid dosage form of pharmaceutical active ingredients due to their ease of use. Their dissolution behaviour depends on the particle size distribution and physicochemical properties of the formulation, and the compression process, which need to be optimised for producing consistently robust tablets, as weaker tablets are often prone to breakage during production, transport and end use. Tablet strength is typically determined by diametric compression and friability tests. The former gives rise to propagation of a crack on a plane along the compression axis, whilst the latter, carried out in a rotating drum, incurs surface damage and produces chips and debris...
November 29, 2017: International Journal of Pharmaceutics
A Matinmanesh, Y Li, A Nouhi, P Zalzal, E H Schemitsch, M R Towler, M Papini
It has been reported that the adhesion of bioactive glass coatings to Ti6Al4V reduces after degradation, however, this effect has not been quantified. This paper uses bilayer double cantilever (DCB) specimens to determine GIC and GIIC, the critical mode I and mode II strain energy release rates, respectively, of bioactive coating/Ti6Al4V substrate systems degraded to different extents. Three borate-based bioactive glass coatings with increasing amounts of incorporated SrO (0, 15 and 25mol%) were enamelled onto Ti6Al4V substrates and then immersed in de-ionized water for 2, 6 and 24h...
November 10, 2017: Journal of the Mechanical Behavior of Biomedical Materials
M Bartosik, C Rumeau, R Hahn, Z L Zhang, P H Mayrhofer
Hard coatings used to protect engineering components from external loads and harsh environments should ideally be strong and tough. Here we study the fracture toughness, K IC, of Ti1-xAlxN upon annealing by employing micro-fracture experiments on freestanding films. We found that K IC increases by about 11% when annealing the samples at 900 °C, because the decomposition of the supersaturated matrix leads to the formation of nanometer-sized domains, precipitation of hexagonal-structured B4 AlN (with their significantly larger specific volume), formation of stacking faults, and nano-twins...
November 28, 2017: Scientific Reports
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