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fracture toughness

Nan Lin, Yuehui He, Xiyue Kang
In this paper, the influence of the extra solid phase reaction on the interface structure and mechanical properties of titanium carbonitride-based cermets were investigated. The extra solid phase reaction in the preparation process of cermets could induce the formation of a core/rim/binder interface with the coherent structure and reinforce the interface bonding strength in cermets. The existence of a coherent structure interface can inhibit crack spread and improve the toughness and abrasion resistance of titanium carbonitride-based cermets significantly...
September 15, 2017: Materials
Samer Mesmar, N Dorin Ruse
PURPOSE: Resin composite blocks (RCB) are advocated as alternative to ceramic blocks (CB). Prior to use, adherence to these materials should characterized. This study aimed to test the null hypothesis (H0 ) that material and surface treatment combinations do not influence interfacial fracture toughness (KIC ) of a self-cured adhesive resin cement [RelyX Ultimate (RXU)] to RCB or CB, under nonaged and aged conditions. MATERIALS AND METHODS: Two RCB, Lava Ultimate (LU) and Enamic (EN), and one CB, IPS e...
September 15, 2017: Journal of Prosthodontics: Official Journal of the American College of Prosthodontists
M Eldafrawy, M G Ebroin, P A Gailly, J-F Nguyen, M J Sadoun, A K Mainjot
The objective of this study was to evaluate the interfacial fracture toughness (IFT) of composite cement with dispersed filler (DF) versus polymer-infiltrated ceramic network (PICN) computer-aided design and computer-aided manufacturing (CAD-CAM) composite blocks after 2 different surface pretreatments using the notchless triangular prism (NTP) test. Two DFs (Cerasmart [CRT] and Lava Ultimate [LVA]), 2 PICNs (Enamic [ENA] and experimental PICN [EXP]), and e.max CAD lithium disilicate glass-ceramic (EMX, control) prism samples were bonded to their counterparts with Variolink Esthetic DC composite cement after either hydrofluoric acid etching (HF) or gritblasting (GR)...
September 1, 2017: Journal of Dental Research
Sivaiah Bathula, M Jayasimhadri, Bhasker Gahtori, Anil Kumar, A K Srivastava, Ajay Dhar
SiGe is one of the most widely used thermoelectric materials for radioisotope thermoelectric generator applications for harnessing waste-heat at high temperatures. In the present study, we report a simple experimental strategy for enhancing the thermoelectric and mechanical properties of n-type SiGe nanoalloys by dispersing SiC nanoparticles in a SiGe nanoalloy matrix. This strategy yielded a high value of figure-of-merit (ZT) of ∼1.7 at 900 °C in the SiGe/SiC nanocomposite, which is nearly twice that reported for its pristine bulk counterpart and ∼15% higher than that of pristine SiGe nanoalloys...
September 8, 2017: Physical Chemistry Chemical Physics: PCCP
Jing-Xiao Chen, Jing Yuan, Ya-Ling Wu, Ping Wang, Peng Zhao, Guo-Zhong Lv, Jing-Hua Chen
In this study, a series of PEG/Col double network (DN) hydrogel is fabricated from poly(ethylene glycol) (PEG) and collagen (Col). Results of the compressive strength test indicate that the strength and toughness of these DN hydrogels are significantly enhanced. The fracture strength of PEG/Col DN hydrogels increases by 9- to 12-fold compared with that of PEG single network (SN) hydrogel, and by 36- to 48-fold compared with that of Col SN hydrogel. Taking advantage of both PEG and Col building blocks, the PEG/Col DN hydrogels possess a strengthened skeleton...
September 7, 2017: Journal of Biomedical Materials Research. Part A
Chi Wang, Ting-Ting Hsiue
Through single-tube electrospinning, the biodegradable core-shell fibers of poly(3-hydroxybutyrate) (PHB) and poly(d,l-lactic acid) (PDLLA) were obtained from blend solutions with different compositions at a total polymer concentration of 7 wt %. Regardless whether PHB is the major or minor component (PHB/PDLLA = 90/10, 75/25, 50/50, and 25/75 wt. ratio), these phase-separated solutions all yielded core-shell fibers with PHB as core and PDLLA as shell. A new scenario of core-shell fiber formation was proposed on the basis of the relative magnitude of the intrinsic relaxation rate of fluids and external extension rate during electrospinning...
August 30, 2017: Biomacromolecules
Sara Gallinetti, Gemma Mestres, Cristina Canal, Cecilia Persson, Maria-Pau Ginebra
Calcium phosphate cements (CPCs) are extensively used as synthetic bone grafts, but their poor toughness limits their use to non-load-bearing applications. Reinforcement through introduction of fibers and yarns has been evaluated in various studies but always resulted in a decrease in elastic modulus or bending strength when compared to the CPC matrix. The aim of the present work was to improve the interfacial adhesion between fibers and matrix to obtain tougher biocompatible fiber-reinforced calcium phosphate cements (FRCPCs)...
August 16, 2017: Journal of the Mechanical Behavior of Biomedical Materials
A Williamson, N A Sims, C D L Thomas, P V S Lee, M Stevenson, R C Whitton
BACKGROUND: Palmar/plantar osteochondral disease (POD) and third metacarpal/-tarsal condylar fractures are considered fatigue injuries of subchondral bone (SCB) and calcified cartilage due to repetitive high loads in racehorses. In combination with adaptive changes in SCB in response to race training, the accumulation of SCB fatigue is likely to result in changes of joint surface mechanical properties. OBJECTIVES: To determine the spatial relationship and correlation of calcified articular surface biomechanical properties with SCB microstructure and training history in the distal palmar metacarpal condyle of Thoroughbred racehorses...
August 21, 2017: Equine Veterinary Journal
Abolfazl Azarniya, Saeed Sovizi, Amir Azarniya, Mohammad Reza Rahmani Taji Boyuk, Temel Varol, Palaniyandi Nithyadharseni, Hamid Reza Madaah Hosseini, Seeram Ramakrishna, M V Reddy
Recently, a wide variety of research works have focused on carbon nanotube (CNT)-ceramic matrix nanocomposites. In many cases, these novel materials are produced through conventional powder metallurgy methods including hot pressing, conventional sintering, and hot isostatic pressing. However, spark plasma sintering (SPS) as a novel and efficient consolidation technique is exploited for the full densification of high-temperature ceramic systems. In these binary nanocomposites, CNTs are added to ceramic matrices to noticeably modify their inferior properties and SPS is employed to produce fully dense compacts...
September 14, 2017: Nanoscale
Junling Wu, Qiang Zhang, Michael D Weir, Thomas W Oates, Chuanjian Zhou, Xiaofeng Chang, Hockin H K Xu
OBJECTIVES: Dental luting cements are widely used to bond indirect restorations to teeth. Microcracks often lead to cement failures. The objectives of this study were to develop the first self-healing luting cement, and investigate dentin bond strength, mechanical properties, crack-healing, and self-healing durability in water-aging for 6 months. METHODS: Microcapsules of poly(urea-formaldehyde) (PUF) shells with triethylene glycol dimethacrylate (TEGDMA) as healing liquid were synthesized...
August 18, 2017: Journal of Dentistry
Michael D Hunckler, Ethan D Chu, Andrew P Baumann, Tyler E Curtis, Matthew J Ravosa, Matthew R Allen, Ryan K Roeder
Small animal models, and especially transgenic models, have become widespread in the study of bone mechanobiology and metabolic bone disease, but test methods for measuring fracture toughness on multiple replicates or at multiple locations within a single small animal bone are lacking. Therefore, the objective of this study was to develop a method to measure cortical bone fracture toughness in multiple specimens and locations along the diaphysis of small animal bones. Arc-shaped tension specimens were prepared from the mid-diaphysis of rabbit ulnae and loaded to failure to measure the radial fracture toughness in multiple replicates per bone...
August 18, 2017: Bone
Grace X Gu, Flavia Libonati, Susan D Wettermark, Markus J Buehler
Creating materials with strength and toughness has been a long-sought goal. Conventional engineering materials often face a trade-off between strength and toughness, prompting researchers seeking to overcome these limitations to explore more sophisticated materials, such as composites. This paradigm shift in material design is spurred by nature, which exhibits a plethora of heterogeneous materials that offer outstanding material properties, and many natural materials are widely regarded as examples of high-performing hybrid materials...
May 4, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Pang Zhu, Yonghong Deng, Chaoyang Wang
Dual crosslinked system has been proved to be an efficient method to obtain tough and high strength hydrogels. Herein, we synthesized a novel graphene oxide/p(acrylamide-co-poly(ethylene glycol) methyl ether methacrylate)/α-cyclodextrin (GO/P(AM-co-PEGMA)/CD) physical dual crosslinked hydrogel via copolymerization of AM and PEGMA in the α-CD/GO solution. The polymer main chains adsorb onto the GO surface resulting in the first crosslinked system and multiple hydrogen bonds between α-CDs that thread on the PEGMA side chains establish the second crosslinked system...
October 15, 2017: Carbohydrate Polymers
Jiang-Yuan Fan, Ting-Ting Lin, Fang-Xuan Hu, Rui-Bin Zheng, Fan Fan, Jian-Feng Ma
PURPOSE: To investigate the effect of sintering temperature on mechanical properties of dental zirconia toughened alumina (ZTA) ceramics prepared by gel-casting technique. METHODS: The samples prepared by gel-casting were sintered at 1100, 1200, 1250, 1300 and 1400degrees centigrade for each group. The flexural strength, fracture toughness, Vickers hardness and brittleness index were obtained and microscopic morphology of each group was observed under scanning electron microscope (SEM)...
April 2017: Shanghai Kou Qiang Yi Xue, Shanghai Journal of Stomatology
Sufyan Garoushi, Pekka K Vallittu, Lippo Lassila
OBJECTIVE: To evaluate and compare certain mechanical properties and wear of five commercial short-fibre reinforced composites (Alert, EasyCore, Build-It, TI-Core, and everX Posterior), in relation to their microstructural characteristics. METHODS: Fracture toughness, work of fracture, and flexural strength were determined for each material following ISO standards. The specimens (n = 6) were dry stored (37 °C for 2 days) before they were tested. A wear test was conducted with 15,000 chewing cycles using a dual-axis chewing simulator...
2017: Chinese Journal of Dental Research
Sang Won Kwak, Joo Yeong Lee, Hye-Jin Goo, Hyeon-Cheol Kim
OBJECTIVES: The aim of this study was to compare the mechanical properties of various nickel-titanium (NiTi) files with similar tapers and cross-sectional areas depending on whether they were surface-treated. MATERIALS AND METHODS: Three NiTi file systems with a similar convex triangular cross-section and the same ISO #25 tip size were selected for this study: G6 (G6), ProTaper Universal (PTU), and Dia-PT (DPT). To test torsional resistance, 5 mm of the straightened file's tip was fixed between polycarbonate blocks (n = 15/group) and continuous clockwise rotation until fracture was conducted using a customized device...
August 2017: Restorative Dentistry & Endodontics
Cijun Shuai, Hang Sun, Chengde Gao, Pei Feng, Wang Guo, Youwen Yang, Mingchun Zhao, Sheng Yang, Fulai Yuan, Shuping Peng
The inherent brittleness of bioceramics restricts their applications in load bearing implant, although they possess good biocompatibility and bioactivity. In this study, molybdenum disulfide nanoplatelets (MSNPs) were used to reinforce bioceramics (Mg2SiO4/CaSiO3) scaffolds fabricated by selective laser sintering (SLS). The fracture mode of scaffolds was transformed from transgranular to mixed trans- and intergranular. It could be explained that MSNPs could slide easily due to their weak interlayer van der Waals interactions and provide elastic deformation due to their high elastic modulus...
July 20, 2017: Journal of the Mechanical Behavior of Biomedical Materials
T Jenkins, O L Katsamenis, O G Andriotis, L V Coutts, B Carter, D G Dunlop, R O C Oreffo, C Cooper, N C Harvey, P J Thurner, The OStEO Group
The influence of ageing on the fracture mechanics of cortical bone tissue is well documented, though little is known about if and how related material properties are further affected in two of the most prominent musculoskeletal diseases, osteoporosis and osteoarthritis (OA). The femoral neck, in close proximity to the most pertinent osteoporotic fracture site and near the hip joint affected by osteoarthritis, is a site of particular interest for investigation. We have recently shown that Reference Point micro-Indentation (RPI) detects differences between cortical bone from the femoral neck of healthy, osteoporotic fractured and osteoarthritic hip replacement patients...
June 30, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Jinrong Wu, Li-Heng Cai, David A Weitz
Self-healing polymers crosslinked by solely reversible bonds are intrinsically weaker than common covalently crosslinked networks. Introducing covalent crosslinks into a reversible network would improve mechanical strength. It is challenging, however, to apply this concept to "dry" elastomers, largely because reversible crosslinks such as hydrogen bonds are often polar motifs, whereas covalent crosslinks are nonpolar motifs. These two types of bonds are intrinsically immiscible without cosolvents. Here, we design and fabricate a hybrid polymer network by crosslinking randomly branched polymers carrying motifs that can form both reversible hydrogen bonds and permanent covalent crosslinks...
August 11, 2017: Advanced Materials
David Taylor
Many biological materials fail by cracking. Examples are bone fractures, contact damage in eggs, splits in bamboo culm and defects in cartilage. The mechanical property that best describes failure by cracking is fracture toughness, which quantifies the ease with which cracks propagate and defines a material's tolerance for pre-existing cracks and other stress concentrating features. The measurement of fracture toughness presents some challenges, especially for biological materials. To obtain valid results requires care and, in many cases, considerable ingenuity to design an appropriate specimen and test protocol...
July 5, 2017: Journal of the Mechanical Behavior of Biomedical Materials
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