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fracture toughness

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
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
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
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
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
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)...
September 30, 2016: Dental Materials: Official Publication of the Academy of Dental Materials
Akimasa Tsujimoto, Wayne W Barkmeier, Toshiki Takamizawa, Hidehiko Watanabe, William W Johnson, Mark A Latta, Masashi Miyazaki
The purpose of this study was to determine the relationship between mechanical properties and bond durability of short fiber-reinforced resin composite with universal adhesive. As controls, micro-hybrid and nano-hybrid resin composites were tested. The universal adhesives used were Scotchbond Universal, Adhese Universal, and G-Premio Bond. The fracture toughness and flexural properties of resin composites, and shear bond strength and shear fatigue strength of universal adhesive with resin composite using both total-etch and self-etch modes were determined...
October 2016: European Journal of Oral Sciences
Kyle B Serkies, Reena Garcha, Laura E Tam, Grace M De Souza, Yoav Finer
OBJECTIVE: Assess the modulating effect of matrix metalloproteinase (MMP) inhibition on simulated human salivary enzyme (SHSE)-catalyzed degradation of interfacial fracture-toughness (FT) of self-etched and total-etched resin-dentin interfaces. METHODS: Miniature short-rod FT specimens (N=10/group) containing a resin composite bonded to human dentin, using a self-etch (Easy Bond, EB) or a total-etch (Scotchbond, SB) adhesives, were prepared with and without application of an MMP inhibitor (galardin)...
September 28, 2016: Dental Materials: Official Publication of the Academy of Dental Materials
Ryan P Wilkerson, Bernd Gludovatz, Jeremy Watts, Antoni P Tomsia, Gregory E Hilmas, Robert O Ritchie
Bioinspired "brick-and-mortar" alumina ceramics containing a nickel compliant phase are synthesized by coextrusion of alumina and nickel oxide. Results show that these structures are coarser yet exhibit exceptional resistance-curve behavior with a fracture toughness three or more times higher than that of alumina, consistent with significant extrinsic toughening, from crack bridging and "brick" pull-out, in the image of natural nacre.
September 30, 2016: Advanced Materials
Ayse Mese, Joseph Ea Palamara, Rafat Bagheri, Mehdi Fani, Michael F Burrow
This study compared the fracture toughness values of seven resin composites and analyzed the consistency of data values using three methods: compact tension, three point and four point bending for Mode I failure. Seven resin composites were selected: Estellite Sigma Quick, Esthet X HD, Filtek Supreme XTE, Heliomolar, Ice, Rok, and Vit-l-escence. For each material, 18 specimens (n=6 for each test) were prepared. Maximum load to failure was recorded using a universal testing machine and fracture toughness was calculated...
September 29, 2016: Dental Materials Journal
Jing Li, Ben-Cang Cui, Yuan-Hua Lin, Xu-Liang Deng, Ming Li, Ce-Wen Nan
OBJECTIVE: To evaluate the microstructure and mechanical behavior of polymer-infiltrated zirconia ceramics as a function of Fe2O3 concentration (0-0.3mol%). METHODS: Polymer-infiltrated zirconia ceramics with different concentrations of Fe2O3 were prepared by infiltration and polymerization. XRD was employed to determine phase structure. The microstructure and fracture mechanism was observed by SEM. Flexural strength and fracture toughness were measured by three-point bending method and single-edge-notched beam method, respectively...
September 23, 2016: Dental Materials: Official Publication of the Academy of Dental Materials
Jason R Garner, Michael N Wajdowicz, Nicholas B DuVall, Howard W Roberts
STATEMENT OF PROBLEM: Two resin-modified glass-ionomer (RMGI)-based luting agents have been recently marketed without independent reports of their physical properties. PURPOSE: The purpose of this in vitro study was to evaluate selected physical properties of 2 newly marketed RMGI luting agents and compare the findings with traditional materials. MATERIAL AND METHODS: Specimens (N=12) of Nexus RMGI, UltraCem, GC Fuji Cem 2, and RelyX Luting Plus were fabricated using standardized molds for flexural strength and fracture toughness according to manufacturer recommendations and stored in physiologic phosphate-buffered saline solution at 37°C until testing...
September 22, 2016: Journal of Prosthetic Dentistry
Shanshan Wang, Zhao Qin, Gang Seob Jung, Francisco J Martin-Martinez, Kristine Zhang, Markus J Buehler, Jamie H Warner
We combine in-situ transmission electron microscopy and large-scale molecular dynamics simulations to investigate brittle fracture in 2D monolayer MoS2, revealing that cracks propagate with a tip of atomic sharpness through the preferential direction with least energy release. We find that sparse vacancy defects cause crack deflections, while increasing defect density shifts the fracture mechanism from brittle to ductile by the migration of vacancies in the strain fields into networks. The fracture toughness of defective MoS2 are found to exceed that of graphene due to interactions between the atomically sharp crack tips and vacancy clusters during propagation...
September 22, 2016: ACS Nano
Keyun Chen, Lei Ren, Zhipeng Chen, Chengfeng Pan, Wei Zhou, Lelun Jiang
Micro-needle electrodes (MEs) have attracted more and more attention for monitoring physiological electrical signals, including electrode-skin interface impedance (EII), electromyography (EMG) and electrocardiography (ECG) recording. A magnetization-induced self-assembling method (MSM) was developed to fabricate a microneedle array (MA). A MA coated with Ti/Au film was assembled as a ME. The fracture and insertion properties of ME were tested by experiments. The bio-signal recording performance of the ME was measured and compared with a typical commercial wet electrode (Ag/AgCl electrode)...
2016: Sensors
Qian Zhao, Yunhong Liang, Zhihui Zhang, Xiujuan Li, Luquan Ren
Reaction behavior, mechanical property and impact resistance of TiC-TiB2/Al composite reacted from Al-Ti-B4C system with various Al content via combination method of combustion synthesis and hot pressed sintering under air was investigated. Al content was the key point to the variation of mechanical property and impact resistance. Increasing Al content could increase the density, strength and toughness of the composite. Due to exorbitant ceramic content, 10wt.% and 20wt.% Al-Ti-B4C composites exhibited poor molding ability and machinability...
September 13, 2016: Micron: the International Research and Review Journal for Microscopy
Bhavana Gandhi, Swetha Bollineni, Ravi Kumar Janga, Disha Saraswati, Mandava Ramesh Babu
INTRODUCTION: Smear layer removal from the root canal wall involves the use of 17% EDTA and 5.25% sodium hypochlorite, which thereby improves the adhesion of obturating materials to root dentin. But these chemical irrigants have shown to decrease micro hardness, increase roughness, cause erosion and reduce the root dentin fracture toughness. To combat these adverse effects, studies can be focussed on the remineralisation of the erosive root dentin and this novel idea has been utilized in the present study...
August 2016: Journal of Clinical and Diagnostic Research: JCDR
Max A Hammond, Tyler J Laine, Alycia G Berman, Joseph M Wallace
The specifics of how the nanoscale properties of collagen (e.g., the crosslinking profile) affect the mechanical integrity of bone at larger length scales is poorly understood despite growing evidence that collagen's nanoscale properties are altered with disease. Additionally, mass independent increases in postyield displacement due to exercise suggest loading-induced improvements in bone quality associated with collagen. To test whether disease-induced reductions in bone quality driven by alterations in collagen can be rescued or prevented via exercise-mediated changes to collagen's nanoscale morphology and mechanical properties, the effects of treadmill exercise and β-aminopropionitrile treatment were investigated...
2016: PloS One
K Okumura
In our previous paper (Eur. Phys. J. E 4, 121 (2001)) we proposed a coarse-grained elastic energy for nacre, or stratified structure of hard and soft layers found in certain seashells . We then analyzed a crack running perpendicular to the layers and suggested one possible reason for the enhanced toughness of this substance. In the present paper, we consider a crack running parallel to the layers. We propose a new term added to the previous elastic energy, which is associated with the bending of layers. We show that there are two regimes for the parallel-fracture solution of this elastic energy; near the fracture tip the deformation field is governed by a parabolic differential equation while the field away from the tip follows the usual elliptic equation...
April 2002: European Physical Journal. E, Soft Matter
A Hohenwarter, B Völker, M W Kapp, Y Li, S Goto, D Raabe, R Pippan
Structural materials used for safety critical applications require high strength and simultaneously high resistance against crack growth, referred to as damage tolerance. However, the two properties typically exclude each other and research efforts towards ever stronger materials are hampered by drastic loss of fracture resistance. Therefore, future development of novel ultra-strong bulk materials requires a fundamental understanding of the toughness determining mechanisms. As model material we use today's strongest metallic bulk material, namely, a nanostructured pearlitic steel wire, and measured the fracture toughness on micron-sized specimens in different crack growth directions and found an unexpected strong anisotropy in the fracture resistance...
2016: Scientific Reports
Iftikhar Ahmad, Mohammad Islam, Tayyab Subhani, Yanqiu Zhu
This paper elucidates the effect of silicon carbide nanoparticles (SiCNP) and graphene nanoplatelets (GNPs), on their own and together, on the densification behavior and fracture toughness of alumina (Al2O3) ceramic matrix. This was investigated by using the high-frequency induction heat sintering (HFIHS) process. While the addition of each nanostructure caused varying degrees of grain refinement and enhancement of mechanical properties, the incorporation of as little as 0.5 wt.% GNPs along with 5.0 wt.% SiCNP promoted uniform dispersion of the latter due to the lateral surface area of the graphene nanosheets with their two-dimensional morphology...
October 21, 2016: Nanotechnology
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