Fracture Toughness of a Silica-Doped Cubic Zirconia (8Y-CSZ)

2010 ◽  
Vol 638-642 ◽  
pp. 3846-3851 ◽  
Author(s):  
Keijiro Hiraga ◽  
Koji Morita ◽  
Byung Nam Kim ◽  
Hidehiro Yoshida
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Glass Phase ◽  
Indentation Method ◽  
Grain Sizes ◽  
Pure Silica ◽  
Beam Method ◽  
The Matrix ◽  
A Site

In a high-purity 8Y-CSZ, the doping of 0.15 - 5 mass% pure silica introduces a glass phase dispersing uniformly along grain-boundary facets and at multiple junctions. For materials with grain sizes of 0.75 - 2.4 m, the dispersion of the glass phase decreases the elastic modulus, the Vickers hardness and the elastic modulus-to-hardness ratio, whereas it affects little in the fracture toughness measured by a Vickers-indentation method and a single-crack-precracked-beam method. Inspection of crack propagation paths shows that the glass phase with sizes smaller than those of the matrix grains is not a site for easy crack-propagation, but provides a site for a crack-deflection mechanism.

scholarly journals Effects of HfC Particles on Crack Initiation and Propagation Behavior of WC/Co Composites

2019 ◽  
Vol 37 (3) ◽  
pp. 628-635
Author(s):  
Xinyu Yan ◽  
Shouren Wang ◽  
Daosheng Wen ◽  
Gaoqi Wang ◽  
Wentao Liu
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Bending Strength ◽  
Crack Tip ◽  
Crack Deflection ◽  
Simulation Software ◽  
Homogeneous Distribution ◽  
The Matrix ◽  
Crack Pinning ◽  
Crack Bifurcation

Tungsten carbide composites were prepared by cold-pressing and hot-pressing sintering; fracture toughness and bending strength of the specimens were tested. The microstructures of HfC/WC/Co composites were observed with the SEM. The mathematical models were established to investigate the relationship between stress intensity factors of crack straight-through, crack deflection, and crack bifurcation with crack length, based on the crack propagation energy release rate. The simulation software ABAQUS was used to verify the four crack propagation methods of crack straight-through, crack deflection, crack bifurcation and crack pinning. The simulation results show that adding appropriate amount of HfC can effectively improve the fracture toughness and bending strength of the composites. The homogeneous distribution of HfC and Co in the matrix has a significant effect on the improvement of the strength and toughness of the composites, and the improvement mechanism is to disperse or transfer the stress at the crack tip to HfC by crack deflection, crack bifurcation, crack pinning, transcrystalline fracture, etc. As a result, the stress concentration at the crack tip in the matrix is reduced, and the toughness of the composites is improved.

scholarly journals Microstructural evolution of h-BN matrix composite ceramics with La-Al-Si-O glass phase during hot-pressed sintering

2020 ◽  
Author(s):  
Baofu Qiu ◽  
Xiaoming Duan ◽  
Zhuo Zhang ◽  
Chen Zhao ◽  
Bo Niu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Elastic Modulus ◽  
Microstructural Evolution ◽  
Glass Phase ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Sintering Process ◽  
Composite Ceramics ◽  
Phase Precipitation

Abstract BN/La-Al-Si-O composite ceramics were fabricated by hot-pressed sintering using h-BN, La2O3, Al2O3 and amorphous SiO2 as the raw materials. The effects of sintering temperature on the microstructural evolution, bulk density, apparent porosity, and mechanical properties of h-BN composite ceramics were investigated. The results indicated that La-Al-Si-O liquid phase was formed during sintering process, which provided an environment for the growth of h-BN grains. With increasing sintering temperature, the cristobalite phase precipitation and h-BN grain growth occurred at the same time, which had the significant influence on the densification and mechanical properties of h-BN composite ceramics. The best mechanical properties of BN/La-Al-Si-O composite ceramics were obtained under sintering temperature of 1700 °C, and the elastic modulus, flexural strength, and fracture toughness were 80.5 GPa, 266.4 MPa and 3.25 MPa·m1/2, respectively.

scholarly journals Guiding and Trapping Cracks With Compliant Inclusions for Enhancing Toughness of Brittle Composite Materials

2020 ◽  
Vol 87 (3) ◽  
Author(s):  
Neal R. Brodnik ◽  
Chun-Jen Hsueh ◽  
Katherine T. Faber ◽  
Blaise Bourdin ◽  
Guruswami Ravichandran ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Heterogeneous Material ◽  
Effective Elastic Modulus ◽  
Elastic Compliance ◽  
Field Approach ◽  
Numerical Predictions ◽  
The Matrix ◽  
3D Printed ◽  
Square Array

Abstract The problem of toughening heterogeneous materials with a stiff matrix and compliant inclusions is investigated through numerical simulations and experiments. Specifically, the problem of optimizing a combination of effective toughness and effective elastic modulus in the context of a square array of compliant inclusions in a stiff matrix is explored. Crack propagation in the heterogeneous material is simulated using a variational phase-field approach. It is found that the crack can meander between or get attracted to and trapped in the inclusions. Composite specimens with a stiff matrix and compliant circular inclusions were 3D printed, and their fracture toughness was measured using a specially designed loading fixture. The experimental results show agreement with the numerical predictions by demonstrating the attraction and trapping of cracks in the inclusions. This study demonstrates the potential for significant enhancement of toughness through elastic compliance contrast between the matrix and the inclusion without notably compromising the effective elastic modulus of the composite material.

Relationships Between Microstructure and Engineering Properties

1986 ◽  
Vol 85 ◽  
Author(s):  
P. L. Pratt
Keyword(s):  
Fracture Toughness ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Realistic Model ◽  
Engineering Properties ◽  
Bend Strength ◽  
Cement Pastes ◽  
Complex Models

ABSTRACTThe calculation of such macroscopic engineering properties as elastic modulus and compressive strength for cement pastes and concrete depends upon the establishment of a realistic model of the microstructure. Increasingly complex models are considered, which appear capable of predicting the elastic modulus in terms of a modified Rule of Mixtures. The same models are able to account for the broad features of the compressive strength, because strength is always scaled by the elastic modulus of the material. The actual value of the compressive or the bend strength is determined by the mechanics of crack initiation and crack propagation in the particular test used. Crack initiation is controlled by the defects present in the material and crack propagation by the fracture toughness of the different phases and the porosity in the microstructure. Thus the strength depends upon microstructure in a number of different but interrelated ways, determined by the fracture toughness of the material.

Machinability Evaluation of Ce-ZrO2/CePO4 Ceramics with Digraph Method

2007 ◽  
Vol 280-283 ◽  
pp. 1079-1082
Author(s):  
Ai Bing Yu ◽  
L.J. Zhong ◽  
Xin Li Tian ◽  
F. Zou
Keyword(s):  
Mechanical Property ◽  
Fracture Toughness ◽  
Elastic Modulus ◽  
Vickers Hardness ◽  
Material Removal ◽  
Ceramic Materials ◽  
Experimental Results ◽  
The Matrix ◽  
Machinability Index ◽  
Machinable Ceramic

A new method is proposed for machinability evaluation of machinable ceramic materials. The relation of machinability attributes is modeled as a digraph, and machinability attribute matrix is defined. Machinability indexes are calculated with permanent function of the matrix, and machinabilities of machinable ceramics are ranked. Five composites consisting of CePO4 and zirconia were fabricated, measured and drilled with tungsten-cobalt carbide bits. Mechanical property parameters of Ce-ZrO2/CePO4 composites, including Vickers hardness, fracture toughness and Elastic modulus, are selected as machinability attributes. The experimental results of material removal rates are consistent with the ranking of machinability index values of Ce-ZrO2/CePO4 ceramics. The machinabilities of Ce-ZrO2/CePO4 ceramics improve with the increase of CePO4 proportions. Machinability of machinable ceramics can be evaluated with digraph method.

scholarly journals Fracture toughness of three heat pressed ceramic systems

2018 ◽  
Vol 17 ◽  
pp. 1-9
Author(s):  
Livia Fiorin ◽  
Guilherme Teixeira Theodoro ◽  
Izabela Cristina Maurício Moris ◽  
Renata Cristina Silveira Rodrigues ◽  
Ricardo Faria Ribeiro ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Glass Ceramic ◽  
Vickers Microhardness ◽  
Dental Ceramics ◽  
Test Results ◽  
Indentation Method ◽  
Clinical Prognosis ◽  
Significant Difference ◽  
Impulse Excitation

Aim: The aim of this study was to evaluate fracture toughness by indentation method of three dental ceramics processed by heat pressing. The ceramics evaluated were fluorapatite glass ceramic (ZIR), glass ceramic containing leucite (POM) and leucite-reinforced glass ceramic (EMP). Materials and methods: Ninety disks (13mm of diameter x 4mm of thickness) and nine rectangular specimens (25x4x2mm) were made to evaluate, respectively, microhardness/fracture toughness (n=30) and elastic modulus (n=3). Samples were obtained by pressing ceramic into refractory molds. After polishing, Vickers microhardness was evaluated under 4,904N load for 20s. Elastic modulus was measured by impulse excitation technique. Data from microhardness and elastic modulus were used to calculate fracture toughness, after measuring crack length under 19,6N load applied for 20s. Results were evaluated by ANOVA and Tukey´s test. Results: Microhardness (VHN) of POM (637.9±53.6) was statistically greater (p<0.05) than ZIR (593.0±14.3), followed by EMP (519.1±21.5); no significant difference (p=0.206) was noted for elastic modulus (GPa) (ZIR: 71.5±9.0; POM: 67.3±4.4; EMP: 61.7±2.3). Fracture toughness (MPa/m) of POM (0.873±0.066) was statistically lower (p<0.05) than ZIR (0.977±0.021) and EMP (0.965±0.035). Conclusion: The results suggest that fluorapatite glass ceramic (ZIR) and leucite-reinforced glass ceramic (EMP) processed by heat pressing presented greater fracture toughness, improving clinical prognosis of metal free restorations.

Indentation Fracture Toughness Testing of and Crack Propagation Mode in Dental Composites

1987 ◽  
Vol 110 ◽  
Author(s):  
Jack L. Ferracane
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Composite Resins ◽  
Dental Composite ◽  
Dental Composites ◽  
Propagation Mode ◽  
Dental Composite Resins ◽  
Indentation Fracture Toughness ◽  
The Matrix ◽  
Toughness Testing

AbstractThe use of a Vicker's indenter to measure the fracture resistance of dental composite resins was correlated to fracture toughness results obtained by bending of notched bars. There is a fair correlation between the methods, but many dental composites do not form cracks by the indentation technique, thereby limiting its usefulness. SEM micrographs reveal a crack propagation mode which is mostly through the matrix and along the filler/matrix interface, with evidence of particle fracture

scholarly journals Efficient Improvement in Fracture Toughness of Laminated Composite by Interleaving Functionalized Nanofibers

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2509
Author(s):  
Seyed Mohammad Javad Razavi ◽  
Rasoul Esmaeely Neisiany ◽  
Moe Razavi ◽  
Afsaneh Fakhar ◽  
Vigneshwaran Shanmugam ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fracture Behavior ◽  
Laminated Composite ◽  
Carbon Phase ◽  
Reinforced Composite ◽  
Reinforcing Agent ◽  
The Matrix ◽  
As Stress ◽  
Double Cantilever Beam Test ◽  
Pan Nanofiber

Functionalized polyacrylonitrile (PAN) nanofibers were used in the present investigation to enhance the fracture behavior of carbon epoxy composite in order to prevent delamination if any crack propagates in the resin rich area. The main intent of this investigation was to analyze the efficiency of PAN nanofiber as a reinforcing agent for the carbon fiber-based epoxy structural composite. The composites were fabricated with stacked unidirectional carbon fibers and the PAN powder was functionalized with glycidyl methacrylate (GMA) and then used as reinforcement. The fabricated composites’ fracture behavior was analyzed through a double cantilever beam test and the energy release rate of the composites was investigated. The neat PAN and functionalized PAN-reinforced samples had an 18% and a 50% increase in fracture energy, respectively, compared to the control composite. In addition, the samples reinforced with functionalized PAN nanofibers had 27% higher interlaminar strength compared to neat PAN-reinforced composite, implying more efficient stress transformation as well as stress distribution from the matrix phase (resin-rich area) to the reinforcement phase (carbon/phase) of the composites. The enhancement of fracture toughness provides an opportunity to alleviate the prevalent issues in laminated composites for structural operations and facilitate their adoption in industries for critical applications.

scholarly journals Influence of Alumina Nanofibers Sintered by the Spark Plasma Method on Nickel Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 548 ◽  
Author(s):  
Leonid Agureev ◽  
Valeriy Kostikov ◽  
Zhanna Eremeeva ◽  
Svetlana Savushkina ◽  
Boris Ivanov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Strength Properties ◽  
Alumina Nanoparticles ◽  
Metal Powders ◽  
Wide Range ◽  
The Matrix ◽  
Spark Plasma ◽  
Average Size

The article presents the study of alumina nanoparticles’ (nanofibers) concentration effect on the strength properties of pure nickel. The samples were obtained by spark plasma sintering of previously mechanically activated metal powders. The dependence of the grain size and the relative density of compacts on the number of nanofibers was investigated. It was found that with an increase in the concentration of nanofibers, the average size of the matrix particles decreased. The effects of the nanoparticle concentration (0.01–0.1 wt.%) on the elastic modulus and tensile strength were determined for materials at 25 °C, 400 °C, and 750 °C. It was shown that with an increase in the concentration of nanofibers, a 10–40% increase in the elastic modulus and ultimate tensile strength occurred. A comparison of the mechanical properties of nickel in a wide range of temperatures, obtained in this work with materials made by various technologies, is carried out. A description of nanofibers’ mechanisms of influence on the structure and mechanical properties of nickel is given. The possible impact of impurity phases on the properties of nickel is estimated. The tendency of changes in the mechanical properties of nickel, depending on the concentration of nanofibers, is shown.

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