Brittle Composites Modeling: Compazisons with MoSi2/ZrO2

1993 ◽  
Vol 322 ◽  
Author(s):  
S. P. Chen ◽  
R. Lesar ◽  
A. D. Rollett
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Transformation Toughening ◽  
Stress Changes ◽  
Simulation Results ◽  
First Time ◽  
Brittle Composites

AbstractWe have calculated the mechanical properties of brittle composites with spring-network (SN) model. The composites that we studied involve the transformation toughening effects and the accompanying micro-cracking. Our simulation results are consistent with experiments of MoSi2 toughened with ZrO2. By monitoring the stress changes due to the transformation and micro-cracking we are able to separate, for the first time, the contributions from these two competing effects. We also found that the fracture toughness of the composite increases as the modulus, interfacial cohesion of particle increases.

Novel Baddeleyite-Based Zirconia Ceramics for Biomedical Applications

2017 ◽  
Vol 13 ◽  
pp. 9-14
Author(s):  
Alexander I. Tyurin ◽  
Andrey O. Zhigachev ◽  
Alexey V. Umrikhin ◽  
Vyacheslav V. Rodaev ◽  
Tatyana S. Pirozhkova
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Tetragonal Phase ◽  
Biomedical Applications ◽  
Zirconia Ceramics ◽  
Engineering Ceramics ◽  
Synthesis Conditions ◽  
Microstructure And Mechanical Properties ◽  
First Time

For the first time nanostructured engineering ceramics were prepared from natural zirconia mineral (baddeleyite) with CaO as a tetragonal phase stabilizer. The effect of synthesis conditions on microstructure and mechanical properties of the baddeleyite-based ceramics is reported, furthermore, the effect of calcia content on hardness and fracture toughness is studied. Optimal calcia concentration and synthesis conditions are found, corresponding hardness and fracture toughness values are 10,8 GPa and 13,3 MPa×m1/2. The reported mechanical properties are comparable to those typically reported for yttria-stabilized engineering zirconia ceramics, prepared from chemically synthesized zirconia.

Effect of Superplastic Deformation on the Properties of Zirconia Dispersed Alumina Nanocomposite

2007 ◽  
Vol 551-552 ◽  
pp. 527-532 ◽  
Author(s):  
Guo Qing Chen ◽  
Shao Hua Sui ◽  
X.D. Wang ◽  
Wen Bo Han
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Superplastic Deformation ◽  
Critical Dimension ◽  
Grain Boundary Sliding ◽  
Transformation Toughening ◽  
Grain Coarsening ◽  
Boundary Sliding ◽  
Phase Transformation Toughening

In this paper constrained extrusion of the zirconia dispersed alumina nanocomposite under superplastic conditions was conducted. The mechanical properties of deformed material were studied and its results were compared with those of the initial materials. The microstructure evolution during superplastic deformation was also analyzed. The results demonstrated that after superplastic extrusion the flexural strength, relative density, Vickers hardness as well as fracture toughness of the material increased noticeably. The flexural strength of the deformed composite even retained at a high value of 310MPa at 800°C. The fracture toughness of the material increased from 6.92 MPa·m1/2 to 8.87 MPa·m1/2 after deformation. After superplastic extrusion due to grain boundary sliding and the compressive stress state, the internal porosities in as-sintered materials were eliminated. During extrusion with grain coarsening the effect of t-ZrO2 to m-ZrO2 transformation toughening increased because more zirconia grains reached the critical dimension. Although grain coarsening may cause the decrease of the fracture toughness in some extent, the phase transformation toughening and strengthening dominated. As a result, the mechanical properties of the deformed material were improved.

Effect of Grain Growth Inhibitors VC/Cr3C2 on WC-ZrO2-Ni Composite Mechanics

2014 ◽  
Vol 604 ◽  
pp. 106-109 ◽  
Author(s):  
Der Liang Yung ◽  
Min Jie Dong ◽  
Irina Hussainova
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Growth ◽  
Growth Inhibitors ◽  
Loading Conditions ◽  
Transformation Toughening ◽  
Composite Mechanics

The effect of VC and Cr3C2 grain growth inhibitors on mechanical properties of the WC-Ni-ZrO2 composites are studied in the present work. The microstructural features responsible for a change in mechanical properties are analysed. Addition of both VC and Cr3C2 results in increase in hardness of the WC-based system, but consequently in decrease in fracture toughness. The transformation toughening effect of ZrO2 is not effective for the loading conditions applied in this study.

Mechanical properties of single-quasicrystalline AlCuCoSi

1991 ◽  
Vol 6 (6) ◽  
pp. 1165-1168 ◽  
Author(s):  
R. Wittmann ◽  
K. Urban ◽  
M. Schandl ◽  
E. Hornbogen
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Friction Coefficient ◽  
Modulus Of Elasticity ◽  
Vickers Indentation ◽  
Indentation Method ◽  
Abrasive Friction ◽  
Highly Strained ◽  
First Time

The mechanical properties of single-quasicrystals of decagonal AlCoCuSi have been studied for the first time by applying the Vickers indentation method. The hardness has been determined as H ≃ 9.6 MPa. Estimates for the modulus of elasticity and the fracture toughness are given. The quasicrystals are highly strained internally. Scratching experiments show slight anisotropies in the abrasive friction coefficient. The dominant abrasive mechanism is microplowing.

Processing and Properties of 2D Cf/Si-O-C Composites Using Silicone Resin

2007 ◽  
Vol 336-338 ◽  
pp. 1251-1253
Author(s):  
Ke Jian ◽  
Zhao Hui Chen ◽  
Qing Song Ma ◽  
Hai Feng Hu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Carbon Fiber ◽  
Flexural Strength ◽  
Thermal Shock ◽  
Silicon Oxycarbide ◽  
Silicone Resin ◽  
Carbon Fiber Cloth ◽  
Thermal Shock Behavior ◽  
First Time

SR-249, a kind of polysiloxane (PSO), was used as the precursor for the first time to fabricate carbon fiber cloth reinforced silicon oxycarbide (2D Cf/Si-O-C) composites. The cure and pyrolysis of the SR-249 as well as the mechanical properties, oxidation and thermal shock behavior of the composites were investigated in the paper. The flexural strength and fracture toughness of the composites reached 217.6 MPa and 12.5 MPa·m1/2, respectively. After soaked at 1300°C under the static air for 10 min, the composites retained 58.5% flexural strength and 64.5% fracture toughness. The thermal shock behavior of the composites was studied by water quenched method. The composites retained 49.3% flexural strength and 47.4% fracture toughness after 10 times of quenching from 1200 to 20°C.

Effect of MnO on the microstructures, phase stability, and mechanical properties of ceria-partially-stabilized zirconia (Ce–TZP) and Ce–TZP–Al2O3 composites

1990 ◽  
Vol 5 (9) ◽  
pp. 1948-1957 ◽  
Author(s):  
J. S. Wang ◽  
J. F. Tsai ◽  
D. K. Shetty ◽  
A. V. Virkar
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Growth ◽  
Phase Stability ◽  
Volume Fraction ◽  
Transformation Toughening ◽  
Composite Ceramics ◽  
Four Point Bending ◽  
Crack Tips ◽  
The Stability

The effects of increasing amounts of MnO additions on the microstructures, phase stability, and mechanical properties of ZrO2–12 mol % CeO2 and ZrO2–12 mol% CeO2–10 wt.% Al2O3 were studied. MnO suppressed grain growth in ZrO2–12 mol% CeO2, while enhancing the mechanical properties significantly (strength = 557 MPa, fracture toughness = 9.3 MPa at 0.2 wt.% MnO). The enhanced mechanical properties were achieved despite an increased stability of the tetragonal phase, as evidenced by a lower burst transformation temperature (Mb) and a reduced volume fraction of the monoclinic phase on the fracture surface. In ZrO2–12 mol% CeO2–10 wt.% Al2O3, the addition of MnO suppressed the grain size of ZrO2, while promoting grain growth and changing the morphology of Al2O3. More significantly, the stability of the tetragonal ZrO2 phase decreased (high Mb temperature) with a concurrent increase in fracture toughness (13.2 MPa at 2 wt.% MnO) and transformation plasticity (1.2% in four-point bending). The widths of the transformation zones observed adjacent to the fracture surfaces showed a consistent inverse relation to the transformation yield stress, as would be expected from the mechanics of stress-induced phase transformation at crack tips. The improvements in mechanical properties obtained in the base Ce–TZP and the Ce–TZP–Al2O3 composite ceramics with the addition of MnO are critically examined in the context of transformation toughening and other possible mechanisms.

Mechanical Properties of ZrO2–LaMgAl11O19 Ceramics

2012 ◽  
Vol 512-515 ◽  
pp. 455-458 ◽  
Author(s):  
Xin Min ◽  
Ming Hao Fang ◽  
Yan Gai Liu ◽  
Zhao Hui Huang ◽  
Feng Jiao Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Room Temperature ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Transformation Toughening ◽  
Flexure Strength ◽  
Phase Transformation Toughening ◽  
Physical And Chemical ◽  
And Chemical Properties

ZrO2 ceramics have been widely used to many fields with its excellent physical and chemical properties, but the mechanical properties of YSZ ceramics, especially the fracture toughness, decline caused by the failure of the phase transformation toughening at high temperature. In this investigation, plate-like LaMgAl11O19 toughened ZrO2 ceramics were prepared by pressureless sintering at 1550 °C for 3h in air . The bulk density of the sintered samples are between 5.5 to 6.0 g/cm3, and the relative density are above 93%. The mechanical properties of the ZrO2-LaMgAl11O19 ceramics were studied systematically at room temperature. The flexure strength and fracture toughness of ZrO2-LaMgAl11O19 ceramic are 811.8 MPa and 13.9 MPa•m½ with the LMA addition of 2wt%.

scholarly journals Ribs of Pinna nobilis shell induce unexpected microstructural changes that provide unique mechanical properties

2021 ◽  
Author(s):  
Kinga Nalepka ◽  
Katarzyna Berent ◽  
Antonio Checa ◽  
Tomasz Machniewicz ◽  
Adrian Harris ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Outer Layer ◽  
Shell Thickness ◽  
Thickness Direction ◽  
Compression Tests ◽  
Oblique Orientation ◽  
Nano Indentation ◽  
Pinna Nobilis ◽  
First Time

Abstract The reinforcement function of shell ribs depends not only on their vaulted morphology but also on their microstructure. They are part of the outer layer which, in the case of the Pinna nobilis bivalve, is built from almost monocrystalline calcitic prisms, always oriented perpendicular to the growth surfaces. Originally, prisms and their c-axes follow the radii of rib curvature, becoming oblique to the shell thickness direction. Later, prisms bend to reach the nacre layer perpendicularly, but their c-axes retain the initial orientation. Calcite grains form nonrandom boundaries. Most often, three twin disorientations arise, with two of them observed for the first time. Nano-indentation and impact tests demonstrate that the oblique orientation of c-axes significantly improves the hardness and fracture toughness of prisms. Moreover, compression tests reveal that the rib area achieves a unique strength of 700 MPa. The detection of the specific microstructure formed to toughen the shell is novel.

Study on Mechanical Properties and Size Effect of Si3N4 Using Discrete Element Method

2009 ◽  
Vol 76-78 ◽  
pp. 719-724 ◽  
Author(s):  
Yuan Qiang Tan ◽  
Sheng Qiang Jiang ◽  
Cai Li ◽  
Dong Min Yang ◽  
Gao Feng Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Compressive Strength ◽  
Size Effect ◽  
Discrete Element Method ◽  
Bending Strength ◽  
Discrete Element ◽  
Poisson's Ratio ◽  
Simulation Results ◽  
Element Method

The mechanical models formed by packed circular discrete elements were used to investigate the mechanical properties of Si3N4. In these models, the distribution of elements is random in the specified region, and the average radius of elements is 6m. The main mechanical properties investigated here are Young’s modulus, compressive strength, Poisson’s ratio, fracture toughness and bending strength. Some numerical simulation analysis of the size effect of the mechanical properties in these discrete element models were carried out. The simulation results suggest that there is no obvious size effect for Young’s modulus, compressive strength and Poisson’s ratio in these discrete element models. However, for bending strength, when the number of elements in model is less than about 9000, there exists obvious size effect, with the increasing of the number of the elements, the size effect will become less and less until disappeared. The value of fracture toughness decreases with the increasing of the number of the model elements. The classical continuum fracture mechanics model about material fracture under tensile stress is also established by discrete element method. The simulation results are just the same as the simulation results of single edge notched bending (SENB) and the experimental values reported in other literatures. The results provide a more reliable foundation for the application of DEM in simulating the mechanical behaviors of advance ceramics.

scholarly journals Mechanical Properties of WC-Si3N4 Composites With Ultrafine Porous Boron Nitride Nanofiber Additive

2021 ◽  
Vol 8 ◽  
Author(s):  
Ting Cao ◽  
Xiaoqiang Li ◽  
Jingmao Li ◽  
Yang Huang ◽  
Shengguan Qu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Liquid Phase ◽  
Boron Nitride ◽  
Probable Mechanism ◽  
Sintering Process ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Catastrophic Fracture ◽  
First Time

WC-10 wt.% Si3N4 composites toughened with ultrafine porous boron nitride nanofiber (0, 0.01, 0.05, 0.1, and 0.15 wt.%) were prepared for the first time by spark plasma sintering. Compared with the WC-Si3N4 composite sintered in the same condition, the obtained WC-10 wt.% Si3N4 composites with ultrafine porous boron nitride were found to possess better hardness and fracture toughness. In addition, the Si3N4 phase in the UPBNNF toughened composites did not exhibit traditional catastrophic fracture as indicated in most investigations. In this study, the phenomena are discussed, and a probable mechanism is elucidated. It is deduced that the approach could be extended to materials with a feature of internal liquid phase during the sintering process and could improve hardness and fracture toughness.

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