Crack Deflection Toughening Mechanism in Brittle Materials

2009 ◽  
pp. 137-137-15 ◽  
Author(s):  
H Awaji ◽  
M Ebisudani ◽  
S-M Choi ◽  
T Ohashi
Keyword(s):  
Brittle Materials ◽  
Crack Deflection ◽  
Toughening Mechanism

scholarly journals The hidden structure of human enamel

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Elia Beniash ◽  
Cayla A. Stifler ◽  
Chang-Yu Sun ◽  
Gang Seob Jung ◽  
Zhao Qin ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Human Body ◽  
Crack Deflection ◽  
Toughening Mechanism ◽  
Space Filling ◽  
Human Enamel ◽  
Dynamics Simulations ◽  
Physical And Chemical ◽  
Enamel Layer

Abstract Enamel is the hardest and most resilient tissue in the human body. Enamel includes morphologically aligned, parallel, ∼50 nm wide, microns-long nanocrystals, bundled either into 5-μm-wide rods or their space-filling interrod. The orientation of enamel crystals, however, is poorly understood. Here we show that the crystalline c-axes are homogenously oriented in interrod crystals across most of the enamel layer thickness. Within each rod crystals are not co-oriented with one another or with the long axis of the rod, as previously assumed: the c-axes of adjacent nanocrystals are most frequently mis-oriented by 1°–30°, and this orientation within each rod gradually changes, with an overall angle spread that is never zero, but varies between 30°–90° within one rod. Molecular dynamics simulations demonstrate that the observed mis-orientations of adjacent crystals induce crack deflection. This toughening mechanism contributes to the unique resilience of enamel, which lasts a lifetime under extreme physical and chemical challenges.

scholarly journals Crack deflection in brittle materials by Finite Fracture Mechanics

2016 ◽  
Vol 2 ◽  
pp. 1975-1982
Author(s):  
Alberto Sapora ◽  
Pietro Cornetti ◽  
Alberto Carpinteri ◽  
Vladislav Mantič
Keyword(s):  
Fracture Mechanics ◽  
Brittle Materials ◽  
Crack Deflection ◽  
Finite Fracture Mechanics

Fracture Mechanics of Interface Failure

1984 ◽  
Vol 40 ◽  
Author(s):  
Kevin Kendall
Keyword(s):  
Composite Materials ◽  
Energy Balance ◽  
Fracture Mechanics ◽  
Brittle Materials ◽  
Crack Deflection ◽  
Balance Theory ◽  
Interface Failure ◽  
Crack Control ◽  
Brittle Solids ◽  
Dislocation Formation

AbstractInterfaces are important in ceramic and other composite materials because they can be used to control cracks, the major source of weakness and unreliability in brittle solids. Brittle materials fracture catastrophically, but may be converted into tough composites by the injection of interfaces which retard or deflect the cracks. This paper examines the behaviour of cracks at interfaces and demonstrates several mechanisms for crack control in brittle systems. Crack stopping, dislocation formation, and crack deflection at interfaces have been illustrated by experiments on rubber models and analysed by the energy balance theory of fracture.

Study on Mechanical Properties and Toughening Mechanism of MWCNTs/Ti(C, N) Cermets-Based Composites

2013 ◽  
Vol 544 ◽  
pp. 291-294
Author(s):  
Shuo Qi Liu ◽  
Wei Liang Liu
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Residual Stress ◽  
Vickers Hardness ◽  
Bending Strength ◽  
Crack Deflection ◽  
Toughening Mechanism ◽  
Hot Pressing Sintering ◽  
Sintering Method

MWCNTs/Ti(C, N) cermets-based composites were prepared by vacuum hot-pressing sintering method. The mechanical properties of samples were examined. XRD and SEM were used to investigate the crystal structure of the composites and microstructure of fractures surface, respectively. The toughening mechanism of composites was discussed particularly. The experimental results showed that the optimum comprehensive mechanical properties of samples were obtained by adding 1wt% MWCNTs in the composites. The bending strength, Vickers hardness and fracture toughness of the composites were 1275.14MPa, 22.75GPa and 10.60MPa•m1/2, respectively, which were improved by 16.89%, 17.15% and 25.59%, respectively, compared to the Ti(C, N)-based cermets without MWCNTs. Bridging and pulling out of MWCNTs, crack deflection, residual stress toughening and micro-voids toughening were attributed to the toughening mechanism of the composites.

Microstructure, chemical aspects, and mechanical properties of TiB2/Si3N4 and TiN/Si3N4 composites

1994 ◽  
Vol 9 (9) ◽  
pp. 2349-2354 ◽  
Author(s):  
Jow-Lay Huang ◽  
Shih-Yih Chen ◽  
Ming-Tung Lee
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Silicon Nitride ◽  
Chemical Stability ◽  
Large Deflection ◽  
Crack Deflection ◽  
Toughening Mechanism ◽  
Β Phase ◽  
Microstructure And Mechanical Properties

The chemical stability of TiB2 and TiN in a silicon nitride matrix under various conditions of temperature and gaseous environments was investigated. The addition of TiB2 and TiN on the microstructure and mechanical properties was also studied. No trace of interactions between TiN and Si3N4 was noticed. The addition of TiB2 to Si3N4 enhanced conversion of the α to β phase of the Si3N4 matrix. Observations of BN and TiN indicated a possible reaction between TiB2 and Si3N4. The fracture toughness of Si3N4 was substantially enhanced with the addition of TiB2 or TiN, while the strength was decreased. Crack deflection was the major toughening mechanism in a Si3N4/TiB2 composite. Most of the microcracks passed through TiN particles and cleavaged along preferred orientations with large deflection angles.

Microstructure and Mechanical Properties of ZrB2-Based Ceramics

2006 ◽  
Vol 312 ◽  
pp. 287-292 ◽  
Author(s):  
Xing Hong Zhang ◽  
Ping Hu ◽  
Song He Meng ◽  
Jie Cai Han ◽  
Bao Lin Wang
Keyword(s):  
Mechanical Properties ◽  
Hot Pressing ◽  
Strengthening Mechanism ◽  
Crack Deflection ◽  
Grain Structure ◽  
Crack Branching ◽  
Grain Refining ◽  
Toughening Mechanism ◽  
Fracture Modes

Two ZrB2-based composites were fabricated by hot-pressing with vacuum. ZrB2+20vol%SiC and ZrB2+20vol%SiC+8vol%TiB2 were selected as the starting compositions. The microstructures and phase constitutions of the composites were investigated and compared to these of monolithic ZrB2 material. For the ZrB2-based composites, with the addition of SiC particles, the excessive growth of ZrB2 materials is restricted and grain structure is refined. Meanwhile the fracture modes are changed, namely, from transgranular to mixed inter/transgranular. Strengthening mechanism is grain refining and the toughening mechanism is crack deflection, crack branching and grain refining. The role of TiB2 as an addition to the ZrB2 matrix was also examined and discussed.

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

Microstructures of SiC and Si3N4 with fibrous inclusions

1986 ◽  
Vol 44 ◽  
pp. 492-493
Author(s):  
N. J. Tighe ◽  
J. Sun ◽  
R.-M. Hu
Keyword(s):  
Vapor Deposition ◽  
Chemical Vapor ◽  
Crack Deflection ◽  
Fiber Bundles ◽  
High Temperature Strength ◽  
Graphite Fiber ◽  
Triple Junctions ◽  
Transmission Electron ◽  
Compact Graphite ◽  
Deposition Techniques

Particles of BN,and C are added in amounts of 1 to 40% to SiC and Si3N4 ceramics in order to improve their mechanical properties. The ceramics are then processed by sintering, hot-pressing and chemical vapor deposition techniques to produce dense products. Crack deflection at the particles can increase toughness. However the high temperature strength and toughness are determined byphase interactions in the environmental conditions used for testing. Examination of the ceramics by transmission electron microscopy has shown that the carbon and boron nitride particles have a fibrous texture. In the sintered aSiC ceramic the carbon appears as graphite fiber bundles in the triple junctions and as compact graphite particles within some grains. Examples of these inclusions are shown in Fig. 1A and B.

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