Crack deflection in compositionally graded Cu–W composites

2002 ◽  
Vol 82 (17) ◽  
pp. 3393-3403 ◽  
Author(s):  
J. Chapa-Cabrera ◽  
I. E. Reimanis
Keyword(s):  
Crack Deflection

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.

Hard and Soft: Principles of Polyner-Impregnated Concrete Using Elastomers

2013 ◽  
Vol 687 ◽  
pp. 118-123 ◽  
Author(s):  
Oliver Weichold ◽  
Udo Antons
Keyword(s):  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Brittle Failure ◽  
Elastic Moduli ◽  
Domain Size ◽  
Glassy Polymers ◽  
Crack Deflection ◽  
Micro Cracks ◽  
Concrete Interface ◽  
Crystalline Matrix

The effect of incorporating elastomeric domains in concrete is described from the point of fracture mechanics. Concrete is subject to brittle failure, since cracks propagate at an enormous speed in the crystalline matrix. However, micro cracks are attracted to volume elements with lower elastic moduli such as elastomeric domains. Cracks that encounter the concrete-elastomer interface are stopped since energy is dissipated by plastic deformation of and/or crack deflection by the elastomer. The domain size and the distribution of the elastomer as well as, and properties of the elastomer-concrete interface are crucial parameters. Such a combination differs substantially from previously prepared polymer-impregnated concretes, in which only glassy polymers were used.

Effect of virtual crack size on the crack deflection criterion at a bi-material interface under wedge loading

2009 ◽  
Vol 36 (2) ◽  
pp. 193-198 ◽  
Author(s):  
Jong-Bong Kim ◽  
Hyunho Shin ◽  
Woong Lee ◽  
Kyong Yop Rhee
Keyword(s):  
Crack Size ◽  
Crack Deflection ◽  
Material Interface

Finite Element Modeling of Microcrack Growth in Cortical Bone

2011 ◽  
Vol 78 (4) ◽  
Author(s):  
Susan Mischinski ◽  
Ani Ural
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Elastic Modulus ◽  
Crack Growth ◽  
Line Strength ◽  
Crack Deflection ◽  
Cement Line ◽  
Fracture Properties ◽  
Cement Lines ◽  
Microcrack Growth

Bone is similar to fiber-reinforced composite materials made up of distinct phases such as osteons (fiber), interstitial bone (matrix), and cement lines (matrix-fiber interface). Microstructural features including osteons and cement lines are considered to play an important role in determining the crack growth behavior in cortical bone. The aim of this study is to elucidate possible mechanisms that affect crack penetration into osteons or deflection into cement lines using fracture mechanics-based finite element modeling. Cohesive finite element simulations were performed on two-dimensional models of a single osteon surrounded by a cement line interface and interstitial bone to determine whether the crack propagated into osteons or deflected into cement lines. The simulations investigated the effect of (i) crack orientation with respect to the loading, (ii) fracture toughness and strength of the cement line, (iii) crack length, and (iv) elastic modulus and fracture properties of the osteon with respect to the interstitial bone. The results of the finite element simulations showed that low cement line strength facilitated crack deflection irrespective of the fracture toughness of the cement line. However, low cement line fracture toughness did not guarantee crack deflection if the cement line had high strength. Long cracks required lower cement line strength and fracture toughness to be deflected into cement lines compared with short cracks. The orientation of the crack affected the crack growth trajectory. Changing the fracture properties of the osteon influenced the crack propagation path whereas varying the elastic modulus of the osteon had almost no effect on crack trajectory. The findings of this study present a computational mechanics approach for evaluating microscale fracture mechanisms in bone and provide additional insight into the role of bone microstructure in controlling the microcrack growth trajectory.

Validity of the Finite Fracture Mechanics Based Asymptotic Analysis for Predictions of Crack Deflection in Thin Layers of Ceramic Laminates

2014 ◽  
Vol 627 ◽  
pp. 237-240 ◽  
Author(s):  
Oldřich Ševeček ◽  
Dominique Leguillon ◽  
Tomáš Profant ◽  
Michal Kotoul
Keyword(s):  
Potential Energy ◽  
Asymptotic Solution ◽  
Asymptotic Analysis ◽  
Crack Extension ◽  
Crack Deflection ◽  
Thin Layers ◽  
Reference Solution ◽  
Finite Fracture Mechanics ◽  
Higher Order Terms ◽  
Good Agreement

The work studies and compares different approaches suitable for predictions of the crack deflection (bifurcation) in ceramic laminates containing thin layers under high residual stresses and discuss a suitability and limits of using of the asymptotic analysis for such problems. The thickness of the thin compressive layers where the crack deflection occurs is only one order higher than the crack extension lengths considered within the solution. A purely FEM based calculation of the energy and stress conditions, necessary for the crack propagation, serves as the reference solution to the problem. The asymptotic analysis is used after for calculations of the same quantities (especially of energy release rate – ERR). This concept enables semi-analytical calculations of ERR or changes in potential energy induced by the crack extensions of different lengths and directions. Such approach can save a large amount of simulations and time compared with the pure FEM based calculations. It was found that the asymptotic analysis provides a good agreement for investigations of the crack increments enough far from the adjacent interfaces but for longer extensions (of length above 1/5-1/10 of the distance from the interface) starts more significantly to deviate from the correct solution. Involvement of the higher order terms in the asymptotic solution or other improvement of the model is thus advisable.

The Competition between Adhesive and Cohesive Fracture at Amicro-Patterned Polymer-Metal Interface

2013 ◽  
Vol 577-578 ◽  
pp. 225-228 ◽  
Author(s):  
Olaf van der Sluis ◽  
Joris J.C. Remmers ◽  
M.A.C. Thurlings ◽  
B.J. Welling ◽  
Sander P.M. Noijen
Keyword(s):  
Crack Deflection ◽  
Surface Roughening ◽  
Adhesive Failure ◽  
Cohesive Failure ◽  
Metal Interface ◽  
Cohesive Fracture ◽  
Micro Patterning ◽  
Polymer Metal ◽  
Metal Interfaces ◽  
Point Bend

It is Common Practice for Polymer-Metal Interfaces, Frequently Encountered in Microelec-Tronic Devices, to Improve Adhesion by Surface Roughening or Micro-Patterning. the Competitionbetween Adhesive Fracture and Cohesive Fracture in the Vicinity of a Patterned Interface, i.e., Inter-Face Crack Deflection, is One of these Key Mechanisms that Contribute Significantly to the Macroscopicadhesion. in this Paper, these Fracture Phenomena are Described Simultaneously by Cohesive Zoneelements with an Exponential Traction-Separation Law (TSL) for the Adhesive Failure and an Initiallyrigid, Exponentially Decaying, TSL for the Cohesive Failure. it is Demonstrated that the Conditions Atwhich Crack Kinking Occurs are Dominated by Fracture Strength Values as Opposed to the Commonlyused Fracture Toughness Values. Experimental Verification is Performed by Means of Four Point Bend-Ing Tests on Specifically Designed Micro-Patterned Polymer-Metal Samples.

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