Download or read book Crack growth Resistance in Reinforced Ceramic Composites written by David Michael Stump and published by . This book was released on 1989 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling Crack Growth Resistance in Ceramics and Ceramic Matrix Composites written by J. LLorca and published by . This book was released on 1992 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crack growth resistance in ceramics and ceramic-matrix composites at ambient temperature is provided mainly by the interaction between the crack surfaces in the crack wake. A cohesive crack model is presented to study the fracture behavior of these materials. The constitutive equation for the cohesive crack is obtained through micromechanical considerations and experimental observations in the crack wake. The model predictions show good agreement with experimental results in one monolithic ceramic (alumina) and two fibeoreinforced ceramic-matrix composites. The applications and limitations of the model are discussed.

Download or read book Fracture Mechanics of Ceramics written by R.C. Bradt and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 592 pages. Available in PDF, EPUB and Kindle. Book excerpt: These volumes, 9 and 10, of Fracture Mechanics of Ceramics constitute the proceedings of an international symposium on the fracture mechanics of ceramic materials held at the Japan Fine Ceramics Center, Nagoya, Japan on July 15, 16, 17, 1991. These proceedings constitute the fifth pair of volumes of a continuing series of conferences. Volumes 1 and 2 were from the 1973 symposium, volumes 3 and 4 from a 1977 symposium, and volumes 5 and 6 from a 1981 symposium all of which were held at The Pennsylvania State University. Volumes 7 and 8 are from the 1985 symposium which was held at the Virginia Polytechnic Institute and State University. The theme ofthis conference, as for the previous four, focused on the mechanical behavior ofceramic materials in terms of the characteristics of cracks, particularly the roles which they assume in the fracture processes and mechanisms. The 82 contributed papers by over 150 authors and co-authors represent the current state of that field. They address many of the theoretical and practical problems ofinterest to those scientists and engineers concerned with brittle fracture.

Download or read book Fracture Mechanics of Ceramics written by R.C. Bradt and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 591 pages. Available in PDF, EPUB and Kindle. Book excerpt: Second part of the proceedings of the Sixth International Symposium held in Karlsruhe, Germany, July 18-20, 1995.

Download or read book Fracture Mechanics of Ceramics written by Richard Carl Bradt and published by . This book was released on 1974 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crack Propagation and Fracture Resistance Behavior Under Fatigue Loading of a Ceramic Matrix Composite written by Dipankar Ghosh and published by . This book was released on 2001 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary objectives of this research are fabrication of a tough fiber reinforced ceramic composite, study of the fracture resistance behavior (R - curve) under fatigue loading, and in situ study of the crack propagation under fatigue conditions both at room and elevated temperatures. Silicon carbide fiber (SCS-6) reinforced zircon (ZrSiO 4) matrix composites are used in this study. The composite is fabricated by uniaxially aligning SiC fibers into a perform and then incorporating the zircon matrix by a tape casting and lamination technique. The green body is then consolidated by hot pressing at about 1640C in a flowing nitrogen atmosphere. Thus, dense composites with uniform fiber distribution and good mechanical properties are fabricated. A novel in situ technique is used to study the crack propagation in the matrix of the composite under fatigue conditions. In situ crack propagation and fracture resistance behavior (R - curve) of these ceramic composite samples are studied both experimentally and numerically under fatigue load conditions between room temperature and 1400ʻC. The stress intensity value at crack initiation decreased with increasing temperature. The fracture resistance results showed a rising R - curve behavior with a decreasing value of the fracture resistance at elevated temperatures. In other words the slope of the R curve decreased as temperature increased, and this effect is very dramatic at 1400ʻC. Numerical analyses/iterations, based on the currently available micromechanical models, are done to determine the relationship between the bridging stress function and the R - curve behavior of the composite. Also, the effect of residual stress and constituent properties like fiber strength, interfacial shear stress etc., on the bridging stress function is also systematically studied both at room and elevated temperature. Fiber strength, Weibull modulus, and interfacial shear stress are found to have a significant effect on the bridging stress functions. Among the three parameters, fiber strength has the most dominant effect on the bridging stress functions. A comparison of the experimental and numerically calculated results on fracture behavior showed that numerical calculations matched reasonably well with the experimental R curve values over the temperature range of 20 - 1400ʻC.

Download or read book High Temperature Mechanical Behaviour of Ceramic Composites written by Karl Jakus and published by Elsevier. This book was released on 1995-06-28 with total page 569 pages. Available in PDF, EPUB and Kindle. Book excerpt: High Temperature Mechanical Behavior of Ceramic Composites provides an up-to-date comprehensive coverage of the mechanical behavior of ceramic matrix composites at elevated temperatures. Topics include both short-term behavior (strength, fracture toughness and R-curve behavior) and long-term behavior (creep, creep-fatigue, delayed failure and lifetime). Emphasis is on a review of fundamentals and on the mechanics and mechanisms underlying properties. This is the first time that complete information of elevated temperature behavior of ceramic composites has ever been compacted together in a single volume. Of particular importance is that each chapter, written by internationally recognized experts, includes a substantial review component enabling the new material to be put in proper perspective. Shanti Nair is Associate Professor at the Department of Mechanical Engineering at the University of Massachusetts at Amherst. Karl Jakus is Professor at the University of Massachusetts at Amherst.

Download or read book Micromechanical Model of Crack Growth in Fiber Reinforced Ceramics written by Asher A. Rubinstein and published by . This book was released on 1990 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Local global Modeling of Crack Growth in Continuously Reinforced Ceramic Matrix Composites written by Sk. Shamim Ahmed and published by . This book was released on 1989 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Local global Analysis of Crack Growth in Continuously Reinforced Ceramic Matrix Composites written by Roberto Ballarini and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Toughening Mechanisms in Quasi Brittle Materials written by S.P. Shah and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 590 pages. Available in PDF, EPUB and Kindle. Book excerpt: A variety of ceramic materials has been recently shown to exhibit nonlinear stress strain behavior. These materials include transformation-toughened zirconia which undergoes a stress-induced crystallographic transformation in the vicinity of a propagating crack, microcracking ceramics, and ceramic-fiber reinforced ceramic matrices. Since many of these materials are under consideration for structural applications, understanding fracture in these quasi-brittle materials is essential. Portland cement concrete is a relatively brittle material. As a result mechanical behavior of concrete, conventionally reinforced concrete, prestressed concrete and fiber reinforced concrete is critically influenced by crack propagation. Crack propagation in concrete is characterized by a fracture process zone, microcracking, and aggregate bridging. Such phenomena give concrete toughening mechanisms, and as a result, the macroscopic response of concrete can be characterized as that of a quasi-brittle material. To design super high performance cement composites, it is essential to understand the complex fracture processes in concrete. A wide range of concern in design involves fracture in rock masses and rock structures. For example, prediction of the extension or initiation of fracture is important in: 1) the design of caverns (such as underground nuclear waste isolation) subjected to earthquake shaking or explosions, 2) the production of geothermal and petroleum energy, and 3) predicting and monitoring earthquakes. Depending upon the grain size and mineralogical composition, rock may also exhibit characteristics of quasi-brittle materials.

Download or read book Theoretical Analysis of Small Crack Growth in Fiber reinforced Ceramic Composite Materials written by Forrest T. Patterson and published by . This book was released on 1994 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cyclic Deformation Fracture and Nondestructive Evaluation of Advanced Materials written by Michael R. Mitchell and published by ASTM International. This book was released on 1992 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Micromechanisms of Cyclic and Environmentally Assisted Subcritical Crack Growth in Ceramic Matrix Composites written by and published by . This book was released on 1991 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: The future use of ceramics for advanced structural applications represents an important precursor to potential major improvements in design performance for high temperature, corrosion and wear resistance applications. The limited use of such brittle materials to date has primarily been attributed to their inherently low toughness and lack of defect tolerance. Scientific research in the last decade, however, has resulted in major advances in the toughening of ceramics by such mechanisms as whisker reinforcement, transformation and microcrack toughening. However, very recent work has shown that such toughened ceramics and composites, contrary to conventional wisdom, may become susceptible to cyclic fatigue. The intent of this program was to study and model the physics and fundamental micromechanisms of environmentally- assisted and principally cyclic fatigue crack-growth processes in several classes of ceramic-matrix composites, chosen to reflect different primary toughening mechanisms. Based on initial studies, the central hypothesis of this work is that the mechanisms of crack-tip shielding, used to enhance fracture toughness, can lead to degradation in crack-growth resistance under cyclic loading. Cyclic Fatigue, Fracture Toughness, Subcritical Crack Growth, Ceramic Matrix Composites, Small Cracks.

Download or read book Micromechanical Model of Crack Growth in Fiber Reinforced Ceramics written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-05 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model based on the micromechanical mechanism of crack growth resistance in fiber reinforced ceramics is presented. The formulation of the model is based on a small scale geometry of a macrocrack with a bridging zone, the process zone, which governs the resistance mechanism. The effect of high toughness of the fibers in retardation of the crack advance, and the significance of the fiber pullout mechanism on the crack growth resistance, are reflected in this model. The model allows one to address issues such as influence of fiber spacing, fiber flexibility, and fiber matrix friction. Two approaches were used. One represents the fracture initiation and concentrated on the development of the first microcracks between fibers. An exact closed form solution was obtained for this case. The second case deals with the development of an array of microcracks between fibers forming the bridging zone. An implicit exact solution is formed for this case. In both cases, a discrete fiber distribution is incorporated into the solution. Rubinstein, Asher A. and Xu, Kang Unspecified Center NAG3-967; RTOP 505-63-1B...

Download or read book Fatigue Crack Growth in Ceramics and Ceramic Matrix Composites written by NE. Ashbaugh and published by . This book was released on 1992 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reliable design of ceramic matrix composite components in aerospace applications requires the knowledge of the crack propagation behavior of these materials at elevated temperatures. The first part of this paper discusses a test setup using a centrally notched disk to conduct mechanical fatigue crack growth testing of brittle matrices used in these composites. The specimen compliance is monitored using the laser interferometric displacement gage system. To evaluate this fatigue crack growth test setup, cyclic crack propagation is studied in an alumina ceramic specimen. Transmission electron microscopy of surface replicates show evidence of irreversible microcracking at the crack tip that could provide the mechanism for fatigue crack growth in this ceramic. The second part of this paper discusses the results from automated fatigue crack growth tests on silicon-carbide fiber-reinforced aluminosilicate glass matrix composites at room and elevated temperatures using the compact tension geometry. Tests conducted at room temperature indicate high damage tolerance in these composites due to energy dissipation through distributed matrix cracking around the tip, fiber bridging, and fiber pull out. In contrast, tests at 650°C reveal Mode 1 self-similar crack growth in these composites and absence of fiber pullout.

Download or read book Fracture Micromechanics of Intermetallic and Ceramic Matrix Continuous Fiber Composites written by and published by . This book was released on 1991 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Micromechanics parameters for fatigue cracks growing perpendicular to fibers were measured through small port holes in the matrix made by electropolishing, were used to determine fiber stresses, which ranged from 1.1 to 4 GPa. Crack opening displacements at maximum load and residual crack opening displacements (at minimum load) were measured. Matrix was removed along the crack flanks after completion of the tests to reveal the extent and nature of fiber damage. Analyses were made of these parameters, and it was found possible to link the extent of fiber debonding to residual COD and the shear stress for debonding, estimated at 245 MPa, to COD. Measured experimental parameters were used to compute crack growth rates using a wall known fracture mechanics model for fiber bridging tailored to these experiments. The potential for microstructural manipulation to yield further increases in fatigue crack growth resistance for the metals and alloys currently being used in gas turbine construction is small. Studies of fatigue crack growth through aluminum, titanium and superalloys have shown that there are many similarities in the mechanisms of crack growth and the crack tip micromechanics for these materials. Conversely, composite materials reinforced with continuous strong fibers offer the promise of drastic increases in fatigue crack growth resistance.