Download or read book Micromechanical Studies of Crack Growth in Ceramic Matrix Composite written by Jed Lyons and published by . This book was released on 1990 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book Ceramic matrix composites and other systems written by Antonio Miravete and published by Woodhead Publishing. This book was released on 1993 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Matrix Cracking in Ceramic Matrix Composites written by Longbiao Li and published by Springer Nature. This book was released on 2022-03-12 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the matrix cracking behavior in ceramic–matrix composites (CMCs), including first matrix cracking behavior, matrix cracking evolution behavior, matrix crack opening and closure behavior considering temperature and oxidation. The micro-damage mechanisms are analyzed, and the micromechanical damage models are developed to characterize the cracking behavior. Experimental matrix cracking behavior of different CMCs at room and elevated temperatures is predicted. The book can help the material scientists and engineering designers to better understand the cracking behavior in CMCs.

Download or read book Micromechanics of Ceramic Matrix Composites at Elevated Temperatures written by Longbiao Li and published by Springer Nature. This book was released on with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Time Dependent Mechanical Behavior of Ceramic Matrix Composites at Elevated Temperatures written by Longbiao Li and published by Springer Nature. This book was released on 2020-04-18 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book investigates the time-dependent behavior of fiber-reinforced ceramic-matrix composites (CMCs) at elevated temperatures. The author combines the time-dependent damage mechanisms of interface and fiber oxidation and fracture with the micromechanical approach to establish the relationships between the first matrix cracking stress, matrix multiple cracking evolution, tensile strength, tensile stress-strain curves and tensile fatigue of fiber-reinforced CMCs and time. Then, using damage models of energy balance, the fracture mechanics approach, critical matrix strain energy criterion, Global Load Sharing criterion, and hysteresis loops he determines the first matrix cracking stress, interface debonded length, matrix cracking density, fibers failure probability, tensile strength, tensile stress-strain curves and fatigue hysteresis loops. Lastly, he predicts the time-dependent mechanical behavior of different fiber-reinforced CMCs, i.e., C/SiC and SiC/SiC, using the developed approaches, in order to reduce the failure risk during the operation of aero engines. The book is intended for undergraduate and graduate students who are interested in the mechanical behavior of CMCs, researchers investigating the damage evolution of CMCs at elevated temperatures, and designers responsible for hot-section CMC components in aero engines.

Download or read book Mechanisms and Mechanics of Composites Fracture written by Ram B. Bhagat and published by . This book was released on 1993 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains 26 papers presented at the International Conference on [title], held to address the latest ideas concerning the mechanisms and mechanics of composite fractures. The main focus was on the "driving forces" behind the various damage events in the inorganic composites at both micro and macro levels. The papers are grouped in five sections: deformation and damage in particulate composites; crack initiation and propagation; micromechanical modeling; fracture and fatigue; and microstructural tailoring, impact, and creep. No index. Annotation copyright by Book News, Inc., Portland, OR

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 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 Modeling of Mixed Mode Crack Growth in Ceramic Composites written by J. Zhai and published by . This book was released on 1999 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamic crack propagation in ceramic composites is analyzed numerically. The simulations concern the effects of microstructural morphologies on fracture. The analysis coniders arbitrary phase distributions in the actual microstructures of alumina/titanium diboride (Al2O3/TiB2) composites. The microstructures analyzed have different phase morphologies and different phase sizes over an order of magnitude in length (from 1-2 to 10-20 ?m). A micromechanical model that provides explicit account for arbitrary microstructures and arbitrary fracture patterns is developed and used. The approach uses both a constitutive law for the bulk solid constituents and a constitutive law for fracture surfaces. The model is based on the cohesive surface formulation of Xu and Needleman and represents a phenomenological characterization for atomic forces on potential crack/microcrack surfaces. This framework of analysis does not require the use of any fracture criteria. Instead, fracture evolves as an outcome of bulk material response, interfacial behavior, and applied loading. This approach provides a unified and self-consistent treatment of mixed mode fracture. The evolutions of crack lengths in different phases and along interphase interfaces are calculated to track crack growth. The overall local crack speed, defined as the time rate of change of arc length along zigzagging crack paths, is found to reach the intersonic range, i.e., greater than the shear wave speeds and smaller than the longitudinal wave speeds in the constituent phases. The model also allows the energy release rate to be evaluated easily. For the same amount of crack surfaces generated, the average energy release rates for fracture patterns in four microstructures analyzed differ by up to 25%. The results demonstrate that larger TiB2 reinforcements significantly impede crack propagation and increase the fracture resistance of the composites, as indicated by higher average energy release rate values.

Download or read book Micromechanical Evaluation of Ceramic Matrix Composites written by and published by . This book was released on 1991 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Analytical and experimental studies have been performed to investigate the thermomechanical properties and failure mechanisms in unidirectional ceramic composites in which the ceramic matrix is flawed and variable. Preliminary model for brittle matrix with a periodic hexagonal array of identical fibers has been analyzed on the basis of numerical fracture mechanics to assess criticality of various kinds of cracks. When this composite model is subjected to axial load, it was found that transverse matrix cracks become unstable for perfect bonding and for disbonding between fibers and matrix, while disbond cracks propagating parallel to the fibers tend to stabilize. The Air Force goal of developing high thrust-to-weight turbine engines depends strongly upon the advancement of high temperature ceramic composites. Ceramic materials retain stiffness at very high temperatures but their extreme brittleness precludes their use as structural materials, since cracks propagate easily and catastrophically. When a ceramic matrix is reinforced with unidirectional fibers the effect of cracks changes fundamentally.

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 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 Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 464 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.