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Author: Publisher: ISBN: Category : Languages : en Pages : 73
Book Description
The focus of the research conducted under Grant No. 91-0106 (a two year effort) was to identifying the fundamental mechanisms of fatigue damage that occur in fiber-reinforced ceramics. Several new findings were made during the research effort: (1) the fatigue life of fiber-reinforced ceramics decreased markedly during high frequency fatigue loading, (2) fiber-reinforced ceramics undergo significant internal heating during cyclic loading, (3) because of frictional wear along the fiber-matrix interface, the frictional shear stress in fiber-reinforced ceramics decreases sharply under cyclic loading. Based upon insight gained from the analytical and experimental parts of the investigation, we developed a novel approach to estimate the level of frictional shear stress that exists along the fiber-matrix interface during fatigue. Since this technique allows confirmation of other techniques for estimating frictional shear stress (e.g., fiber pushout technique developed by Marshall at Rockwell Science Center). Moreover, it is the only approach that allows determination of the in-situ change in frictional shear stress during cyclic loading (note that the level of frictional shear stress controls many mechanical properties such as strength, toughness and mechanical damping as well as thermophysical properties such as thermal diffusivity). The analysis that was developed to estimate frictional shear stress can also be used to understand the relationship between composite microstructure and cyclic energy dissipation in fiber-reinforced ceramics.
Author: Publisher: ISBN: Category : Languages : en Pages : 73
Book Description
The focus of the research conducted under Grant No. 91-0106 (a two year effort) was to identifying the fundamental mechanisms of fatigue damage that occur in fiber-reinforced ceramics. Several new findings were made during the research effort: (1) the fatigue life of fiber-reinforced ceramics decreased markedly during high frequency fatigue loading, (2) fiber-reinforced ceramics undergo significant internal heating during cyclic loading, (3) because of frictional wear along the fiber-matrix interface, the frictional shear stress in fiber-reinforced ceramics decreases sharply under cyclic loading. Based upon insight gained from the analytical and experimental parts of the investigation, we developed a novel approach to estimate the level of frictional shear stress that exists along the fiber-matrix interface during fatigue. Since this technique allows confirmation of other techniques for estimating frictional shear stress (e.g., fiber pushout technique developed by Marshall at Rockwell Science Center). Moreover, it is the only approach that allows determination of the in-situ change in frictional shear stress during cyclic loading (note that the level of frictional shear stress controls many mechanical properties such as strength, toughness and mechanical damping as well as thermophysical properties such as thermal diffusivity). The analysis that was developed to estimate frictional shear stress can also be used to understand the relationship between composite microstructure and cyclic energy dissipation in fiber-reinforced ceramics.
Author: Longbiao Li Publisher: Springer Nature ISBN: 9811532745 Category : Technology & Engineering Languages : en Pages : 373
Book Description
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.
Author: Karl Jakus Publisher: Elsevier ISBN: 0080523889 Category : Technology & Engineering Languages : en Pages : 569
Book Description
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.
Author: Longbiao Li Publisher: Springer Nature ISBN: 9811621411 Category : Technology & Engineering Languages : en Pages : 205
Book Description
This book presents the relationships between tensile damage and fracture, fatigue hysteresis loops, stress-rupture, fatigue life and fatigue limit stress, and stochastic loading stress. Ceramic-matrix composites (CMCs) possess low material density (i.e., only 1/4 - 1/3 of high-temperature alloy) and high-temperature resistance, which can reduce cooling air and improve structure efficiency. Understanding the failure mechanisms and internal damage evolution represents an important step to ensure reliability and safety of CMCs. This book investigates damage and fracture of fiber-reinforced ceramic-matrix composites (CMCs) subjected to stochastic loading, including: (1) tensile damage and fracture of fiber-reinforced CMCs subjected to stochastic loading; (2) fatigue hysteresis loops of fiber-reinforced CMCs subjected to stochastic loading; (3) stress rupture of fiber-reinforced CMCs with stochastic loading at intermediate temperature; (4) fatigue life prediction of fiber-reinforced CMCs subjected to stochastic overloading stress at elevated temperature; and (5) fatigue limit stress prediction of fiber-reinforced CMCs with stochastic loading. This book helps the material scientists and engineering designers to understand and master the damage and fracture of ceramic-matrix composites under stochastic loading.
Author: Longbiao Li Publisher: Springer ISBN: 9811317836 Category : Technology & Engineering Languages : en Pages : 249
Book Description
This book focuses on the damage, fracture and fatigue of ceramic-matrix composites. It investigates tensile damage and fracture, fatigue hysteresis, and the properties of interfaces subjected to cyclic fatigue loading. Further, it predicts fatigue life at room and elevated temperatures using newly developed damage models and methods, and it analyzes and compares damage, fracture and fatigue behavior of different fiber performs: unidirectional, cross-ply, 2D and 2.5D woven. The developed models and methods can be used to predict the damage and lifetime of ceramic-matrix composites during applications on hot section components.Ceramic-matrix composites (CMCs) are high-temperature structural materials with the significant advantages of high specific strength, high specific modulus, high temperature resistance and good thermal stability, which play a crucial role in the development of high thrust weight ratio aero engines. The critical nature of the application of these advanced materials makes comprehensive characterization a necessity, and as such this book provides designers with essential information pertaining not only to the strength of the materials, but also to their fatigue and damage characteristics.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The AFOSR funded two year project (which expires March 1, 1997) addresses the effect of loading frequency and friction heating on the ambient temperature fatigue life of continuous fiber ceramic matrix composites (CFCMCs). The project, which involves mechanics modeling, mechanical testing and microscopy, examined several composite systems and has provided details concerning the damage mechanisms that occur during high frequency fatigue. The current research effort of high-frequency fatigue has been performed at the Ceramic Composites Research laboratory, in the Mechanical Engineering and applied Mechanics Department at the University of Michigan. 1. "Soft" matrix composites with strong interface bonding were shown to provide superior resistance to high frequency fatigue damage. 2. thick fiber coatings were more effective in reducing the amount of fiber wear and damage which occur during high frequency fatigue. 3. The effect of laminate stacking sequence has a profound effect on high frequency fatigue behavior of CFCMCs. 4. Surface roughness in Nicalon fibers can be determined using Atomic force Microscopy (AFM). 5. Elongated crystalline grains and a small volume fraction of whiskers in the matrix can improve the high frequency fatigue behavior of CFCMCs. 6. Loading rate was found to significantly effect monotonic tensile behavior of CFCMCs.
Author: Longbiao Li Publisher: John Wiley & Sons ISBN: 3527822593 Category : Technology & Engineering Languages : en Pages : 636
Book Description
Guides researchers and practitioners toward developing highly reliable ceramic-matrix composites The book systematically introduces the thermomechanical fatigue behavior of fiber-reinforced ceramic-matrix composites (CMCs) and environmental barrier coatings, including cyclic loading/unloading tensile behavior, cyclic fatigue behavior, dwell-fatigue behavior, thermomechanical fatigue behavior, and interface degradation behavior. It discusses experimental verification of CMCs and explains how to determine the thermomechanical properties. It also presents damage evolution models, lifetime prediction methods, and interface degradation rules. Thermomechanical Fatigue of Ceramic-Matrix Composites offers chapters covering unidirectional ceramic-matrix composites and cross-ply and 2D woven ceramic-matrix composites. For cyclic fatigue behavior of CMCs, it looks at the effects of fiber volume fraction, fatigue peak stress, fatigue stress ratio, matrix crack spacing, matrix crack mode, and woven structure on fatigue damage evolution. Both the Dwell-fatigue damage evolution and lifetime predictions models are introduced in the next chapter. Experimental comparisons of the cross-ply SiC/MAS composite, 2D SiC/SiC composite, and 2D NextelTM 720/Alumina composite are also included. Remaining sections examine: thermomechanical fatigue hysteresis loops; in-phase thermomechanical fatigue damage; out-of-phase thermomechanical fatigue; interface degradation models; and much more. -Offers unique content dedicated to thermomechanical fatigue behavior of ceramic-matrix composites (CMCs) and environmental barrier coatings -Features comprehensive data tables and experimental verifications -Covers a highly application-oriented subject?CMCs are being increasingly utilized in jet engines, industrial turbines, and exhaust systems Thermomechanical Fatigue of Ceramic-Matrix Composites is an excellent book for developers and users of CMCs, as well as organizations involved in evaluation and characterization of CMCs. It will appeal to materials scientists, construction engineers, process engineers, and mechanical engineers.
Author: Longbiao Li Publisher: John Wiley & Sons ISBN: 3527831789 Category : Technology & Engineering Languages : en Pages : 386
Book Description
High Temperature Mechanical Behavior of Ceramic-Matrix Composites Covers the latest research on the high-temperature mechanical behavior of ceramic-matrix composites Due to their high temperature resistance, strength and rigidity, relatively light weight, and corrosion resistance, ceramic-matrix composites (CMCs) are widely used across the aerospace and energy industries. As these advanced composites of ceramics and various fibers become increasingly important in the development of new materials, understanding the high-temperature mechanical behavior and failure mechanisms of CMCs is essential to ensure the reliability and safety of practical applications. High Temperature Mechanical Behavior of Ceramic-Matrix Composites examines the behavior of CMCs at elevated temperature—outlining the latest developments in the field and presenting the results of recent research on different CMC characteristics, material properties, damage states, and temperatures. This up-to-date resource investigates the high-temperature behavior of CMCs in relation to first matrix cracking, matrix multiple cracking, tensile damage and fracture, fatigue hysteresis loops, stress-rupture, vibration damping, and more. This authoritative volume: Details the relationships between various high-temperature conditions and experiment results Features an introduction to the tensile, vibration, fatigue, and stress-rupture behavior of CMCs at elevated temperatures Investigates temperature- and time-dependent cracking stress, deformation, damage, and fracture of fiber-reinforced CMCs Includes full references and internet links to source material Written by a leading international researcher in the field, High Temperature Mechanical Behavior of Ceramic-Matrix Composites is an invaluable resource for materials scientists, surface chemists, organic chemists, aerospace engineers, and other professionals working with CMCs.
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Author: Longbiao Li
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Author: Longbiao Li