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Evolution Of Bridging Fiber Stress In Titanium Metal Matrix Composites At Elevated Temperature
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Book Synopsis Evolution of Bridging Fiber Stress in Titanium Metal Matrix Composites at Elevated Temperature by : H. Ghonem
Download or read book Evolution of Bridging Fiber Stress in Titanium Metal Matrix Composites at Elevated Temperature written by H. Ghonem and published by . This book was released on 1996 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper deals with the determination of stress evolution in bridging fibers during fatigue crack growth in a SM1240/Timetal-21S composite using the finite element method. Several parameters affecting this evolution were considered, namely, the process-induced residual stress, the creep characteristics of the matrix layer surrounding the fiber, the test temperature, and the loading frequency. In support of these calculations, a series of elevated temperature fatigue crack growth tests was conducted to identify the crack growth behavior of the composite when subjected to different temperatures at both high and low loading frequencies. Results of this numerical/experimental work were then utilized in conjunction with a postulated fiber fracture criterion based on the notion that a competition exists between the increase in the axial fiber stress and the continuous degradation of the fiber strength due to cyclic wear induced by the interface frictional shear stress. The conclusions of this study show that the axial stress in the bridging fibers increases with an increase in temperature and with a decrease in both the loading frequency and the matrix grain size. A combination of high-temperature, low-frequency, and small-matrix grain size would enhance creep deformation of the matrix, thus leading to an increase in the rate of the load transfer from the matrix to the bridging fibers. Furthermore, the presence of a compressive residual stress state in the bridging fibers retards the time-dependent increase of their axial stress. The fatigue strength of the bridging fibers was estimated to range from 720 to 870 MPa within the temperature range of 500 to 650°C. This strength was found to depend on both the temperature and the loading frequency.
Book Synopsis Titanium Matrix Composites by : Shankar Mall
Download or read book Titanium Matrix Composites written by Shankar Mall and published by CRC Press. This book was released on 2020-01-29 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review and summary of advancements related to mechanical behavior and related mechanics issues of titanium matrix composites (TMCs), a class of high-temperature materials useful in the propulsion and airframe components in advanced aerospace systems. After an introduction to TMCs, different authors review and summarise the advancements related to mechanical behavior and related mechanics issues of TMCs.
Book Synopsis Damage Development in Titanium Metal Matrix Composites Subjected to Cyclic Loading by :
Download or read book Damage Development in Titanium Metal Matrix Composites Subjected to Cyclic Loading written by and published by . This book was released on 1992 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Durability and Damage Tolerance of High Temperature Advanced Titanium Metal Matrix Composites by :
Download or read book Durability and Damage Tolerance of High Temperature Advanced Titanium Metal Matrix Composites written by and published by . This book was released on 2000 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: The bridging fatigue crack growth damage mechanisms in a unidirectional SiC/Ti MMC include matrix cracking, fiber/matrix interface debonding and sliding along bridging fibers and fracture of these fibers. The basic components of these mechanisms are examined in this program. The evolution features of residual stresses indicated that stress relaxation occurred in the Ti matrix phase of the composite following post-fabrication cool down to 600 00. Parametric study of the SiC fiber coating materials showed that the effective residual stress component has an inverse relationship with the thickness of the fiber reaction zone. The debonding shear strength of the composite is determined by the localized shear stress distribution along the fiber/matrix interface at the onset of debonding. An interphase debonding model, which combine fracture mechanics with FE results on interphase shear stress and bridging fiber traction range, is proposed to establish a distribution of debonding lengths along a fiber-bridged matrix crack length as a function of temperature. The driving force for the interface debond crack, however, has an inverse relationship with the test temperature. The concurrent damage events of fiber stress evolution and continuous fiber strength degradation were postulated into a fiber fracture criterion to describe the fracture process of a bridging fiber. Furthermore, the fiber crack density has been correlated with the density of crack initiation sites observed in the interphase region along the reinforcing fibers in a SCS-6/Ti-21S composite.
Book Synopsis Aspects of High Temperature Damage in Fiber Reinforced Titanium Metal Matrix Composites by :
Download or read book Aspects of High Temperature Damage in Fiber Reinforced Titanium Metal Matrix Composites written by and published by . This book was released on 1993 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aspects associated with high temperature damage in fiber reinforced Metal Matrix Composites were investigated and are presented in this report in the form of five separate sections. In the first section, the fatigue and fatigue crack growth characteristics in neat laminates made of Timetal 21S were studied in relation to both temperature and loading frequency effects. The second section deals with the evolution of the thermal residual stresses in the composite when cooling from consolidation temperature or subjecting the composite to then-nal cycles. A new mechanical simulation method capable of measuring the induced residual stress on real; time basis has been developed in this study. The third section extends this issue to the time-dependent internal stress and strain states of MMCs under the thermomechanical loading conditions. Here, a new micromechanical model employing the four-phase concentric cylinder configuration has been proposed. Based on this model, the time-dependent behavior of continuous fiber reinforced metal matrix composites has been evaluated for the SCS-6/Timetal 21S composite. These results are presented in the fourth section. The last section of this report deals with the high temperature fatigue crack growth characteristics of the continuous fiber reinforced titanium metal matrix composite sigma l240/Timetal 12IS. The time- dependent features of the crack growth was examined in relation to the variation of both testing temperature and loading frequency. the principal damage mechanism of this composite under the load condition employed was identified to be the crack bridging and fiber/matrix debonding confined to regions near the crack surfaces ... Bridging, Fiber pullout length, Viscoplasticity, Composite interface.
Book Synopsis Implementation of Thermal Residual Stresses in the Analysis of Fiber Bridged Matrix Crack Growth in Titanium Matrix Composites by :
Download or read book Implementation of Thermal Residual Stresses in the Analysis of Fiber Bridged Matrix Crack Growth in Titanium Matrix Composites written by and published by . This book was released on 1994 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fatigue Crack Growth Mechanisms in Titanium Metal Matrix Composites by :
Download or read book Fatigue Crack Growth Mechanisms in Titanium Metal Matrix Composites written by and published by . This book was released on 1996 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report details studies carried out to identify the high temperature fatigue crack growth damage mechanisms in fiber-reinforced titanium metal matrix composites. The report consists of eight separate sections. In the first section, the fatigue and fatigue crack growth characteristics in neat laminates made of Timetal 21S were studied in relation to both temperature and loading frequency effects. The second section deals with the evolution of the thermal residual stresses in the composite when cooling from consolidation temperature or subjecting the composite to thermal cycles. A new mechanical simulation method capable of measuring the induced residual stress on real time basis has been developed in this study. The third section extends this issue to the time-dependent internal stress and strain states of MMCs under the thermomechanical loading conditions. Here, a new micromechanical model employing the four-phase concentric cylinder configuration has been proposed. Based on this model, the time-dependent behavior of continuous fiber reinforced metal matrix composites. It has been evaluated. These results are presented in the fourth section. The fifth, sixth and seventh sections of this report describe the influence of temperature and loading frequency on the crack growth process and suggest a fatigue-creep interactive mechanism acting at the crack tip during high temperature loadings. The last section of the report deals with the determination of the stress evolution in bridging fibers during the fatigue crack growth in SM 1240/Timetal-21S composite using the finite element method. Several parameters affecting this evolution were considered; namely, the process-induced residual stress, the creep characteristics of the matrix layer surrounding the fiber, the test temperature and the loading frequency.
Book Synopsis A Methodology to Predict Damage Initiation, Damage Growth and Residual Strength in Titanium Matrix Composites by :
Download or read book A Methodology to Predict Damage Initiation, Damage Growth and Residual Strength in Titanium Matrix Composites written by and published by . This book was released on 1994 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advances in Fatigue Lifetime Predictive Techniques by : Michael R. Mitchell
Download or read book Advances in Fatigue Lifetime Predictive Techniques written by Michael R. Mitchell and published by ASTM International. This book was released on 1996 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Contemporary Research in Engineering Science by : Romesh C. Batra
Download or read book Contemporary Research in Engineering Science written by Romesh C. Batra and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue failures occur in aerospace,marine,nuclear structures and automobile com ponents from initiation and propagation of cracks from holes,scratches or defects in the material. To design against these failures, crack propagation life and fracture strength need to be accurately predicted. It is reported in the literature, that these failures often initiate as surface cracks, corner cracks and cracks emanating from fastner holes. Such cracks are with elliptic or nearly elliptic in shapes. The deviation from elliptic shape is due to varying constraint effect along the crack front. Even in situations, when the cracks are through the thickness of the material, there would be thicknesswise variation of constraint effects leading to three dimensional nature of crack growth. Accurate predictions of the crack growth in these cases by numerical methods can be made only by solving three-dimensional boundary value problems. Empirical relationships have been developed [1] based on Linear Elastic Fracture Mechanics over years describing fatigue crack growth response. Some of these empirical relationships required modifications in the later stages, to meet the design applications. The Crack closure phenomenon discovered by Elber[2, 3] during the crack growth phase is mainly attributed to the local material yielding near the crack tip and the consequent residual plastic wake behind the crack tip. It helped considerably in understanding several aspects of fatigue crack growth and rewrite these relations.
Book Synopsis High Temperature/High Frequency Fatigue Crack Growth in Titanium Metal Matrix Composites by : H. Ghonem
Download or read book High Temperature/High Frequency Fatigue Crack Growth in Titanium Metal Matrix Composites written by H. Ghonem and published by . This book was released on 1996 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was conducted to examine the effects of high temperature/high frequency loading on the crack growth behavior in titanium composites. Fatigue crack growth tests were performed on the unidirectional SM 1240/TIMETAL-21S composite in air environment at three different temperatures: 24, 500, and 650?gC with a loading frequency of 10 Hz and a stress ratio of 0.1. Tests were also carried out in vacuum and on aged specimens. In all the tests, the crack length was measured continuously while the crack opening displacement (COD) was measured at discrete positions along the crack length. Results show that, at all temperatures, the crack progresses in two sequential stages; a stage in which the crack growth rate decreases as the crack length increases followed by a stage characterized by an accelerated crack growth rate. The first stage corresponds to a crack-bridging condition and is the focus of the analysis in this paper. In additional to COD measurements, the microstructural features associated with the fracture process during this stage was examined by scanning electron microscopy with emphasis being placed on the matrix crack morphology, debonding location, temperature, and environmental influences on the fiber coatings. An analytical procedure, employing concepts of the theory of fracture mechanics and micromechanics analysis of the stress state along bridging fibers, was applied in order to calculate the fiber-bridging stress, the frictional shear stress, and the effective stress intensity factor. Results of this work suggest that the fiber-bridging stress and the frictional shear stress are variables along the crack length and are test temperature dependents. Furthermore, it was concluded that both the crack-tip opening displacement and the effective stress intensity factor can be used as measurements of the crack-tip driving force in the crack-bridging stage. Based on the experimental and analytical results collected in this study, a bridging damage mechanism under the loading condition specified here is suggested. This mechanism argues that the effect of temperature on the high frequency crack growth process is established through the temperature-related modification of the frictional shear stress and the resulting adjustment of the internal stress state in the debonded regions of the bridging fibers.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781722241032 Total Pages :56 pages Book Rating :4.2/5 (41 download)
Book Synopsis Application of Fiber Bridging Models to Fatigue Crack Growth in Unidirectional Titanium Matrix Composites by : National Aeronautics and Space Administration (NASA)
Download or read book Application of Fiber Bridging Models to Fatigue Crack Growth in Unidirectional Titanium Matrix Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-06 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several fiber bridging models were reviewed and applied to study the matrix fatigue crack growth behavior in center notched (0)(sub 8) SCS-6/Ti-15-3 and (0)(sub 4) SCS-6/Ti-6Al-4V laminates. Observations revealed that fatigue damage consisted primarily of matrix cracks and fiber matrix interfacial failure in the (0)(sub 8) SCS-6/Ti-15-3 laminates. Fiber-matrix interface failure included fracture of the brittle reaction zone and cracking between the two carbon rich fiber coatings. Intact fibers in the wake of the matrix cracks reduce the stress intensity factor range. Thus, an applied stress intensity factor range is inappropriate to characterize matrix crack growth behavior. Fiber bridging models were used to determine the matrix stress intensity factor range in titanium metal matrix composites. In these models, the fibers in the wake of the crack are idealized as a closure pressure. An unknown constant frictional shear stress is assumed to act along the debond or slip length of the bridging fibers. The frictional shear stress was used as a curve fitting parameter to available data (crack growth data, crack opening displacement data, and debond length data). Large variations in the frictional shear stress required to fit the experimental data indicate that the fiber bridging models in their present form lack predictive capabilities. However, these models provide an efficient and relatively simple engineering method for conducting parametric studies of the matrix growth behavior based on constituent properties. Bakuckas, J. G., Jr. and Johnson, W. S. Langley Research Center...
Book Synopsis Life Prediction Methodology for Titanium Matrix Composites by : W. Steven Johnson
Download or read book Life Prediction Methodology for Titanium Matrix Composites written by W. Steven Johnson and published by ASTM International. This book was released on 1996 with total page 625 pages. Available in PDF, EPUB and Kindle. Book excerpt: Papers presented at the March 1994 symposium are organized into five sections that progress from basic understanding of mechanical damage mechanisms and environmental effects to life prediction methodology. Five papers discuss the interplay between interfacial strength, residual thermal stresses, an
Book Synopsis Time-dependent Deformation of Titanium Metal Matrix Composites by :
Download or read book Time-dependent Deformation of Titanium Metal Matrix Composites written by and published by . This book was released on 1995 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis International Aerospace Abstracts by :
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Application of Fiber Bridging Models to Fatigue Crack Growth in Unidirectional Titanium Matrix Composites by :
Download or read book Application of Fiber Bridging Models to Fatigue Crack Growth in Unidirectional Titanium Matrix Composites written by and published by . This book was released on 1992 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781722907068 Total Pages :36 pages Book Rating :4.9/5 (7 download)
Book Synopsis Time-Dependent Deformation of Titanium Metal Matrix Composites by : National Aeronautics and Space Administration (NASA)
Download or read book Time-Dependent Deformation of Titanium Metal Matrix Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-13 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A three-dimensional finite element program called VISCOPAC was developed and used to conduct a micromechanics analysis of titanium metal matrix composites. The VISCOPAC program uses a modified Eisenberg-Yen thermo-viscoplastic constitutive model to predict matrix behavior under thermomechanical fatigue loading. The analysis incorporated temperature-dependent elastic properties in the fiber and temperature-dependent viscoplastic properties in the matrix. The material model was described and the necessary material constants were determined experimentally. Fiber-matrix interfacial behavior was analyzed using a discrete fiber-matrix model. The thermal residual stresses due to the fabrication cycle were predicted with a failed interface, The failed interface resulted in lower thermal residual stresses in the matrix and fiber. Stresses due to a uniform transverse load were calculated at two temperatures, room temperature and an elevated temperature of 650 C. At both temperatures, a large stress concentration was calculated when the interface had failed. The results indicate the importance of accuracy accounting for fiber-matrix interface failure and the need for a micromechanics-based analytical technique to understand and predict the behavior of titanium metal matrix composites. Bigelow, C. A. and Bahei-El-din, Y. A. and Mirdamadi, M. Unspecified Center NAS1-19708; RTOP 505-63-50-04...
