Fatigue Behavior of a Cross-ply Metal Matrix Composite at Elevated Temperature Under Strain Controlled Mode PDF Download
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Author: Leon B. Dennis (CAPT, USAF.)
Publisher:
ISBN:
Category : Metallic composites
Languages : en
Pages : 232
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Book Description
Author: Leon B. Dennis (CAPT, USAF.)
Publisher:
ISBN:
Category : Metallic composites
Languages : en
Pages : 232
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 127
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Book Description
This research extends the existing knowledge of cross-ply metal matrix composites (MMC) to include fatigue behavior under strain-controlled fully reversed loading. This study investigated fatigue life, failure modes and damage mechanisms of the SCS-6/Ti-15-3, (O/9O)2s, MMC. The laminate was subjected to fully reversed fatigue at elevated temperature (427 deg C) at various strain levels. Stress, strain and modulus data were analyzed to characterize the macro-mechanical behavior of the composite. Microscopy and fractography were accomplished to identify and characterize the damage mechanisms at the microscopic level. Failure modes varied according to the maximum applied strain level showing either mixed mode (i.e. combination of both fiber and matrix dominated modes) or matrix dominated fatigue failures. As expected, higher strain loadings resulted in more ductility of the matrix at failure, evidenced by fracture surface features. For testing of the same composite laminate, the fatigue life under strain controlled mode slightly increased, compared to its load-controlled mode counterpart, using the effective strain range comparison basis. However, the respective fatigue life curves converged in the high cycle region, suggesting that the matrix dominated failure mode produces equivalent predicted fatigue lives for both control modes.
Author: Alvin Ruiz
Publisher:
ISBN: 9781423579571
Category : Metallic composites
Languages : en
Pages : 109
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Book Description
The objective of this study was to investigate the residual strength of a cross-ply, SCS-6/Ti-15-3, metal matrix composite (MMC) at elevated temperature (427 deg C) when exposed to fatigue loading. Several specimens were subjected to a strain-controlled, fully reversed loading (R=-1), at various strain levels. The specimens were fatigued up to a portion of their life expectancy and then loaded to failure. Stress and strain data obtained during the test provided useful information for the macro-mechanical behavior of the material. It was determined that the residual strength was directly related to the amount of damage present in the matrix, meanwhile, the amount of matrix damage was dependent on the number of cycles and strain level the specimen had been exposed to. It was also observed that the residual strength under the strain controlled mode degraded more consistently than its counterpart under load controlled mode. This variation, however, may be due to the frequency and R-ratio differences between the two loading modes. The comparison of the residual strength degradation of the cross-ply vs. unidirectional laminates reflected a significant difference due to ply orientation. The unidirectional composite exhibited much less residual strength degradation due to the absence of the crack initiation action attributed to the 90 deg plies in the cross-ply.
Author: BP. Sanders
Publisher:
ISBN:
Category : Automotive medicine
Languages : en
Pages : 8
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Book Description
The present paper is a continuation of Part I to investigate the transverse fatigue behavior of a unidirectional titanium-based metal matrix composite (MMC) (SCS-6/Ti-15-3) at elevated temperature. In Part I of this paper, fatigue tests were conducted under the strain-controlled mode, and a systematic microscopic evaluation was undertaken to identify the damage and deformation mechanisms. In this paper (Part II), the fatigue response is modeled using a micromechanical approach where the fiber-matrix interfacial damage is incorporated along with the inelastic behavior of the matrix. The analysis provided additional insight into the transverse fatigue response of the MMC. Combining the results obtained from this micromechanical analysis, and that obtained from the macroscopic response (that is, stress and modulus) and microscopic evaluation in Part I, the transverse fatigue response of the MMC was thoroughly characterized.
Author: S. Mall
Publisher:
ISBN:
Category : Automotive medicine
Languages : en
Pages : 10
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Book Description
The fatigue characteristics of a unidirectional titanium-based metal matrix composite (MMC) (SCS-6/Ti-15-3) were investigated at elevated temperature (427°C). A hybrid strain controlled loading mode was employed for this purpose. This hybrid control mode did not allow the specimen to experience compressive stress in order to prevent any possible buckling effects. To fully understand the fatigue behavior of the MMC under this control mode, fatigue tests, microscopic evaluation, and micromechanical analysis were performed. Based on this combination of activities, the damage and deformation mechanisms were systematically identified. It was found that the fatigue behavior was initially dominated by creep deformation of the matrix. This was accompanied by plastic deformation in those specimens that were subjected to a maximum strain level of 0.55% or higher. Depending on the maximum strain level, the specimen failure was a result of either fiber fracture or matrix cracking. Using the combined approach involving experiments, microscopy, and analysis, the interrelationships among applied strain levels, fatigue life, damage mechanisms, and macroscopic response were established to characterize the longitudinal fatigue characteristics of the tested MMC.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 165
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Book Description
This research, the first load-controlled tension-compression fatigue testing to be performed on a MMC, extends the existing knowledge of MMC fatigue damage mechanisms to include the tension compression loading condition. To accomplish this, a (0/90)2, SCS-6/Ti-15-3 laminate was subjected to tension- tension fatigue at room temperature, and tension-compression fatigue at both room temperature and 427 deg C. Stress and strain data was taken to evaluate the macro-mechanic behavior of the material. Microscopy and fractography were performed to characterize the damage on a micro-mechanic level. On a maximum applied stress basis, the room temperature tension-tension specimens had longer fatigue lives than the room temperature tension-compression specimens. The room and high temperature tension-compression fatigue lives were nearly identical in the fiber-dominated high stress region of the SN curve. However, the increased ductility and diffused plasticity of the titanium matrix at 427 deg C delayed the onset and severity of matrix cracking, and thus increased the elevated temperature fatigue lives in the matrix dominated region of the SN curve. In all cases, matrix damage initiated at reaction zone cracks which nucleated both matrix plasticity and matrix cracking.
Author: Michael J. Verrilli
Publisher: ASTM International
ISBN: 080312001X
Category :
Languages : en
Pages : 382
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Book Description
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 602
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Sen-Tzer Chiou
Publisher:
ISBN: 9781423572695
Category : Metallic composites
Languages : en
Pages : 93
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Book Description
This study investigated the residual strength of the unidirectional and cross-ply laminates of SCS-6 / Ti-15-3, metal matrix composite at elevated temperature 427 deg C (800 deg F) after under tension-tension load controlled mode. For this purpose, several specimens were fatigued to various fractions of the fatigue life and then loaded monotonically to failure. The purpose of this study was to determine the effects of different levels of fatigue damage on the composite's strength. The unidirectional specimens were cycled at a 900 MPa maximum stress at a frequency of 10 Hz, while, the cross-ply specimens were tested at both 300 MPa and 450 MPa at 5 Hz and 10 Hz, respectively. The residual strength results for the three cases showed similar trends in that residual strength drop with cycles was small until near the end of the fatigue life. Both the unidirectional and cross-ply specimens demonstrated only a small drop of the residual strength with cycles until near the end of the fatigue life. (Author)
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 170
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Book Description
The objective of this research was to investigate the initiation and progression of damage which develops in notched (0/90) sub 2S SCS-6/Ti-15-3 at elevated temperature. Testing consisted of a monotonic tensile test at 427 deg C followed by fatigue testing performed under load control with a stress ratio of 0.1 at a frequency of 10 Hz. A crack was defined to have initiated when it had attained a length greater than or equal to 0.124 mm. Crack initiation and progression was monitored by strain and modulus observations and visual inspection via telemicroscope. The cracks were recorded with edge and face replicas. Metallographic and fractographic analysis was performed after specimen failure. Fatigue cracks initiated in the matrix at four locations on the front and back faces of each specimen. Two of these cracks became through-cracks and eventually developed into major cracks which caused the fracture. The applied stress (S) and fatigue lives (N) curves for both initiation and fatigue life were established. Also, crack growth curves as the function of fatigue cycles were established. A detailed metallographic analysis was performed to understand the damage mechanisms and its implication on the observed notched fatigue behavior.
