Characterization of Fatigue Damage in a Metal Matrix Composite (SCS-6/ TI-15-3) at Elevated Temperature

Characterization of Fatigue Damage in a Metal Matrix Composite (SCS-6/ TI-15-3) at Elevated Temperature
Author:
Publisher:
Total Pages: 322
Release: 1993
Genre:
ISBN:

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The fatigue characteristics of a unidirectional titanium based metal matrix composite site (MMC) were investigated at elevated temperature (427 deg C). A hybrid strain controlled loading made was used to subject the 0 deg and 90 deg laminas to fatigue. Along with the fatigue tests, microscopy and analytical modeling were also conducted. This combination of activities led to defining the initiation and progression of damage and deformation in the MMC. When loading was parallel to the fiber direction, the fatigue behavior was initially dominated by creep deformation of the matrix. Then, depending on the maximum strain, specimen failure was the result either fiber fractures or matrix cracking. In contrast, when loading was perpendicular to the fiber direction, the fatigue response was first dominated by the initiation of fiber-matrix interface damage. Then, if the maximum strain was above .35%, the dominant damage mechanism was matrix cracking. Below this strain level, the damage was a mixture of matrix microcracks and the progression of fiber-matrix interface damage. The analysis for this fiber orientation included unique methods to model the interface damage. This hybrid approach involving experiments, microscopy, and analytical modeling provided better understanding of the fatigue behavior of the MCC.

Characterization of Unnotched SCS-6/Ti-15-3 Metal Matrix Composites at 650°C

Characterization of Unnotched SCS-6/Ti-15-3 Metal Matrix Composites at 650°C
Author: WS. Johnson
Publisher:
Total Pages: 17
Release: 1992
Genre: Composite materials
ISBN:

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TI-15-3 reinforced with SCS-6 silicon carbide fibers, in five different lay-ups, was tested at 650°C to determine monotonic and fatigue strengths, basic mechanical properties, and damage initiation and progression. The elevated temperature results were compared to those obtained at room temperature. Analytical predictions were made of the monotonic stress-strain response as well as cyclic stress-strain hysteresis. The fiber reinforcement was found to increase significantly the static and fatigue strengths of the laminates over those of the matrix material at elevated temperature; the increase was insignificant at room temperature. Initial damage, in either the fibers or the matrix, was partitioned as a function of the life and applied strain range in the constituents. High strains and short lives resulted in multiple fiber failure with no signs of matrix fatigue cracking. Low strains and long lives resulted in extensive matrix cracking and no fiber breaks away from the fracture surface. At 650°C, the matrix was too weak to cause fiber-matrix interface failure before matrix yielding. Laminate fatigue lives were hypothesized to be a function of the 0° fiber stress. More scatter was found in the 0° fiber stress versus high temperature fatigue life data than in the room temperature data. An initial unloading modulus that was greater than the initial loading modulus was observed in the elevated temperature fatigue tests.

Applied Mechanics Reviews

Applied Mechanics Reviews
Author:
Publisher:
Total Pages: 354
Release: 1993
Genre: Mechanics, Applied
ISBN:

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NASA Technical Memorandum

NASA Technical Memorandum
Author:
Publisher:
Total Pages: 492
Release: 1994
Genre: Aeronautics
ISBN:

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Applications of Continuum Damage Mechanics to Fatigue and Fracture

Applications of Continuum Damage Mechanics to Fatigue and Fracture
Author: David L. McDowell
Publisher: ASTM International
Total Pages: 238
Release: 1997
Genre: Composite materials
ISBN: 0803124732

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Contains papers from the May 1996 Symposium on Applications of Continuum Damage Mechanics (CDM) to Fatigue and Fracture. Papers in Section I deal with various aspects of modeling damage in composite materials, such as high temperature environmental degradation, fatigue, and viscous damage in metal a