SYMPOSIA PAPER Published: 01 January 1992

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


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.

Author Information

Pollock, WD
Analytical Services and Materials, NASA Langley Research Center, Hampton, VA
Johnson, WS
NASA Langley Research Center, Hampton, VA
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Developed by Committee: D30
Pages: 175–191
DOI: 10.1520/STP20154S
ISBN-EB: 978-0-8031-5184-0
ISBN-13: 978-0-8031-1426-5