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The Effect of Elevated Temperature Exposure of Composites on the Strength Distribution of the Reinforcing Fibers

Published online by Cambridge University Press:  15 February 2011

M. L. Gambone  and
F. E. Wawner
M. L. Gambone
Affiliation:
Wright Laboratory/MLLM, 2230 Tenth St. Ste. 1, WPAFB, OH 45433-7187
F. E. Wawner
Affiliation:
University of Virginia, Department of Materials Science and Engineering, Thornton Hall, Charlottesville, VA 22903
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Abstract

Unidirectionally-reinforced Timetal® 21S composite specimens were subjected to elevated temperature heat treatments. The SiC fibers were then chemically extracted from the matrix, and their tensile strengths were measured at room temperature. A Weibull statistical analysis of fiber strength distribution was performed to compare the Weibull parameters of fibers from the as-consolidated and heat-treated composites. Fractographic analysis of the tested fibers was used to identify the flaws which caused failure in each condition. Surface flaws were found to initiate low strength failures in all conditions, and the number of surface initiated failures increased with an increase in severity of heat-treatment. A relationship between the fiber/matrix chemical reaction and surface flaw development is demonstrated. A fracture mechanics analysis that explains the relationship between surface flaw size, fiber fracture toughness, and the measured tensile strengths is suggested.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 350: Symposium U – Intermetallic Matrix Composites III , 1994 , 111
Copyright
Copyright © Materials Research Society 1994

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