Monolithic ceramic materials have been used in industry for hundreds of years. These
materials have proven their usefulness in many applications, yet, their potential for
critical structural applications is limited. The existence of an imperfection in a monolithic
ceramic on the order of several microns in size may be critical, resulting in catastrophic
failure. To overcome this extreme sensitivity to sman material imperfections, reinforced
ceramic materials have been developed. A ceramic matrix which has been reinforced with
continuous fibers is not only less sensitive to microscopic flaws, but is also able to sustain
significant damage without suffering catastrophic failure.
A borosilicate glass reinforced with several layers of plain weave silicon carbide cloth
(Nicalon) has been studied. The mechanical testing which was performed included both
flexural and tensile loading configurations. This testing was done not only to determine the
material properties, but also to initiate a controlled amount of damage within each specimen.
Several nondestructive testing techniques, including acousto-ultrasonics (AU), were
performed on the specimens periodically during testing. The AU signals were monitored
through the use of an IBM compatible personal computer with a high speed data acquisition
board. Software has been written which manipulates the AU signals in both the time and
frequency domains, resulting in quantitative measures of the mechanical response of the
material.
This paper will compare the measured AU parameters to both the mechanical test results
and data from other nondestructive methods including ultrasonic C-scans and penetrant
enhanced X-ray radiography.
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