Characterization and control of the fiber-matrix interface in ceramic ...

2. HISTORICAL DEVELOPMENTS IN CERAMIC COMPOSITES
??le co.ncept of fiber-reinforced ceramic materials i.s not new.
Throughout history, fibers have been added to brittle materials to
improve their properties.
Straw and animal hair were mixed with clay and
the mixture formed into bricks or pottery. The fiber acted to improve
the handleability of the materials prior to drying or firing and to
increase the strength and fracture resistance of the finished product.
It has been suggested that goat hair was added to po,ttery in ancient
times and upon firing was converted to carbon.
These mat:erials may be
the first examples of carbon-fiber-reinforced eerami.~ composites (5-7).
Composite jars and vessels were supposedly less prone to breakage than
their unreinforced counterparts.
Although the advantages of ceramic camposltes have been recognized
for many years, most of the developments in fi.l>er-reinforced ceramic
materials have occurred in the past twenty years, In some early work,
randomly oriented, discontinuous metal fibers were incorporated into a
range of ceramic matrices { 5,7,8-10). The result was improved toughness,
and in some cases, increased strength, Unfortunately, ,these i~iodest
improvements were accompanied by significant disadvantages in that the
densities were increased relati.ve to the monolithic materials, the
ceramic matrices failed to protect the fibers from degradation in
damaging environments, and the thermal expansion mismatch between fibers
and matrices resulted in premature failure of the composites because of
matrix cracking upon temperature cycling. By the late 1960s, the
development of these composite materials had been abandoned to pursue
more promising ventures.
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