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

The development of low-density, high-strength Carbon fibers led to a
renewed interest in fiber-reinforced composites.
In contrast to the
earlier researc-h that attempted to improve the toughness of brittle
ceramics by the addition of ductile metal fibers, researchers began to
investigate the possibility of reinforcing brittle matrices with the
relatively brittle carbon fibers.
The majority of the i.nitia1 efforts
were in the deve1.opment of carbon-carbon composites for defense
applications; however, carbon-carbon composites begin to oxidize in
air at temperatures above 700 K, thereby li.miting their usefulness.
Alternative ii1atri.x materials were examined, and again, ceramics were.
produced that possessed the desired attributes of hi.gh strength, thermal
stability, chemical inertness, and oxidation resistance.
Some of the original research examining the toughening of ceramic
matrices by the addition of carbon fibers was initiated in the late 1960s
and early 1.970s at Harwell and at the National Physics Laboratory in
Engl.and (1,11-15). Large increases in the work of fracture were attained
by incorporating carbon fibers i.nto glass axid glass -ceramic matrices.
The composites demonstrated hi.gh strength and toughness and could be
fabricated using techniques similar to those already well established i.n
the production of polymeric matri-x composites.
As with metal matrix and
metal fiber-reinforced ceramic composites, these materials lacked thermal
stahi-lity because of the relnti.vely large differences in the fiber and
matri-x thermal expansions and the poor oxidation resistance of the carbon
fibers.
Interest: in the materials waned as efforts to improve the
oxidation resistance of the carbon-fiber-glass matrix composites were
unsuccessful.