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

10
lay-ups or filaiiients wound into cylindrical shdpes and densified,
usually hy hpt pressing.
The object of consolidation is to produce a dense material while
inflicting minimal damage to the fiber or whisker reinforcement.
The
majority of densification processes employ high temperatures and some,
such as hot pressing, utilize elevated temperature combined with extreme
pressui-e.
These condi t i o m nay have detrimental effects on the
propertie4 of the reinforcing component.
3.2 Hot Pressing
The inost widely used technique ~ O K producing ceramic matrix
coinposi tes is hot pressing.
Hot pressing has been used to fabricate
composites from a large selection of polycrystalline ceramic matvices
(21,32,35). The properties of the composites depend on fabrication
parameters such as the particle size distribution of the powders and the
temperatures and pressures employed.
These pdrameters control the
porosity OL the matrix and the damage introduced into the fibers and can
affect f iber-matrix bond strength.
Hot pressing has yieldpd fiber-
reinforced ceramic composites with reproducible properties, and the
materials and processing conditions have been studied in depth.
However,
the tcmper,?tures and pressores necessary to attain the required densities
in the matrices severely damage many of the available fibers.
An advantage of hot pressing is that the procedure does not require
binders 1-0
stiffen preforms prior to densification; thus, components can
be fabricated with close dimensional tIolerances,
The technique is
restricted to relatively simple shapes but a similar process, hot