Recent studies of the high temperature consolidation of titanium alloy
coated a-alumina fiber lows and SiC monofilaments have both revealed
the widespread occurrence of fiber bending and fracture during early s
tage consolidation. This damage was shown to arise from the bending of
unaligned fibers during consolidation and was found to be affected by
the mechanical behavior of the metal-metal contacts al fiber crossove
rs. To predict the incidence of fiber fracture during early stage high
temperature consolidation, a time-temperature dependent micromechanic
al model incorporating the evolving contact geometry and mechanical be
havior of both the metal matrix and the ceramic fibers has been combin
ed with a statistical representation of crossovers in the pre-consolid
ated layup. The damage predictions are found to compare Favorably with
experimental results. The model has subsequently been used to explore
the effects of fiber strength, matrix constitutive properties and the
processing conditions upon the incidence of fiber Fracture. It reveal
s the existence of a temperature dependent pressurization rate below w
hich fracture is relatively unlikely. This critical pressure rate can
be significantly increased by the 'enhanced' superplasticity of the in
itially nanocrystalline coating. Copyright (C) 1997 Acta Metallurgica
Inc.