Page 113 - Fiber Fracture

98 M.-H. Berger

Fig. 11. Detail of a failure surface of Nextel 610 fibre broken in tension at room temperature. The arrow
indicates the crack initiation defect surrounded by a mirror zone.

Fig. 12. Typical tensile fracture morphology of a pure alumina fibre at high temperature (Fiber FP at
1300°C). Fracture occurs by the coalescence of microcracks leading to a non-flat fracture surface.

which is five times smaller than in the other two fibres. Damage occurs by the growth
of cavities at triple points and the coalescence of intergranular microcracks (Fig. 12)
induces a non-flat failure (Fig. 13). The times to failure in creep are considerably
reduced in the Almax fibre by the build-up of large intergranular pores.
These three fibres are stiff and chemically stable. They can therefore be used to
reinforce matrices, such as light alloys, working in intermediate temperature ranges,
or for applications at higher temperatures, but for which no load bearing capacity is