Page 99 - Fiber Fracture

84 A.R. Bunsell

h
2 2.0
9.
% 1.5
c
!?!
c
cn
a, 1.0
-
.-
cn
c 0.5 t 0 NLM202 b
Hi-Nicalon
0.0 I
0 200 400 600 800 1000 1200 1400

Tern pe rat u re ("C)

Fig. 10. Strength as a function of temperature in air revealing the greater resistance of the Hi-Nicalon fibre
compared to other fibres which contain oxygen-rich intergranular phases.

fibres so that the Tyranno LOX-E fibre has a Young modulus of 199 GPa and the
Hi-Nicalon a value of 263 GPa. The strengths of these fibres are shown in Fig. 10 as
a function of temperature. It can be seen that the Hi-Nicalon fibres maintained their
strengths up to 1200°C in air whilst the other fibres which contained more oxygen
and hence a greater amount of intergranular amorphous phase lost strength at lower
temperatures (Berger et al., 1997).

Hi-Nic.
0.5 -- LOX-E
0.15 GPa
o= I I I p.17 GPg I
I
I
0 20000 40000 60000 80000 I00000 120000 140000
Time (s)
Fig. 11. The Hi-Nicalon fibre shows lower creep rates than does the Tyranno LOX-E fibre because of the
absence of an oxygen-rich intergranular phase.