TOOLED THICK COMPOSITES by ARVEN H. SAUNDERS III ...
TOOLED THICK COMPOSITES by ARVEN H. SAUNDERS III ...
TOOLED THICK COMPOSITES by ARVEN H. SAUNDERS III ...
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S<br />
ii<br />
2<br />
f<br />
r<br />
=<br />
4k<br />
ii<br />
( 1−<br />
V<br />
where rf is the fiber diameter (m) and Vf is the fiber volume fraction. Figure 3.3 portrays the<br />
permeability as a function of Vf.<br />
Sii (square meters)<br />
3.0E-12<br />
2.5E-12<br />
2.0E-12<br />
1.5E-12<br />
1.0E-12<br />
5.0E-13<br />
0.0E+00<br />
29<br />
V<br />
Permeability<br />
0.45 0.5 0.55 0.6 0.65 0.7 0.75<br />
Fiber Volume Fraction<br />
Figure 3.3. Permeability as a Function of Fiber Volume Fraction.<br />
Gebart [1992] also proposed expressions for both longitudinal and transverse permeability<br />
which have been adopted in the model. The principal permeability directions are longitudinal<br />
(along the fiber direction) as given <strong>by</strong><br />
K<br />
l<br />
2<br />
f<br />
8r ( 1−<br />
V<br />
=<br />
gV<br />
and transverse (90° to fiber direction), as is sim ilarly given <strong>by</strong><br />
K<br />
t<br />
⎛<br />
= C⎜<br />
⎜<br />
⎝<br />
V<br />
f max<br />
V<br />
f<br />
f<br />
f<br />
f<br />
f<br />
)<br />
)<br />
3<br />
3<br />
5 / 2<br />
⎞<br />
−1⎟<br />
rf<br />
⎟<br />
⎠<br />
where Vf is the fiber volume fraction, rf is the fiber diameter (m), and g is a constant. Values<br />
used are rf = 5µm for IM7 fibers, Vfmax=0.785, C= 0.4, and g= 57.<br />
2
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