Table 4-4. Permeability of textile composites for various number of cryogenic cycles.
 Logarithm
 Specimen Cryogenic Permeance, P Permeability, P of
 cycles (mol/sec/m2/Pa) (mol/sec/m/Pa)
 Tl 0 4.79x10-18 7.30x10-21 -20.1
 1 6.77x10-18 1.03 x 1020 -20.0
 5 8.41x10-18 1.28x10-20 -19.9
 20 8.75x 10-18 1.33 x 10-20 -19.9

Table 4-5. Permeability of laminated composites embedded with nano-particles for
 various number of cryogenic cycles.
 Logarithm
 Specimen Cryogenic Permeance, P Permeability, P
 cycles (mol/sec/m2/Pa) (mol/sec/m/Pa)
 N1 0 6.82x10-18 1.04x10-20 -20.0
 1 2.72x10-15 4.15x10-18 -17.4
 5 1.30x10-14 1.98x10-17 -16.7
 20 9.83x10-15 1.50x10-17 -16.8


 The test results show the permeability increases as the number of cryogenic cycles

increases (see Figure 4-7). The permeability increased rapidly and becomes constant with

further increase of cryogenic cycles. For specimens C2 and C3, which have

approximately same thickness, the permeability of the specimen C3 was lower since the

specimen C3 has the plies dispersed and not grouped together compared to the specimen

C2.

 The textile specimen T maintained constant permeability with the increase of

cryogenic cycles. The textile composites resulted lower permeability than the laminated

composites.

 The specimen N1 has same layer stacking orientations with the specimen C5 and

nano-particles were dispersed between two 90-degree layers. Before cryogenic cycling,

the permeabilities of the specimens N1 and C5 were approximately the same. However,

as the number of cryogenic cycles increased, the permeability of the specimen N1