16 V. Ayyagari et al. Fig. 4 Pressure decay test schematic Experimental Results Three specimens with the desired test geometry were fabricated and tested, as well as another two specimens that had slightly thicker polymer support, The resulting variation of pressure with time for one of the specimens with the thinner polymer supports is shown inFigure 5. The pressure decay test started at 50 PSI and was held for 10 minutes before being increased in 25 psi steps holding 10 minutes between steps, and was carried out at 25 PSI increments. At each pressure level, the UUT was shut off from the pump to obtain the pressure decay rate. At 275 psi, a water droplet was observed on the outer surface of the specimen at the metal wire/polymer matrix interface, indicating leakage, which was considered a catastrophic failure and ended the test. A similar testing protocol was carried out on two other specimens and three samples of coupon2 and the pressure decay rate at each pressure level is reported in Figure 6. As seen from the figure, until 150 PSI, the pressure decay rate stays relatively constant. However, the decay rate increases significantly with further increases in pressure above 150 PSI. This transition point at 150 PSI indicates that it should be considered the pressure limit. Additionally, the decay rates are different for each step above 150 PSI, which could potentially be attributed to the number of failure locations, since there are multiple metal wire/polymer support interfaces. For the second specimen geometry, the pressure decay rate transition Fig. 5 Pressure decay test on the first sample from coupon 1, coupon-1-1
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