Nondestructive testing of defects in adhesive joints

Elongation at Break
The elongation at break shows a decreasing trend with increasing irradiation dosage for
both rubbers with either precipitated or fumed silica figure 5(a). The rate of decrease in
elongation at break is higher in fluorocarbon when compared with silicone rubber. The
most interesting observation here is that EB curing shows very high elongation at break for
fluorocarbon and very low elongation at break of silicone rubber.
On comparison between types of cure the chemically cured silicone rubber shows higher
elongation at break when reinforced with precipitated silica and lower elongation at
Elongation at Break (%)
1600
1400
1200
1000
800
600
400
200
Q+Ppt Silica
Q+Fumed Silica
FKM+Ppt Silica
FKM+Fumed Silica
0
5 10 15 20 25
Irradiation dosage (MRads)
Elongation at Break (%)
600
500
400
300
200
100
0
EB Cure
Chemical Cure
Q+Ppt Silica Q+Fumed Silica FKM+Ppt Silica Q+Fumed Silica
Elastomer
Figure 5 (a): Variation in Elongation at Figure 5 (b): Comparison of lowest Elongation
Break (%) with increasing irradiation at Break (%) obtained of irradiated sample
dosage with other types of cure
break when reinforced with fumed silica (figure 5(b)). The changes are more prominent
with precipitated silica and only marginal with fumed silica. In the case of fluorocarbon the
elongation at break is higher than chemical cure when EB cured irrespective of type of
filler and the amount of increment also similar.
Electrical Properties
DC Volume Resistivity
The DC volume resistivity for all the rubbers shows marginal increase though not
substantial with increasing irradiation dosages for both the rubbers with the two different
fillers on EB cure. On chemical cure there is increase in resistivity only in the case of
silicon rubber with precipitated silica reinforcement while in all other cases there is
noticeable drop in resistivity by a small degree (figure 7).