0.95 --- -/ -
0.9
0.85 /r -
0.8 -- -
C 0.75-------- --- --- I-----
0.7 -
0.65 ------- ---- ---
0 .6 ------
0.55 ------- ---
0.5
0 1 2 3 4 5 6 7 8
Square Root of 'lme (sec1/2)
Figure 6-63. Two-dimensional correlation coefficient, R, for Defect A50 (Specimen A-2)
Specimen A-1
Only defects with diameters 12.7 mm or larger were considered in the analysis. A
plot of ATdef vs. t1/2 is provided in Figure 6-64. There is a distinct divergence between
ATdef and ATnonr for the perimeter of each defect area at t1/2 = 2. Ideally, the initial slopes
for the IB, A75, and A50 defects would be the same since F at the FRP/defect interface is
the same. Defect A50 does not line up with the others. It is also interesting to note how
the ATdef curves begin to level off as time increases. This is a result of two-dimensional
effects as the heat flows from the center of the defect towards the edges. The divergence
is most pronounced for the smaller defects. The epoxy-filled defects, E75 and E50,
follow a similar trend, but the initial slopes of the respective ATdef curves is less than
what was observed for the air-filled defects. This is a result ofF at the FRP/defect
interface being closer to 0 for the epoxy-filled defects.