Figure 8. Loading ratio vs. cycles to failure graphs for the
(a) 6AL15b, (b) 6AL20b and (c) 9AL10b specimens
Figure 9 shows the fatigue test results for the 6CFRP10a, 6CFRP10b and
6CFRP10c specimens. It was seen that the specimen affected most by the
preliminary impact damage was 6CFRP10c with a face sheet material
thickness of 1.5 mm. The reason for this could be that increasing face
sheet thickness increased the preliminary damage resistance of the face
sheet, which caused more cores to be crushed. Cycles to failure values
determined in 6CFRP10b specimen damaged by 5 Joules of impact energy
diverged from the cycles to failure value of the undamaged specimen due
to the decreasing loading ratio. Loading ratio vs. cycles to failure
graph of specimens damaged by 10 Joules of energy corresponded to that
of the undamaged specimen.