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.