Figure 11. (a)Tan (δ) vs. Log (N) graph for the 6AL10b and 6CFRP10b specimens, (b) Stiffness reduction vs normalized cycle graph for 6AL10b and 6CFRP10b specimens

Figure 12 shows the effect of impact energy on the damping ratio for the 9AL10b specimen. Increasing impact energy increased the damping ratio while increasing cycles to failure decreased the damping ratio. After 100 cycles, when the stable region starts, the reduction in the damping ratio of damaged specimens (5 Joules and 10 Joules) was less compared to the undamaged specimen.
Damping ratio of undamaged specimens was lower than that of damaged specimens (Figure 10). The reason for this may be that undamaged structure transmits vibration more 32.