Effect of delamination introduced in different layers (Type A and B)
Velocity magnitude vs frequency plots for healthy and delaminated specimens were obtained with delaminations introduced in middle layer and in the offset layer of the four ply laminates of different orientations. Two such plots are presented in Figure 40.4 and 40.5 for comparing the responses of healthy and Delam Type-I plate specimens. It is observed that velocity magnitude is quite high in comparison to the healthy ply for 00 plies as well as for 900 plies when delamination is introduced in the middle layer (Type A). A decrease in velocity magnitude is observed in the case of delamination in offset layer (Type B) for both the cases of delamination i.e. Delam Type-I and Delam Type-II.
Figure 40.4: Comparison of velocity amplitude for 00 plies with delamination
Figure 40.5: Comparison of velocity amplitude for 900 plies with delamination
A good damping is observed in both the types of delaminations for all the ply orientations if the delamination is introduced in the middle layer. A decrease in damping behavior is observed in 00 ply laminate while fairly good damping is observed in 900 plies in case of delamination in the offset layer (Type B). Summary of modal damping changes in the healthy and the delaminated specimens when delamination is introduced in middle and offset layers are presented in Table 40.2.
Table 40.2 Summary of modal damping changes in healthy and delaminated specimen
