Comparison of the modal frequencies

Changes in modal frequencies of delaminated specimens are presented in comparison to the healthy laminate in percentage term in Figure 38.4 (a). It is evident that percentage decrease in first four modal frequencies in Delam Type-II is higher than in Delam Type-I. A frequency decrease of the order of 15 and 22 per cent in Delam Type-II for first and second bending mode is observed with respect to healthy laminate.

Figure 38.4 (a) Change in modal frequency with respect to the healthy laminate (0^o plies)