A Case Study: Results and discussion

Similarly, the mechanical impedances for plies 2, 3 and 4 are shown in Figures 28.3 to 28.5. Perusal of Figures 28.2 to 28.5 suggests a general decrease in impedance response in all the elements across the plies due to delamination. This loss in response is the reflection of loss of stiffness in the locality of damage represented by various elements of the laminate. The loss of stiffness in damaged element results in increased velocity of vibration of the particles in the vicinity of damage, resulting in a drop of mechanical impedance response for an applied force at the centre of the plate. It is also observed that the impedance response is fairly prominent in the lower frequency range and it goes on diminishing with increase in the frequency.

Figure 28.3 (a) Mechanical impedance for damage in element 1 of ply 2

Figure 28.3 (b) Mechanical impedance for damage in element 2 of ply 2