Conclusions

The voltage responses are compared both for healthy and damaged composite laminates for the chosen configurations. All the elements have shown decrease in voltage at the point of damage. Configuration 1 chosen for numerical analysis is symmetric about the vertical line and Configuration 2 has a diagonal symmetry. This symmetry is reflected in the voltage profiles of the healthy and the damaged laminates. Elements which are symmetrically located with respect to each other have similar voltage responses. Delamination simulated in a particular element causes redistribution of the stresses in the nearby elements. The stress increase in nearby elements depends on their respective orientations. The redistribution of stresses in case of delamination in a particular element is not very prominent in Configuration 1 as all other elements are sharing incremental load due to symmetrical arrangement of the elements. However, in Configuration 2, delamination introduced in elements situated close to the centre of the composite plate results in sharp increase in stresses in nearby elements as elements located away from the centre seems to receive little increase in redistributed load.

Mechanical impedance responses are also compared for both healthy and damaged composite plates. A general decrease in impedance response for elements with damage is observed in comparison to the healthy ones. Delamination leads to loss of stiffness in the locality of damage and thus, changes in the dynamic response of the laminate. The loss of stiffness in damaged element results in increased velocity of vibration of the particles in the vicinity of the damage, resulting in drop of mechanical impedance response for an applied force at the centre of the plate. Mechanical impedance responses are fairly prominent in lower frequency range and they go on diminishing with increase in the frequency. Shift in peaks to lower frequency values and presence of additional local peaks in low frequency range are also predicted in delaminated composite plates.

A knowledge based database is created for ribbon reinforced composite for detection of damages and monitoring of the severity, type and location of damage using piezoelectric sensory layer. The results of dynamic analysis presented here can be helpful in efficient damage diagnosis of composite structures. Voltage response from piezoelectric sensory layer and its mechanical impedance response can provide vital information regarding the state of the structure on real time basis.