Structural damage detection has gained increasing attention from the scientific community since unpredicted major hazards, most with human losses, have been reported .Modal analysis was performed on a composite cantilever plate with a small crack, using finite element analysis. Modal parameters such as natural frequencies, displacement mode shapes were calculated against cracking in the plate. It was found that the crack in the structure will affect most of the modal parameters, such as the natural frequencies of the structure and mode shapes. Structures are weakened by cracks. When the crack size increases in course of time, the structure becomes weaker than its previous condition. Finally, the structure may breakdown due to a minute crack. Therefore, crack detection and classification is a very important issue. In this study free vibration analysis of a cracked plate was performed in order to identify the crack in a cantilever plate. The study results suggest that free vibration analysis provides suitable information for the detection of cracks. In the present study, vibration analysis is carried out on a cantilever plate with a crack, to study the response characteristics and damage identification is based on the damage index method. Suitable boundary conditions are used to find out natural frequency and mode shapes. The simulations have done with the help of ANSYS software. The importance of using damage patterns from the damage index method is that only measured mode shapes are required in the damage identification. The results shows, the damage index based method is capable of identification of damage and severity of damage in a structure.

Keywords:Structural damage, natural frequencies, displacement mode shapes, damage index method, free vibration analysis