Publication

Abstract : It is required that structures must safely work during its service life. But, damages initiate a breakdown period on the structures. Cracks are among the most encountered damage types in the structures. 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 plays an important role for structural health monitoring applications. Delamination is the separation of layers which are bonded together in composite laminate. In the case of bending loads delamination usually leads to significant loss of bending stiffness and strength. Therefore it is important to detect the presents of delamination at an early stage. The delamination causes reduction of stiffness and thereby the modal frequencies also change. In order to find the damage location and size present in the composite materials, we have to determine changes in modal frequencies of the damaged structure as a function of the damage parameters such as delamination and crack location, size, interface at which it is present. In this work modal analysis is used to determine the crack and delamination in the composite structure. This is done by creating a four layer multi directional laminate of E-Glass /Epoxy in the lamination code of 90/0/0/90 in ANSYS. A parametric study is conducted by varying location, width and length of the crack and delamination.The change in frequency of undamaged and damaged shows that the natural frequency is affected by delamination and crack. The results are validated with experimental modal analysis. From the results, a reverse design process is implemented for finding the damage location at a particular natural frequency.