Numerical and experimental investigations on vibration of delaminated composite shell

Abstract

The laminated composite shell structures are acting as most desired structure in various field of modern engineering. These are frequently used in various industries such as aerospace, construction, nuclear field, automotive, petrochemical industries, ship & rocket building due to high specific strength and stiffness of composite materials. Because of their ability to meet the design requirements of strength & stiffness, composite materials have greater importance in recent years. But during the manufacturing and service life, there will be delamination damage in composite laminate which is not visible due to embedded within the composite structures. However it reduces the strength and stiffness of the laminated structures and also effects on the vibration characteristics of the structures. The present work deals with the numerical and experimental investigation on free vibration characteristics of delaminated composite cylindrical shell. Experimental setup and procedure of the modal testing were described. Fabrication procedure of the shell was also described. Natural frequencies were determined using a computer programme in MATLAB environment based on finite element method (FEM). The results using the present formulation were compared with other existing literature. Also comparison was made between the experimental values and numerical predictions using FEM. The effects of percentage delamination on natural frequency of the composite shell were studied. The influence of various parameters i.e. curvature, delamination area, ply lay-up and aspect ratio on vibration response were discussed for different boundary conditions.