Effect of cross-section and discontinuities on damping enhancement in composites: An experimental study

Damping in structures is an important aspect from the vibration control and dynamic stability point of views. These days, significant emphasis is placed on the damping in composite structures due to involvement of different mechanisms for controlling damping at micro (fibre-matrix interface, fibre orientation etc.) and macro levels (fibre orientation, stacking sequence etc.) under dynamic loading. This study scrutinizes the specimen cross-sectional effect on the damping capacity of hollow tubes. For this purpose, carbon fibre reinforced tubes of square and hexagonal cross-sections were investigated. To improve the damping capacity further, circular holes were drilled at different positions along the tube. Free vibration and base excitation tests were performed to induce vibration in tubes and responses at different locations (i.e., along the tube length) were recorded using accelerometers and strain gauges. It is observed from the experimental results that the damping ratio increases in presence of holes in tube specimens. Further, damping enhancement is found to be more for tubes containing smaller holes (owing to more localized stresses) in comparison to the tubes containing larger holes. Typically, damping of hexagonal tubes is found to be slightly less in comparison to the square tube.