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Development of a constrained layer surface damping treatment with optimized spacer geometry for plates

Ulubalcı, Barkan
For aviation applications, the noise and vibration cancellation is so important that there are many damping methods and applications used in the field. In military configurations the weight and the visual elegance is not so important that even a blanket may solve the problem. In civil configurations, on the other hand, there should be a lightweight solution for vibration damping. For this reason, since shell structures are widely used on aerospace applications, it is common to use surface damping solutions on aircrafts. Because, surface damping treatments are generally used on shell structures, such as plates and beams, where transverse vibrations problems are critical and resonant frequency vibrations are dominant in a wide broadband due to low thickness. In this thesis study, different novel designs for surface damping treatments are studied and compared by means of their effectiveness. A fuselage like structure is designed and validated by finite element modelling and by experimental results in order to estimate the damping solution effect on application point. Furthermore, due to broadband random vibrations induced on fuselage geometry, a metric is suggested considering the loading condition in order to estimate damping effectiveness. In literature it is seen that in order to increase damping performance, a layer with reduced density and elastic modulus, a spacer layer, is added to the surface damping treatments. By this spacer layer addition, the viscoelastic layer can be shifted away from neutral axis which increases the induced shear strain hence damping performance. Due to high performance low additional weight, standoff damping treatment, a slotted and a sophisticated version of space layered surface damping treatments, is generally used in aerospace structures. With the help of literature and previously optimized spacer geometries for beams, six novel designs are suggested through finite element models and their damping effectiveness are compared with commonly used configurations and adapted versions.