A comparison of two cocured damped composite torsion shafts

Abstract

Cocuring layers of viscoelastic damping materials with composite material systems offers the possibility of manufacturing light-weight, stiff, highly damped structural components. The objective of this work was to design two cocured damped composite torsion shafts and compare their respective performances. The first shaft uses the extension-twist coupling mechanism of off-angle composite materials to enhance the performance of a damping material. The second shaft uses a constraining layer embedded inside the shaft that floats between two layers of damping material. Finite element analysis was used to determine optimal damping material shear modulus and ply orientation to maximize shaft imaginary stiffness. Four shafts in total (two of each type) were built and modal tests were performed. Torsion damping increased by factors of 5.8 to 20.0 and 6.1 to 10.9 over the undamped case for the extension-twist and floating constraining layer dampers, respectively. While both damping concepts provide significant levels of damping, the performance of each was hindered due to the increase in shear modulus of the damping material as it was cocured with the composite material.