Extension-Twist Coupled Graphite/Epoxy Composite Driveshafts for Gear-Mesh Vibration Suppression

It is well known that periodic tooth meshing stiffness variations are a significant source of torsional vibration and parametric instability in geared power transmission systems. This paper explores the use of a Graphite/Epoxy (Gr/Ep) composite shaft with dynamically tailored extension-twist (ET) coupling and viscoelastic material (VEM) core aimed at suppressing the gear mesh induced instabilities. Through structural tailoring of the Gr/Ep-VEM shaft ply angles and VEM core thickness, this study demonstrates that coupled gear-shaft modal interactions can be enhanced resulting in the introduction of significant damping into gear mesh mode vibrations and increased stability margin. For a given level of extension-twist coupling there is an optimal VEM core thickness that maximizes the modal energy exchange where the highly damped VEM core become dynamically linked with the gear mesh mode increasing the stability margin by roughly a factor of 2.