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Spencer, Graham Thornton

Mechanical Engineering

2006

MS

Advancements in composite materials technologies have made a significant contribution to the development of high-efficiency, or "green" technologies. Specifically, more efficient means of transmitting shaft power have been developed through the use of fiberreinforced composite materials for military and aerospace applications. These carbon fiber and carbon/glass reinforced shafts are capable of operating at higher speeds, over longer spans at a fraction of the weight of their steel counterparts. Their implementation into mainstream automotive power transmission applications has been relatively slow to emerge, however. Drive shafts used commonly on cars, trucks and busses are typically manufactured from steel owing to well understood dynamic behavior and low cost of manufacture. Recent advancements in the economical manufacturing of tubular composites and fiber cost reductions have presented new opportunities for the automotive composite drive shaft. This research is dedicated to better understanding the dynamic behavior and structural optimization for composite shafts, and will advance their transition into mainstream automotive applications, offering the potential for significant reduced energy consumption in the coming years.
Lateral and torsional vibrations are a concern with all shaft systems, particularly with the higher speeds and longer spans that composite shafts have made possible. Despite the excellent fatigue properties of carbon fiber, vibrations from a poorly designed drive shaft may cause damage to bearings, couplers, gear teeth and contribute to noise complaints in cars and trucks. Often these vibrations are controlled by ensuring that the shaft has sufficient bending and torsional stiffness to prevent resonance from occurring within the operating speed range. The composite shaft laminate requires strategically oriented fiber layers throughout to handle torsional loads, buckling torque and torsional/lateral vibrations. A holistic understanding of the interactions of mass-elastic properties is necessary to achieve a reliable shaft system. This research employs three-dimensional classical lamination theory along with vibration analysis to model and characterize the dynamic response of a composite drive shaft system.