(A) study on the smart cure method and joining method of the automotive co-cured hybrid aluminum/composite propeller shaft

Abstract

The composite propeller shaft has many benefits such as reduced weight, less noise and vibration. However, because of the high material cost of carbon fiber epoxy composite materials, rather inexpensive aluminum materials may be used combined partly with composite materials to make a hybrid type aluminum/composite propeller shaft, in which the aluminum has a role to transmit the required torque, while the carbon fiber epoxy composite increases the bending natural frequency above 9200 rpm. To establish reliable hybrid structures, the co-cure joining method for hybrid structures is attractive because the co-cure joining between a composite adherend and a metallic adherend is realized using excess resin extracted from the composite prepreg during the curing process of the composite, which eliminates the separate joining process. However, sophisticated joining technology between metal and composite is required and large fabricational thermal residual stresses may be generated during co-cure joining process due to the difference of coefficient of thermal expansion (CTE) between metallic and composite adherends. The fabricational thermal residual stress decreases much the fatigue life and dimensional accuracy of hybrid structures. Also, the hybrid propeller shaft requires a reliable joining method for the hybrid shaft to the steel or aluminum yoke of universal joint, which is often the most difficult task. Therefore, in this study, to obtain more reliable and robust hybrid propeller shafts, smart cure method and smart curing system using a dielectrometry were devised to decrease or eliminate the fabricational thermal residual stress of co-cure bonded hybrid metal/composite structure. Also, press fit joining method between hybrid aluminum/composite shaft and metal yoke was devised. Finally, the hybrid aluminum/composite propeller shaft was designed and manufactured and the performance of the propeller shaft was tested.