Hybrid metal/composite automobile propeller shaft

Abstract

Propeller shafts are automobile powertrain parts transmitting the engine torque to the wheels of rear wheel drive cars. To avoid whirling vibration of the propeller shaft, its fundamental bending natural frequency has to exceed the maximum rotational speed of the shaft. Also, the NVH (Noise, Vibration and Harshness) characteristics can be improved by incorporating elevated damping characteristics. To develop a propeller shaft meeting the frequency requirement with increased damping and robustness compared to pure composite shafts, a metal shaft is reinforced with composite material inside, where the inner composite material increases the natural frequency, while the outer metal bears the transmitted torque and protects the composite against impact loading, chemicals and moisture. Usually, the composite inside is laminated and subsequently co-cure bonded to the outer metal shaft in an autoclave. This process, however, requires a long processing time and makes automation unrealizable due to complicated handling of the composite prepreg inside the metal shaft and the requires the application of vacuum bags. Moreover, autoclave-curing is ineffective in terms of energy requirements and initial costs for equipment. This study concentrates on the development of an automatable production process basing on a novel out-of-autoclave method to produce the metal/composite propeller shaft with increased productivity. The requirements for the propeller shaft production process were investigated based on expert consultations. The adaptability of the production process was ensured by the investigation of design parameters in the shaft design and possible improvement approaches to the hybrid propeller shaft design. The developed out-of-autoclave curing method was experimentally tested and evaluated.