Design of Helicopter Main Drive Flexible Shaft with Hybrid Construction for Weight Reduction

With the advancement of lighter and stronger composite materials over the last decades, metal structures are being continuously replaced by them. Structural members are built with composites with new lamination technologies and the bonding techniques in order to form airframes. In the view of this, the focus of present paper is to look in to the aspect of weight reduction by replacing metallic shaft through composites. Several literatures have demonstrated different composite usage in industry. Drive shaft undergoes twisting moment, so generally unidirectional laminate is not preferred as they may undergo de-lamination during torque transmission.

In the present investigation, analytical calculations were done to find the stresses acting on present metallic flexible shaft. The cross section details and loads acting were obtained from literature survey. Numerical investigation was carried out for the metallic shaft and compared with analytical results. Further analysis was carried out by replacing the existing metallic shaft with woven fibre composites. Validation study for the methodology adopted in MSC NASTRAN was done by comparing the results with literature.

It was observed that the woven fabric in composite have better torque conversion than unidirectional fibres in composite. Metallic shaft was finally replaced by a hybrid construction of steel and woven carbon/epoxy laminate and analysed. Failure analysis was carried out and it was found to be safe under the loading conditions of flexible shaft. This type of construction resulted in around 55% weight reduction for the flexible shaft.