Materials for rotationally dynamic components: rationale for higher performance rotor-blade design

The design of rotating components demands a good understanding of the effect on materials under dynamic stress conditions. Depending on the operating conditions, the components have to possess appropriate stiffness and strength properties to ensure stresses are kept within acceptable limits, and geometrical stability is maintained to ensure correct functioning. The loads may also fluctuate throughout the rotational cycle, inducing fatigue in the component. In addition, any adverse effects of environmental impact have to be taken into consideration. The design is clearly complicated and utilising the most appropriate material or materials is challenging. This paper discusses the design decision-making involved for a rotationally dynamic component using the example of a helicopter rotor blade. The specification and outline design provide the context for evaluating and comparing metallic and composite constructions.