Development of a Quasi-Static Span-Extending Blade Tip for a Morphing Helicopter Rotor

This work presents the design and validation results for a quasi-static morphing helicopter rotor blade with an adaptive tip. The adaptive tip can increase its local span by 100% while maintaining a constant chord, effectively doubling the airfoil area of the morphing section leading to an overall increase in the full rotor radius. The technology components include a morphing honeycomb-like core structure that has a Poisson's ratio of zero as it extends and an elastomer-matrix-composite skin that is bonded to the core structure. Design analyses along with experimental validation on hardware specimens are presented. The validated model is used in a numerical optimization to design a system that will self-actuate under a rotor's normal operating conditions. Feasibility of the design is demonstrated in terms of hardware fabrication methods and overall performance to satisfy system design goals.