Structural Stability

Buckling Instability of Deployable Propeller Blades

Deployable propeller blades can be collapsed and folded or rolled up during storage and launching, and self-deploy during operation. To utilize deployable blades for propellers, sufficient pre-buckling stiffness to resist aerodynamic loads but compliant behavior after buckling are necessary. Consequently, predicting and characterizing the bending stiffness and propagation moment is important for structural design. While buckling of thin-shells with uniform curvatures have been studied, the behavior of non-uniformly curved thin-shells is not well understood. This paper presents experimental and numerical modeling studies of deployable propeller blades, which have non-uniform transverse curvature and twist along the blade span. A rotation-controlled bending apparatus is employed to probe the instability response of deployable propeller blades under pure bending. Multi-axis sensors are utilized in this developed experimental testing to capture the multi-axial forces and moments resulted from the asymmetric geometry. The top skin of deployable blade is studied first for buckling behavior. Then two deployable blade designs, with and without a reinforcing internal deployable spar, are studied for their pre-buckling stiffness, buckling load, and buckle propagation moment.