| Advanced composite rotors such as propellers, turbines, and jet engines have become increasingly popular as an alternative to traditional metallic rotors. It has been shown that by exploiting the intrinsic anisotropy and resulting bend-twist coupling characteristics of the material, advanced composite rotor blades can be tailored to allow automatic, passive, three-dimensional adaptive/morphing capabilities such that they outperform their rigid counterparts both hydrodynamically and structurally. The load-dependent deformation responses of adaptive blades, however, make the design and analysis of these structures highly non-trivial, as performance is affected by changes in operating conditions as well as material and geometric uncertainties. The objective of this work is to improve the current understanding of the transient responses and failure mechanisms of adaptive composite marine structures while considering the effects of material, geometric, and loading uncertainties. Adaptive composite propellers are evaluated under both steady and unsteady operating conditions; their response and performance are compared with their rigid metallic counterparts. A novel, probabilistic-based global design and optimization strategy for both rigid and adaptive composite marine rotors is developed and implemented. The method considers hydrodynamic and structural performance across a probabilistic operational space based on expected ship advance speeds, sea conditions, and thrust requirements dictated by the vessel. This method can improve the design of rigid structures, and it is necessary for adaptive structures because the load-dependent fluid-structure interaction (FSI) response depends on the required operating conditions. To demonstrate the method, it is applied for the design and analysis of two metallic and composite propellers for a twin-shafted naval combatant craft. The corresponding damage tolerance levels and safe operating envelopes for both hydrodynamic and structural performance requirements are discussed. It is shown herein that, through proper design, an adaptive composite propeller can provide improved performance over its rigid counterpart across the expected range of operating conditions. While the proposed framework is demonstrated for marine propellers, the probabilistic-based design and analysis methodology can be generally applied for any marine, aerospace, or wind energy structure that must operate in a wide range of loading conditions for which the performance depends on its FSI response. |
