Decomposition-based optimization procedure for high-speed prop-rotors using composite tailoring

A multilevel optimization procedure is developed to investigate the effect of changes in blade planform and composite tailoring on blade aerodynamic and structural performance of prop-rotor aircraft. Both high-speed cruise and hover performance are considered simultaneously. A composite box beam model is used to represent the principal load carrying member in the rotor blade. The upper level objective is to simultaneously maximize the high-speed cruise propulsive efficiency and the hover figure of merit using planform design variables. Constraints are imposed on other aerodynamic performance requirements and also on the physical dimensions of the blade. The lower-level objective is to reduce the critical tip displacements in both hover and cruise using composite tailoring. Optimization is performed using a nonlinear programming approach in the upper level and integer programming technique in the lower level. Optimum designs are compared with the XV-15 rotor blade performance at 300 kn, which is used as a baseline or reference design, and also with the results obtained from a purely aerodynamic optimization procedure. The results show significant improvements in both the aerodynamic and structural performance.