Multi-objective optimization of a composite rotor blade cross-section

This paper deals with the optimization of the ply angles and the internal geometry of a composite helicopter blade with a D-spar internal construction. The design involves the simultaneous optimization of several conflicting objectives such as: attaining three stiffness parameters, minimizing the blade mass and the distance between the mass-center and the aerodynamic-center. Optimization methods with a priori and a posteriori articulation of preferences are used to solve the problem. Among the a priori approaches, the min–max approach is used to transform multiple objective functions into a single criterion which is optimized with Particle Swarm Optimization (PSO). Alternatively, the design problem is tackled using a posteriori approach by using our in-house Non-dominated Sorting Hybrid Algorithm (NSHA). The results obtained with NSHA demonstrate trade-off designs which could not be captured with the min–max approach. The multi-objective approach allows identifying a window of 10% adjustment in mass and 20% adjustment in the distance between the mass center and the aerodynamic center with no significant deviation from the target stiffness vector. Furthermore, we have observed that the target stiffness vector can be attained more easily if the internal geometry, besides the ply angles, is considered as a design variable.