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This paper demonstrates the experimental result of changeable pitch propellers in composite material. The use of this composite material is to apply its characteristic of bend-twist coupling; this characteristic is applied to better performance design requirements of the propeller. Two stacking sequences are considered: the first one is a quasi isotropic sequence, while the second one is an optimum sequence obtained using a genetic algorithm. Experiments are designed considering two original propellers manufactured by the first and the second stacking sequence, respectively, and a pre-deformed propeller with the second sequence. Experimental results correspond to the same trend as the calculations and confirm the method of optimization.

The material and ply angles of a fiber-reinforced plastic (FRP) rotor blade of a helicopter are optimized using a genetic algorithm (GA) with local search. The variation of the structural stiffness with material and ply angle is investigated. The aim of the optimization is to find an optimal stacking sequence that minimizes twist deformation. An optimum rotor blade is obtained using the ply angles as variables; failure, natural frequency, and minimum moment of inertia are used to constrain the optimization. The GA is employed as an optimization tool. A simplified local search is implemented in the final stage of optimization to reduce the searching time.

Traditional propellers are made of high-stiffness metal material. They deform only slightly and are usually designed to work at a constant speed, operating at reduced efficiency at other speeds. This research designs a composite propeller that operates over a wider range of speeds. The deformation of propeller is determined by orientating fibers to produce propellers that are more efficient than those made of metal. First, structural and fluid dynamic calculations are performed to determine the deformation, the fluid pressure, and the performance of the propeller. An optimizing genetic algorithm is then used to determine the best stacking sequence of the propeller; however, if the optimal stacking sequence does not outperform a metal propeller, a predeformed design is then used to solve this problem. A smallest pitch stacking sequence is obtained using a genetic algorithm first, and then the propeller is displaced in the opposite direction to form a predeformed propeller. The predeformed propelle...

Some optimization methods have recently been developed to deal with discrete variable problems such as that involving the ply angles and stacking sequence of composite laminates. However, much calculation is still required for the algorithms. A regression equation of the response surface would allow the finite element analysis to be replaced with the regression equation, saving much time in optimization design. The response surface of composite laminated structures is estimated using regression analysis in this study. The information of the surface can be obtained quickly and accurately. Usually, simple polynomials are used as base functions in regression, but the results obtained unsatisfactory in this work. Considering the periodic and directional property of the design variables (ply angles), trigonometric functions are used as base functions in regression and they fit the surface very well. According to the characteristics of ply angle and trigonometric function, the value of variable can be chosen to smoothen the response surface, greatly increasing the accuracy of the regression. This study first establishes the regression procedure, and then applies it to examples of a marine propeller and a rotor wing. The regression is used with a genetic algorithm to search for optimum ply angles in the examples, saving much time while maintaining accuracy.

The present study employs a numerical approach to investigate the post-buckling behavior of laminates connected by rivets. In order to reduce the calculation time, the rivets are replaced with springs, while the stiffness of the springs is induced from the study that analyzes the bending behavior and the interaction between the rivet and the laminate. The finite element software ABAQUS is used to inspect the post-buckling behavior of composite laminates connected by rivets. Several parameters are considered like the stacking sequence, the arrangement of the rivets, and the span between the stiffener. In all these cases, springs can fully present the behavior around the rivets. Finally, the validity of this method is verified by experiment.