Optimization of natural frequency of laminated composite rudder

Abstract

[Objectives] A rudder structure will inevitably vibrate while a ship is at sea. This is why it is necessary to make the first order natural frequency and working frequency of a rudder staggered through reasonable design.[Methods] This paper discusses the problem of optimization for the first order natural frequency of composite rudders in 3 aspects. Finite element software ABAQUS is used to build a simulated model of a composite rudder. Initial design parameters are provided to calculate the natural frequency. Ten types of skeleton layouts are designed and compared with each other, and an optimized design is obtained. Then, with the help of Isight software, the gradient optimization algorithm NLPQL is used to optimize the thickness of the skeleton and the LSGRG algorithm is used to obtain the optimal fiber orientation ply thicknesses. Finally, 10 types of ply sequence are designed.[Results] The results show that the first order natural frequency of the rudder is increased by 169.19% and its weight decreased by 16.63%.[Conclusions] The ideas and methods proposed in this paper are feasible for the optimization of the first natural frequency of a composite rudder, and a satisfactory design scheme can be obtained.

Keywords

• composite rudder
• natural frequency
• gradient algorithm