Optimization of the base frequency of cylindrical stiffened composite shells with internal fluid

Subject Areas : Vibration Transmision

Jafar Eskandari Jam ¹ , Mohamad Ali Nikjoo ²

1 - Composite Materials and Technology Center, MUT, Tehran, Iran
2 - Composite Materials and Technology Center, MUT, Tehran, Iran

Received: 2015-04-20 Accepted : 2015-04-20 Published : 2011-05-22

Keywords: Genetic Algorithm, stiffener, Ring, stringer,

Abstract :

The free vibration of cylindrical composite shell with internal liquid is studied in this paper. The shell composed of several layers and stiffeners which are rings and stringers. The first order shear theory was used for shell and stiffeners. Stiffeners were used in equations as discrete elements. The Raily-Ritz method was used for solving the problem. This method is based on minimum potential energy principle. The potential and kinetic energy of shell and each stiffeners and kinetic energy of liquid are subsituted in the functional of energy. The section shape of each stiffener is rectangle. The liquid is ideal and sloshing was neglected. For caching the best and the biggest natural base frequencies, shell and stiffeners were optimized by genetic algorithm. With use of genetic algorithm the best fiber angles of each layer of composite were obtained to reach the maximum base frequency, also best ratio of height to width was obtained and in last the number of rings and stringers and theirs height to width ratio were obtained to reach the optimized stiffened shell with highest base frequency.