Design and Numerical Analysis of Composite Pressure Vessel based on Unit Load Method

The present work is aimed to design of type ІV composite pressure vessels for storing compressed natural gas (CNG) that used in bi-fuel vehicle based on finite element method. This type of vessels consisting of polymer liner with reinforcement fiber that wounded over the liner by filament wounding method. Dimensions and pressure of CNG pressure vessel in this paper are similar to the same in ISO 11439 standard. The propose of design is to find fiber angles, number of layers and thickness of vessel. In this paper, different hemispherical, semi-ellipsoidal and torispherical domes is considered for vessel. This design is based on BS 4994 standard and unit load method. The vessel simulated in 3-D (1/8 model) with Solid 46 element type using commercial ANSYS software. In order to verify finite element method (FEM), result compare with result of other results reported in literatures. Composite damage is considered based on maximum strain and Tsai-Wu criterions. Consideration showed that the first design needs modification, because of ignoring effects of stress concentration effects and bending stress. Redesign done with increase of layers based on try and error in FEM. Finally a ±9/90 laminate is used in flament wound pressure vessels with 20 MPa as working pressure and 1000 cycle as fatigue life.