COMPARATIVE STUDY FOR THE DESIGN OF OPTIMAL COMPOSITE PRESSURE VESSELS

Abstract

Filament wound composite pressure vessels have been used in aerospace applications since long and in recent past this technology has been adopted for the development of commercial products such as pressure vessels, pipes, sporting goods and high strength products of mostly axi-symmetric profiles. Attributed to the manufacturing technology from which these products are developed, special design schemes and theories have been devised for the design purposes. Pressure vessels are one of these products which are designed with special attention to the filament winding process. Cylindrical pressure vessels consist of a cylindrical portion and dome regions (end caps). A proper design would require a structure of uniform strength with loads evenly distributed in the dome region. The dome regions require that along their contours, stresses remain constant and hence derive their name isotensoid. The most common design theory comes from Netting Analysis procedure in which it is assumed that only fibers carry the loads. This procedure is easy and simple to use but shows a decrease in volume of the dome region and an increase in structural weight compared to a technique derived from optimal design concept. A comparative study for both netting analysis and optimal design procedures is presented and a trial design is then calculated and analyzed in ANSYS. Special attention is given to the dome region where stress field varies with varying winding angles. The dome profile though was designed with monotropic property but after analyzing the structure in ANSYS it was observed that with transversely isotropic assignment, the dome still exhibited isotensoid behavior. The dome contours are classified as ellipsoid and hence elliptic integrals were used for generation of dome profiles. These profiles produced domes with varying thicknesses and wind angles