A Design Study of Thick Multilayered Composite Spherical Pressure Vessels

Abstract

A design study of a multilayered spherical composite pressure vessel is presented. Layers of the vessel are composed of quasi-isotropic lay-ups of composite laminae. For the stress analysis layers are assumed to be homogeneous, having the three- dimensional properties equivalent to that of the quasi-isotropic laminates. The linear theory of elasticity is employed so that the analysis is not limited to any thickness of the vessel. The Tsai Wu failure criterion is found suitable for the strength analysis. Based on coupon tests, the value of interaction term F*yz of the failure criterion is found approx imately to be - 0.84. The failure criterion is applied to each lamina using the lamina con stitutive law and lamination angle. It is found that the first-ply-failure (FPF) controls the final failure. Further, a design study of a spherical vessel for operating at 200 MPa of in ternal pressure is presented. In view of current manufacturing difficulties a design restric tion of b/a ≤ 1.25 (b: outer radius, a: inner radius) was imposed for this design. How ever, a two-layered hybrid sphere of b/a = 1.25 with T300/5208 and IM6/epoxy outside is considered to be an acceptable design. The test data of two vessels are also reported in this study.