Strength Analysis and Design of Multilayered Thick Composite Spherical Pressure Vessels

A design study of a multilayered spherical composite pressure vessel is presented. Each layer of the vessel is composed of quasi-isotropic layups of composite plies. For the stress analysis, however, each layer is assumed to be homogeneous whose three dimensional properties are equivalent to that of the quasi-isotropic plies. The linear theory of elasticity is employed so that the analysis is not limited to any thickness of the vessel. For the strength analysis the Tsai-Wu failure criterion is used. Using the ply constitutive law and lamination angle, the ply stresses and strains are determined from the layer stress strain relations. Then the failure criterion is used for each ply. The objective of this study is to design a spherical vessel with an acceptable safety factor to operate at an internal pressure of 200 MPa. In view of the winding and manufacturing difficulties, a design restriction of ba or 1.25 was set for this design. However a two-layered hybrid sphere of ba 1.25 b outer radius, a inner radius with T3005208 and IM6epoxy outside is considered to be an acceptable design.