Novel Design Methods for Composite Toroidal Pressure Vessels
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Pressure vessels are commonly used for different applications in various industries. For some applications with limited space, spherical and ellipsoidal shapes are inappropriate, and a toroid is an efficient alternative configuration for pressure vessels. Toroidal shapes can be defined as curved, endless, hollow shapes that eliminate the need for end caps when used as a geometry for pressure vessels. Spare tyre cavities in passenger vehicles or tanks used to store propellant in rockets and missiles are examples of applications for toroidal pressure vessels. Recent developments in manufacturing technology and material availability have considerably enlarged the design space to realize efficient pressure vessels. Recently, Daghighi et al. [1] proposed an efficient design of super ellipsoids of revolution that exploits the stiffness tailoring capabilities via the Variable Angle Tow (VAT) technique in which the fibre tow trajectories vary spatially throughout the structure to suppress inefficient bending stresses and strains that arise in those structures. They showed an improvement in the load-carrying potential of their proposed design by investigating the failure performance of their designed pressure vessels [2]. In light of these premises, this study presents an analytical formulation using lamination parameters for the novel design of toroidal pressure vessels. The proposed design is based on stiffness tailoring by changing the fibre tow trajectories spatially through the structure to suppress the direct stress and strain gradients in the thickness direction, leading to reduced structural weight. The VAT distribution through the structure to suppress bending is obtained for a toroidal pressure vessel with a fixed geometry. Subsequently, the bending stresses and strain levels in the designed VAT toroidal pressure vessels are assessed numerically and compared with those of the isotropic and constant stiffness composite counterparts. Results show that the designed VAT toroidal pressure vessel presents considerably lower bending levels than its corresponding isotropic and constant stiffness composite counterparts.