Efficient Design Methods for Variable Stiffness Composite Toroidal Pressure Vessels

Pressure vessels are widely used in various aerospace and automotive applications. For some applications with limited space, spherical and ellipsoidal shape are inappropriate and an efficient alternative configuration for pressure vessels is a toroid. Toroidal shapes can be defined as curved, endless hollow shapes that eliminate the need for end caps when used for pressure vessels. 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 fiber tow trajectories spatially through the structure to suppress the direct stress and strain gradients in the thickness direction, leading to reduced structural weight, defined as bend-free Variable Angle Tow (VAT) toroidal pressure vessels. For a toroidal pressure vessel with a fixed geometry, the VAT distribution through the structure to suppress bending is obtained. 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.