Bend-free design of super ellipsoids of revolution composite pressure vessels

Shells are thin-walled curved structures that are widely used in many engineering applications because of their structural performance in reacting transverse loads via generating membrane stresses. However, bending deformations and stresses are also generated, yet, alleviating them can result in more efficient use of material and improvement of load carrying capacity of shells. Ideally, a bend-free design provides scope for exploiting the full potential of load carrying in shell structures because of the uniform load distribution through the thickness. In this study, a family of so-called super ellipsoids of revolution are designed to have bend-free states under uniform internal pressure. Super ellipsoids of revolution have several advantages compared to conventional geometries such as higher packing efficiency, smoother stress flow variation, alleviating stress concentrations and cost associated with assembly processes. In this work, a new generalised set of governing equations representing bend-free states in composite super ellipsoids of revolutions are developed and solved analytically. Stiffness tailoring via tow steering is used to realise bend-free states. A parametric study is performed on several super ellipsoids of revolution for finding the required distribution of fibre orientations. The analytical solution is verified by finite element modelling and results are compared with an isotropic baseline.