Modeling and optimization of variable angle tow composite underwater cylindrical pressure hull based on isogeometric analysis method

Composite cylindrical shells are commonly used in the lightweight design of underwater pressure hulls. The use of variable angle tow (VAT) design is expected to further reduce the weight. To address the issues of low efficiency in buckling calculation and the large number of design variables in VAT composite structures, this paper proposes a buckling optimization framework based on an isogeometric shell model. The suitable layup form and the buckling performance of VSC hulls are studied. Isogeometric analysis (IGA) shell elements with unidirectional order elevation and C0 continuous element boundaries are introduced in the hull model to reduce the time required for a single calculation. With the proposed IGA hull model, the optimization framework is built by using the Kriging model and Latin Hypercube Sampling methods. The optimization performance of two common VAT layups is examined by comparing their buckling results and computational costs. Based on the layup with better performance, the distribution of the approximate optimal buckling load of variable stiffness composite (VSC) hulls under different geometric parameters is investigated and compared with constant stiffness composite (CSC) hulls to find the reasonable application area of multi-layer VAT design.