Optimization of load-carrying performance for thick-walled composite cylindrical shells under hydrostatic pressure in AUVs

The optimization problem of thick-walled composite cylindrical shells under hydrostatic load is investigated in this study. Analytical solutions for critical buckling and material failure pressures are established through the shell's shear deformation theory. Based on the analytical framework, an optimization model for thick-walled composite cylindrical shells is developed which is not dependent on FE simulations. The optimization results are presented for composite shells with varying length-to-radius and thickness-to-radius ratios. The results manifest that optimal layups in the design space can be categorized into three distinct failure regions: buckling failure region, material failure region, and transitional region. Optimal layups for buckling and material failure regions are hoop-longitudinal winding and single helical winding, respectively. However, optimal layups for transition region are variable. The three failure regions are separated by two distinct boundary curves, and empirical formulas for these curves are proposed. A case study is proposed which shows the optimization design process of thick-walled composite shells. This study provides valuable insights for the optimization design of thick-walled composite cylindrical shells, offering a comprehensive understanding of failure mechanisms.