Buckling behavior of filament-wound carbon/basalt hybrid composite cylindrical shells under external hydrostatic pressure

Carbon/basalt hybrid composites have attracted considerable interest as a cost-effective alternative to conventional carbon-fiber composites. However, their application in filament-wound composite pressure shells subjected to external hydrostatic pressure has received limited attention. This study experimentally and numerically investigated the buckling behavior and failure mechanisms of carbon/basalt hybrid cylindrical shells with different stacking sequences. The symmetric hybrid configuration achieved an average collapse pressure of 6.53 MPa, close to 6.57 MPa for the all-carbon shell, while replacing two-thirds of the carbon fiber layers with basalt fiber. A nonlinear finite element model incorporating initial geometric imperfections predicted the collapse pressures with a maximum relative error of 4.0%. Thickness-normalized simulations, which isolated the influence of wall-thickness variation, further confirmed the structural efficiency of the proposed hybrid stacking strategy, with the symmetric hybrid shell retaining 88.2% of the nonlinear buckling load of the all-carbon shell. Micro-computed tomography and scanning electron microscopy observations revealed brittle fracture in carbon fiber layers and more progressive damage in basalt fiber layers. A reinforcing-fiber material cost assessment showed that performance gains exceeded fiber-cost increases below approximately 27% carbon fiber content. These findings offer practical guidance for the design of lightweight, cost-efficient filament-wound composite pressure shells subjected to external hydrostatic pressure.