Mechanical properties and failure analysis of ring-stiffened composite hulls under hydrostatic pressure

Ring stiffeners improve the buckling resistance of thin-walled hulls. In this study, theoretical models of buckling and strength failure of ring-stiffened composite hulls (RSCHs) were used to determine the design parameters. The hulls were prepared by filament winding on a mould composed of multi-petal-combined foams and steel shafts. The experimental results showed that the hydrostatic bearing performance of RSCHs was 1.79 times that of an unstiffened composite hull (USCH) with the same weight-to-displacement ratio (WDR). The crack in the damaged stiffened hulls penetrated the entire axis and expanded circumferentially, resulting in a stiffener fracture. Imperfections related to thickness deviations were introduced into a nonlinear buckling model by considering progressive damage. In contrast to the failure mechanism of USCH, the failure pressure of RSCHs was not at the peak of nonlinear buckling, and fibre compressive failure at 90 degrees on the outermost layer of the skin was dominant. The error between simulated and experimental results was 4.64 %. The parameter analysis indicated that the stiffener height and width had different effects on the buckling load. However, when only the same type of strength failure occurred, both were independent of the load. This study demonstrated the load-bearing advantages of RSCHs for ocean engineering applications.