Buckling and material failure analyses for ring-stiffened composite shells subjected to hydrostatic pressure

In this paper, both the buckling and material failure for ring-stiffened composite shells under hydrostatic pressure are studied by theoretical and finite element (FE) methods. Theoretical formulas to predict the critical buckling pressure and material failure load for ring-stiffened composite shells are proposed. To validate the proposed analytical solutions, FE models are built and the buckling and material failure analyses are performed. Moreover, two experimental tests on unstiffened and ring-stiffened composite shells were carried out. Analytical solutions, FE results and experimental tests were compared and it shows great accuracy of the proposed theoretical solution. Parametric studies are performed, the effects of rib height, width, and number on the stability as well as the effects of winding angle and thickness on the material failure are discussed. The buckling mode of a ring-stiffened composite shell will transform from overall to local buckling as the rib height, width, and number increase. The material failure pressures are mainly affected by winding angle and thickness. The composite shell with winding angles of [90/±40/90] or [±50/±50] have larger material failure pressure than other winding angles.