Search

The buckling problems of composite shells with initial imperfections under hydrostatic pressure are studied in this paper. A novel initial imperfection model is introduced. The analytical solutions of critical buckling pressures for composite shells both with and without the initial imperfection are derived based on the Sanders-type kinematic relations, respectively. The analytical results are compared with published experimental results and finite element (FE) results and agree well. The numerical examples are presented and the effects of initial imperfection parameters and ply angle as well as stacking sequence on the critical buckling pressures of composite shells are discussed. The results show that if the initial imperfection parameters are properly controlled, the critical buckling pressure can be dramatically improved. This could be valuable for the practical design of composite pressure hulls of an underwater vehicle. [ABSTRACT FROM AUTHOR]

This paper presents buckling solutions for composite laminated cylindrical shells in the underwater environment. Under the equilibrium governing equation of the bending stress state, two calculation formulas are proposed to predict the buckling pressure for the underwater composite cylinders with different boundary conditions. The validation of the proposed solutions in the elastic range is proved by comparison with experimental data. The influences of the geometrical imperfections generated from the process are considered by correcting the stiffness coefficients of the proposed analytical model. The results, compared with the finite element method, show that the evolution trend of the buckling pressure calculated by the developed model is close to the finite element analysis. Therefore, the proposed analytical solutions can provide a practical and efficient way for the designers to evaluate the buckling pressure of the composite shells in the design stage. • Buckling solutions for composite laminated cylindrical shells in the underwater environment are presented. • Two formulas are proposed for the buckling pressure of underwater composite cylinders with different boundary conditions. • The validation of the proposed solutions is proved by comparison with experimental data. • The influences of the geometrical imperfections generated from the process are considered. • The trend of the buckling pressure calculated by the developed model is close to the finite element analysis. [ABSTRACT FROM AUTHOR]

The buckling and strength failure of composite cylindrical shells under hydrostatic pressure are studied in this paper by experimental tests and finite element method. Experimental tests were carried out for three composite cylindrical shells with different stacking sequences. In parallel, finite element models are built to predict the buckling and strength failure pressures. The finite element results agree well with the corresponding experimental tests. A parametric study is conducted and the effects of length-radius ratio, thickness-radius ratio, ply angle and stacking sequence on the critical buckling pressure and strength failure pressure are discussed. The results show that length-radius ratio has little influence on the strength failure pressure while thickness-radius ratio, ply angle and stacking sequence have significant influences on the critical buckling pressure and strength failure pressure. The boundary line formed by the intersections between the critical buckling pressure and strength failure pressure of composite shells with same configuration is nonlinear and it is a function of length-radius ratio, thickness-radius ratio, ply angle and stacking sequence. • Buckling & strength failure of composite shells are studied by tests and FE method. • Effects of geometric & ply parameters on buckling & strength failure are analyzed. • Boundary lines between the buckling and strength failure pressures are discussed. [ABSTRACT FROM AUTHOR]

Composite materials have been widely used in the field of pressure shells for underwater vehicles due to their great potential. This paper presents an experimental study of composite cylindrical shells with and without the circular hole subjected to external hydrostatic pressure. The mechanical response of the composite cylindrical shells under external hydrostatic pressure is recorded by the strain acquisition system, and the buckling deformation process of the shells is also captured by the high-speed camera system. According to the experimental results, the entire compression process of the shell can be divided into three stages based on variations in strain. Based on the findings that buckling starts very early and accounts for about 35 % of the entire process, the concept of initial buckling pressure is proposed to distinguish the critical point of the shell transition from a stable state to an unstable state. It is found that the damage positions of the three shells all correspond to the troughs in the buckling waveform, and the final fiber breakage of the perforated shells with the reinforcements both occur near the reinforcement component. Finally, a comparative analysis of the strain response of the shell with the hole and the complete shell is carried out to explore their similarities and differences. The experimental results in this paper provide valuable information for the design of perforated composite pressure shells for underwater vehicles. [ABSTRACT FROM AUTHOR]