Buckling of Externally Pressurized Shallow Spherical Caps from Composites
ABSTRACT Buckling of shallow spherical shells subjected to external pressure has been exploited, for example, in pressure safety devices. Shallow spherical caps have also been used as mirrors and more recently they have been considered as energy concentrators in space applications. Hence there is a renewed interest in their static stability performance. This paper addresses two issues: (1) buckling performance of caps, with shallowness parameter, lambda, varying from 3.5 to 7.5, and (2) the effect of boundary conditions on the buckling strength. In the first case, for elastic buckling of caps, there is a sudden drop in the buckling strength for small magnitude of cap’s geometrical parameter lambda, i.e., for lambda ≈ 4.0. This has recently been re-confirmed for steel caps. However, it is not clear whether this drop can be eliminated or reduced in caps made from composites mainly through the lamination sequence and also by appropriate supporting of the caps perimeter—as typically used in inflatable space antenna. The current paper examines spherical caps made from composites subjected to quasi-static external pressure. The effect of different lamination sequences on the buckling strength is examined for a range of the shallowness parameter. In the second part, it is proposed to use a closed toroidal shell as means of supporting the cap’s perimeter. The supporting toroidal shells can be of different cross-section, i.e., circular or elliptical. The toroids can also be internally pressurized, differently laminated, etc. Additionally the point of attachment can be chosen in such a way that buckling load is as large as possible. The effect of some of these parameters on the buckling pressures is quantified. This is an entirely numerical study.
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ABSTRACT: Here, the nonlinear axisymmetric dynamic behavior of clamped laminated angle-ply composite spherical caps under suddenly applied loads of infinite duration is studied. The formulation is based on first-order shear deformation theory and it includes the in-plane and rotary inertia effects. Geometric nonlinearity is introduced in the formulation using von Karman’s strain–displacement relations. The governing equations obtained are solved employing the Newmark’s integration technique coupled with a modified Newton–Raphson iteration scheme. The load corresponding to a sudden jump in the maximum average displacement in the time history of the shell structure is taken as the dynamic buckling pressure. The performance of the present model is validated against the available analytical/three-dimensional finite element solutions. The effect of shell geometrical parameter and ply angle on the axisymmetric dynamic buckling load of shallow spherical shells is brought out.Composite Structures 04/2003; · 3.12 Impact Factor
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ABSTRACT: The purpose of the many examples of buckling presented here is to give the reader a physical feel for shell buckling. Section 1 contains a brief description of two kinds of buckling, collapse and bifrucation. Section 2 concerns shell structures in which the cause of failure is nonlinear collapse due to either large deflections or to both large deflections and nonlinear material behavior. Section 3 gives examples of axisymmetric shells in which failure is due to bifurcation buckling. Section 4 provides examples that illustrate the effects of boundary conditions and eccentric loading on bifurcation buckling of shells of revolution. Section 5 is devoted to combined loading of cylindrical shells and nonsymmetric loading of shells of revolution. Section 6 is on bifurcation buckling and collapse of ring-stiffened shells with emphasis given to cylindrical shells. Section 7 contains several illustrations of buckling of prismatic shells and panels, that is, structures that have a cross section that is constant in one of the coordinate directions. Section 8 focuses on the sensitivity of predicted buckling loads to initial geometrical imperfections. Section 9 demonstrates axisymmetric collapse and bifurcation buckling of bodies of revolution that consist of combinations of thin shell segments and solid segments to which shell theory cannot be applied with sufficient accuracy.Journal of Applied Mechanics-transactions of The Asme - J APPL MECH. 05/1981; 53(4):805.
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ABSTRACT: The nonlinear thermal buckling of symmetrically laminated cylindrically orthotropic shallow spherical shell under temperature field and uniform pressure including transverse shear is studied. Also the analytic formulas for determining the critical buckling loads under different temperature fields are obtained by using the modified iteration method. The effect of transverse shear deformation and different temperature fields on critical buckling load is discussed.Applied Mathematics and Mechanics 03/2008; 29(3):291-300. · 0.65 Impact Factor