Buckling of Fibre-Reinforced Plastic-Steel Torispherical Shells Under External Pressure

Abstract

The paper deals with the buckling of torispherical shells consisting of a steel external layer plus different numbers of composite layers. It is assumed that the total thickness of the fibre-reinforced plastic (FRP)-steel shell is constant but that the thickness of the steel and of the composite may be varied. In the paper it is shown (a) how the orientation of the fibres and the composite lamina thicknesses affect the elastic buckling modes and (b) how substantial increases in elastic buckling pressures may be achieved by reinforcing the steel torispheres with layers of composite. The analysis is carried out for various values of the geometrical parameters describing torispheres, including spherical caps. The influence of the yielding of the steel layer on the buckling pressures of FRP-steel torispheres is also discussed. As might be expected, it is necessary to take plasticity into account when predicting the buckling pressures of these shells. Some experimental results are given which confirm this expectation. The effect of initial shape imperfections in the shells is also considered briefly. However, the dearth of experimental results on FRP-steel shells prevents a proper evaluation of the way in which imperfections decrease their buckling strength.