Determination of the thickness of a composite layer of a spherical shell taking into account the width of a winding ribbon
The thickness of a wound layer in the vicinity of polar holes of a shell of revolution increases indefinitely according to a classical formula. At the same time, the formula is valid if the distance from the edge of the polar hole is greater than twice the width of a winding ribbon. The number of wound layers in the spherical shell may be greater than 20, which leads to an uncertainty in the calculation of strength of a composite shell as a whole. In this paper, the problem of analytical determination of the thickness of a single wound layer on the entire spherical surface is formulated and solved taking into account the width of a winding ribbon. Formulas for calculating the thickness and reinforcement angles on the entire spherical surface are presented. It is shown that the layer thickness in different zones of a composite spherical shell depends on the number of zones and the ribbon width. The thickness of a composite layer is determined for the first time for a spherical shell taking into account the width of a winding ribbon. The conducted research formed the basis for developing an engineering technique for calculating structural and technological parameters of the multi-zone winding process for spherical shells. The obtained formulas for determining the thickness and reinforcement angles in each layer allow the stress state of a multi-zone spherical shell under internal fluid or gas pressure to be calculated with required accuracy. The presented results of pressure tests of membrane and fiberglass spherical shells made by zonal winding of wide Mylar ribbons and narrow fiberglass strips will be useful in the design of new thin-walled spherical structures.