Computer analysis of filament-reinforced metallic-spherical pressure vessels

Abstract

A computer analysis of filament-reinforced-metallic spherical vessels is presented. The design method uses the load-bearing liner approach and leak-before-rupture as a design criterion. The specific thicknesses of liner and filament composite required to sustain the pressure load are based on the equation of load compatibility and controlled by (1) buckling strength of the metal liner, (2) the maximum strain range for the required operating cycles and (3) the maximum strain capability remaining after cycling. The desirable filament winding pattern is such that the composite has, to the greatest extent possible, uniform thickness and isotropic elastic constants. To account for discontinuity effects, and the slippage between the liner and the composite, the stress and strain levels are best determined using finite element techniques. Aerojet's “AB5U” computer program for axisymmetric bodies having anisotropic material properties is used for the elastic-plastic stress (strain) analysis. Three pre-processor computer programs, “EPCS”, “FIBER” and “REVNOD”, developed by the authors, calculate (from specified filament properties, resin properties, winding pattern, and other geometric data) the necessary input to “AB5U” which includes the geometric data, and elastic constants. A post-processor “POST” was developed to calculate the residual stresses following the proof cycle, the operating strain ranges, and the burst pressure prediction. This capability provides accurate results for use in optimization of the design and enables the analyst to converge quickly to the lightest weight tank possible consistent with specification requirements.