Analysis of elastic stresses in thick, polar-orthotropic, C-shaped rings

The discrepancies observed in the measured strains and those calculated on the basis of a plane-stress elasticity solution for a thick, polar-orthotropic, C-shaped ring with end loading are investigated by finite element analysis (FEA). Thick C-rings are used as test specimens for determining the tensile radial strength of composite flywheel rotors. The C-ring is modeled in three dimensions and the strains predicted on the surface of the specimen are compared with the measured strains to validate the model. The discrepancies in the strains and stresses predicted by the plane-stress elasticity and 3-D finite element approaches are attributed to the Poisson's effect, which gives rise to a significant variation of stresses and strains across the axial thickness. The discrepancies depend on the geometry of the specimen. Therefore, the effects of the geometric dimensions on the variation of stresses are studied using the 3-D FEA and a guideline is proposed for selecting a C-ring specimen geometry to have approximately uniform stresses through the axial thickness.