A Shear Deflection Theory for Analysis of End Plugs for External Pressure Tests of Composite Cylinders

A shell theory, based on the Donnell approximation with modifications to include transverse shear deformations, is applied to the analysis of contoured end plugs for external pressure tests of composite cylinders. Solutions are derived for constant radius and linear taper end plugs. The effect of finite shear stiffness on stresses and end plug contact length is determined and results compared with earlier shell solutions based on bending deformations only. Computed stress values for finite and infinite shear stiffness are compared for a graphite composite cylinder. Results indicate that the effect of shear deformations is large for transverse shear stiffness values typical of composite cylinders. The effects are evident in both results for stresses and contact length. Solutions which neglect shear effects underestimate the contact length and overestimate the maximum stresses. Further conclusions are drawn as to the preferred plug contour for reducing the end effect.