Stress Analysis and Weight Savings of Internally Pressurized Composite-Jacketed Isotropic Cylinders

An isotropic cylinder designed to have a specific bore displacement per unit of internal pressure can be made lighter by removing material from the outer diameter and replacing it with the correct amount of a stiff lightweight composite material. A stress solution is presented for an internally pressurized compound cylinder constructed from an isotropic liner jacketed with a cylindrically orthotropic composite material. The solution is used to determine the set of compound cylinder geometries which have equivalent bore hoop strain to that of an isotropic monoblock cylinder. An equation for predicting the equivalent compound cylinder geometry which provides the maximum possible weight savings over the isotropic design is also presented. To verify the theory, an experimental study was conducted involving the measurement of bore strain for internally pressurized steel liners jacketed with a graphite bismaleimide composite.