Buckling of 45° Eccentric-Stiffened Waffle Cylinders

Abstract

The cylindrical tankage which forms part of the primary structure of missiles and space vehicles may be subjected to high compressive axial and bending loads. Since allowable compressive stresses for monocoque construction are generally low because of small bending rigidity and sensitivity to geometric imperfection, it is advantageous to use some type of wall stiffening. One such choice is the integrally milled-out 45° waffle. This consists of a square gridwork of ribs which form 45° helices over the cylindrical surface. The panel is generally milled out in the flat and then bent up to form a circular cylinder. An advantage of the 45° construction is the exclusion of buckling modes between hoop reinforcement; such modes are frequently critical for the 0° to 90° type of stiffening.