Derivation of Buckling Knockdown Factors for Pressurized Orthogrid-Stiffened Cylinders of Launch Vehicle Structures

Postbuckling analyses are conducted to derive the buckling KnockDown Factor (KDF) of pressurized orthogrid-stiffened cylinders for space launch vehicles. The pressurized orthogrid-stiffened cylinders are based on the NASA ETTA1 model. The commercial finite element analysis program, ABAQUS, is used for the numerical analyses. Two different initial imperfection modeling techniques, namely, the Single Perturbation Load Approach (SPLA) and the Single Boundary Perturbation Approach (SBPA), are used to represent the geometric initial imperfection only and geometric and loading imperfections, respectively. The KDFs considering the internal pressure are improved when compared to those with pure axial compression. The KDFs using the SBPA can provide a conservative buckling design that satisfies the lightweight structural design and prevents buckling failure.