Composite, Grid-Stiffened Panel Design for Post Buckling Using Hypersizer

TLDR: In this article, a composite, grid stiffened, cylindrical panel loaded in axial compression was used for the Minotaur OSP space launch vehicle to carry operational loads past the initial postbuckling.

Abstract: Due to weight and cost goals, a grid-stiffened panel concept is being used for redesign of a structural component on the Minotaur OSP space launch vehicle. By designing the structural panels to carry operational loads past the point of initial buckling (local postbuckling), the resulting grid stiffened panel concept is lighter and 30% less costly to manufacture than other design candidates such as the existing honeycomb sandwich panel concept flown today. During June 2001 in Seattle, Boeing performed a structural certification experiment of a composite, grid stiffened, cylindrical panel loaded in axial compression. Pretest predictions were made for linear elastic (bifurcation) buckling, and non-linear post buckling. The tools used for pretest analysis were HyperSizer, and the FEM based tools MSC/NASTRAN and STAGS. Local buckling of the facesheet triangular shaped skin pocket occurred at a load of around 230 (lb/in). The test panel was able to sustain considerable additional loading, with post buckling failure occurring at 1320 (lb/in). The HyperSizer post buckling pretest prediction was 1300 (lb/in), the STAGS pretest prediction was 1250 (lb/in), and the MSC/NASTRAN pretest prediction ranged from 1425 to 2000 (lb/in). HyperSizer’s implementation of local post buckling based on an effective width approach is presented.