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

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 post- buckling). the resulting grid stiffened panel concept is lighter and 300- 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(Registered). and the FEM based tools MSC/NASTRAN(TradeMade) and STAGS(TradeMade). 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.