Optimum design of composite stiffened panels under combined loading

Minimum-weight designs of T-stiffened and hat-stiffened panels made of laminated composite material are found with the PANDA2 program. The panels, subjected to axial compression, in-plane shear, and normal pressure, are designed for service in their locally postbuckled states. A program called STAGSMODEL is used for transforming output from PANDA2 to input for STAGS, a general-purpose nonlinear finite element code. STAGS is then used to evaluate the optimum designs. Agreement between results obtained with PANDA2 and STAGS is reasonable for these very complex, very nonlinear problems. Therefore, PANDA2 appears to qualify as a preliminary design tool for composite panels operating in their locally postbuckled states.