Semi-analytical study of buckling response for grid-stiffened panels during creep age forming

The elastic–plastic buckling response of panels with grid stiffeners during creep age forming (CAF) has been studied using a semi-analytical method in this research. A simplified model for panels with multiple grid stiffeners under bending has been established and the effective width has been applied to consider the flexible skin effect and multiple stiffener effect. In the semi-analytical method, the equilibrium equation for the simplified model has been solved via differential quadrature method to acquire the buckling stress of grid-stiffened panels, using deformation theory (DT) and incremental theory (IT) of plasticity. The results with IT show good agreements with both the published experimental and non-linear FE results, demonstrating its effectiveness. Based on the method, the effects of geometric dimensions of grid-stiffened panels, multiple stiffeners and temperature on buckling response in the elastic and plastic regions have been studied. It is found that the transverse stiffener provides a 13.9% higher buckling stress of grid-stiffened panels than blade-stiffened panels, and buckling may occur in the heating stage during CAF. The proposed semi-analytical method based on IT provides accurate predictions of buckling stress during either CAF or cold forming, which can guide the parameter optimisation of grid-stiffened panels in design.