Buckling optimization of curved grid-stiffened helicoidal composite panel including the factor of mode shape in multiple load cases

The buckling mode of helicoidal composite panel are non-axisymmetric, resulting its different capability to resist loads in different orientation and the irregular buckling mode after curvilinearly stiffened. A method was proposed to design asymmetric curved stiffeners considering the local displacement gradient of the buckling mode shape. The displacement gradient depends on the bending stiffness and yields a better optimization. The basic unit of the stiffener family includes two stiffeners that pass through the midpoint of the panel; the remainder can be formed from this unit via translation. A simply supported curved grid-stiffened panel using uniaxial compression or shear loads under multiple load cases was addressed, and an integrated design framework was developed to obtain the designs. The curved grid-stiffened helicoidal composite panel yields a weight reduction of up to 13.26% compared to angle-grid designs under uniaxial compression and 11.68% for shear loads in multiple load cases.