minimal mass and maximal buckling load of composite hexagonal-triangle grid structure using fsdt under external hydrostatic pressure

Grid-stiffened composite shells are one of the most important structures in many industries. these structures based on their fabrication method, provide both high strength and light structural weight. in this study, buckling analysis under external hydrostatic pressure is performed to obtain critical buckling pressure and the optimum values of parameters for stiffeners. first-order shear deformation theory (fsdt) based on the ritz method is used to calculate the critical buckling load of these structures. the effects of shell thickness, angle of helical stiffeners, rib section area, and the stiffeners number into the buckling load are determined. comparing the calculated buckling load for stiffened and non-stiffened structures shows that stiffeners significantly optimize structural performance. furthermore, optimization of stiffener parameters is done by genetic algorithm. the results show that the introduced structure has the minimum mass. so, the stiffener parameters would be better. according to the results, the optimum dimensions for stiffener buckling load for the optimal stiffener have been increased by about 80% compared to non-stiffened.