This numerical study is devoted to the stiffened composite vessel design for deep submarine exploration housings and autonomous underwater vehicles [
]. The structures under investigation are lengthy laminated cylinders with circumferential and longitudinal (rings and stringers, respectively) unidirectional composite stiffeners and rigid end closures. Structural buckling induced by the high external hydrostatic pressure is considered as the major risk factor under service conditions. The objective of this work is the development of an optimization tool allowing the search of the reinforcement definition (lamination and stiffener characteristics) that maximize the limit of stability.
An analytical model of cylindrical composite shell buckling, with transverse shear effects, has been developed. The contribution of the stiffeners is taken into account by correcting the overall laminate stiffness coefficients. The search of optimal design solutions is achieved by coupling this model to a developed genetic algorithm procedure: it manipulates directly integer parameters and, according to results taken from the literature and preliminary tests, the tournament selection, the whole arithmetical crossover and the random uniform mutation are applied.
Numerical tests have been performed: multi-parameter (number of composite plies and stacking sequence of the cylinder, numbers of rings and stringers) optimization calculations have been carried out applying user’s fixed amounts of material. The results showed substantial buckling pressure increases measured with respect to reference design solutions. FEM calculations have confirmed the corresponding gains. Besides, the results of the present work corroborate design tendencies validated previously by experiments [
]: the optimized laminations exhibit typical patterns and the rings play a major role.