Thin-walled cylindrical shells are nowadays widely used for principal structures in the aerospace field. Despite the capacity to sustain high levels of axial compressive loads they are also easily prone to fall into buckling. One of the methods currently studied to increase the value of the critical load associated with this phenomenon consists in the use of curvilinear fibers, through which it is possible to continuously change the stiffness, and consequently the local behavior of the structure. The paper describes an optimization methodology developed for the buckling optimization of thin-walled variable stiffness cylindrical shells subjected to axial load, together with a general fibers path formulation. The framework proposed involves a synergic work between the finite element method and artificial intelligence techniques. The optimal configuration shows an increase of the buckling load of about 4% together with an increase of the pre-buckling stiffness of about 6%.

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The paper proposes an optimisation strategy for the design of structures made of three-dimensional woven composites. The knowledge of the weaving architecture is essential to properly optimise the design of the structural components subjected to specific load conditions. Owing to the hierarchy and periodicity of the textile composite materials, a multi-scale parameterisation modelling strategy combining the adoption of a representative volume element and periodic boundary conditions is employed to estimate the behaviour of stiffened panels. In order to minimise the expensive computational cost, response surface method techniques are used to generate the approximated structural responses in an efficient and applicable way. The approach here proposed consists of a multi-scale parameterization analysis strategy and an optimisation framework based on the response surface technique and genetic algorithms. The optimal design results are verified by finite element analysis proving that the response surface method integrated with genetic algorithms allows to easily investigate the influence of the fabrics constitutive parameters on the structural behaviour.@en