Optimisation of a Composite Advanced Sail Structure with Buckling Constraints

Abstract

Through linear and nonlinear design variable-to-sizing relationships, low- and high-complexity finite element models of a composite advanced sail (CAS) structure art-developed and optimized to determine the optimal placement of internal stiffeners in presence of stringent stability constraints associated with many closely clustered local buckling modes. The pseudo-topology optimization problem is formulated and solved using VR&D GENESIS as a constrained sizing optimization problem for minimum strain energy. To improve the computational efficiency of the high-complexity model, the contribution of the geometric stiffness matrix to the buckling sensitivities are ignored with no significant loss of accuracy. Based on the results of the pseudo-topology optimization for the low- and high-complexity models, a detailed finite-element model of the new CAS design with optimal stiffener layout is developed and optimized for minimum weight. Depending upon the degree of variability in skin thickness, the results show a weight saving of up to 19% over the baseline model while satisfying all structural requirements.

Summary

Guided by the topology optimization results, a new detailed finite element model was developed with the stiffeners placed near their optimal locations. By solving the corresponding constrained sizing optimization problem, the optimal wall thickness values for individual stiffeners and skin panels were obtained. As expected, the model with the most variability in skin thickness resulted in the lowest structural weight, which is 19% lighter than the baseline CAS model with a less optimal stiffener layout.

1st Buckling Mode of Optimised Structure Optimised Stiffener Layout

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