A floating connector element formulation for multi-level modelling of composite structures

Design and optimisation of large structures, including the positioning of lower-level components, typically require extensive user involvement and sequential mechanical analysis/optimisation iterations. This paper presents an original method that enables adaptive positioning of lower-level models (such as components) within higher level-models (such as large structures), and that achieves a combined mechanical/optimisation problem for the design of structures with various hierarchical levels (such as the positioning of stiffeners within a wing box). As the position of the lower-level model evolves, our proposed method does not require re-generating of the geometry, remeshing or modifying the stiffness matrix of the elements corresponding to the various hierarchical levels. Instead, we achieve the adaptive positioning via an original concept that we propose here: Floating Connector (FC) elements. In this paper, we validate the FC elements against reference purely mechanical solutions, show that they can be combined with gradient-descent method and genetic algorithms, and that they can be applied to optimise the positioning of a stiffener runout taking into account a debonding manufacturing defect.