Free Mesh Morphing Optimisation Applied on Composite Stiffened Panels Under Stability and Strength Constraints

The paper presents a novel free mesh morphing technology based on Moving Least Square (MLS) applied to Structural Optimisation. The proposed approach moves from the field of surface reconstruction from 3D scattered data. From a more general standpoint, MLS methods seem promising methodologies to solve different morphing problems where existing meshes can be modified without specific needs to change their topology, i.e. their connectivity information. In this respect, MLS is a very effective and promising methodology for mesh morphing. The proposed MLS morphing methodology has been applied to the optimisation of composite stiffened panels. The goal of the optimisation is to reduce the overall panel weight finding the best layups (thickness and percentages) for skin and stringers as well as the optimal shape for the stringers via MLS morphing, considering stability and strength constraints. The optimisation process acts on the shape of the stringers, via the proposed MLS approach, without requiring any remeshing towards the optimisation process. Nonlinear Finite Element analyses are used to predict the overall behaviour of the panels in terms of force vs. shortening curve up to final failure, discriminate between local skin instabilities and global ones, eventually leading to the overall failure of the structure. Strength criteria are additionally accounted by monitoring the maximum Tsai-Wu failure index overall the structure.