Topological Optimisation Of Large, Additively Manufactured Composite Structures With A Graded Lattice Core

Interest in the use of additive manufacturing has grown within many engineering sectors. A notable application is that of low density core structures, utilising repeated unit cell graded lattices to enable improved efficiency and manufacturability. Used in combination, composite laminates and 3D printed graded lattices can achieve the high specific strength and stiffness required for large-scale structures such as wind turbine blades.

In this study, a novel methodology based on topology optimisation for additive manufacturing was applied to the design of two composite-graded lattice-hybrid structures. The novel methodology involves a multi-step topology optimisation process which first generates composite laminate designs based on the main load paths and then finds the optimal distribution of 3D printed material in the form of self-supporting graded lattices. This work aims to create initial design points for his methodology through idealised load cases so that simple comparisons can be drawn between designs produced through topology optimisation and conventional solutions such as composite beams and sandwich panels.

It was found that there are significant performance differences between the idealised graded density field and the optimised graded lattice geometry. This is shown to be affected by the input parameters to the optimisation and by the choice of unit cell size in the lattice. The composite laminate sizing process is shown to produce structurally feasible and manufacturable solutions, showing that the design can be tailored for mass and cost. This work indicates that the novel design methodology can potentially produce improvements in performance over traditional sandwich composite structures.