Stephen Daynes, Stefanie Feih, Wen Feng Lu, Jun Wei, Optimisation of functionally graded lattice structures using isostatic lines, Materials & Design, Volume 127, 2017, Pages 215-223, ISSN 0264-1275, https://doi.org/10.1016/j.matdes.2017.04.082.
Functionally graded lattice core structures show a gradual and localised variation in their mechanical properties with the aim of improving structural performance whilst minimising weight. We present a novel approach to generate optimised functionally graded lattice core structures. Firstly, topology optimisation is performed to return the optimal core density distribution to minimise the structure's compliance subject to a mass constraint. A series of isostatic lines are then constructed with respect to the local principal stresses to generate a lattice structure spatially graded with respect to lattice cell size, aspect ratio and orientation. To validate this novel approach, optimisation is performed on a sandwich core structure subject to three point bending. Experimental tests confirm the greatly improved stiffness and strength properties (101% and 172% respectively) of the core as a result of spatially grading the lattice cells when compared to a benchmark core with uniform cell size of the same density. The new approach also significantly outperforms lattice structures with graded diameters as optimised by state-of-the-art commercial software packages. Non-dimensional core performance indices are formulated to express the relative specific stiffness and strength properties of the core for the three design approaches.
Agency for Science, Technology and Research (A*STAR) and Science and Engineering Research Council (SERC) of Singapore through the Additive Manufacturing Centre (AMC) Initiative – SIMTech-led R&D projects (SERC Grant No 142 6800088)