Azam, Farooq I; (2025) Shape optimisation of architected materials: stiffness, plastic and buckling strengths. Doctoral thesis (Ph.D), UCL (University College London).

Text UCL_PhD_Thesis___Farooq__(Final).pdf - Accepted Version Access restricted to UCL open access staff until 1 April 2026. Download (54MB)

Abstract

This work focuses on developing and optimising architected materials with tailored properties through a deliberate re-arrangement of solid material to enhance mechanical properties such as stiffness, plastic and buckling strengths. The optimisation is achieved through multi-objective parametric optimisation using a combination of analytical calculations, numerical computational tools, and machine learning-based algorithms. These methods are employed to explore the design space and identify Pareto optimal configurations that meet the desired properties. The research investigates two-dimensional and three-dimensional strut- and shell-based lattices, including those that are bending- and stretch-dominated. The aim is to quantify the impact of solid material distribution on their mechanical response. Various strategies for redistributing the material along the strut or surface are assessed, benchmarking them against regular-shaped lattices with uniform-thickness cell walls. By comparing these optimised configurations with traditional designs, the study highlights significant improvements in mechanical performance, especially for bending-dominated architectures. Metamaterials with optimised configurations are fabricated using polymeric and metallic additive manufacturing techniques. These lattice materials are then subjected to compression testing to validate the theoretical models' predictions. When compared to regular lattices with the same relative density, the results show that material redistribution offers substantial enhancements of stiffness and plastic strength for bending-dominated architectures, while limited or null improvements are observed for the buckling strength and stretch-dominated lattices. Moreover, it is shown that redistributing material can induce a strain-dependent auxetic behaviour. Overall, this research presents a material redistribution strategy and a data-driven multi-objective shape optimisation as valuable tools for exploring complex design spaces. These methods allow for the efficient prediction of underlying mechanical properties and achieve lightweight, stiff, and strong topologies. The findings underscore the potential of these optimised architected materials in various engineering applications, where enhancing mechanical performance while maintaining or reducing weight is crucial. This approach offers a systematic framework for developing advanced materials with superior mechanical properties through rational design and optimisation.

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