Analysing the Impact of Shape Complexity on Mechanical Performance in Additive Manufacturing: Investigation on Aluminium Alloy and Polymer Specimens

Laser-Powder Bed Fusion is one of the most widely used Additive Manufacturing processes for metal and polymeric parts, enabling the realisation of complex, free-form, and low-density structures that are impossible or difficult to produce using conventional manufacturing techniques. However, this process is characterised by defects such as porosity, roughness, layer delamination, and others that limit mechanical behaviour. This work aims to analyse the correlation between mechanical performance and shape complexity in additive manufacturing parts. A complexity index was adopted to characterise the geometry of specimens and lattice structures, and prototyping and testing activities were carried out to evaluate the correlation between shape complexity and performance. The metals used in the experimental analysis are Al-Si-Mg and Al-Cu alloys produced by Laser Powder Bed Fusion. To extend the approach and determine whether comparable results can be obtained in polymers, the authors also considered specimens made from PA12 by Powder Bed Fusion, and from a biocompatible resin produced by VAT photopolymerization. The results show a dependence between shape complexity and mechanical performance, highlighting a non-linear behaviour. A higher shape complexity is associated with lower internal porosity. However, contrary to initial assumptions, it also shows lower tensile strength. Although shape complexity offers a significant advantage in tailoring component performance in mechanical products, the results show that designers must use it with particular attention because material performance fluctuates as shape complexity increases.