Modeling and validation of lightweight lattice structures for high specific energy absorption

The introduction of lattice structures, in order to reduce weight and increase structural performances, is becoming more and more requested in fields such as automotive, aerospace and biomedical. These challenges are satisfied by the advent of increasingly innovative additive manufacturing techniques, which have enabled not only the realization of complex structures, but also the implementation of alloys whose characteristics can be well suited to demanding fields of application. Within the scope of this thesis, the main characteristics of these structures are explored, outlining the differences according to the constituent topology, arrangement and density of unit cells. The main aim is the implementation of a structural optimization method by which, based on the above-mentioned properties, each different configuration shows significant improvements in energy absorption characteristics. A central part of the work is the analysis of how the topology impacts mechanical and energy performances, whereby lattice samples are tested using FEA (Ansys), carrying out static simulations. The material AlSi10Mg implemented follows a bilinear model and it is currently one of the most widely used for additive manufacturing of light-weight lattice structures. Identified the basic properties, the ultimate goal has been to improve them through structural optimization, based on the stress field within the specimens, with considerations of manufacturability to ensure desired printing quality. The optimization is performed through the implementation of a Matlab code, that aims to construct two iterative processes of thickness reassignment, based on the homogenization of the stress field. The same code is able to extrapolate 3D databases containing all mechanical and energy characteristics, automatically performing a static analysis of the specimens, with reduced computational time. The results obtained are validated again by means of software and ultimately through the experimental campaign. As achievements, it is shown that the implementation of the two different iterative processes leads to an improvement of the stiffness, comparing the models with the uniform original design and, at the same time, to a reduction of the Von-Mises stress and the maximum displacement, gaining good control even on the cracking mechanism, which is managed by the optimization process, generating a well-determined ’failure path’. The main final gain is in the result concerning energy absorption, as both in specific (SEA) and volumetric (VEA) terms exhibit significant percentages of increment, which is a fundamental requirement for many of the applications of interest.