PSI - Issue 53

Costanzo Bellini et al. / Procedia Structural Integrity 53 (2024) 227–235 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Materials with excellent mechanical properties and low weight are needed in the automotive and aviation industries because fuel consumption and, by extension, polluting gas emissions, must be decreased without compromising safety requirements (Maskery et al. (2016)). For these purposes, lattice constructions are appropriate, as stated by Bellini et al. (2021a, 2021b). In fact, particularly for metallic materials, the dense form of the base material is unable to attain the unique mechanical properties of cellular solids, such as strength-to-weight and stiffness-to-weight ratios (Liu et al. (2017)). Multiple unit cells that are methodically organized in space in accordance with a topological pattern make up lattice structures, as defined by Bellini et al. (2022). Lattice structures can be created using a number of techniques, including casting, machining, filament winding, and hot pressing. However, modern additive manufacturing techniques have attained a high level of reliability; as a result, they may be used to create lattice and porous structures, as indicated by Cantaboni et al. (2022) and Dong et al. (2017). In former times, lattice structures with various unit cell sizes were developed and examined by Epasto et al. (2019) who discovered that the structure with the largest cell exhibited the worst mechanical behavior. In contrast, lattice parts with functionally graded density were investigated by Mahbod and Asgari (2019) to produce an improved reaction to crush load. Due to their striking advantages over honeycomb from the perspectives of both the mechanical attributes and the production process, lattice structures can be used as the core material in sandwich structures, as assessed by Bellini et al. (2021). Sandwich skin can also be produced simultaneously with the core or added during a later manufacturing process, allowing for blending various materials and creating hybrid constructions (Bellini et al. (2020)). Developing new design techniques could aid engineers in their design procedure in order to get the best possible result. Ashby (2011, 2013) outlined the justification for developing material architecture as well as the standards for determining which arrangements and layouts have the best chance of succeeding. A wide variety of stiffness, strength, and fracture toughness can be provided by micro-architecture lattice materials, according to Fleck et al. (2010), who also underlined the importance of nodal connection and structural ordering. Deshpande et al. (2001) studied the octet-truss lattice structure intrinsic structural properties from an experimental, computational, and theoretical perspective. They thoroughly studied the collapse characteristics with and without buckling cases, and the elastic properties. Additionally, they compared the stiffness and strength of metallic foam with octet-truss lattice material. The octet-truss lattice material stiffness and strength were between three and ten times more than their analogues for metallic foams and were roughly half the highest achievable values for isotropic voided materials. Therefore, the octet-truss lattice material represents an appealing replacement for metallic foams due to its high strength-to-weight ratio, relative simplicity of fabrication, and the prospect of multi-functional applications. It is generally known that items created using additive techniques may contain a number of flaws, as found by Del Guercio et al. (2020) and Echeta et al. (2020). These imperfections, like pores, may impact how efficiently the structural elements operate, so it is also necessary to include them in computational models. However, the mechanical properties of the material should be as accurate as possible. When the component sizes are tiny enough, as in the case of lattice structures where the diameter of each truss is less than a millimetre, such flaws play a significant impact. While Ferrigno et al. (2019) proposed a method for embedding generic defects with a random distribution in lattice structures with regular octet cells, Hernández-Nava et al. (2016)presented an extensive analysis of the defects observed in lattice structures created through EBM. This method can be used to assess how discrete flaws produced by EBM techniques affected the mechanical reliability of such structures. To be used for structural applications, computational instruments are needed to calculate and design lattice components. In contrast to monolithic materials, a novel design for additive manufacturing technique was proposed by Rosen (2007) for the design of meso-structure within a product to provide enhanced strength, stiffness, or other needed characteristics. Zhang et al. (2014) presented the process planning for additive manufacturing, examined the factors that must be taken into account and potential limitations when designing for additive, and then suggested a two-level framework for the abovementioned design as well as a list of common indicators for evaluation. In order to be used in combination with multi-objective evolutionary algorithms, Di Caprio et al. (2019) created a numerical method for developing optimal lattice components using full-parametric numerical models. In a previous work of Di Caprio et al. (2022), in which a numerical model suitable for the mechanical behaviour simulation of lattice structures was presented, a mismatch between theoretical and actual bending properties was found and partially attributed to geometrical unconformities; in fact, the produced specimens were weighed and resulted