PSI - Issue 79

Alessandra Ceci et al. / Procedia Structural Integrity 79 (2026) 73–80

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Fig 6. Stress-Strain curves a) Structure 1, b) Structure 2 The mean values are 3.93 � 0.15 J/cm³ for Structure 1 and 30.87 � 3.16 J/cm³ for Structure 2, the latter confirming the superior energy absorption capability. At 60% strain, the denser Structure 2 shows a markedly higher SEA. This is consistent with earlier and stronger densification, which raises stress levels and therefore the integrated area in Eq. (6). The more porous Structure 1 maintains a low-stress plateau, leading to a lower cumulative SEA when integration extends to 60% strain. The collapse modes observed from the load–extension curves and visual inspection of the specimens confirm the structural differences between the two configurations. For Structure 1 collapse occurs progressively and locally: struts fail sequentially, generating the characteristic peaks and oscillations of the plateau stage. This behavior is typical of low relative density lattices, where deformation localizes in bands before spreading to the whole structure. For Structure 2, by contrast, failure is more uniform without a well-defined plateau: the absence of significant load drops indicates that plastic deformation involves the structure more continuously, without marked instabilities. In this case, densification starts earlier and contributes to the high SEA value recorded at 60% strain. The SEA values obtained are consistent with those reported in the literature for metallic lattices based on Kelvin and Diamond cells produced by additive manufacturing (Ashby et al., 2000; Yan et al., 2012), which exhibit comparable energy absorption at similar relative densities. In contrast, Structure 2 achieves SEA values at 60% strain exceeding those typically reported for lattices of comparable density (Maskery et al., 2015; Tancogne-Dejean et al., 2016) due to its higher mechanical resistance and earlier densification. 4. Conclusions In this work, two cellular structures in AA6082 aluminum alloy were designed and manufactured using the Lost PLA process. Both were based on the same parametric unit cell but characterized by different relative densities. The main findings can be summarized as follows: Manufacturing reliability. Comparison between theoretical and real weights showed deviations below 2%, confirming the accuracy and repeatability of the Lost-PLA technique in producing complex lattice geometries. Effect of porosity. Compression tests revealed the typical behavior of cellular materials with three distinct stages (elastic, collapse plateau, and densification). Structure 1 ( ρ ∗ / ρ s =0.18) exhibited progressive collapse with local instabilities, whereas Structure 2 ( ρ ∗ / ρ s =0.32) showed a more uniform deformation and earlier densification.