Structural integrity and collapse behavior of TPMS-based aluminum cellular structures manufactured by Lost-PLA

Triply Periodic Minimal Surface (TPMS)-based cellular structures have attracted increasing interest for lightweight structural applications due to their high stiffness-to-weight ratio and energy absorption capability. The main contribution of this work is the experimental isolation of density effects on collapse behavior in TPMS-based aluminum cellular structures through a controlled parametric design, combined with a detailed analysis of damage evolution and structural integrity beyond conventional energy absorption metrics. In this study, a controlled parametric approach is adopted, in which the relative density is varied through a geometric parameter while preserving topology and connectivity, enabling the isolation of density effects on collapse behavior. However, energy-based metrics alone are often insufficient to fully describe their structural integrity under large deformations, as different architectures dissipate energy through markedly different collapse mechanisms. Two TPMS-inspired aluminum cellular structures with different relative densities were designed, manufactured by the Lost-PLA process using AA6082 alloy and experimentally characterized under quasi-static compression. Both configurations originate from the same parametric TPMS unit cell defined by an implicit formulation, in which the geometry of the cell is governed by two independent geometric parameters. In the present study, one parameter was kept constant, while the other was varied to modify the relative density. As a result, the two structures share identical topology and differ exclusively in relative density, enabling a controlled investigation of density effects on the mechanical behaviour. The mechanical behaviour was analysed in terms of load–strain and engineering stress–strain curve, complemented by a detailed assessment of collapse stability, damage evolution and densification onset. Volumetric energy absorption (VEA) was evaluated by integrating the stress–strain behaviour up to 60% strain. The results reveal a clear density-dependent transition in collapse behaviour. The lower-density structure exhibits a stable and progressive collapse characterized by an extended plateau and distributed local damage, leading to a damage-tolerant behaviour despite lower overall energy absorption. Conversely, the higher-density configuration shows increased stiffness and volumetric energy absorption but undergoes a more localized collapse with earlier densification and reduced collapse stability. These findings demonstrate that structural integrity and collapse mode must be considered alongside energy absorption metrics when assessing the performance of TPMS-based cellular structures. The combined quantitative and qualitative analysis presented in this work provides a comprehensive framework for evaluating the mechanical performance and integrity of additively manufactured metallic cellular structures under compressive loading.