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Digital design, intelligent manufacturing systems, and integrating modular construction and advanced materials drive innovation in structural engineering, addressing global material consumption challenges and fostering a sustainable future. This research continues developing the recently proposed lightweight hybrid lattice-filled profile (HLFP) concept for modular engineering. The HLFP combines a thin-walled tubular shell and additively manufactured lattice structure (AMLS) as a lightweight core. The possibility of combining different materials in a mechanically resilient HLFP ensures the target structural efficiency. In particular, steel, aluminum, and even fiber-reinforced polymeric profiles can form the thin-walled, mechanically resilient shell; the sparse core ensures local stability and reduces stress concentrations in the shell, avoiding premature failure of the structural components.
Increasing the profile thickness describes the typical solution to mechanical resistance. However, it causes excessive utilization of structural materials and is not economically efficient. The proposed concept solves this drawback efficiently by combining materials and forming sparse structures in the core using additive manufacturing (3D printing) technology, which achieves precise shape, internal structure, and stiffness, ensuring the decided structural performance with minimum materials. The preliminary mechanical tests of HLFP, including aluminum and steel profiles, revealed that the adhesive bonding of HLFP components improves the mechanical resistance but complicates the deformation state and stress redistribution between its components. The tests demonstrated that the adhesively bonded AMLS increases the load-bearing capacity by an additional 130% during the elastic stage. Even after partial debonding, it retains 50% of its mechanical resistance compared to the theoretical sum of the HLFP components. Reducing the infill density does not significantly impact the load-bearing capacity of the HLFP. A fourfold decreasing density (from 10% to 2.5%) of the polymeric insert has resulted in only a 20% reduction in its load-bearing capacity. However, the sparse lattice structure changes the failure mechanism of the AMLS from favorable ductile behavior to potentially dangerous brittle behavior, highlighting the need for further optimization.
Thus, this study is limited to the mechanical performance of polymeric AMLS with different manufacturing layouts to generate a reliable experimental database for verifying theoretical and numerical models and further optimizing the polymeric core’s mechanical resistance. All geometries replicate polymeric inserts from previous studies with slight modifications to verify the effect of 3D printing parameters on the mechanical resistance of the polymeric core under axial compression. The compressive tests include 104 × 46 × 40 mm AMLS specimens with different fabrication layouts, including adhesively connected rectangular fragments fabricated with various patterns and continuous structures replicating the inserts as a single part (without adhesion). The experimental campaign employs two AMLS fabrication pathways: one is orthogonal to the compression loading direction, and another introduces the 45-degree inclination of the printing plane regarding the loading direction. The mechanical tests revealed exceptional reliability of the specimens built in the loading direction, and these specimens were chosen to optimize the internal lattice structure further. At the same time, the fabrication plane inclination substantially impaired the deformation manner, leading to brittle failure and making AMLS barely suitable for structural applications. The insert fragmentation and further adhesive connection of the AMLS fragments did not compensate for fabrication defects, raising the scatter of the test results and making these inserts unreliable for structural use.
The optimization process of the “efficient” AMLS samples employs the finite element modeling software ABAQUS with a standard optimization solver. However, the optimization process includes the buildability condition, accounting for the printing pathway inclination limitations introduced in this study. Previous experimental studies and a developed theoretical model of HLFP also determine the inequality of ALMS stiffness regarding the loading direction when the core fully supports the loaded flange and just fixes webs from stability losses. Therefore, the optimized AMLS model ensures this theoretical condition, too. At the same time, the variety of possible arrangements of internal lattices makes the optimization problem weakly determined. So, the study presents only several potential solutions and allows for further AMLS optimization using advanced optimization algorithms and considering complex structural cases.
