Design, structural optimization and experimental validation of an additively manufactured aerospace sandwich panel with different lattice cores

Date

2025-4-10

Author

Gençarslan, Hasan

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Sandwich structures are widely used in the aerospace and defense industries due to their high stiffness-to-weight ratio. However, conventional manufacturing methods constrain these structures to uniform foam or honeycomb cores, thereby limiting their mechanical performance. Recent advancements in additive manufacturing (AM), however, now enable the precise fabrication of sandwich structures with intricate and variable-density lattice cores, unlocking new opportunities for tailored performance optimization. This study presents a homogenization-based topology optimization (HMTO) framework utilizing a modified Solid Isotropic Material with Penalization (SIMP) method for aerospace sandwich panels. Unlike conventional designs, the sandwich panel configuration in this study incorporates different lattice core types, including Body-Centered Cubic (BCC), Octet, Primitive, and Gyroid. The panel consists of upper and lower face-sheets, a lattice core, and solid insert regions designed for fastener installation. In the optimization process, the face-sheets and lattice core serve as design domains, whereas the insert regions remain unmodified. The equivalent isotropic material properties of the lattice structures are determined through numerical homogenization, employing the Gibson-Ashby model along with cubic polynomial fitting. To optimize the aforementioned sandwich panel design by minimizing compliance (i.e., maximizing stiffness) while satisfying constraints on the minimum fundamental natural frequency and the maximum total mass, a custom MATLAB script is developed. This script integrates a modified SIMP-based HMTO approach with the OptiStruct finite element (FE) solver and the Method of Moving Asymptotes (MMA) optimization algorithm. The optimization results are reconstructed within the nTopology software using Radial Basis Function (RBF) interpolation and subsequently validated through finite element analysis (FEA). Further validation is performed by fabricating the optimized sandwich panels using Multi Jet Fusion (MJF) 3D printing and conducting experimental modal testing. Both numerical and experimental results confirm the accuracy of the proposed HMTO method. For strut-based lattices, including BCC and Octet structures, the optimization achieves a significant reduction in structural compliance, along with a 50% reduction in mass and approximately a 25% increase in the fundamental natural frequency compared to the fully solid panel. Similarly, for triply periodic minimal surface (TPMS) lattices, including Primitive and Gyroid structures, the optimization results in a substantial reduction in structural compliance, a 50% mass reduction, and approximately a 30% increase in the fundamental natural frequency relative to the fully solid panel. These findings demonstrate the effectiveness of functionally graded lattice cores in enhancing structural stiffness and fundamental natural frequency while achieving significant mass reduction.

Subject Keywords

Structural optimization, Homogenization, Gibson-Ashby model, Homogenization based topology optimization, Modified SIMP method, Additive manufacturing, Lattice structures, Sandwich structures

URI

https://hdl.handle.net/11511/114552

Collections

Graduate School of Natural and Applied Sciences, Thesis