Mostafa S. A. ElSayed

This study presents a computational comparison of 24 lattice topologies over their geometrically feasible relative density ranges. Conjugate heat transfer simulations were performed in ANSYS Fluent 2024 R2 using 10 mm unit cells, inlet air at 300 K and 0.05 m/s, a constant base temperature of 312 K, and gravity acting in the negative z direction. The inlet Reynolds number was approximately 32.5. The prescribed temperature difference of 12 K gives a Grashof number of 1.68 × 10³ and a Richardson number of 1.59, indicating that buoyancy and the imposed flow are both relevant. The operating condition was therefore classified as low-speed mixed convection with perpendicular forced flow and buoyancy directions. The hydrodynamic model was benchmarked against published pressure gradient data for a body-centered cubic lattice. Thermal performance was compared using interfacial area, the magnitude of the ANSYS Fluent surface heat transfer coefficient, interfacial heat transfer rate, and interfacial thermal resistance. At 10% relative density, Auxetic gave the lowest resistance, 112.34 K/W, compared with 327.51 K/W for Cube. At 70%, FBCC reached 97.56 K/W, whereas Cube reached 1028.12 K/W. Increasing relative density improved or degraded thermal performance depending on topology. The database provides comparative guidance for lattice selection and subsequent multiscale design optimization of lightweight aerospace and electronic heatsinks.

This paper presents a unified aerodynamic design and optimization framework for morphing Blended-Wing-Body (BWB) Unmanned Aerial Vehicles (UAVs) operating in subsonic and near-transonic regimes. The proposed framework integrates parametric CAD modeling, Computational Fluid Dynamics (CFD), and surrogate-based optimization using Response Surface Methodology (RSM) to establish a generalized approach for geometry-driven aerodynamic design under multi-Mach conditions. The study integrates classical aerodynamic principles with modern surrogate-based optimization to show that adaptive morphing geometries can maintain efficiency across varied flight conditions, establishing a scalable and physically grounded framework that advances real-time, high-performance aerodynamic adaptation for next-generation BWB UAVs. The methodology formulates the optimization problem as drag minimization under constant lift and wetted-area constraints, enabling systematic sensitivity analysis of key geometric parameters, including sweep, taper, and twist across varying flow regimes. Theoretical trends are established, showing that geometric twist and taper dominate lift variations at low Mach numbers, whereas sweep angle becomes increasingly significant as compressibility effects intensify. To validate the framework, a representative BWB UAV was optimized at Mach 0.2, 0.4, and 0.8 using a parametric ANSYS Workbench environment. Results demonstrated up to a 56% improvement in lift-to-drag ratio relative to an equivalent conventional UAV and confirmed the theoretical predictions regarding the Mach-dependent aerodynamic sensitivities. The framework provides a reusable foundation for conceptual design and optimization of morphing aircraft, offering practical guidelines for multi-regime performance enhancement and early-stage design integration.

This study investigates the influence of strut cross-sectional geometry and orientation on the crashworthiness of octet truss lattice structures produced via Multi Jet Fusion (MJF) using Polyamide 12 (PA12) material. All lattice configurations were designed and printed at a constant relative density of approximately 30%, ensuring equal mass and material usage across geometries. Quasi-static compression tests were conducted on lattices featuring circular, elliptical, rectangular, and square struts, with the latter two also evaluated at 0° and 90° orientations relative to the loading direction. Energy absorption (EA), specific energy absorption (SEA), crush force efficiency (CFE), and mean plateau stress metrics were employed to evaluate the structural energy absorption efficiency. The results highlight that strut geometry and orientation significantly alter mechanical behavior due to differences in moments of inertia. The circular strut lattice, used as the reference configuration, achieved an SEA of 0.79 J/g. Among the tested designs, the elliptical lattice exhibited the most pronounced variation: the non-rotated version showed the lowest SEA (0.63 J/g, ~20% lower than the reference), whereas the 90° rotated version yielded the highest SEA (0.92 J/g, ~16% higher). Rectangular struts displayed a similar trend, with rotated specimens outperforming their non-rotated counterparts. Square struts, however, showed negligible differences between orientations, as their rotational inertia remained constant. Overall, the findings demonstrate that optimizing strut cross-sections can enhance crashworthiness by improving energy dissipation and stabilizing deformation mechanisms under compressive loading. The rotated elliptical cross-section emerged as the most efficient configuration, offering superior SEA and crush stress efficiency. The findings highlight that cross-sectional design and orientation provide an effective mechanism for tuning mechanical performance in lightweight lattice materials without altering overall density or topology. These insights emphasize the potential of geometric tailoring in lattice design to meet safety and lightweight requirements in transportation, defense and biomedical applications.

In this paper, voxel-based Asymptotic Homogenization (AH) is employed to calculate the thermal expansion and thermal conductivity characteristics of lattice materials that have a Representative Volume Element (RVE) with non-orthogonal periodic bases. The non-orthogonal RVE of the cellular lattice is discretized using voxel elements (iso-parametric hexahedral element, on a cartesian grid). A homogenization framework is developed in python that uses a fast-nearest neighbor algorithm to approximate the (non-orthogonal) periodic boundary conditions of the discretized RVE. Validation studies are performed where results of the homogenized Thermal Expansion Coefficient (TEC) and thermal conduction performed in this paper are compared with results generated by commercially available software. These included comparison with the results for (a) bi-material unidirectional composite with orthogonal RVE cell envelope; (b) bi-material hexagon lattice with orthogonal cell envelope; (c) bi-material hexagon lattice with non-orthogonal cell envelope; and (d) bi-material square lattice. A novel approach of visualizing the contribution of each voxel towards the individual terms within the homogenized thermal conductivity matrix is presented, which is necessary to mitigate any potential errors arising from the numerical model. Additionally, the effect of the thermal expansion and thermal conductivity for bi-material hexagon lattice (orthogonal and non-orthogonal RVE cell envelope) are presented for varying internal cell angles and all permutations of material assignments for a relative density of 0.3. It is found that when comparing the non-orthogonal RVE with the Orthogonal RVE as a reference model, the numerical error due to approximating the periodic boundary condition for the non-orthogonal bi-material hexagon is generally less than 2% as the numerical error is pseudo-cyclically dependent on the discretization along the cartesian axis.

Cellular materials offer industries the ability to close gaps in the material selection design space with properties not otherwise achievable by bulk, monolithic counterparts. Their superior specific strength, stiffness, and energy absorption, as well as their multi-functionality, makes them desirable for a wide range of applications. The objective of this paper is to compile and present a review of the open literature focusing on the energy absorption of periodic three-dimensional cellular materials. The review begins with the methodical cataloging of qualitative and quantitative elements from 100 papers in the available literature and then provides readers with a thorough overview of the state of this research field, discussing areas such as parent material(s), manufacturing methods, cell topologies, cross-section shapes for truss topologies, analysis methods, loading types, and test strain rates. Based on these collected data, areas of great and limited research are identified and future avenues of interest are suggested for the continued maturation and growth of this field, such as the development of a consistent naming and classification system for topologies; the creation of test standards considering additive manufacturing processes; further investigation of non-uniform and non-cylindrical struts on the performance of truss lattices; and further investigation into the performance of lattice materials under the impact of non-flat surfaces and projectiles. Finally, the numerical energy absorption (by mass and by volume) data of 76 papers are presented across multiple property selection charts, highlighting various materials, manufacturing methods, and topology groups. While there are noticeable differences at certain densities, the graphs show that the categorical differences within those groups have large overlap in terms of energy absorption performance and can be referenced to identify areas for further investigation and to help in the preliminary design process by researchers and industry professionals alike.

Periodic truss-based lattice materials, a particular subset of cellular solids that generally have superior specific properties as compared to monolithic materials, offer regularity and predictability that irregular foams do not. Significant advancements in alternative technologies—such as additive manufacturing—have allowed for the fabrication of these uniquely complex materials, thus boosting their research and development within industries and scientific communities. However, there have been limitations in the comparison of results for these materials between different studies reported in the literature due to differences in analysis approaches, parent materials, and boundary and initial conditions considered. Further hindering the comparison ability was that the literature generally only focused on one or a select few topologies. With a particular focus on the crashworthiness of lattice topologies, this paper presents a comprehensive study of the impact performance of 24 topologies under dynamic impact loading. Using steel alloy parent material (manufactured using Selective Laser Melting), a numerical study of the impact performance was conducted with 16 different impact energy–speed pairs. It was possible to observe the overarching trends in crashworthiness parameters, including plateau stress, densification strain, impact efficiency, and absorbed energy for a wide range of 3D lattice topologies at three relative densities. While there was no observed distinct division between the results of bending and stretching topologies, the presence of struts aligned in the impact direction did have a significant effect on the energy absorption efficiency of the lattice; topologies with struts aligned in that direction had lower efficiencies as compared to topologies without.