Georgios Maliaris

This study investigates the mechanical behaviour of additively produced Voronoi lattice structures with controlled anisotropy and a constant porosity of 80%, simulating the porous structure of trabecular bones. Anisotropy was tuned by adjusting the size of the structures along the z-axis using a generative Computer-Aided Design (CAD) algorithm, resulting in five different types: an isotropic one and four anisotropic variations. All samples were subjected to uniaxial compressive loading in the z-direction to measure their elastic modulus, yield strength, and ultimate stress. Statistical analysis of strut orientation revealed that the struts of elongated variables, oriented in the z-direction and presented enhanced stiffness and load-carrying capacity, whereas the struts of compressed lattices shifted towards the XY plane and were prone to bending, thus producing long plateaus in the stress–strain diagrams. These findings demonstrate the influence of geometric anisotropy on the mechanical properties of stochastic lattices, with implementations in structures design for tuneable performance in biomimetic structures.

This study examines the effect of geometrically controlled anisotropy on the compressive behaviour of additively manufactured Voronoi cellular structures. Three configurations—an isotropic reference and two anisotropic variants generated by scaling the design domain along the Z-axis—were fabricated by stereolithography using a tough photopolymer resin. All specimens exhibited an approximate nominal porosity of 80%. Compressive tests were conducted along the X, Y, and Z directions in accordance with ASTM D1621. The elongated structure showed enhanced stiffness and strength when loaded parallel to the scaling axis, whereas the compressed structure exhibited improved performance in the transverse directions. The isotropic structure displayed similar responses in all axes. These results demonstrate that geometric scaling effectively induces directional mechanical anisotropy without altering relative density, offering a simple route to tailor the load-bearing behaviour of lightweight architected materials.

Additive manufacturing is rapidly expanding across industries but generates substantial polymer waste, particularly in Selective Laser Sintering (SLS), of which considerable quantities of unfused powder and faulty prints are typically discarded

This study investigates the structural and mechanical properties of Cu–Se-based thermoelectric materials with varying Cu:Se stoichiometries (1.8, 1.9, and 2.0). Phase composition was examined using X-ray diffraction (XRD), revealing a transition from a mixed α/β-phase in Cu:Se = 2.0 to a fully cubic β-phase Cu_2−xSe in Cu:Se = 1.8. Crystallite size analysis showed a reduction with increasing Cu content, which strongly influenced mechanical behavior. Vickers microhardness and nanoindentation tests were employed to assess hardness, elastic modulus, and elastic recovery. The Cu:Se = 2.0 sample exhibited the highest hardness but the lowest elastic recovery and elastic modulus from indentation, suggesting strong intragrain cohesion but limited elastic deformation due to fine grain structure. In contrast, the sub-stoichiometric Cu:Se = 1.8 phase displayed higher elastic modulus and recovery, possibly due to a more rigid Se sub-lattice and defect-mediated deformation mechanisms. Compression tests confirmed the higher bulk modulus in the Cu-deficient phase. Bending tests also showed that the Cu-deficient phase exhibited the highest bending modulus, further supporting its enhanced stiffness under elastic deformation. These results highlight the significant role of stoichiometry and crystallite structure in tuning the mechanical response of thermoelectric Cu–Se compounds, with implications for their durability and performance in practical applications.

Triply periodic minimal surfaces (TPMSs) structures are particularly suited for energy-absorbing, light-weight applications in fields such as medicine and engineering due to their ability to achieve maximum stress distribution with minimum density. Advances in stereolithography apparatus (SLA) three-dimensional (3D) printing and hard resins make it possible to fabricate such complex geometries precisely. The present study contrasts the mechanical performance of six geometries of TPMS under com-pressive loading with particular focus on how wall geometry and thickness affect it but at a fixed porosity of 75% and size of 70 × 70 × 70 mm³. Among the structures, the peak compressive stress was the maximum in Gyroid (2.1 MPa), while Neovius demonstrated remarkably good performance (0.9 MPa) despite its low wall thickness. The objective is to analyze geometry-dependent performance trends in order to inform future structural design. These results imply that TPMS geometry can have a significant effect on mechanical response, regardless of wall thickness alone.

Glass was introduced as an additive to filaments used for the manufacturing of composite materials, employed by Additive Manufacturing applications. Glass accounts for a large waste electric and electronic equipment (WEEE) percentage, and its recovery and recycling can lead to the production of sustainable composite materials. In this work, poly(lactic acid) (PLA)/commercially available silicon oxide composite filaments were manufactured and their structural, thermal, rheological, and mechanical properties were assessed. Scanning Electron Microscopy confirmed the 1:2 ratio of silicon: oxygen, along with the relatively low adhesion between the filler and the matrix. Differential Scanning Calorimetry presented steady glass transition and melting temperatures of composites, whereas a crystallization temperature of 10% wt. and a crystallinity of 15% wt. composite slightly increased. Rheological analysis showcased that the viscosity of the composite filaments decreased compared to PLA (10–100 compared to 300–400 Pa·s), with a more shear-thinning behavior. Dynamic mechanical analysis exhibited increased elastic, flexural moduli, and flexural strength of composites (up to 16, 23, and 11%, respectively), whereas tensile strength and elongation decreased. The affordability of raw materials (with the future introduction of recycled ones) and the minimal processing steps can lead to the potential scaling up of the study.

The thermoelectric materials community has made significant progress on nanostructured and processable materials to improve efficiency and flexibility, reducing manufacturing costs. Selenide compounds, such as Ag₂Se and Cu₂Se, have received a lot of attention because of their promising capabilities in thermoelectric applications. Additionally, Se is significantly more abundant than Te, with approximately ten times higher availability. High-energy ball milling (HEBM) process is a powerful solid-state synthesis/powder mechanical alloying method. The objective of this work is to form selenide compounds at different milling times (1–20 h) by HEBM process. The structural characterization of the compounds was studied by X-ray Diffraction and X-ray Photoelectron Spectroscopy, while the thermal stability of the prepared samples was examined by Thermogravimetric Analysis. The experimental results show that the Ag₂Se sample synthesized at 20 h presents lower thermal stability because of the higher specific surface area and the increased porosity as a result of the hardening effect. Additionally, Cu₂Se presents Cu₂O(SeO₃) as the main phase at low temperatures, while at higher temperatures, CuO is the dominant phase. Therefore, as the heating temperature increases, there is a complete evaporation of Se and a conversion of the remaining copper into copper oxide. The present study demonstrates a simple method for the synthesis of Ag₂Se and Cu₂Se thermoelectric materials with high oxidation resistance.