This paper deals with the selection of the optimal material for railway wagons, from among three different steel and three aluminium based materials, by using four different Multicriteria Decision Making Methods (MCDM) and comparing their ranking of the materials. We analysed: Dual-Phase 600 steel, Transformation-Induced Plasticity (TRIP) 700 steel, Twinning-Induced Plasticity (TWIP) steel, Aluminium (Al) alloys, Al 6005-T6, and Al 6082-T6, and porous Al structure with closed cells. Four different MCDM methods were used: VIKOR, TOPSIS, PROMETTHEE and the Weighted aggregated sum product assessment method (WASPAS). Key material properties that were used in the MCDM analysis were: density, yield strength (Y.S.), tensile strength (T.S.), Y.S./T.S. ratio, Youngs modulus (Y.M.), cost and corrosion resistance (C.R.). Research results indicate that aluminium and its alloys prove to be the most suitable material, based on setup criteria. Advanced steels also achieved good ranking, making them a valid option, immediately behind lightweight aluminium alloys. Porous aluminium did not perform well, according to the used MDCM methods, mainly due to the significantly lower strength exhibited by the porous structures in general.

This paper presents 3D-printed micro-porous structures made of a Cu/PLA composite by using material extrusion 3D printing technology. A metallic filament made of 80% copper and 20% polylactic acid (PLA) was used for the 3D printing of the porous samples. We varied printing parameters, aiming to obtain a micro-range porosity that can serve as a water-filtering structure. The produced samples were analyzed from the aspects of dimensional accuracy, level of porosity, and capacity for water flow. Several samples were fabricated, and the water flow was exhibited for the samples with an approximate 100 µm size of the interconnected open porosity. The application of material extrusion 3D printing, as a cost-effective, widely available technology for producing micro-range porous structures, is still challenging, especially for interconnected predefined porosity with metal-based filaments. Our research showed that the optimization of 3D printing parameters can enable the fabrication of copper-based micro-porous structures, but further research is still needed.

Gelatin-based hydrogels are attractive bioinks for extrusion bioprinting because they combine biocompatibility, tunable rheology, and the ability to incorporate bioactive compounds. In this study, a novel multicomponent gelatin hydrogel containing fish oil, Tween 80, lecithin, glycerin, psyllium husk, and ascorbic acid was initially designed using AI-supported formulation screening and subsequently optimized experimentally for extrusion-based 3D printing. Nine acellular hydrogel constructs were fabricated using printing speeds of 1, 2, and 5 mm/s and infill densities of 5, 15, and 30%. Optical imaging, storage stability, experimentally measured density, water-contact-angle measurements, ATR-FTIR spectroscopy, and compression testing using flat cylindrical and spherical indenters were employed to characterize the printed constructs. Mass losses exceeded 60% after 7 days and reached approximately 91% after 110 days. Measured densities ranged from 0.22 to 1.24 g/cm³ across samples. All samples were hydrophilic, with contact angles of 30.07–50.63°, and higher infill increased contact angle. ATR-FTIR showed similar chemical profiles, with no clear infill-related chemical changes, suggesting that mechanical differences mainly reflected physical architecture and heterogeneity. Flat indentation generally produced higher maximum loads, except for sample S6, which reached 396.24 N under spherical loading and had the highest density (1.24 g/cm³), suggesting that its exceptional mechanical response may be associated with local material compactness and structural heterogeneity. Stress-ratio analysis yielded a mean σr/σtrue value of 4.43 with a coefficient of variation of 97.41%, while Bland–Altman analysis showed a mean bias of 0.15 MPa and limits of agreement from −0.70 to 1.01 MPa, demonstrating that the two testing methods are not directly interchangeable. Overall, hydrogel composition, internal network structure, printing infill, and local contact mechanics influenced mechanical behavior, highlighting the need for reproducible, method-specific hydrogel characterization.

This paper investigated the influence of FDM 3D printing input parameters and presented short analysis of various parameters on some specific properties of the printed parts. We examined the effect of layer height on dimensional precision of the printed parts made of polylactic acid (PLA). We experimentally tested three different layer heights (0.16 mm, 0.20 mm, 0.24 mm) and their influence on the geometric accuracy, using cross hatch infill pattern at 70% infill density. Simple 3D model of the printed structure was created to evaluate the porosity in printed part, depending on the layer height. Experimental study, as well as the computational model, both indicated that layer height showed significant influence on the dimensional precision of the printed parts. Layer height as input parameter in 3D printing also impact the accuracy of internal infill structures.