Search Results (86)

Material extrusion (MEX) additive manufacturing can produce material-dependent variations in dimensional fidelity, internal structure, and deposition stability, even under identical processing conditions. In this study, a comprehensive experimental investigation is conducted on MEX-printed specimens manufactured from a broad set of PLA-based composite materials to quantify these variations and assess their mutual interdependence. Dimensional behavior, internal structural characteristics, and process behavior were systematically investigated using complementary geometric, physical, and deposition-related descriptors. All properties were determined from replicated specimens to ensure statistical robustness, and the resulting datasets were examined using both conventional metrics and multivariate 3D correlation approaches. Compact PLA-based formulations exhibit consistent internal packing, characterized by relative density (RD) values of approximately 0.40–0.46, porosity (ϕ) levels around 55–60%, reduced (≤0.15%) density variability (CV), and small (−0.4–0.0%) volumetric deviations (ΔV). These features reflect stable extrusion and predictable dimensional response. In contrast, foamed, fiber-reinforced, and organic-filled composites display reduced internal packing (RD < 0.40), increased ϕ (>60%), elevated CV (0.27–0.58%), and systematically larger positive ΔV (up to +1.4%), indicating a higher sensitivity to process-induced heterogeneity. Multivariate correlations further reveal that volumetric dimensional distortion is jointly governed by internal packing efficiency and extrusion stability. Overall, the results demonstrate that dimensional accuracy in MEX of PLA-based composites arises from coupled structure–process interactions rather than isolated material or process parameters. The experimental framework proposed here provides quantitative guidance for material selection and process optimization aimed at enhancing geometric fidelity in composite filament fabrication. Full article

Additive manufacturing enables the fabrication of personalized protective equipment with locally tailored mechanical properties. In this work, a low-cost scan-to-print workflow is proposed for the fused filament fabrication (FFF) of personalized dual-zone shin guards combining a stiff outer load-distribution layer with a compliant inner energy-absorbing layer. Subject-specific leg geometry was acquired via structured-light 3D scanning and used to design a shin guard with two 3.5 mm thick zones (total thickness 7 mm). Foamable filaments of PLA, ASA, and TPU were employed to manufacture unfoamed and foamed regions by controlling extrusion temperature. Mechanical performance was assessed through three-point bending tests and dynamic finite element impact simulations. Unfoamed PLA and ASA exhibited flexural strengths of approximately 88 MPa and 72 MPa, respectively, while foaming reduced these values by about 74%. Dual-zone configurations partially restored stiffness, reaching 41 MPa for PLA and 29 MPa for ASA. TPU showed lower flexural stresses with a smaller reduction of 23% upon foaming. Impact simulations revealed maximum deformations of 1.97 mm and 2.02 mm for PLA and ASA outer zones, respectively, while TPU exhibited large deformations leading to penetration of the 3.5 mm thick inner layer. The results demonstrate that dual-zone designs manufactured via foaming-enabled FFF can effectively balance stiffness, weight, and impact response for personalized shin guard applications. Full article

Degradable polymers are essential in tissue engineering due to their capacity to mimic the extracellular matrix and promote regeneration. To be functional, they require interconnected porous structures that allow for nutrient exchange and cell migration. Although methods exist to optimize porosity, many compromise biocompatibility because pore-forming substances are used. In this context, hydrothermal pretreatment emerges as a promising technique to simultaneously improve both the porosity and mechanical properties of polymers without using potentially toxic reagents. This study proposes a novel route that combines hydrothermal pretreatment with supercritical CO₂ foaming, evaluating whether the structures obtained present better characteristics for biomedical applications compared to those obtained using supercritical CO₂ foaming alone. A screening of this novel route has been tested on individual polymers (PCL, PLA, PLGA, PVA, PBS, chitosan) and various binary combinations (PCL-PBS, chitosan-PBS, PVA-PBS, PLGA-PEDOT: PSS). The resulting materials were characterized using electron microscopy to analyze pore diameter and distribution, as well as structural stability and homogeneity. For the individual polymers, the hydrothermal pretreatment clearly improved the results obtained. However, most polymer combinations showed drawbacks such as mass losses, heterogeneity, or unsatisfactory pore formation. This research highlights the potential of hydrothermal pretreatment to optimize scaffolds, which is crucial for viability in biomedical applications. Full article

Biocomposites based on natural fibres represent a promising solution for the circular economy. The aim of this study was to develop and characterise a biodegradable composite based on sheep wool from herds raised in the Kyrgyz Republic and polylactide (PLA 4032D). Composite samples with a wool–PLA ratio of 50:50 were fabricated by thermoforming at a temperature of 168 °C for 30 s (n = 10). Mechanical properties tests were performed (PN-EN ISO 604—compression tests), for impact resistance (Charpy method), differential scanning calorimetry (DSC), and measurements of density and thermal conductivity. Biodegradation samples were subjected to enriched soil conditions for 6 weeks in two variants (with and without irrigation). The results showed that the addition of sheep wool to the PLA matrix significantly increased compressive strength (23.56 ± 5.23 MPa) and impact energy absorption (226.2 ± 23.8 kJ/m²) compared to neat PLA. After biodegradation, a 59% reduction in compressive strength was observed while maintaining an increase in fracture energy, suggesting a change in the failure mechanism. The density (0.27 ± 0.02 g/cm³) and the thermal conductivity (0.127 W/m·K) comparable to polymer foams indicate potential for thermal insulation applications. Microscopy and DSC analysis confirmed complete biodegradation under soil conditions. The developed biocomposite from Kyrgyz sheep wool demonstrates the potential for valorisation of local fibrous waste for biodegradable materials with functional insulation properties. Full article

Polylactic acid (PLA) is considered as an attractive polymer due to its renewable origin, biodegradability, and promising tensile strength and modulus. However, its inherent brittleness, characterized by a low impact resistance and elongation at break, can significantly restrict its application. This work proposes a new insight to improve the toughness of PLA while keeping its biocompatibility by incorporating two biocompatible ionic liquids (ILs), 1-ethyl-3-methylimidazolium ethyl sulfate ([emim][EtSO₄]), and tris(2-hydroxyethyl) methylammonium methylsulfate ([Tris][MeSO₄]). The modified PLA systems were thoroughly characterized to evaluate their mechanical and thermal behavior. Results demonstrated that the addition of 1 wt% of either IL resulted in significant improvement in modulus. Increasing the amount of IL resulted in an increase in the toughness while maintaining the material’s original stiffness and also the thermal stability. Furthermore, the foaming potential of the modified PLA using supercritical CO₂ was investigated as an environmentally friendly processing method. The ionic liquids contributed positively to the foamability of the material, suggesting improved gas solubility and cell nucleation during the foaming process. The addition of both IL decreased the cell size and resulted in narrower cell size distribution. These findings highlight the potential of ionic liquid-modified PLA systems for the processing of lightweight, and high-performance packaging materials. Full article

Lightweight PLA (LW-PLA) filaments enable material-saving designs in fused filament fabrication (FFF), yet optimizing their mechanical performance remains challenging due to temperature-sensitive foaming behavior. This study aims to enhance the structural strength and material efficiency of LW-PLA parts using a multi-objective statistical approach. Four key process parameters—infill density (Id), material flow rate (Mf), wall line count (Wlc), and infill pattern (Ip)—were systematically varied using a Taguchi L₁₆ orthogonal array. Tensile strength (Ts), flexural strength (Fs), and material consumption (Mc) were selected as the critical response metrics. Grey Relational Analysis (GRA) was used to aggregate these responses into a single performance index, and ANOVA determined each factor’s contribution. The optimal combination of 60% infill density, 70% material flow, 4 wall lines, and line infill pattern yielded a 9.02% improvement in the overall performance index compared to the baseline, with corresponding Ts and Fs values of 13.58 MPa and 20.51 MPa. Mf and Wlc were the most influential parameters on mechanical behavior, while Id mainly affected Mc. These findings confirm that integrating Taguchi and GRA enables effective parameter tuning for LW-PLA, balancing strength and efficiency. This work contributes to the development of lightweight, high-performance parts suitable for functional applications such as UAVs and prototyping. Full article

This study investigates the valorization of agri-food residues by repurposing industrial rosehip oil waste for sustainable food packaging development. Market demands for environmentally friendly alternatives to conventional packaging materials prompted the development of laminated multilayer materials for trays through thermo-compression, using modified cassava starch with citric acid as a compatibilizer. Physicochemical characterization revealed appropriate surface roughness (Rz of 31–64 μm) and controlled water absorption capacities of the composite materials (contact angle of 85–95°), properties critical for food quality preservation and safety. The incorporation of polylactic acid (PLA) films in the laminates significantly enhanced the mechanical performance, increasing the stress resistance by 5 to 10 times, and improved moisture resistance, showing a 78–82% reduction in the materials’ water absorption capacity and an almost 50% decrease in water content and solubility, depending on the processing method. Results indicated that these biocomposite laminates represent a viable alternative to conventional polystyrene foam trays for food packaging. Two distinct multilayer manufacturing processes were comparatively evaluated to optimize production efficiency by reducing the energy consumption and processing time. This research contributes to circular economy principles by transforming agricultural waste into value-added laminated materials with commercial potential. Full article

This study explored the innovative foaming behavior of a novel biodegradable polymer blend consisting of polylactic acid/poly(butylene succinate)/poly(butylene adipate-co-terephthalate) (PLA/PBS/PBAT) enhanced with nanohydroxyapatite (nHA), using supercritical carbon dioxide (SCCO₂) as an environmentally friendly physical foaming agent. The aim was to investigate the effects of various foaming strategies on the resulting cell structure, aiming for potential applications in tissue engineering. Eight foaming strategies were examined, starting with a basic saturation process at high temperature and pressure, followed by rapid decompression to ambient conditions, referred to as the (1T-1P) strategy. Intermediate temperature and pressure variations were introduced before the final decompression to evaluate the impact of operating parameters further. These strategies included intermediate-temperature cooling (2T-1P), intermediate-temperature cooling with rapid intermediate decompression (2T-2P), and intermediate-temperature cooling with gradual intermediate decompression (2T-2P, stepwise ΔP). SEM imaging revealed that the (2T-2P, stepwise ΔP) strategy produced a bimodal cell structure featuring small cells ranging from 105 to 164 μm and large cells between 476 and 889 μm. This study demonstrated that cell size was influenced by the regulation of intermediate pressure reduction and the change in intermediate temperature. The results were interpreted based on classical nucleation theory, the gas solubility principle, and the effect of polymer melt strength. Foaming results of average cell size, cell density, expansion ratio, porosity, and opening cell content are reported. The hydrophilicity of various foamed polymer blends was evaluated by measuring the water contact angle. Typical compressive stress–strain curves obtained using DMA showed a consistent trend reflecting the effect of foam stiffness. Full article

Halloysite nanoclay (HNC) and as-polymerized polytetrafluoroethylene powder (PTFE) were introduced into biodegradable polylactic acid (PLA) via a melt mixing technique to enhance its mechanical, rheological properties and foaming ability. The synergetic effects of these fillers on the morphological, mechanical, thermal, and foaming properties of PLA were investigated. Results indicated that the tensile properties were improved in comparison to neat PLA. Differential Scanning Calorimetry (DSC) revealed a decrease in PLA crystallization time with increasing filler concentration, indicating a strong nucleating effect on PLA crystallization. Extensional flow tests showed that strain hardening in PLA composites is influenced by fillers, with PTFE particularly exhibiting a more pronounced effect, attributed to nanofibrillation and entanglement during melt processing. The addition of a dual-filler system improved the melt strength and viscosity of PLA, resulting in foams with decreased cell size and increased cell density. Full article

The growing demand for sustainable composites has increased interest in natural fiber reinforcements as alternatives to synthetic materials. This study evaluates the bending properties of sandwich structures with flax fibers and 3D-printed lightweight foaming PLA cores compared to conventional designs using glass fibers and traditional cores. Three-point bending tests (EN 310) and density profile analysis showed that, despite its lower density, the 3D-printed foaming PLA core achieved a modulus of elasticity of 2269.19 MPa and a bending strength of 31.46 MPa, demonstrating its potential for lightweight applications. However, natural fibers influenced resin absorption, affecting core saturation compared to glass fibers. The use of bio-based epoxy and foaming PLA contributes to a lower environmental footprint, while 3D printing enables precise material optimization. These findings confirm that 3D-printed cores offer a competitive and sustainable alternative, with future research focusing on further optimization of internal structure to enhance mechanical performance. Full article

Modern tissue engineering requires not only degradable materials promoting cell growth and differentiation, but also vascularization of the engineered tissue. Porous polylactide/polycaprolactone (PLA/PCL, ratio 3/5) foam scaffolds were prepared by a combined porogen leaching and freeze-drying technique using NaCl (crystal size 250–500 µm) and a water-soluble cellulose derivative (Klucel^TM E; 10–100% w/w relative to the total PLA/PCL concentration) as porogens. Scanning electron microscopy, micro-CT, and Brunauer–Emmett–Teller analysis showed that all scaffolds contained a trimodal range of pore sizes, i.e., macropores (average diameter 298–539 μm), micropores (100 nm to 10 μm), and nanopores (mostly around 3.0 nm). All scaffolds had an open porosity of about 90%, and the pores were interconnected. The size of the macropores and the nanoporosity were higher in the scaffolds prepared with Klucel. Nanoporosity increased water uptake by the scaffolds, while macroporosity promoted cell ingrowth, which was most evident in scaffolds prepared with 25% Klucel. Human adipose-derived stem cells co-cultured with endothelial cells formed pre-vascular structures in the scaffolds, which was further enhanced in a dynamic cell culture system. The scaffolds are promising for the engineering of pre-vascularized soft tissues (relatively pliable 10% Klucel scaffolds) and hard tissues (mechanically stronger 25% and 50% Klucel scaffolds). Full article

Conventional techniques for incorporating active ingredients into polymeric matrices are accompanied by certain disadvantages, primarily attributable to the inherent characteristics of the active ingredient itself, including its sensitivity to temperature. A potential solution to these challenges lies in the utilization of supercritical carbon dioxide (scCO₂) for the formation of polymeric foam and the incorporation of active ingredients, in conjunction with the encapsulation of inclusion complexes (ICs), to ensure physical stability and augmented bioactivity. The objective of this study was to assess the impact of IC impregnation and subsequent foam formation on PLA films and PLA/PBAT blends that had been previously impregnated. The study’s methodology encompassed the formation and characterization of ICs with caffeic acid (CA) and β-cyclodextrin (β-CD), along with the thermal, structural, and morphological properties of the resulting materials. Higher incorporation of impregnated IC into the PLA(42)/PBAT(58) blend was observed at 12 MPa pressure and a depressurization rate of 1 MPa/min. The presence of IC, in addition to a lower rate of expansion, contributed to the formation of homogeneous cells with a size range of 4–44 um. On the other hand, the incorporation of IC caused a decrease in the crystallinity of the PLA fraction due to the interaction of the complex with the polymer. This study makes a significant contribution to the advancement of knowledge on the incorporation of compounds encapsulated in β-CD by scCO₂, as well as to the development of active materials with potential applications in food packaging. Full article

In this study, the mechanical behavior of AA6082 foams with Weaire–Phelan (WP) cell structures under compressive loading was analyzed. The foams were produced using the lost-PLA replication method, a cost-effective and straightforward manufacturing technique. A total of six aluminum alloy samples were fabricated and subjected to compression tests to assess both their mechanical performance and the repeatability of the results. The produced foams demonstrated a well-defined morphology and high-quality surface finish, accurately replicating the geometries of the original PLA 3D-printed templates. The experimental density of the foams closely matched theoretical values, confirming the consistency of the replication process. The compressive stress–strain response of the Weaire–Phelan cell foams displayed an initial linear elastic region, followed by three distinct plateau regions with increasing stress levels. The final densification phase occurred when the structure could no longer accommodate further plastic deformation, leading to a sharp increase in the compression load. From the stress–strain data, the specific energy absorption of the foams was calculated. The average specific energy absorption was measured to be 4 J/cm³, with a standard deviation of 0.49 J/cm³ across the six tested samples. These results indicate reliable mechanical performance and reproducibility of the manufacturing process, making these foams suitable for applications requiring energy absorption and lightweight structural components. Full article

Built indoor IoT-based urban farms successfully combine the cultivation of fresh vegetables with attractive architectural designs. Moreover, implementing IoT-driven urban agriculture requires installing multiple IoT devices containing sensors, controllers, transceivers, and antennas for real-time data transmission. In this context, several factors, including the height of the IoT device above the soil level and the water content in the soil, can affect antenna performance and, consequently, the propagation of radio waves. This paper presents the results from numerical and experimental studies that evaluate the impact of soil on the performance of a monopole antenna for three different antenna positions relative to the soil in a pot and two soil water contents, presented by twelve scenarios. The results show that the antenna has a stable performance in six of the twelve scenarios, with a minimal shift in the resonant frequency of 3% and a narrowing of the frequency bandwidth by 2% compared to the antenna in free space. In the worst-case scenario, the antennas demonstrate a reduction in radiation efficiency of 44%, with the frequency bandwidth narrowing by up to 14% for the antenna fabricated on a PLA substrate and up to 17% for the one built on a foam board substrate. Full article

The mechanical behavior of AA6082 Kelvin cell foams under compressive tests has been investigated in this work. The lost-PLA replication technique, a simple and cheap technique, has been adopted as the production method. Six Al alloy samples have been made and successively subjected to compressive tests in order to examine the mechanical response and the repeatability too. The manufactured foams show good morphology and surface finishing, replicating the PLA 3D-printed foams with adequate accuracy. The experimental density of the foam has been found in good agreement with the theoretical one. When subjected to static compression, the Kelvin cell foams exhibit a load–strain diagram characterized by the initial linear stage followed by two plateaus at successively increasing load levels. Final densification occurs when there is no more space available for further plastic deformation and the load sharply increases. The specific absorbed energy has been calculated from load–strain curves: the average measured value was found to be 2.3 J/cm³, and standard deviation in the six compression tests was 0.3 J/cm³. Full article