Search Results (166)

To address the growing demand for sustainable materials in advanced manufacturing, the objective of this study was to develop and characterize a novel 3D-printable biocomposite using ruminant-digested corn stover (DCS) as a reinforcement for polylactic acid (PLA). The methodology involved systematically optimizing DCS particle size (80–140 mesh) and loading concentration (5–20 wt.%), followed by fabricating composite filaments via melt extrusion and 3D printing test specimens. The resulting materials were comprehensively characterized for their morphological, physical, and mechanical properties. The optimal formulation, achieved with 120-mesh particles at 15 wt.% loading, exhibited a 15.6% increase in tensile strength to 64.17 MPa and a 21.1% enhancement in flexural modulus to 4.19 GPa compared to neat PLA. In addition to the mechanical improvements, the biocomposite offers an advantageous density reduction, enabling the fabrication of lightweight structures for resource-efficient applications. Comprehensive characterization revealed effective interfacial integration and uniform fiber dispersion, validating biological preprocessing as a viable method for unlocking the reinforcement potential of this abundant biomass. While the composite exhibits characteristic trade-offs, such as reduced impact strength, the overall performance profile makes it a promising candidate for structural applications in sustainable manufacturing. This research establishes a viable pathway for agricultural waste valorization, demonstrating that biological preprocessing can convert agricultural residues into value-added engineering materials for the circular bioeconomy. Full article

Three-dimensional (3D) concrete printing (3DCP) has gained significant attention over the last decade due to its many claimed benefits. The absence of effective real-time quality control mechanisms, however, can lead to inconsistencies in extrusion, compromising the integrity of 3D-printed structures. Although the importance of quality control in 3DCP is broadly acknowledged, research lacks systematic methods. This research investigates the feasibility of using ultrasonic pulse velocity (UPV) as a practical, in situ, real-time monitoring tool for 3DCP. Two different groups of binders were investigated: limestone calcined clay (LC³) and zeolite-based mixes in binary and ternary blends. Filaments of 200 mm were extruded every 5 min, and UPV, pocket hand vane, flow table, and viscometer tests were performed to measure pulse velocity, shear strength, relative deformation, yield stress, and plastic viscosity, respectively, in the fresh state. Once the filaments presented printing defects (e.g., filament tearing, filament width reduction), the tests were concluded, and the open time was recorded. Isothermal calorimetry tests were conducted to obtain the initial heat release and reactivity of the supplementary cementitious materials (SCMs). Results showed a strong correlation (R² = 0.93) between UPV and initial heat release, indicating that early hydration (ettringite formation) influenced UPV and determined printability across different mixes. No correlation was observed between the other tests and hydration kinetics. UPV demonstrated potential as a real-time monitoring tool, provided the mix-specific pulse velocity is established beforehand. Further research is needed to evaluate UPV performance during active printing when there is an active flow through the printer. Full article

Concrete printing technologies play a key role in the modernization of construction practices. One factor that mitigates their progress is the development of standards and characterization tools for concrete during printing. The aim of this work is to point out correlations between some printability descriptors of mortars and the data obtained from low-field nuclear magnetic resonance (NMR) relaxometry techniques. In this context, the superposed effects of an acrylic-based superplasticizer and calcium nitrate accelerator were investigated. The mortars under study are based on white Portland cement, fine aggregates, and silica fume at fixed ratios. Extrusion tests and visual inspection of the filaments evaluate the extrudability and the printing window. The selected compositions were also investigated via transverse $\left(T_2\right)$ and longitudinal $\left(T_1\right)$ NMR relaxation times. The results indicate that both additives increase the printing window of the mortar, while the accelerator induces a faster increase in specific surface area of capillary pores $\left(S/V\right)$ only after 30–60 min of hydration. Some correlations were found between the printing window and the range where the transverse relaxation rates $\left(1/T_2\right)$ and the pore surface-to-volume ratios $\left(S/V\right)$ increase linearly. This suggests some promising connections between NMR techniques and the study of structural buildup of cementitious materials. Full article

This study developed sustainable biocomposites composed of polylactic acid (PLA) and surface-treated pineapple core powder (PACP), fabricated via extrusion and fused deposition modelling (FDM). PACP loadings of 1–3 vol% were combined after chemical modification with NaOH and silane to improve interfacial bonding. Particle morphology showed increased porosity and surface roughness following treatment. The melt flow index (MFI) increased from 31.56 to 35.59 g/10 min at 2 vol% PACP, showing improved flowability. Differential scanning calorimetry (DSC) showed the emergence of cold crystallization (T_cc ~121 °C) and an increase in crystallinity from 35.7% (neat PLA) to 47.3% (2 vol% PACP). Thermogravimetric analysis showed only slight decreases in T₅ and T_max, showing the thermal stability. The mechanical testing of extruded filaments showed increased modulus (1463 to 1518 MPa) but a decrease in tensile strength and elongation. For the 3D-printed samples, elongation at break increased slightly at 1–2 vol% PACP, likely because of the improvement in interlayer fusion. Though, at 3 vol% PACP, the mechanical properties declined, consistent with filler agglomeration observed in SEM. Overall, 2 vol% PACP offered the optimal balance between printability, crystallinity, and mechanical performance. These results reveal the possibility of PACP as a value-added biowaste filler for eco-friendly PLA composites suitable for extrusion and 3D printing applications. Full article

In this research, novel biocomposite filaments were developed by incorporating coffee silver skin (CSS) waste into polylactic acid (PLA) for use in Fused Filament Fabrication (FFF) technology. CSS was blended with PLA at concentrations of 0, 5, 10, and 15 wt.% to address the waste disposal challenge and produce environmentally friendly composite biofilaments for FFF, supporting circular economic efforts. These filaments have the potential to be used in sustainable prototyping, functional parts, and consumer products. A comprehensive analysis was conducted to examine the effect of printing temperature on dimensional accuracy, melt flow index (MFI), and mechanical properties. Higher printing temperatures and increased CSS content led to larger dimensions due to increased material fluidity, as confirmed by MFI results, which increased from 3.5 g/10 min (0% CSS) to 5.8 g/10 min (15% CSS) at 180 °C, reaching 26.3 g/10 min at 220 °C. Tensile tests on 3D-printed specimens indicated an improvement in elastic modulus with increasing CSS content at lower temperatures (180 °C), rising from 1622 MPa (0% CSS) to 1952 MPa (15% CSS), representing about a 20% increase. However, at higher temperatures, the elastic modulus decreased, possibly due to the poor dispersion and agglomeration of filler particles. Tensile strength generally decreased with CSS addition, especially at higher loadings, while yield elongation remained low (~1.4–1.7%), indicating a more brittle material. The findings also revealed no significant thermal changes with increasing CSS content, and good printability was achieved for all compositions, which was characterized by good layer adhesion, the absence of warping, and the ease of extrusion. Full article

This study investigates the potential of low-density polymeric materials to enhance the deformation energy absorption of drone fuselage components manufactured using fused filament fabrication (FFF). Two materials—PLA (polylactic acid) and LW-PLA (lightweight polylactic acid)—were selected based on their accessibility, printability, and prior mechanical characterizations. While PLA is widely used in additive manufacturing, its brittleness limits its suitability for components subjected to accidental or impact loads. In contrast, LW-PLA exhibits greater ductility and energy absorption, making it a promising alternative where weight reduction is critical and structural redundancy is available. To evaluate the structural efficiency, a simplified analysis scenario was developed using a theoretical 300 J collision energy, not as a design condition, but as a comparative benchmark for assessing the performance of various metastructural configurations. The experimental results demonstrate that a stiffening core of the LW-PLA metastructure can reduce the component weight by over 60% while maintaining or improving the deformation energy absorption. Modified prototypes with hybrid internal structures demonstrated stable performances under repeated loading; however, the tests also revealed a buckling-like failure of the internal core in specific configurations, highlighting the need for core stabilization within metastructures to ensure reliable energy dissipation. Full article

This study introduced a systematic framework to develop practical design guidelines specifically for filament-based material extrusion of metals (MEX/M), an additive manufacturing (AM) process defined by ISO/ASTM 52900. MEX/M provides a cost-efficient alternative to conventional manufacturing methods, which is particularly valuable for rapid prototyping. Although AM offers significant design flexibility, the MEX/M process imposes distinct geometric and process constraints requiring targeted optimization. The research formulates and validates design guidelines tailored for the MEX/M using an austenitic steel 316L (1.4404) alloy filament. The feedstock consists of a uniform blend of 316L stainless steel powder and polymeric binder embedded within a thermoplastic matrix, extruded and deposited layer by layer. Benchmark parts were fabricated to examine geometric feasibility, such as minimum printable wall thickness, feature inclination angles, borehole precision, overhang stability, and achievable resolution of horizontal and vertical gaps. After fabrication, the as-built (green-state) components undergo a two-step thermal post-processing treatment involving binder removal (debinding), followed by sintering at elevated temperatures to reach densification. Geometric accuracy was quantitatively assessed through a 3D scan by comparing the manufactured parts to their original CAD models, allowing the identification of deformation patterns and shrinkage rates. Finally, the practical utility of the developed guidelines was demonstrated by successfully manufacturing an impeller designed according to the established geometric constraints. These design guidelines apply specifically to the machine and filament type utilized in this study. Full article

Due to the significantly increasing demand for plastic components, it has become necessary to investigate polymer recycling solutions to eliminate their adverse environmental impact. The focus of this study is to examine the feasibility of recycling polypropylene and a thermoplastic elastomer up to five times using additive manufacturing. This study also focuses on the production and evaluation of the quality of hybrid components based on polypropylene and thermoplastic elastomers. A thermomechanical recycling approach is used, which involves subjecting polymers to thermal and mechanical processes to obtain a usable material form after each recycling cycle. Additive manufacturing was used to produce specimens using the material in both filament and granular form. The thermal, mechanical, and rheological properties of the specimens were characterized by means of various analytical techniques, including tensile test, impact test, optical microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, dynamic scanning calorimetry, and rheological tests in order to study the degradation characteristics of the recycled polymers. The results generally indicate that the chosen recycling procedure causes only slight alterations in the material properties by means of thermal and rheological tests, while impacting mechanical properties and printability. Full article

To promote environmental sustainability, this research investigated the potential of utilizing recycled polymethylmethacrylate (PMMA) as raw material in material extrusion (MEX) additive manufacturing (AM). To enhance its mechanical response, carbon black (CB) was employed as the filler in nanocomposite formation. Filament extrusion of the mixture at different concentrations produced printable feedstocks for MEX AM. Rheological analysis (viscosity and material flow rate) showed that the CB introduction to the matrix was beneficial for consistent layer deposition, while differential scanning calorimetry and thermogravimetric analyses verified the thermal stability of the nanocomposites during processing. Mechanical properties were optimized, with increases in modulus (27.8% and 25.8%, respectively, in tensile and bending loadings) and tensile strength at optimal CB loadings. Dynamic mechanical analysis revealed the viscoelastic response of the nanocomposites. Raman and energy dispersive spectroscopy provided element-related insights. Surface morphology and parts structure were observed employing scanning electron microscopy and micro-computed tomography, respectively, revealing a positive impact on the AM parts due to the CB presence in the nanocomposites. The 4 wt.% in CB content nanocomposite was the optimum one. This research pioneers the development of new sustainable nanocomposite filaments and highlights the potential of next-generation MEX-based AM. Full article

Poly(ether ketone ketone) (PEKK), as a representative of high-performance poly(aryl ether ketones), shows outstanding thermomechanical properties, opening up a huge range of different applications in various technical fields. Its appearance as a quasi-amorphous polymer with a certain suppression of the crystallization process facilitates melt processing via additive manufacturing processes like material extrusion (MEX), especially in fused filament fabrication (FFF). The quality of the printing process is proven in this work by tensile testing and surface roughness measurements of suitable specimens. The MEX printing of semicrystalline PEKK faces two major challenges: on the one hand, the very high printing temperature is in contrast to established engineering plastics, and on the other hand, it is difficult to avoid crystallization after printing. The first issue can be addressed by using suitably enhanced MEX printers and the second one by selecting adapted printing parameters. The measured Young’s modulus (3.49 GPa) and tensile strength (104 MPa) values are higher than the related vendors’ data given for filaments (3.0 GPa and 92 MPa, respectively). In addition, the temperature-dependent thermal conductivity is determined, and the values of well-established PEEK (poly(ether ether ketone)) in the temperature range from 20 to 180 °C are mostly slightly higher in comparison to the related PEKK data. Based on the results, PEKK can be a useful substitute for well-established PEEK because of their comparable properties. However, PEKK has a pronouncedly lower FFF printing temperature, combined with a reduced tendency of the device to warp after printing. A larger printed test part with some surface structures shows the improved printability of PEKK in comparison to PEEK. Full article

Resorbable microparticles can be added to hydrogel-based biocompatible scaffolds to improve their mechanical characteristics and allow localised drug delivery, which will aid in tissue repair and regeneration. It is well-known that bioprinting is important for producing scaffolds personalised to patients by loading them with their own cells and printing them with specified shapes and dimensions. The question is how the addition of such particles affects the rheological responsiveness of the hydrogels (which is critical during the printing process) as well as mechanical parameters like the elastic modulus. This study tries to answer this question using a specific system: an alginate-gelatine hydrogel containing polyhydroxybutyrate-co-hydroxyvalerate (PHBV) microparticles. Scaffolds were made by bioprinting and moulding incorporating PHBV microspheres (7–12 μm in diameter) into alginate–gelatine inks (4.5 to 9.0% w/v). The microparticles (MP) were predominantly located within the polymeric matrix at concentrations up to 10 mg MP/mL ink. Higher particle concentrations disrupted their spatial distribution. Inks pre-crosslinked with 15 mM calcium and containingMPat concentrations ranging from 0 to 10 mg/mL demonstrated rheological characteristics appropriate for bioprinting, such as solid-like behaviour (G′ = 1060–1300 Pa, G″ = 720–930 Pa), yield stresses of 320–400 Pa, and pseudoplastic behaviour (static viscosities of 4000–5600 Pa·s and ~100 Pa·s at bioprinting shear rates). Furthermore, these inks allow high printing quality, assessed through scaffold dimensions, filament widths, and printability (Pr > 0.94). The modulus of elasticity in compression (E) of the scaffolds varied according to the content of MP and the manufacturing technique, with values resembling those of soft tissues (200–600 kPa) and exhibiting a maximum reinforcement effect with 3 mg MP/mL ink (bioprinted E = 273 ± 28 kPa; moulded E = 541 ± 66 kPa). Over the course of six days, the sample’s mass and shape remained stable during degradation in simulated body fluid (SBF). Thus, the alginate–gelatine hydrogel loaded with PHBV microspheres inks shows promise for targeted drug delivery in soft tissue bioengineering applications. Full article

There is a pressing need to produce novel food ingredients from sustainable sources to support a growing population. Filamentous fungi can be readily cultivated from low-cost agricultural byproducts to produce functional proteins for food biomanufacturing of structured products. However, there is a lack of scientific knowledge on the gelling characteristics of fungal proteins or their potential in additive biomanufacturing. Therefore, this study investigated the feasibility of utilizing fungal protein extracts and flours from Aspergillus awamori, Pleurotus ostreatus, Auricularia auricula-judae as sole gelling agents in 3D-printed products. Protein extracts were successfully prepared using the alkaline extraction–isoelectric precipitation method and successful physical gels were created after heating and cooling. Results indicated that shear-thinning gel materials could be formed with acceptable printability at mass inclusion rates between 15% and 25% with the best performance obtained with P. ostreatus protein extract at 25% inclusion. A. auricula-judae demonstrated promising rheological characteristics but further optimization is needed to create homogeneous products appropriate for extrusion-based 3D printing. This work provides valuable insights for continued development of 3D-printed foods with filamentous fungi. Full article

The excessive use of materials that are generally difficult to discard, such as stone materials, has caused growing ecological concern. Among these, marble is extracted from quarries, but when the raw material is exhausted, these places are deserted. For this reason, several measures have been adopted in recent years to requalify these areas. In addition, recent technological developments involve the creation of innovative green materials that privilege the circular economy and waste recycling. This research presents the development of innovative, sustainable filaments for the fused filament fabrication (FFF) printing technique from recycled marble waste (MW) and biocompostable and biodegradable polylactic acid (PLA) matrix. MW was added to the polymer in concentrations of 10 wt.%, 20 wt.%, and 30 wt.%, and the blends were extruded to develop innovative green filaments. The chemical/structural properties of the raw materials and the thermal and mechanical features of the new composites were investigated. Composites containing 10 and 20 wt.% of MW showed good printability. In contrast, extrusion and printing difficulties were observed with 30 wt.% of MW. Finally, this paper proposes a project to renaturalize and requalify a disused marble quarry located in Trani (Apulia, Italy) with 3D printing devices using the newly produced eco-filaments, which have better features. The main purpose of this article is to propose a concrete, economic, and sustainable application of 3D printing involving processes such as waste and by-product recycling and renaturalization of disused quarries, with both economic and environmental benefits. Full article

The amount of non-revenue water, mostly due to leakage, is around 126 billion cubic meters annually worldwide. A more efficient wastewater management strategy would use a parametric design for on-demand, customized pipe fittings, following the principles of distributed manufacturing. To fulfill this need, this study introduces an open-source parametric design of a 3D-printable easy-connect pipe fitting that offers compatibility with different dimensions and materials of pipes available on the market. Custom pipe fittings were 3D printed using a RepRap-class fused filament 3D printer, with polylactic acid (PLA), polyethylene terephthalate glycol (PETG), acrylonitrile styrene acrylate (ASA), and thermoplastic elastomer (TPE) as filament feedstocks for validation. The 3D-printed connectors underwent hydrostatic water pressure tests to ensure that they met the standards for residential, agricultural, and renewable energy production applications. All the printed parts passed numerous hydrostatic pressure tests. PETG couplings can tolerate up to 4.551 ± 0.138 MPa of hydrostatic pressure, which is eight times greater than the highest standard water pressure in the residential sector. Based on the economic analysis, the cost of 3D printing a pipe coupling is from three to seventeen times lower than purchasing a commercially available pipe fitting of a similar size. The new open-source couplings demonstrate particular potential for use in developing countries and remote areas. Full article

Three-dimensional bioprinting allows for the fabrication of structures mimicking tissue architecture. This study aimed to develop a gelatin-based bioink for a bioprinted simplified skin model. The bioink printability and chemical-physical properties were evaluated by varying the concentrations of gelatin (10, 15, and 20%) in a semi-crosslinked alginate-based bioink and calcium chloride (100, 150, and 200 mM) in post-printing crosslinking. For increasing the gelatin concentration, the gelatin-based formulations have a shear thinning behavior with increasing viscosity, and the filament bending angle increases, the spreading ratio value approaches 1, and the shape fidelity and the printing resolution improve. However, the formulation containing 20% of gelatin was not homogeneous, resulting also in poor printability properties. The morphology of the pores, degradation, and swelling depend on gelatin and CaCl₂ concentrations, but not in a significant way. The samples containing 15% of gelatin and crosslinked with 150 mM CaCl₂ have been selected for the bioprinting of a bilayer skin model containing human fibroblasts and keratinocytes. The model showed a homogeneous distribution of viable and proliferating cells over up to 14 days of in vitro culture. The gelatin-based bioink allowed for the 3D bioprinting of a simplified skin model, with potential applications in the bioactivity of pro-reparative molecules and drug evaluation. Full article