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Short fiber reinforced thermoplastic composites (SFRTC) have gained popularity in the material extrusion (MEX) method, which is an additive manufacturing (AM) technology, allowing for the simpler and more cost-effective production of polymer composites. However, parts produced using MEX 3D printing technology often exhibit poor mechanical properties and surface quality compared to products manufactured using injection molding, which is one of the main disadvantages of this method. Various methods are used to overcome these challenges, such as production in a vacuum environment, heat-based processes, ultrasonic vibrations, and others. The objective of this study was to achieve parts with lower porosity and improved mechanical properties when printed in a vacuum environment compared to an atmospheric environment. Additionally, an investigation into the optimization of printing parameters was conducted to determine the parameters that yield the highest mechanical properties. For this purpose, SFRTC parts were printed at different vacuum levels (0.5, 10, 100 mbar), and they were subjected to flexural tests to determine their mechanical properties. The results showed that the flexural stress and elastic modulus of the samples produced in a 0.5 mbar vacuum environment increased by 79.75% and 39.41%, respectively, compared to samples produced in an atmospheric environment. Furthermore, the cross-sectional images of the samples were examined using an optical microscope, revealing the lowest porosity in the samples printed in 0.5 mbar vacuum environment. [ABSTRACT FROM AUTHOR]

In this study, we investigated the performance improvement caused by the addition of copper (Cu) nanoparticles to high-density polyethylene (HDPE) matrix material. Composite materials, with filler percentages of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 wt% were synthesized through the material extrusion (MEX) 3D printing technique. The synthesized nanocomposite filaments were utilized for the manufacturing of specimens suitable for the experimental procedure that followed. Hence, we were able to systematically investigate their tensile, flexural, impact, and microhardness properties through various mechanical tests that were conducted according to the corresponding standards. Broadband Dielectric Spectroscopy was used to investigate the electrical/dielectric properties of the composites. Moreover, by employing means of Raman spectroscopy and thermogravimetric analysis (TGA) we were also able to further investigate their vibrational, structural, and thermal properties. Concomitantly, means of scanning electron microscopy (SEM), as well as atomic force microscopy (AFM), were used for the examination of the morphological and structural characteristics of the synthesized specimens, while energy-dispersive Xray spectroscopy (EDS) was also performed in order to receive a more detailed picture on the structural characteristics of the various synthesized composites. The corresponding nanomaterials were also assessed for their antibacterial properties regarding Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with the assistance of a method named screening agar well diffusion. The results showed that the mechanical properties of HDPE benefited from the utilization of Cu as a filler, as they showed a notable improvement. The specimen of HDPE/Cu 4.0 wt% was the one that presented the highest levels of reinforcement in four out of the seven tested mechanical properties (for example, it exhibited a 36.7% improvement in the flexural strength, compared to the pure matrix). At the same time, the nanocomposites were efficient against the S. aureus bacterium and less efficient against the E. coli bacterium. The use of such multi-functional, robust nanocomposites in MEX 3D printing is positively impacting applications in various fields, most notably in the defense and security sectors. The latter becomes increasingly important if one takes into account that most firearms encompass various polymeric parts that require robustness and improved mechanical properties, while at the same time keeping the risk of spreading various infectious microorganisms at a bare minimum. [ABSTRACT FROM AUTHOR]

In this study, we investigated the performance improvement caused by the addition of copper (Cu) nanoparticles to high-density polyethylene (HDPE) matrix material. Composite materials, with filler percentages of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 wt% were synthesized through the material extrusion (MEX) 3D printing technique. The synthesized nanocomposite filaments were utilized for the manufacturing of specimens suitable for the experimental procedure that followed. Hence, we were able to systematically investigate their tensile, flexural, impact, and microhardness properties through various mechanical tests that were conducted according to the corresponding standards. Broadband Dielectric Spectroscopy was used to investigate the electrical/dielectric properties of the composites. Moreover, by employing means of Raman spectroscopy and thermogravimetric analysis (TGA) we were also able to further investigate their vibrational, structural, and thermal properties. Concomitantly, means of scanning electron microscopy (SEM), as well as atomic force microscopy (AFM), were used for the examination of the morphological and structural characteristics of the synthesized specimens, while energy-dispersive X-ray spectroscopy (EDS) was also performed in order to receive a more detailed picture on the structural characteristics of the various synthesized composites. The corresponding nanomaterials were also assessed for their antibacterial properties regarding Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with the assistance of a method named screening agar well diffusion. The results showed that the mechanical properties of HDPE benefited from the utilization of Cu as a filler, as they showed a notable improvement. The specimen of HDPE/Cu 4.0 wt% was the one that presented the highest levels of reinforcement in four out of the seven tested mechanical properties (for example, it exhibited a 36.7% improvement in the flexural strength, compared to the pure matrix). At the same time, the nanocomposites were efficient against the S. aureus bacterium and less efficient against the E. coli bacterium. The use of such multi-functional, robust nanocomposites in MEX 3D printing is positively impacting applications in various fields, most notably in the defense and security sectors. The latter becomes increasingly important if one takes into account that most firearms encompass various polymeric parts that require robustness and improved mechanical properties, while at the same time keeping the risk of spreading various infectious microorganisms at a bare minimum.

In this study, titanium nitride (TiN) was selected as an additive to a high-density polyethylene (HDPE) matrix material, and four different nanocomposites were created with TiN loadings of 2.0–8.0 wt. % and a 2 wt. % increase step between them. The mixtures were made, followed by the fabrication of the respective filaments (through a thermomechanical extrusion process) and 3D-printed specimens (using the material extrusion (MEX) technique). The manufactured specimens were subjected to mechanical, thermal, rheological, structural, and morphological testing. Their results were compared with those obtained after conducting the same assessments on unfilled HDPE samples, which were used as the control samples. The mechanical response of the samples improved when correlated with that of the unfilled HDPE. The tensile strength improved by 24.3%, and the flexural strength improved by 26.5% (composite with 6.0 wt. % TiN content). The dimensional deviation and porosity of the samples were assessed with micro-computed tomography and indicated great results for porosity improvement, achieved with 6.0 wt. % TiN content in the composite. TiN has proven to be an effective filler for HDPE polymers, enabling the manufacture of parts with improved mechanical properties and quality. [ABSTRACT FROM AUTHOR]

By enabling the development of complex structures with adaptable qualities, techniques for additive manufacturing have opened new routes for material development and research. In this research, silicon nitride (Si3N4) ceramic nanoparticles are incorporated into polypropylene (PP) matrices. Various loading levels and standardized test specimens that adhere to ASTM criteria are created. The main goal is to thoroughly characterize these composites with an emphasis on their mechanical capabilities. The rheological, thermomechanical, and morphological properties of 3D-printed PP/Si3N4 composites created using material extrusion (MEX) 3D printing are examined. Thermogravimetric analysis and differential scanning calorimetry are exploited to study thermal stability and phase transitions in composite materials. Mechanical testing is conducted to determine mechanical qualities, such as flexural and tensile strength and modulus of elasticity. For detailed characterization of the nanocomposites, scanning electron microscopy, and Raman spectroscopy are also performed. The results provide insight into the impact of Si3N4 nanoparticles on the mechanical properties, thermal stability, and rheological behavior of PP/Si3N4 composites. The 2 wt% Si3N4 filler showed overall the best performance improvement (21% in the tensile modulus of elasticity, 15.7% in the flexural strength, and high values in the remaining properties assessed). The nanocomposite with the maximum Si3N4 loading of wt% showed a 33.6% increased microhardness than the pure PP thermoplastic, showing a promising wear resistance for the parts built with it. This research reveals the ability of Si3N4 ceramic nanoparticles to improve the mechanical characteristics of PP-based compounds produced by MEX 3D printing. [ABSTRACT FROM AUTHOR]

Large-Scale Material Extrusion (LS-MEX) is increasingly being used in small-scale production and prototyping due to its ability to create components in new temporal and spatial dimensions. However, the use of this manufacturing process poses microscopic and macroscopic challenges not encountered in previous small-scale production systems. These challenges arise primarily from the prolonged retention of heat in the material, which leads to insufficient strength in the extruded strands at the macrostructural level. As a result, the component can collapse, a phenomenon known as 'slumping'. Thermal energy also influences microstructural changes, such as crystallisation kinetics, which affect properties such as the strength and stiffness of the final product. The duration and dynamics of thermal energy are influenced by manufacturing parameters and the possible use of additional peripheral equipment, which affects component quality. In this study, the influence of thermal energy on structural processes through simulations of polyamide 6 with 40% carbon fibres (PA6 wt.%40 CF) is investigated. The results show that by adjusting the process parameters and using modification units, the thermal profile of the material can be accurately controlled, which allows the microstructural processes to be precisely controlled. This leads to the targeted modification of the macroscopic material properties. The focus of this work is on the combination of numerical simulations of the LS-MEX process with semi-empirical methods for the analysis of crystallisation processes. The application of the Nakamura model, which is used throughout similar investigations, allows a detailed description and prediction of the crystallisation kinetics during the manufacturing process. The study shows that the absolute degree of crystallisation can be determined with simplified assumptions using a combination of thermal simulations and semi-empirical approaches. It was found that the absolute degree of crystallisation increases from the outer interface of the strand to the print bed across the cross-section. This can be attributed to the specific thermal boundary conditions and the resulting temperature profiles at different points. [ABSTRACT FROM AUTHOR]

In this study, poly (ethylene terephthalate) (PETG) was combined with Antimony-doped Tin Oxide (ATO) to create five different composites (2.0–10.0 wt.% ATO). The PETG/ATO filaments were extruded and supplied to a material extrusion (MEX) 3D printer to fabricate the specimens following international standards. Various tests were conducted on thermal, rheological, mechanical, and morphological properties. The mechanical performance of the prepared nanocomposites was evaluated using flexural, tensile, microhardness, and Charpy impact tests. The dielectric and electrical properties of the prepared composites were evaluated over a broad frequency range. The dimensional accuracy and porosity of the 3D printed structure were assessed using micro-computed tomography. Other investigations include scanning electron microscopy and energy-dispersive X-ray spectroscopy, which were performed to investigate the structures and morphologies of the samples. The PETG/6.0 wt.% ATO composite presented the highest mechanical performance (21% increase over the pure polymer in tensile strength). The results show the potential of such nanocomposites when enhanced mechanical performance is required in MEX 3D printing applications, in which PETG is the most commonly used polymer. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate glycol (PETG) and silicon nitride (Si3N4) were combined to create five composite materials with Si3N4 loadings ranging from 2.0 wt.% to 10.0 wt.%. The goal was to improve the mechanical properties of PETG in material extrusion (MEX) additive manufacturing (AM) and assess the effectiveness of Si3N4 as a reinforcing agent for this particular polymer. The process began with the production of filaments, which were subsequently fed into a 3D printer to create various specimens. The specimens were manufactured according to international standards to ensure their suitability for various tests. The thermal, rheological, mechanical, electrical, and morphological properties of the prepared samples were evaluated. The mechanical performance investigations performed included tensile, flexural, Charpy impact, and microhardness tests. Scanning electron microscopy and energy-dispersive X-ray spectroscopy mapping were performed to investigate the structures and morphologies of the samples, respectively. Among all the composites tested, the PETG/6.0 wt.% Si3N4 showed the greatest improvement in mechanical properties (with a 24.5% increase in tensile strength compared to unfilled PETG polymer), indicating its potential for use in MEX 3D printing when enhanced mechanical performance is required from the PETG polymer. [ABSTRACT FROM AUTHOR]

In this work, a novel dual-phase metamaterial, named as “hybrid lattice metamaterial (HLM),” are designed and fabricated by combining reentrant and sea-urchin (SU) based surface-lattice (SL) structure with polyamide12 (PA12) material via material extrusion (MEX) process. Four different designs with varying reentrant truss thicknesses of 0.8 mm (H1), 1.0 mm (H2), 1.2 mm (H3), and 1.5 mm (H4) have been modified to assemble seamlessly with the empty spaces within the SL structure. Quasistatic compression tests were conducted to evaluate the deformation modes and compression characteristics. The findings from quasistatic experiments were subsequently validated using numerical simulations. The H4 metamaterial exhibited superior structural properties, with 42 % increase in stiffness and 35 % enhancement in specific energy absorption compared to only SL structure. Additionally, dynamic sinusoidal compression tests were conducted to evaluate the dynamic elastic ratio (DER), hysteresis work and viscoelastic properties using the tan δ. The H4 metamaterial outperformed the SL in all dynamic properties, with a 50 % increase in elastic modulus and 36 % increase in hysteresis work. This study shows metamaterial properties can be tailored for specific requirements. SL structure facilitate elastic recovery, while H4 metamaterials offer superior energy absorption and stability, making it well-suited for protective equipment and impact-resistant components.

In the realm of material innovation, the remarkable versatility of thermoplastic-based highly filled composites emerges as a pivotal advantage for fabricating metal parts, seamlessly integrating design flexibility. This study delves into the fusion of design and manufacturing, spotlighting the convergence of material extrusion additive manufacturing (MEX) and metal injection moulding (MIM) processes through the adept utilization of three distinct in-house developed copper-feedstocks. Each feedstock had a different composition that influenced their processability; two feedstocks were for solvent and thermal debinding, and one was only for thermal debinding. The sintering was carried out under the same conditions for all produced specimens to assess the effect of binder composition on the properties of the sintered components. Structural integrity evaluations of sintered specimens encompassed 3-point bending, hardness tests, and metallography. It was possible to perform MEX with all produced filaments and MIM with the pellets of the same feedstocks and to obtain acceptable-quality specimens. Regardless of the shaping method, specimens shaped with binders containing a soluble binder survived the thermal and sintering steps. The specimens produced from the feedstock intended solely for thermal debinding experienced a nearly complete loss of shape during the debinding process. For the specimens that could be debound and sintered without defects, a relative density between ∼88 and 94 % was measured for MEX components and ∼93 and 95 % for MIM components after sintering. All sintered components showed the same diffraction peaks as pure copper powder, confirming that the reductive hydrogen atmosphere provided protection from contamination and reduced the oxides that could have appeared during thermal debinding in air. Moreover, adequate shrinkage of ∼10–18 % was observed in the sintered specimens. Vickers microhardness of the MEX and MIM sintered components were ∼32 HV and ∼36 HV, respectively. Compared to MEX, MIM-produced sintered components showed a higher maximum stress (i.e., σmax = 79 ± 3.2 MPa). These results demonstrate that the binder composition plays a crucial role in determining the success of metal MEX and MIM processes. Having the possibility to choose between MEX and MIM allows for greater design flexibility for copper parts.

AbstractHerein, a new generation of printable bio-composite nanofilaments is explored. The aim was to explore the efficiency of Titanium nitride (TiN) as a reinforcing agent for the Fused Filament Fabrication (FFF) 3D printing technique. TiN, a common ceramic in medical devices, in nanopowder form, was used as a polymer enhancer for the also popular medical devices polypropylene thermoplastic. Such filaments with superior performance are needed for demanding app­lications, in which common polymers do not meet the specifications. To fully comprehend the material qualities and behaviour, a variety of tests, including mechanical testing, thermal and rheological investigation, and spectroscopic analysis, were carried out following standards. The effect of the filler percentage was also considered. The morphological properties of the materials were also assessed. The mechanical response of the nanocomposite with a ‑2.0 wt. % filler concentration showed the best improvements in all experiments conducted, including tensile (41.5%), flexural (33.7%), and impact (18.0%) strength. The microhardness was improved 44.8% by the 2.0 wt. % filler concentration nanocomposite. Overall, the efficiency of TiN as a reinforcement agent in FFF 3D printing was proven, making the proposed nanocomposites a sufficient solution when improved performance is required.

Metal-based additive manufacturing (MBAM) has enabled rapid prototyping and one-off production, but the cost of equipment has limited widespread adoption. Recent developments in hybrid filaments and processes have created more accessible methods for MBAM, leveraging common fused filament fabrication (FFF) printers and Ultrafuse 316L metal filament. This technique has shown promise but suffered from large pore formations along parallel print paths. To reduce the formation of process-dependent pores, a design of experiments (DOE) was conducted to investigate the effects of varying extrusion parameters such as layer height, line width, and extrusion multiplier for tensile samples produced on a Creality Ender 3 V2 and MakerBot Method X. Characterization techniques included tensile testing, microhardness, density measurements, and optical microscopy; findings were compared to samples produced via laser-powder bed fusion (L-PBF) and from 316L plate. The Method X produced components with approximately 1% porosity and the Ender 4% porosity. Mechanical properties for both FFF printers were comparable to previous research, with an increase in tensile strength for the Method X. Despite the increased porosity in the Ender samples, only a 7% reduction in strength from the average yield in Method X samples (153.6 MPa) was observed. It was found that a combination of increased layer height and extrusion rate led to improved mechanical properties in parts printed on the Ender, while the default Makerbot settings resulted in the best overall performance for Ultrafuse 316L samples. [ABSTRACT FROM AUTHOR]

This study investigated the influence of specimen geometry on the mechanical properties of 3D‐printed parts by material extrusion (MEX). Four widely used technical standards were evaluated (ASTM D638, ASTM D3039/D3039M‐14, ISO 527/2, and ISO 37), and all possible geometries were tested. The specimens were subjected to uniaxial tensile loading using a universal testing machine to obtain the mechanical properties of ultimate tensile strength, yield strength, and Young modulus. Mean, SD, and CV values, as well as NS10 (number of specimens tested to reach at least 10 valid data) are geometry‐dependent. A critical analysis of these data allowed proposing the standard evaluation index (ISE) of the specimen geometry (standard) based on data variance and test efficiency to achieve valid data. The results indicate that ASTM D638 performed better than any other standard. For investigations involving the mechanical properties of tensile strength Types I and II (ASTM D638) are the most recommended specimens geometry (standard) for 3D MEX printing because it combines the lowest CV¯ with the minimum NS10. By following it, researchers and material suppliers can ensure accurate and reliable assessments of the mechanical properties of 3D‐printed parts, contributing to increased safety, reliability, and quality in additive manufacturing. Notes: MEX – Material Extrusion, ASTM – American Society for Testing and Materials, ISO – International Organization for Standardization, SD – Standard Deviation, CV – Coefficient of Variation, NS10 – Number of specimens tested to reach at least 10 valid data, ISE – Standard Evaluation Index. [ABSTRACT FROM AUTHOR]

Material Extrusion (MEX) Additive Manufacturing of metal components is increasingly applied in recent years due to its low cost and potential for multi-material printing, with filament-based MEX being widely developed among all subdivisions of MEX. This technology utilises a compounded filament of polymeric binders and metal powder. The printing process involves hot extrusion of the compounded filament, which acts as a carrier of the metal powder and is deposited along a programmed print path to construct a 3D part. The as-printed parts are debound in several steps to ensure complete binder removal and pressureless sintered, targeting high densification levels. In this work, a copper-based filament was utilised as feedstock material and a full factorial design of experiments was performed to study the effect of layer height, volumetric speed and flowrate multiplier on the density of the as-printed part. Selected specimens from the DoE were debound and sintered and characterised. Various tests including density measurements, SEM, optical microscopy, micro-CT, etc., were applied at different stages to evaluate the porosity in the filament and printed parts. As a result, a relative density of 94% and an electrical conductivity of 63 %IACS (international annealed copper standard) were achieved for the sintered copper, which could be directly linked to the purity of the feedstock material. [ABSTRACT FROM AUTHOR]

This research focused on developing medical-grade polypropylene (PP)/silver (Ag) nanocomposites for the production of components through material extrusion (MEX) three-dimensional printing (3DP). The objective was to improve the performance of PP by enhancing its mechanical properties and imparting antibacterial characteristics. An industrially scalable process was utilized to fabricate PP/Ag nanocomposites through the reactive melt mixing technique. Polyethylene glycol (PEG) served as the reduction agent, and silver nitrate (AgNO3) was incorporated as the additive. During the extrusion of the three-dimensional printing (3DP) filaments, reactive melt mixing occurred, resulting in the production of specimens for various standard tests. The addition of 5.0 wt% AgNO3 and 2.5 wt% PEG in the PP thermoplastic led to a slight improvement in mechanical performance, with a 9.9 % increase in tensile strength observed. The antibacterial properties of the composites were assessed through agar well diffusion tests against Escherichia coli (E-coli) and Staphylococcus aureus (S. aureus). A more significant biocidal effect was observed for S. aureus compared to E-coli. These composites have the potential to be utilized in industrial applications that require enhanced mechanical properties and durability, as well as important biocidal properties, such as in the medical equipment industry or the defense sector.

Improving the resilience of 3D-printed composites through material extrusion technology (MEX) is an ongoing challenge in order to meet the rigorous requirements of critical applications. The primary objective of this research was to enhance the impact resistance of 3D-printed composites by incorporating continuous hybrid fibers. Herein, continuous virgin carbon (1k) and Kevlar (130D and 200D) fibers were used with different weight and volume fractions as reinforcing fibers to produce hybrid and non-hybrid composites for impact resistance testing to obtain energy absorption with different impact energies: 20 J, 30 J, 40 J, and 50 J. Moreover, 0°/90° fiber orientations were used. Hybrid composites with combinations of PLA + CF + 130D KF and PLA + CF + 200D KF showed higher impact resistance, less damaged areas (71.45% to 90.486%), and higher energy absorption (5.52–11.64% more) behaviors compared to PLA + CF non-hybrids. CT scan images provided strong evidence to resist the fracture and breakage patterns, because the stiffness and elongation properties of the fibers acted together in the hybrids specimens. Furthermore, positive hybrid effects of the PLA + CF + KF hybrids also showed an ideal match of toughness and flexibility in order to resist the impacts. In the future, these hybrids will have the potential to replace the single type of composites in the fields of aerospace and automobiles. [ABSTRACT FROM AUTHOR]

The goal of this paper is to investigate tungsten carbide (WC) as a reinforcement in the popular material extrusion (MEX) additive manufacturing (AM) procedure. The impressive characteristics of WC demonstrate its potential as a valuable additive for commonly used polymeric matrices in MEX 3D printing, offering reinforcement and stabilization properties. The mechanical properties of hybrid polymer/ceramic nanocomposites made up of various filler loadings (0–10 wt. %) of medical-grade polylactic acid (PLA) and WC were studied. The mechanical characteristics, structure, and thermomechanical properties of the resulting compounds were fully characterized following the respective standards. The fracture mechanisms were revealed with Scanning Electron Microscopy. Overall, a laborious effort was implemented with fifteen different tests to fully characterize the nanocomposites prepared. In comparison to the raw PLA material, the tensile strength of the 4.0 wt. % WC PLA/WC nanocomposite was improved by 42.5% and the flexural strength by 41.9%. In the microhardness test, a 120.4% improvement was achieved, justifying the properties of WC ceramic. According to these findings, PLA nanocomposites reach high-performance polymer specifications, expanding their potential use, especially in wear-related applications. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) composites reinforced with hexagonal boron carbide (B4C) nanoparticles were constructed using a Material Extrusion (MEX) 3D printing method. The goal was to provide nanocomposites for MEX 3D printing with enhanced mechanical properties by exploiting the superior properties of the B4C additive. The fabricated 3D-printed specimens were subjected to standard evaluation tests to determine the effect of the B4C nanofiller level inside the polymer framework on their mechanical, thermal, and rheological properties. The structures and fracture patterns of the filaments and specimens were inspected by electron microscopy. Raman spectroscopy and energy-dispersive spectroscopy were used to determine the chemical compositions of the nanocomposites. Comparing the unfilled polymeric matrix to the B4C-filled nanocomposites reveals that the mechanical strength of the novel nanocomposite material was substantially increased. The optimum nanocomposite concentration of PP/ B4C 6.0 wt% outperformed reference PP by 18.3%, 10.8%, 11.8%, and 15.6% in terms of flexural and impact strength, as well as tensile and flexural toughness, respectively, while having notably improved performance in the remaining mechanical properties. The nanocomposites presented herein can support applications that require polymeric materials with advanced mechanical properties.

Abstract The development of sustainable and functional biocomposites remains a robust research and industrial claim. Herein, the efficiency of using eco-friendly biochar as reinforcement in Additive Manufacturing (AM) was investigated. Two AM technologies were applied, i.e., vat photopolymerization (VPP) and material extrusion (MEX). A standard-grade resin in VPP and the also eco-friendly biodegradable Polylactic Acid (PLA) in the MEX process were selected as polymeric matrices. Biochar was prepared in the study from olive trees. Composites were developed for both 3D printing processes at different biochar loadings. Samples were 3D-printed and mechanically tested after international test standards. Thermogravimetric Analysis and Raman revealed the thermal and structural characteristics of the composites. Morphological and fractographic features were derived, among others, with Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Biochar was proven to be sufficient reinforcement agent, especially in the filament MEX process, reaching more than 20% improvement at 4 wt.% loading in tensile strength compared to the pure PLA control samples. In the VPP process, results were not as satisfactory, still, a 5% improvement was achieved in the flexural strength with 0.5 wt.% biochar loading. The findings prove the strong potential of biochar-based composites in AM applications, too. Graphical Abstract

In this study, titanium nitride (TiN) was selected as an additive to a high-density polyethylene (HDPE) matrix material, and four different nanocomposites were created with TiN loadings of 2.0–8.0 wt. % and a 2 wt. % increase step between them. The mixtures were made, followed by the fabrication of the respective filaments (through a thermomechanical extrusion process) and 3D-printed specimens (using the material extrusion (MEX) technique). The manufactured specimens were subjected to mechanical, thermal, rheological, structural, and morphological testing. Their results were compared with those obtained after conducting the same assessments on unfilled HDPE samples, which were used as the control samples. The mechanical response of the samples improved when correlated with that of the unfilled HDPE. The tensile strength improved by 24.3%, and the flexural strength improved by 26.5% (composite with 6.0 wt. % TiN content). The dimensional deviation and porosity of the samples were assessed with micro-computed tomography and indicated great results for porosity improvement, achieved with 6.0 wt. % TiN content in the composite. TiN has proven to be an effective filler for HDPE polymers, enabling the manufacture of parts with improved mechanical properties and quality.

Large-Scale Material Extrusion (LS-MEX) is increasingly being used in small-scale production and prototyping due to its ability to create components in new temporal and spatial dimensions. However, the use of this manufacturing process poses microscopic and macroscopic challenges not encountered in previous small-scale production systems. These challenges arise primarily from the prolonged retention of heat in the material, which leads to insufficient strength in the extruded strands at the macrostructural level. As a result, the component can collapse, a phenomenon known as ‘slumping’. Thermal energy also influences microstructural changes, such as crystallisation kinetics, which affect properties such as the strength and stiffness of the final product. The duration and dynamics of thermal energy are influenced by manufacturing parameters and the possible use of additional peripheral equipment, which affects component quality. In this study, the influence of thermal energy on structural processes through simulations of polyamide 6 with 40% carbon fibres (PA6 wt.%40 CF) is investigated. The results show that by adjusting the process parameters and using modification units, the thermal profile of the material can be accurately controlled, which allows the microstructural processes to be precisely controlled. This leads to the targeted modification of the macroscopic material properties. The focus of this work is on the combination of numerical simulations of the LS-MEX process with semi-empirical methods for the analysis of crystallisation processes. The application of the Nakamura model, which is used throughout similar investigations, allows a detailed description and prediction of the crystallisation kinetics during the manufacturing process. The study shows that the absolute degree of crystallisation can be determined with simplified assumptions using a combination of thermal simulations and semi-empirical approaches. It was found that the absolute degree of crystallisation increases from the outer interface of the strand to the print bed across the cross-section. This can be attributed to the specific thermal boundary conditions and the resulting temperature profiles at different points.

In this study, poly (ethylene terephthalate) (PETG) was combined with Antimony-doped Tin Oxide (ATO) to create five different composites (2.0–10.0 wt.% ATO). The PETG/ATO filaments were extruded and supplied to a material extrusion (MEX) 3D printer to fabricate the specimens following international standards. Various tests were conducted on thermal, rheological, mechanical, and morphological properties. The mechanical performance of the prepared nanocomposites was evaluated using flexural, tensile, microhardness, and Charpy impact tests. The dielectric and electrical properties of the prepared composites were evaluated over a broad frequency range. The dimensional accuracy and porosity of the 3D printed structure were assessed using micro-computed tomography. Other investigations include scanning electron microscopy and energy-dispersive X-ray spectroscopy, which were performed to investigate the structures and morphologies of the samples. The PETG/6.0 wt.% ATO composite presented the highest mechanical performance (21% increase over the pure polymer in tensile strength). The results show the potential of such nanocomposites when enhanced mechanical performance is required in MEX 3D printing applications, in which PETG is the most commonly used polymer.

Polyethylene terephthalate glycol (PETG) and silicon nitride (Si3N4) were combined to create five composite materials with Si3N4 loadings ranging from 2.0 wt.% to 10.0 wt.%. The goal was to improve the mechanical properties of PETG in material extrusion (MEX) additive manufacturing (AM) and assess the effectiveness of Si3N4 as a reinforcing agent for this particular polymer. The process began with the production of filaments, which were subsequently fed into a 3D printer to create various specimens. The specimens were manufactured according to international standards to ensure their suitability for various tests. The thermal, rheological, mechanical, electrical, and morphological properties of the prepared samples were evaluated. The mechanical performance investigations performed included tensile, flexural, Charpy impact, and microhardness tests. Scanning electron microscopy and energy-dispersive X-ray spectroscopy mapping were performed to investigate the structures and morphologies of the samples, respectively. Among all the composites tested, the PETG/6.0 wt.% Si3N4 showed the greatest improvement in mechanical properties (with a 24.5% increase in tensile strength compared to unfilled PETG polymer), indicating its potential for use in MEX 3D printing when enhanced mechanical performance is required from the PETG polymer.

Material extrusion (MEX) is a popular additive manufacturing (AM) method that can process a wide range of feedstock materials, most commonly in filament form. Currently, there is no standardized testing method for filament tensile properties, and researchers resort to 3D-printed dog-bone specimens, which necessarily include the effects of the printing process. In this study, the impact of the strain measurement device, knife-edge type, gage length, testing speed, and oven treatment on filament tensile properties was explored using an off-the-shelf fixture. It was observed that an extensometer with blunt knife edges, a filament gage length of 165 mm, and a 6.35 mm/min (0.25 in./min) testing speed could accurately evaluate the tensile properties of acrylonitrile butadiene styrene (ABS) filaments. In addition, an optimized raster path, 3D printing design, and process parameters were used to manufacture dog bone tensile specimens according to ASTM D638-22 from the same ABS filament spool. The tensile properties of the filaments were validated using the results of 3D-printed dog-bone specimens. Young's modulus, stress at yield, and stress at break for the optimum filament test set (2.20 GPa, 43.9 MPa, and 39.1 MPa) were very similar to those of the 3D-printed specimens (2.26 GPa, 44.9 MPa, and 37.3 MPa). The optimum filament tensile testing parameters determined in this study for ABS can be used for the initial test setup for other filament materials to provide baseline values that can serve as the foundation for AM process development.

3D printing of continuous fiber‐reinforced thermoplastic composites (CFRPCs) has expanded potential structural application in recent years. However, it is still challenging to tailor the mechanical and energy absorption properties of 3D‐printed composites to fulfill the requirements for critical application conditions. Herein, hybrid fiber (HF) reinforced composites have been prepared by 3D printing of CFRPCs and investigated on the mechanical and energy absorption behaviors. Continuous virgin carbon fibers (CF), Kevlar fibers (KF) (130 Deniers (D), and 200 Deniers (D)) and E‐glass fibers (GF) were used as reinforcing fibers to produce hybrid and non‐hybrids composites. Hybrid composites with different combination of CF + GF, CF + 130D KF, and CF + 200D KF showed tailorable behaviors, such as flexural modulus (16,691.74, 20,372.38, and 19,017.44 MPa), tensile modulus (15,022.6, 16,269.41, and 15,320.58 MPa). And energy absorption behaviors of CF + 130D KF and CF + 200D KF were tailored in both tensile (18,865.25 and 20,302.07 N‐mm, respectively) and bending (3594.54 and 3570.80 N‐mm, respectively) tests compared to other composites which will be ideal for energy absorption applications. Moreover, CF + GF showed tailored strength which could be used in the need of high stiffness. SEM images were providing strong evidence to resist the fracture and breakage patterns, by tailoring the stiffness and elongation properties of fibers in hybrids specimens. Furthermore, positive hybrid effects of CF + KF hybrids in tensile and bending tests were also showing an ideal match of toughness and flexibility. In future, these cost and weight effective hybrids will have potential to apply in aerospace and automobile. [ABSTRACT FROM AUTHOR]

In this study, innovative nanocomposite materials for material extrusion (MEX) 3D printing were developed using a polypropylene (PP) polymer with tungsten carbide (WC) nanopowder. The raw materials were converted into filaments using thermomechanical extrusion. The samples were then fabricated for testing according to the international standards. Extensive mechanical testing was performed on the 3D-printed specimens, including tensile, impact, flexural, and microhardness assessments. In addition, the impact of ceramic additive loading was examined. The thermal and stoichiometric characteristics of the nanocomposites were examined using thermogravimetric analysis, energy-dispersive X-ray spectroscopy, differential scanning calorimetry, and Raman spectroscopy. The 3D-printed shape, quality, and fracture process of the specimens were examined using scanning electron microscopy. The results showed that the filler significantly enhanced the mechanical characteristics of the matrix polymer without reducing its thermal stability or processability. Notably, the highest level of nanocomposite mechanical responsiveness was achieved through the inclusion of 6.0 and 8.0 wt. % fillers. The 10.0 wt. % loading nanocomposite showed significantly increased microhardness, indicating a possible high resistance to wear. [ABSTRACT FROM AUTHOR]

This paper focuses on a wear evaluation conducted for prototype spur and herringbone gears made from PET-G filament using additive manufacturing. The main objective of this study is to verify if 3D-printed gears can be considered a reliable choice for long-term exploitation in selected mechanical systems, specifically automated retail kiosks. For this reason, two methods were applied, utilizing: (1) vision-based inspection of the gears' cross-sectional geometry and (2) the statistical characterization of the selected kinematic parameters and torques generated by drives. The former method involves destructive testing and allows for identification of the gears' operation-induced geometric shape evolution, whereas the latter method focuses on searching for nondestructive kinematic and torque-based indicators, which allow tracking of the wear. The novel contribution presented in this paper is the conceptual and experimental application of the identification of the changes of 3D-printed parts' geometric properties resulting from wear. The inspected exploited and non-exploited 3D-printed parts underwent encasing in resin and a curing process, followed by cutting in a specific plane to reveal the desired shapes, before finally being subjected to a vision-based geometric characterization. The authors have experimentally demonstrated, in real industrial conditions, on batch production parts, the usefulness of the presented destructive testing technique providing valid indices for wear identification. [ABSTRACT FROM AUTHOR]

To successfully implement additive manufacturing (AM) techniques for custom medical device (MD) production with low-cost resources, it is imperative to understand the effect of common and affordable sterilization processes, such as formaldehyde or steam sterilization, on pieces manufactured by AM. In this way, the performance of low-risk MDs, such as biomodels and surgical guides, could be assessed for complying with safety, precision, and MD delivery requirements. In this context, the aim of the present work was to evaluate the effect of formaldehyde and steam sterilization on the dimensional and mechanical stability of standard polylactic acid (PLA) test pieces produced by fused deposition modeling (FDM). To achieve this, PLA samples were sterilized according to the sterilization protocol of a public hospital in the city of Bucaramanga, Colombia. Significant changes regarding mechanical and dimensional properties were found as a function of manufacturing parameters. This research attempts to contribute to the development of affordable approaches for the fabrication of functional and customized medical devices through AM technologies, an issue of particular interest for low- and middle-income countries. [ABSTRACT FROM AUTHOR]

Featured Application: The findings presented herein can be directly applied for the prediction and optimization of the compressive strength and the energy consumption of parts to be manufactured with the material extrusion 3D printing process with the Polyamide 6 polymer. Both energy efficiency and robustness are popular demands for 3D-printed components nowadays. These opposing factors require compromises. This study examines the effects of seven general control variables on the energy demands and the compressive responses of polyamide (PA6) material extrusion (MEX) 3D printed samples. Nozzle Temperature, Layer Thickness, Orientation Angle, Raster Deposition Angle, Printing Speed, Bed Temperature, and Infill Density were studied. An L27 orthogonal array was compiled with five replicas. A total of 135 trials were conducted, following the ASTM D695-02a specifications. The stopwatch method was used to assess the construction time and energy usage. The compressive strength, toughness, and elasticity modulus were experimentally determined. The Taguchi technique ranks each control parameter's impact on each response measure. The control parameter that had the greatest impact on both energy use and printing time was layer thickness. Additionally, the infill density had the greatest influence on the compressive strength. Quadratic regression model equations were formed for each of the response measures. The ideal compromise between mechanical strength and energy efficiency is now reported, with merit related to technological and economic benefits. [ABSTRACT FROM AUTHOR]

This study was conducted on different models of biodegradable SMP (shape-memory polymer) scaffolds. A comparison was conducted utilizing a basic FDM (fused deposition modeling)/MEX (material extrusion) printer with a standard printing technique and a novel, modified, four-axis printing method with a PLA (poly lactic acid) polymer as the printing material. This way of making the 4D-printed BVS (biodegradable vascular stent) made it possible to achieve high-quality surfaces due to the difference in printing directions and improved mechanical properties—tensile testing showed a doubling in the elongation at break when using the four-axis-printed specimen compared to the regular printing, of 8.15 mm and 3.92 mm, respectfully. Furthermore, the supports created using this method exhibited a significant level of shape recovery following thermomechanical programming. In order to test the shape-memory effect, after the thermomechanical programming, two approaches were applied: one approach was to heat up the specimen after unloading it inside temperature chamber, and the other was to heat it in a warm bath. Both approaches led to an average recovery of the original height of 99.7%, while the in-chamber recovery time was longer (120 s) than the warm-bath recovery (~3 s) due to the more direct specimen heating in the latter case. This shows that 4D printing using the newly proposed four-axis printing is an effective, promising technique that can be used in the future to make biodegradable structures from SMP. [ABSTRACT FROM AUTHOR]

The development of sustainable and functional biocomposites remains a robust research and industrial claim. Herein, the efficiency of using eco-friendly biochar as reinforcement in Additive Manufacturing (AM) was investigated. Two AM technologies were applied, i.e., vat photopolymerization (VPP) and material extrusion (MEX). A standard-grade resin in VPP and the also eco-friendly biodegradable Polylactic Acid (PLA) in the MEX process were selected as polymeric matrices. Biochar was prepared in the study from olive trees. Composites were developed for both 3D printing processes at different biochar loadings. Samples were 3D-printed and mechanically tested after international test standards. Thermogravimetric Analysis and Raman revealed the thermal and structural characteristics of the composites. Morphological and fractographic features were derived, among others, with Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Biochar was proven to be sufficient reinforcement agent, especially in the filament MEX process, reaching more than 20% improvement at 4 wt.% loading in tensile strength compared to the pure PLA control samples. In the VPP process, results were not as satisfactory, still, a 5% improvement was achieved in the flexural strength with 0.5 wt.% biochar loading. The findings prove the strong potential of biochar-based composites in AM applications, too. Highlights: The reinforcement of VPP and MEX 3D printed parts with eco-friendly biochar. Resin and biocompatible eco-friendly PLA were the matrices. Eco-friendly composites achieved high-performance mechanical properties. [ABSTRACT FROM AUTHOR]

The influence of nanoparticles (NPs) in zirconium oxide (ZrO2) as a strengthening factor of Polylactic Acid (PLA) and Polyamide 12 (PA12) thermoplastics in material extrusion (MEX) additive manufacturing (AM) is reported herein for the first time. Using a melt-mixing compounding method, zirconium dioxide nanoparticles were added at four distinct filler loadings. Additionally, 3D-printed samples were carefully examined for their material performance in various standardized tests. The unfilled polymers were the control samples. The nature of the materials was demonstrated by Raman spectroscopy and thermogravimetric studies. Atomic Force Microscopy and Scanning Electron Microscopy were used to comprehensively analyze their morphological characteristics. Zirconium dioxide NPs showed an affirmative reinforcement tool at all filler concentrations, while the optimized material was calculated with loading in the range of 1.0–3.0 wt.% (3.0 wt.% for PA12, 47.7% increase in strength; 1.0 wt.% for PLA, 20.1% increase in strength). PA12 and PLA polymers with zirconium dioxide in the form of nanocomposite filaments for 3D printing applications could be used in implementations using thermoplastic materials in engineering structures with improved mechanical behavior. [ABSTRACT FROM AUTHOR]

Herein, polytetrafluoroethylene (PTFE) is evaluated as a reinforcement agent in material extrusion (MEX) additive manufacturing (AM), aiming to develop nanocomposites with enhanced mechanical performance. Loadings up to 4.0 wt.% were introduced as fillers of polylactic acid (PLA) and polyamide 12 (PA12) matrices. Filaments for MEX AM were prepared to produce corresponding 3D-printed samples. For the thorough characterization of the nanocomposites, a series of standardized mechanical tests were followed, along with AFM, TGA, Raman spectroscopy, EDS, and SEM analyses. The results showed an improved mechanical response for filler concentrations between 2.0 and 3.0 wt.%. The enhancement for the PLA/PTFE 2.0 wt.% in the tensile strength reached 21.1% and the modulus of elasticity 25.5%; for the PA12/PTFE 3.0 wt.%, 34.1%, and 41.7%, respectively. For PLA/PTFE 2.0 wt.%, the enhancement in the flexural strength reached 57.6% and the modulus of elasticity 25.5%; for the PA12/PTFE 3.0 wt.%, 14.7%, and 17.2%, respectively. This research enables the ability to deploy PTFE as a reinforcement agent in the PA12 and PLA thermoplastic engineering polymers in the MEX AM process, expanding the potential applications. [ABSTRACT FROM AUTHOR]

The industrial demand for functional filaments made of bio-sourced, biocompatible, biodegradable, and/or recyclable polymers and composites for material extrusion (MEX) 3D printing is continuously growing. Polylactic acid (PLA), the most popular filament, combines such properties, yet its reinforcement with low-cost, inert, and/or recycled fillers remains challenging. Herein, glass in three different micro/nano-forms was the reinforcement agent in PLA. Three different experimental tiers were elaborated by producing composite filaments with glass in powder, beads, and flake forms in various loadings to optimize the concentrations. A thermomechanical process, i.e., melt filament extrusion, was exploited. The composites were evaluated for their thermal degradation stability and composition using thermogravimetric analysis and Raman. MEX 3D printing was used to produce tensile, flexural, impact, and microhardness specimens, to quantitatively evaluate their mechanical response. Field emission scanning electron microscopy evaluation and fractography were carried out to depict fracture patterns of the specimens after their tests. All three glass types induced impressive reinforcement effects (up to 60% in flexural loading), especially in the flake form. The impact of the additional process cost through glass fillers implementation was also assessed, indicating that such composites are cost-effective. [ABSTRACT FROM AUTHOR]

The current research aimed to examine the thermomechanical properties of new nanocomposites in additive manufacturing (AM). Material extrusion (MEX) 3D printing was utilized to evolve acrylonitrile butadiene styrene (ABS) nanocomposites with silicon nitride nano-inclusions. Regarding the mechanical and thermal response, the fabricated 3D-printed samples were subjected to a course of standard tests, in view to evaluate the influence of the Si3N4 nanofiller content in the polymer matrix. The morphology and fractography of the fabricated filaments and samples were examined using scanning electron microscopy and atomic force microscopy. Moreover, Raman and energy dispersive spectroscopy tests were accomplished to evaluate the composition of the matrix polymer and nanomaterials. Silicon nitride nanoparticles were proved to induce a significant mechanical reinforcement in comparison with the polymer matrix without any additives or fillers. The optimal mechanical response was depicted to the grade ABS/Si3N4 4 wt. %. An impressive increase in flexural strength (30.3%) and flexural toughness (47.2%) was found. The results validate that these novel ABS nanocomposites with improved mechanical properties can be promising materials. [ABSTRACT FROM AUTHOR]

Acrylonitrile butadiene styrene (ABS) is a multipurpose thermoplastic and the second most popular material in material extrusion (MEX) additive manufacturing (AM). It is widely used in various types of industrial applications in the automotive sector, housing, and food processing, among others. This work investigates the effect of seven generic control parameters (orientation angle, raster deposition angle, infill density, layer thickness, nozzle temperature, printing speed, and bed temperature) on the performance and the energy consumption of 3D-printed ABS parts in compression loading. Raw material with melt extrusion was formed in a filament form for MEX 3D printing. Samples after the ASTM D695-02a standard were 3D printed, with the seven control parameters, three levels, and five replicas each (135 experiments in total). Results were analyzed with statistical modeling tools regarding the compressive and the energy consumption metrics (printing time, weight, energy printing consumption/EPC, specific printing energy/SPE, specific printing power/SPP, compression strength, compression modulus of elasticity, and toughness). The layer thickness was the most critical control parameter. Nozzle temperature and raster deposition angle were the less critical parameters. This work provides reliable information with great technological and industrial impact. [ABSTRACT FROM AUTHOR]

Process sustainability vs. mechanical strength is a strong market-driven claim in Material Extrusion (MEX) Additive Manufacturing (AM). Especially for the most popular polymer, Polylactic Acid (PLA), the concurrent achievement of these opposing goals may become a puzzle, especially since MEX 3D-printing offers a variety of process parameters. Herein, multi-objective optimization of material deployment, 3D printing flexural response, and energy consumption in MEX AM with PLA is introduced. To evaluate the impact of the most important generic and device-independent control parameters on these responses, the Robust Design theory was employed. Raster Deposition Angle (RDA), Layer Thickness (LT), Infill Density (ID), Nozzle Temperature (NT), Bed Temperature (BT), and Printing Speed (PS) were selected to compile a five-level orthogonal array. A total of 25 experimental runs with five specimen replicas each accumulated 135 experiments. Analysis of variances and reduced quadratic regression models (RQRM) were used to decompose the impact of each parameter on the responses. The ID, RDA, and LT were ranked first in impact on printing time, material weight, flexural strength, and energy consumption, respectively. The RQRM predictive models were experimentally validated and hold significant technological merit, for the proper adjustment of process control parameters per the MEX 3D-printing case. [ABSTRACT FROM AUTHOR]

The energy efficiency of material extrusion additive manufacturing has a significant impact on the economics and environmental footprint of the process. Control parameters that ensure 3D-printed functional products of premium quality and mechanical strength are an established market-driven requirement. To accomplish multiple objectives is challenging, especially for multi-purpose industrial polymers, such as the Poly[methyl methacrylate]. The current paper explores the contribution of six generic control factors (infill density, raster deposition angle, nozzle temperature, print speed, layer thickness, and bed temperature) to the energy performance of Poly[methyl methacrylate] over its mechanical performance. A five-level L25 Taguchi orthogonal array was composed, with five replicas, involving 135 experiments. The 3D printing time and the electrical consumption were documented with the stopwatch approach. The tensile strength, modulus, and toughness were experimentally obtained. The raster deposition angle and the printing speed were the first and second most influential control parameters on tensile strength. Layer thickness and printing speed were the corresponding ones for the energy consumption. Quadratic regression model equations for each response metric over the six control parameters were compiled and validated. Thus, the best compromise between energy efficiency and mechanical strength is achievable, and a tool creates significant value for engineering applications. [ABSTRACT FROM AUTHOR]

The weldability of 3D printed (3DP), through material extrusion (MEX), of Polyamide 6 (PA6) plates joined with FSW is investigated. FSW has its challenges in polymers, especially for 3D printed parts, while it is used for various industrial applications in the automotive and airspace sector, in joints, and in other types of parts. Herein, a full factorial experimental course was deployed, to quantitatively document the impact of three critical process parameters (e.g., the rotational speed and the travel speed of the tool, as well as the pin geometry of the tool) and to optimize their levels. A set of identical PA6 prismatic workpieces was prepared and then welded. Throughout the welding process, the temperature profiles were monitored and logged, to ensure the solid state of the workpiece material. The welding efficiency of the joints was then determined through mechanical tests, while unwelded 3D printed specimens were employed as control samples. Thorough morphological evaluations and characterization with microscopy (Scanning Electron and optical Microscopy) were performed for the welding zones. The evaluation of the metrics with statistical modeling tools led to the quantitative correlation of the process parameters, as well as their interactions, and finally optimization. The feasibility of joining 3DP PA6 with FSW was verified, reaching a welding efficiency of up to 120.40% for threaded cylindrical pin profile, rotational speed 1200 rpm, and travel speed 3 mm/min. The results of the study provide valuable information and merit for the FSW of 3DP PA6, which can be exploited in various industrial applications. [ABSTRACT FROM AUTHOR]

Sustainability and energy efficiency of additive manufacturing (AM) is an up-to-date industrial request. Likewise, the claim for 3D-printed parts with capable mechanical strength remains robust, especially for polymers that are considered high-performance ones, such as polycarbonates in material extrusion (MEX). This paper explains the impact of seven generic control parameters (raster deposition angle; orientation angle; layer thickness; infill density; nozzle temperature; bed temperature; and printing speed) on the energy consumption and compressive performance of PC in MEX AM. To meet this goal, a three-level L27 Taguchi experimental design was exploited. Each experimental run included five replicas (compressive specimens after the ASTM D695-02a standard), summating 135 experiments. The printing time and the power consumption were stopwatch-derived, whereas the compressive metrics were obtained by compressive tests. Layer thickness and infill density were ranked the first and second most significant factors in energy consumption. Additionally, the infill density and the orientation angle were proved as the most influential factors on the compressive strength. Lastly, quadratic regression model (QRM) equations for each response metric versus the seven control parameters were determined and evaluated. Hereby, the optimum compromise between energy efficiency and compressive strength is attainable, a tool holding excessive scientific and engineering worth. [ABSTRACT FROM AUTHOR]

Material extrusion (MEX), frequently known as fused filament fabrication (FFF), is a material extrusion 3D printing process for fabricating cost-effectively functional polymeric parts. Even if the MEX process fabricates fully dense or lightweight specimens with a relatively complex geometry in a reduced time and cost, it presents some drawbacks in shape accuracy, surface roughness, and anisotropic mechanical response. Herewith, the interaction between material design, 3D printing, and laser post-processing is investigated for efficient printable nanocomposite materials. Polylactic acid (PLA)/carbon black (CB) nanocomposites were prepared with a thermomechanical process and characterized for their mechanical and electrical properties. Then, they were processed with a low-cost CO2 laser, to assess their behavior in the process. Critical geometrical characteristics were measured, and results were analyzed with statistical modeling, to optimize the process and evaluate the effect of the laser cutting parameters on the quality of the samples. This paper points out new data on low-cost CO2 laser cutting of MEX thin plates fabricated using PLA/CB nanocomposite filament and an affordable material extrusion MEX 3D printing process. The data produced are helpful for the improvement of the shape accuracy and surface roughness of parts and components used in nanocomposite-based innovative assemblies and systems. [ABSTRACT FROM AUTHOR]

The cost-effectiveness and the environmental impact of Additive Manufacturing (AM) are nowadays two of the hottest process-related industrial and research topics. Energy efficiency is a strong claim, and so is the demand for durable and functional 3D-printed workpieces. These contradictory aspects usually require flexibility and compromises. Especially for Material Extrusion (MEX) 3D printing, the plurality of the control parameters makes such optimizations complicated. This research explores the effect of seven generic and machine-independent control factors (e.g., Raster Deposition Angle; Orientation Angle; Layer Thickness; Infill Density; Nozzle Temperature; Bed Temperature, and Printing Speed) on energy consumption of Polylactic Acid over the compressive response of MEX 3D printed specimens. To make it possible, a three-level L27 orthogonal array was compiled. Each experimental run included five specimen replicas (after the ASTM D695-02a standard) summing up 135 experiments. The fabrication time and the energy consumption were determined by the stopwatch method, whereas the compressive strength, elasticity modulus, and toughness were derived with compressive tests. The Taguchi analysis ranked the impact of each control parameter on each response metric. The printing speed and the layer thickness were the most influential control parameters on energy consumption. Furthermore, the infill density and the orientation angle were found as the most dominant factors in the compressive strength. Finally, Quadratic Regression Model (QRM) equations for each response metric over the seven control parameters were compiled and validated. Hereto, the best settlement between energy efficiency and mechanical strength is now possible, an option with great technological and industrial merit.

Improving the resilience of 3D-printed composites through material extrusion technology (MEX) is an ongoing challenge in order to meet the rigorous requirements of critical applications. The primary objective of this research was to enhance the impact resistance of 3D-printed composites by incorporating continuous hybrid fibers. Herein, continuous virgin carbon (1k) and Kevlar (130D and 200D) fibers were used with different weight and volume fractions as reinforcing fibers to produce hybrid and non-hybrid composites for impact resistance testing to obtain energy absorption with different impact energies: 20 J, 30 J, 40 J, and 50 J. Moreover, 0°/90° fiber orientations were used. Hybrid composites with combinations of PLA + CF + 130D KF and PLA + CF + 200D KF showed higher impact resistance, less damaged areas (71.45% to 90.486%), and higher energy absorption (5.52–11.64% more) behaviors compared to PLA + CF non-hybrids. CT scan images provided strong evidence to resist the fracture and breakage patterns, because the stiffness and elongation properties of the fibers acted together in the hybrids specimens. Furthermore, positive hybrid effects of the PLA + CF + KF hybrids also showed an ideal match of toughness and flexibility in order to resist the impacts. In the future, these hybrids will have the potential to replace the single type of composites in the fields of aerospace and automobiles.

Polycarbonate-based nanocomposites were developed herein through a material extrusion (MEX) additive manufacturing (AM) process. The fabrication of the final nanocomposite specimens was achieved by implementing the fused filament fabrication (FFF) 3D printing process. The impact of aluminum nitride (AlN) nanoparticles on the thermal and mechanical behavior of the polycarbonate (PC) matrix was investigated thoroughly for the fabricated nanocomposites, carrying out a range of thermomechanical tests. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) provided information about the morphological and surface characteristics of the produced specimens. Using energy dispersive spectroscopy (EDS), the elemental composition of the nanocomposite materials was validated. Raman spectroscopy revealed no chemical interactions between the two material phases. The results showed the reinforcement of most mechanical properties with the addition of the AlN nanoparticles. The nanocomposite with 2 wt.% filler concentration exhibited the best mechanical performance overall, with the highest improvements observed for the tensile strength and toughness of the fabricated specimens, with a percentage of 32.8% and 51.6%, respectively, compared with the pure polymer. The successful AM of PC/AlN nanocomposites with the MEX process is a new paradigm, which expands 3D printing technology and opens a new route for the development of nanocomposite materials with multifunctional properties for industrial applications. [ABSTRACT FROM AUTHOR]

This work aims to better understand the type of thermoplastic binders required to produce highly loaded copper filaments that can be successfully printed via low-cost filament-based material extrusion (MEX). Compounding feedstock material with 55 vol.% of copper and three multi-component binder systems has been performed. The MEX behavior of these feedstocks was evaluated by depositing material at different speeds and appropriately selecting the extrusion temperature depending on the binder composition. The rest of the MEX parameters remained constant to evaluate the printing quality for the different feedstocks. Printable filaments were produced with low ovality and good surface quality. The filaments showed good dispersion of the powder and polymeric binder system in SEM analysis. The feedstock mechanical properties, i.e., the tensile strength of the filament, were sufficient to ensure proper feeding in the MEX machine. The viscosity of the feedstock systems at the adjusted printing temperatures lies in the range of 102–103 Pa·s at the shear rate of 100–1000 s−1, which appears to be sufficient to guarantee the correct flowability and continuous extrusion. The tensile properties vary greatly (e.g., ultimate tensile strength 3–9.8 MPa, elongation at break 1.5–40.5%), and the most fragile filament could not be reliably printed at higher speeds. Micrographs of the cross-section of printed parts revealed that as the printing speed increased, the porosity was minimized because the volumetric flow of the feedstock material increased, which can help to fill pores. This study offers new insights into the feedstock requirements needed to produce low-cost intricate copper components of high quality in a reliable and efficient manner. Such components can find many applications in the electronics, biomedical, and many other industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel hybrid lattice metamaterial was designed by combining surface-lattice with modified reentrant trusses. • Hybridization of metamaterials significantly influenced mechanical properties and energy absorption. • HLM with thicker reentrant trusses and varied shell thickness demonstrated superior mechanical properties and dynamic performance. • Novel hybrid lattice metamaterial's behavior proven by FEA and experimental tests. • The synergistic design enhances stability and performance by effectively resisting and dissipating compressive stresses. In this work, a novel dual-phase metamaterial, named as "hybrid lattice metamaterial (HLM)," are designed and fabricated by combining reentrant and sea-urchin (SU) based surface-lattice (SL) structure with polyamide12 (PA12) material via material extrusion (MEX) process. Four different designs with varying reentrant truss thicknesses of 0.8 mm (H1), 1.0 mm (H2), 1.2 mm (H3), and 1.5 mm (H4) have been modified to assemble seamlessly with the empty spaces within the SL structure. Quasistatic compression tests were conducted to evaluate the deformation modes and compression characteristics. The findings from quasistatic experiments were subsequently validated using numerical simulations. The H4 metamaterial exhibited superior structural properties, with 42 % increase in stiffness and 35 % enhancement in specific energy absorption compared to only SL structure. Additionally, dynamic sinusoidal compression tests were conducted to evaluate the dynamic elastic ratio (DER), hysteresis work and viscoelastic properties using the tan δ. The H4 metamaterial outperformed the SL in all dynamic properties, with a 50 % increase in elastic modulus and 36 % increase in hysteresis work. This study shows metamaterial properties can be tailored for specific requirements. SL structure facilitate elastic recovery, while H4 metamaterials offer superior energy absorption and stability, making it well-suited for protective equipment and impact-resistant components. [ABSTRACT FROM AUTHOR]

The goal of this paper is to investigate tungsten carbide (WC) as a reinforcement in the popular material extrusion (MEX) additive manufacturing (AM) procedure. The impressive characteristics of WC demonstrate its potential as a valuable additive for commonly used polymeric matrices in MEX 3D printing, offering reinforcement and stabilization properties. The mechanical properties of hybrid polymer/ceramic nanocomposites made up of various filler loadings (0–10 wt. %) of medical-grade polylactic acid (PLA) and WC were studied. The mechanical characteristics, structure, and thermomechanical properties of the resulting compounds were fully characterized following the respective standards. The fracture mechanisms were revealed with Scanning Electron Microscopy. Overall, a laborious effort was implemented with fifteen different tests to fully characterize the nanocomposites prepared. In comparison to the raw PLA material, the tensile strength of the 4.0 wt. % WC PLA/WC nanocomposite was improved by 42.5% and the flexural strength by 41.9%. In the microhardness test, a 120.4% improvement was achieved, justifying the properties of WC ceramic. According to these findings, PLA nanocomposites reach high-performance polymer specifications, expanding their potential use, especially in wear-related applications.