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26 pages, 3586 KiB

Open AccessArticle

Establishing a Framework for Fused Filament Fabrication Process Optimization: A Case Study with PLA Filaments

by Jack Grubbs, Bryer C. Sousa and Danielle L. Cote

Polymers 2023, 15(8), 1945; https://doi.org/10.3390/polym15081945 - 19 Apr 2023

Cited by 5 | Viewed by 2212

Abstract

Developments in polymer 3D printing (3DP) technologies have expanded their scope beyond the rapid prototyping space into other high-value markets, including the consumer sector. Processes such as fused filament fabrication (FFF) are capable of quickly producing complex, low-cost components using a wide variety [...] Read more.

Developments in polymer 3D printing (3DP) technologies have expanded their scope beyond the rapid prototyping space into other high-value markets, including the consumer sector. Processes such as fused filament fabrication (FFF) are capable of quickly producing complex, low-cost components using a wide variety of material types, such as polylactic acid (PLA). However, FFF has seen limited scalability in functional part production partly due to the difficulty of process optimization with its complex parameter space, including material type, filament characteristics, printer conditions, and “slicer” software settings. Therefore, the aim of this study is to establish a multi-step process optimization methodology—from printer calibration to “slicer” setting adjustments to post-processing—to make FFF more accessible across material types, using PLA as a case study. The results showed filament-specific deviations in optimal print conditions, where part dimensions and tensile properties varied depending on the combination of nozzle temperature, print bed conditions, infill settings, and annealing condition. By implementing the filament-specific optimization framework established in this study beyond the scope of PLA, more efficient processing of new materials will be possible for enhanced applicability of FFF in the 3DP field. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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12 pages, 2558 KiB

Open AccessArticle

Micro 3D Printing Elastomeric IP-PDMS Using Two-Photon Polymerisation: A Comparative Analysis of Mechanical and Feature Resolution Properties

by Pieter F. J. van Altena and Angelo Accardo

Polymers 2023, 15(8), 1816; https://doi.org/10.3390/polym15081816 - 7 Apr 2023

Cited by 9 | Viewed by 4216

Abstract

The mechanical properties of two-photon-polymerised (2PP) polymers are highly dependent on the employed printing parameters. In particular, the mechanical features of elastomeric polymers, such as IP-PDMS, are important for cell culture studies as they can influence cell mechanobiological responses. Herein, we employed optical-interferometer-based [...] Read more.

The mechanical properties of two-photon-polymerised (2PP) polymers are highly dependent on the employed printing parameters. In particular, the mechanical features of elastomeric polymers, such as IP-PDMS, are important for cell culture studies as they can influence cell mechanobiological responses. Herein, we employed optical-interferometer-based nanoindentation to characterise two-photon-polymerised structures manufactured with varying laser powers, scan speeds, slicing distances, and hatching distances. The minimum reported effective Young’s modulus (YM) was 350 kPa, while the maximum one was 17.8 MPa. In addition, we showed that, on average, immersion in water lowered the YM by 5.4%, a very important point as in the context of cell biology applications, the material must be employed within an aqueous environment. We also developed a printing strategy and performed a scanning electron microscopy morphological characterisation to find the smallest achievable feature size and the maximum length of a double-clamped freestanding beam. The maximum reported length of a printed beam was 70 µm with a minimum width of 1.46 ± 0.11 µm and a thickness of 4.49 ± 0.05 µm. The minimum beam width of 1.03 ± 0.02 µm was achieved for a beam length of 50 µm with a height of 3.00 ± 0.06 µm. In conclusion, the reported investigation of micron-scale two-photon-polymerized 3D IP-PDMS structures featuring tuneable mechanical properties paves the way for the use of this material in several cell biology applications, ranging from fundamental mechanobiology to in vitro disease modelling to tissue engineering. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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12 pages, 10301 KiB

Open AccessArticle

The Effect of Heat Treatment on a 3D-Printed PLA Polymer’s Mechanical Properties

by Mariam Shbanah, Márton Jordanov, Zoltán Nyikes, László Tóth and Tünde Anna Kovács

Polymers 2023, 15(6), 1587; https://doi.org/10.3390/polym15061587 - 22 Mar 2023

Cited by 16 | Viewed by 4485

Abstract

Three-dimensional printing is a useful and common process in additive manufacturing nowadays. The advantage of additive polymer technology is its rapidity and design freedom. Polymer materials’ mechanical properties depend on the process parameters and the chemical composition of the polymer used. Mechanical properties [...] Read more.

Three-dimensional printing is a useful and common process in additive manufacturing nowadays. The advantage of additive polymer technology is its rapidity and design freedom. Polymer materials’ mechanical properties depend on the process parameters and the chemical composition of the polymer used. Mechanical properties are very important in product applicability. The mechanical properties of polymers can be enhanced by heat treatment. Additive-manufactured PLA’s mechanical properties and structure can be modified via heat treatment after the 3D printing process. The goal of this research was to test the effect of heat treatment on the mechanical and structural parameters of additive-manufactured PLA. This was achieved via the FDM processing of standard PLA tensile test specimens with longitudinal and vertical printing orientations. After printing, the test specimens were heat-treated at 55 °C, 65 °C and 80 °C for 5 h and after being held at 20 °C for 15 h. The printed and heat-treated specimens were tested using tensile tests and microscopy. Based on the test results, we can conclude that the optimal heat treatment process temperature was 65 °C for 5 h. Under the heat treatment, the test specimens did not show any deformation, the tensile strength increased by 35% and the porosity of the PLA structure decreased. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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19 pages, 5214 KiB

Open AccessArticle

A Mechanical Performance Study of Dual Cured Thermoset Resin Systems 3D-Printed with Continuous Carbon Fiber Reinforcement

by Md Atikur Rahman, Eric Hall, Luke Gibbon, Md Zahirul Islam, Chad A. Ulven and John J. La Scala

Polymers 2023, 15(6), 1384; https://doi.org/10.3390/polym15061384 - 10 Mar 2023

Cited by 15 | Viewed by 3339

Abstract

Additive manufacturing (AM) is one of the fastest-growing manufacturing technologies in modern times. One of the major challenges in the application of 3D-printed polymeric objects is expanding the applications to structural components, as they are often limited by their mechanical and thermal properties. [...] Read more.

Additive manufacturing (AM) is one of the fastest-growing manufacturing technologies in modern times. One of the major challenges in the application of 3D-printed polymeric objects is expanding the applications to structural components, as they are often limited by their mechanical and thermal properties. To enhance the mechanical properties of 3D-printed thermoset polymer objects, reinforcing the polymer with continuous carbon fiber (CF) tow is an expanding direction of research and development. A 3D printer was constructed capable of printing with a continuous CF-reinforced dual curable thermoset resin system. Mechanical performance of the 3D-printed composites varied with the utilization of different resin chemistries. Three different commercially available violet light curable resins were mixed with a thermal initiator to improve curing by overcoming the shadowing effect of violet light by the CF. The resulting specimens’ compositions were analyzed, and then the specimens were mechanically characterized for comparison in tensile and flexural performance. The 3D-printed composites’ compositions were correlated to the printing parameters and resin characteristics. Slight enhancements in tensile and flexural properties from some commercially available resins over others appeared to be the result of better wet-out and adhesion. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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16 pages, 9787 KiB

Open AccessArticle

Experimental Analysis of the Relationship between Textile Structure, Tensile Strength and Comfort in 3D Printed Structured Fabrics

by Jorge I. Fajardo, Marco V. Farez and César A. Paltán

Polymers 2023, 15(1), 152; https://doi.org/10.3390/polym15010152 - 29 Dec 2022

Cited by 4 | Viewed by 2936

Abstract

In this article, an experimental investigation was conducted to study the effects of 3D printed structured fabrics on the tensile strength of two additive manufacturing technologies: (i) fused deposition modeling (FDM); and (ii) stereolithography (SLA). Three types of structured fabrics were designed in [...] Read more.

In this article, an experimental investigation was conducted to study the effects of 3D printed structured fabrics on the tensile strength of two additive manufacturing technologies: (i) fused deposition modeling (FDM); and (ii) stereolithography (SLA). Three types of structured fabrics were designed in a linked fabric structure, which resembled the main characteristics of a conventional textile. Through computer-aided design (CAD), the textile structures were sketched, which, in a STL format, were transferred to 3D printing software, and consequently, they were printed. The specimens were subjected to tensile tests to analyse the behaviour of the linked structures under tensile loads. The results obtained indicated that the elements structured in a linked fabric pattern showed a statistically significant effect between the design of the 3D printed structured fabric and its tensile strength. Some important properties in textiles, fabric areal density, fineness (tex) and fabric flexibility were also analysed. This study opens an important field of research on the mechanical resistance of textile structures manufactured by 3D printing, oriented for applications in wearables that have a promising future in the fields of medicine, aerospace, sports, fashion, etc. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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16 pages, 5781 KiB

Open AccessArticle

Additive Manufacturing and Mechanical Characterization of PLA-Based Skull Surrogates

by Ramiro Mantecón, Miguel Marco, Ana Muñoz-Sanchez, George Youssef, José Díaz-Álvarez and Henar Miguélez

Polymers 2023, 15(1), 58; https://doi.org/10.3390/polym15010058 - 23 Dec 2022

Cited by 3 | Viewed by 2042

Abstract

Several occupational and leisure activities involve a high risk of head impacts, resulting in varying degrees of injuries with chronic consequences that adversely affect life quality. The design and manufacturing of effective head protections rely on proper head simulators to mimic the behavior [...] Read more.

Several occupational and leisure activities involve a high risk of head impacts, resulting in varying degrees of injuries with chronic consequences that adversely affect life quality. The design and manufacturing of effective head protections rely on proper head simulators to mimic the behavior to impact loading. 3D-printed human skulls are reported herein to address the need for reproducible, cost-effective, anatomically-correct surrogates. To demonstrate the viability of the investigated approach, surrogate bone sections and skulls were mechanically tested under quasi-static loading conditions. The 3D-printed bone sections were flexural tested, elucidating the effect of printing orientations and the sample geometry on their mechanical behavior. The printing orientation minimally influenced the results due to the high infill percentage, while the sample geometry played a major role in the flexural properties because of the change in the section properties. The surrogate skulls were submitted to lateral compression and frontal penetration tests to assess the impact of the sectioning strategy on the overall mechanical performance. Results indicate that PLA-based surrogates reasonably reproduce the behavior of skulls. In addition, the sectioning strategy elucidated the effect of skull sutures, while streamlining the additive manufacturing process. The outcomes lay the foundation for future research seeking a complete surrogate head. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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15 pages, 2511 KiB

Open AccessArticle

Magnetic Resonance Imaging: Time-Dependent Wetting and Swelling Behavior of an Auxetic Hydrogel Based on Natural Polymers

by Sandra Haas, Barbara Schmieg, Paul Wendling, Gisela Guthausen and Jürgen Hubbuch

Polymers 2022, 14(22), 5023; https://doi.org/10.3390/polym14225023 - 19 Nov 2022

Cited by 2 | Viewed by 2164

Abstract

A time-dependent understanding of swelling characteristics and external stimuli behavior is crucial for the development and understanding of functional hydrogels. Magnetic resonance imaging (MRI) offers the opportunity to study three-dimensional (3D) soft materials nondestructively. This technique is already widely used as an image-based [...] Read more.

A time-dependent understanding of swelling characteristics and external stimuli behavior is crucial for the development and understanding of functional hydrogels. Magnetic resonance imaging (MRI) offers the opportunity to study three-dimensional (3D) soft materials nondestructively. This technique is already widely used as an image-based medical diagnostic tool and is applied here to evaluate complex structures of a hydrogel—a double network of chemically crosslinked casein enhanced with alginate—fabricated by 3D printing. When hydrogel disks immersed in four different liquid systems were analyzed, the material exhibited distinct system-dependent behavior characterized by rheological and mechanical measurements. Further material functionalization was achieved by macroscopic structuring of the hydrogel as an auxetic material based on a re-entrant honeycomb structure. MRI offers the advantage of monitoring overall changes in the area of the analyzed specimen and internal structural changes simultaneously. To assess the behavior of this complex structure, a series of short MRI measurements, each lasting 1.7 min, captured liquid diffusion and thus structural swelling behavior. A clear dependence of external and internal structural changes as a function of liquid properties causing these changes was observed. In conclusion, this approach might pave the way for prospective applications to monitor liquid diffusion into (e.g., vascularization) and swelling behavior of functional hydrogels. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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15 pages, 4101 KiB

Open AccessArticle

Height-to-Diameter Ratio and Porosity Strongly Influence Bulk Compressive Mechanical Properties of 3D-Printed Polymer Scaffolds

by José I. Contreras Raggio, Carlos Toro Arancibia, Carola Millán, Heidi-Lynn Ploeg, Ameet Aiyangar and Juan F. Vivanco

Polymers 2022, 14(22), 5017; https://doi.org/10.3390/polym14225017 - 18 Nov 2022

Cited by 4 | Viewed by 2707

Abstract

Although the architectural design parameters of 3D-printed polymer-based scaffolds—porosity, height-to-diameter (H/D) ratio and pore size—are significant determinants of their mechanical integrity, their impact has not been explicitly discussed when reporting bulk mechanical properties. Controlled architectures were designed by systematically varying porosity (30–75%, H/D [...] Read more.

Although the architectural design parameters of 3D-printed polymer-based scaffolds—porosity, height-to-diameter (H/D) ratio and pore size—are significant determinants of their mechanical integrity, their impact has not been explicitly discussed when reporting bulk mechanical properties. Controlled architectures were designed by systematically varying porosity (30–75%, H/D ratio (0.5–2.0) and pore size (0.25–1.0 mm) and fabricated using fused filament fabrication technique. The influence of the three parameters on compressive mechanical properties—apparent elastic modulus E_app, bulk yield stress σ_y and yield strain ε_y—were investigated through a multiple linear regression analysis. H/D ratio and porosity exhibited strong influence on the mechanical behavior, resulting in variations in mean E_app of 60% and 95%, respectively. σ_y was comparatively less sensitive to H/D ratio over the range investigated in this study, with 15% variation in mean values. In contrast, porosity resulted in almost 100% variation in mean σ_y values. Pore size was not a significant factor for mechanical behavior, although it is a critical factor in the biological behavior of the scaffolds. Quantifying the influence of porosity, H/D ratio and pore size on bench-top tested bulk mechanical properties can help optimize the development of bone scaffolds from a biomechanical perspective. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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14 pages, 6339 KiB

Open AccessArticle

Structural Analysis of Carbon Fiber 3D-Printed Ribs for Small Wind Turbine Blades

by Víctor A. Ramírez-Elías, Noemi Damian-Escoto, Kyosung Choo, Miguel A. Gómez-Martínez, Antonio Balvantín-García and José Angel Diosdado-De la Peña

Polymers 2022, 14(22), 4925; https://doi.org/10.3390/polym14224925 - 15 Nov 2022

Cited by 3 | Viewed by 2461

Abstract

This work provides a structural analysis of small-scale 3D-printed wind turbine ribs subjected to compression. The ribs were manufactured according to NACA 23015 and NACA 633618 geometries, with polylactic acid (PLA) and polylactic acid with carbon fiber additives (CF-PLA). In addition, holes were [...] Read more.

This work provides a structural analysis of small-scale 3D-printed wind turbine ribs subjected to compression. The ribs were manufactured according to NACA 23015 and NACA 633618 geometries, with polylactic acid (PLA) and polylactic acid with carbon fiber additives (CF-PLA). In addition, holes were manufactured into the sample bodies by either 3D printing or drilling for being compared with solid samples. The compression testing was performed by following the ASTM 695D standard, whereas the beginning and propagation of delamination were assessed with the ASTM 5528 standard. Experimental results revealed that 3D-printed built-in holes provided higher compression strength, hence higher structural efficiency, than the drilled samples. Significant improvement by adding carbon fiber additives into the PLA resin system in comparison to raw PLA was detected for at least one of the studied airfoil profiles. NACA geometries also represented a key parameter for avoiding stress concentration areas, as the FEM modeling supported. However, in damaged areas, fracture mechanisms were observed such as bead-bridging, which is a key parameter in reinforcing and consolidating the specimen bodies. Working in better interphase bonding and different additives between beads and layers is highly suggested for future studies. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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19 pages, 6632 KiB

Open AccessArticle

Low Impact Velocity Modeling of 3D Printed Spatially Graded Elastomeric Lattices

by Jose Angel Diosdado-De la Peña, Charles M. Dwyer, David Krzeminski, Eric MacDonald, Alberto Saldaña-Robles, Pedro Cortes and Kyosung Choo

Polymers 2022, 14(21), 4780; https://doi.org/10.3390/polym14214780 - 7 Nov 2022

Cited by 3 | Viewed by 2790

Abstract

Additive manufacturing technologies have facilitated the construction of intricate geometries, which otherwise would be an extenuating task to accomplish by using traditional processes. Particularly, this work addresses the manufacturing, testing, and modeling of thermoplastic polyurethane (TPU) lattices. Here, a discussion of different unit [...] Read more.

Additive manufacturing technologies have facilitated the construction of intricate geometries, which otherwise would be an extenuating task to accomplish by using traditional processes. Particularly, this work addresses the manufacturing, testing, and modeling of thermoplastic polyurethane (TPU) lattices. Here, a discussion of different unit cells found in the literature is presented, along with the based materials used by other authors and the tests performed in diverse studies, from which a necessity to improve the dynamic modeling of polymeric lattices was identified. This research focused on the experimental and numerical analysis of elastomeric lattices under quasi-static and dynamic compressive loads, using a Kelvin unit cell to design and build non-graded and spatially side-graded lattices. The base material behavior was fitted to an Ogden 3rd-order hyperelastic material model and used as input for the numerical work through finite element analysis (FEA). The quasi-static and impact loading FEA results from the lattices showed a good agreement with the experimental data, and by using the validated simulation methodology, additional special cases were simulated and compared. Finally, the information extracted from FEA allowed for a comparison of the performance of the lattice configurations considered herein. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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16 pages, 4251 KiB

Open AccessArticle

Flexible Investment Casting Wax Patterns for 3D-Printing: Their Rheological and Mechanical Characterizations

by László Szabó, György Deák, Dávid Nyul and Sándor Kéki

Polymers 2022, 14(21), 4744; https://doi.org/10.3390/polym14214744 - 5 Nov 2022

Cited by 6 | Viewed by 3053

Abstract

The mechanical and rheological characterizations of flexible investment casting patterns capable of 3D printing are reported. The wax pattern was composed of microcrystalline hydrocarbon wax (DMW7478), Piccotex 75 (a copolymer of α–methyl–styrene and vinyl toluene with a 75/25 molar ratio, respectively) and Escorene [...] Read more.

The mechanical and rheological characterizations of flexible investment casting patterns capable of 3D printing are reported. The wax pattern was composed of microcrystalline hydrocarbon wax (DMW7478), Piccotex 75 (a copolymer of α–methyl–styrene and vinyl toluene with a 75/25 molar ratio, respectively) and Escorene (a copolymer of ethylene and vinyl acetate with a 72/28 mass ratio, respectively). It was found that in order to obtain a wax pattern with appreciable mechanical properties, the content of the microcrystalline hydrocarbon wax in these blends should not exceed 30% (m/m). Thus, a series of patterns with 28% (m/m) wax and varying Piccotex and Escorene contents spanning from 0 to 72% (m/m) was prepared. The dependence of the dynamic viscosities of the wax patterns on the composition was described using a stretched exponential model, whereas their variations with the temperature were interpreted in terms of the Arrhenius–Guzman equation. Furthermore, the slopes of the lines fitted to the viscosity versus temperature curves at the pour point decreased linearly with the Piccotex content. Non-Newtonian changes in the shear stress with the shear rate and shear stress crystallization were observed at temperatures near the pour points. The mechanical properties were evaluated using the uniaxial tensile mode and by three-point bending experiments. It was found that the stress (σ) versus the relative elongation (ε) curves can effectively be rendered by means of the standard linear solid (SLS) viscoelastic model. In addition, it was also established that the Young’s modulus varied according to a sigmoid-type curve with the piccotex content, while the yield stress decreased linearly with the concentration of Piccotex. In addition, based on the spooling suitability and printability, the patterns were rated and it was found that the most appropriate wax pattern compositions for 3D printing were those which contained 30% (m/m) and 35% (m/m) Piccotex. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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23 pages, 5730 KiB

Open AccessArticle

On the Effect of Lattice Topology on Mechanical Properties of SLS Additively Manufactured Sheet-, Ligament-, and Strut-Based Polymeric Metamaterials

by Aliaa M. Abou-Ali, Dong-Wook Lee and Rashid K. Abu Al-Rub

Polymers 2022, 14(21), 4583; https://doi.org/10.3390/polym14214583 - 28 Oct 2022

Cited by 17 | Viewed by 3862

Abstract

Cellular lattices with architectural intricacy or metamaterials have gained a substantial amount of attention in the past decade due to the recent advances in additive manufacturing methods. The lattice topology controls its physical and mechanical properties; therefore, the main challenge is selecting the [...] Read more.

Cellular lattices with architectural intricacy or metamaterials have gained a substantial amount of attention in the past decade due to the recent advances in additive manufacturing methods. The lattice topology controls its physical and mechanical properties; therefore, the main challenge is selecting the appropriate lattice topology for a desired function and application. In this work, we comprehensively study the topology–property relationship of three classes of polymer metamaterials based on triply periodic minimal surfaces (TPMS) of sheet/shell and ligament types, and other types of well-known strut-based lattices. The study uses a holistic approach of designing, additive manufacturing, microstructural characterization, and compressive uniaxial mechanical testing of these polymer lattices that are 3D-printed using the laser powder bed fusion technique known as selective laser sintering (SLS). In total, 55 lattices with different topologies and relative densities were 3D-printed and tested. Printing quality was assessed using scanning electron microscopy and micro-computed tomography. The extracted mechanical properties of elastic modulus, yield strength, plateau strength, and energy absorption are thoroughly compared between the different lattice architectures. The results show that all the investigated ligament-based TPMS polymer lattices exhibit bending-dominated elastic and plastic behavior, indicating that they are suitable candidates for energy absorbing applications. The sheet-based TPMS polymer lattices, similarly to the well-known Octet-Truss lattice, exhibited an elastic stretching-dominated mode of deformation and proved to have exceptional stiffness as compared to all other topologies, especially at low relative densities. However, the sheet-based TPMS polymer lattices exhibited a bending-dominated plastic behavior which is mainly driven by manufacturing defects. Overall, however, sheet-based TPMS polymer lattices exhibited the best mechanical properties, followed by strut-based lattices and finally by ligament-based TPMS lattices. Finally, it is depicted that at high relative densities, the mechanical properties of lattices of various architectures tend to converge, which implies that the topological effect is more significant at low relative densities. Generally, this study provides important insights about the selection of polymer mechanical metamaterials for various applications, and shows the superiority of TPMS-based polymer metamaterials as compared to several other classes of polymer mechanical metamaterials. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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14 pages, 3805 KiB

Open AccessArticle

Thermoforming Characteristics of PLA/TPU Multi-Material Specimens Fabricated with Fused Deposition Modelling under Different Temperatures

by Neilson Peter Sorimpuk, Wai Heng Choong and Bih-Lii Chua

Polymers 2022, 14(20), 4304; https://doi.org/10.3390/polym14204304 - 13 Oct 2022

Cited by 12 | Viewed by 4230

Abstract

Multi-material products are required in fused deposition modelling (FDM) to meet a desired specification such as a rigid structure with soft material for impact protection. This paper focuses on the thermoformability and shape recovery characteristics of three-dimensional (3D)-printed multi-material specimens under different thermoforming [...] Read more.

Multi-material products are required in fused deposition modelling (FDM) to meet a desired specification such as a rigid structure with soft material for impact protection. This paper focuses on the thermoformability and shape recovery characteristics of three-dimensional (3D)-printed multi-material specimens under different thermoforming temperatures. The multi-material specimens consist of polylactic acid (PLA) and thermoplastic polyurethane (TPU). The PLA/TPU specimens were prepared by depositing the TPU component on top of the PLA component using a fused deposition modelling (FDM) machine. Simple thermoforming tests were proposed, where the specimens were bent under load and molded into a circular shape at different thermoforming temperatures. The bent specimens were then reheated at 60 °C to evaluate their shape memory ability. The test results were quantified into apparent bending modulus and shape recovery percentage. The PLA/TPU specimens showed a better apparent bending modulus of 143 MPa than a PLA specimen at a temperature between 60 °C to 90 °C. However, only the PLA/TPU specimens being thermoformed into a circular shape at 100 °C or greater showed good shape retention accuracy and interfacial surface bonding. The PLA/TPU specimens that were thermoformed at 60 °C to 90 °C showed reasonable shape memory of about 60% recovery when reheated. Finally, suitable thermoforming temperatures for thermoforming PLA/TPU specimens were suggested based on design needs. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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24 pages, 17876 KiB

Open AccessArticle

Mechanical Response of Carbon Composite Octet Truss Structures Produced via Axial Lattice Extrusion

by Pritam Poddar, Mark Olles and Denis Cormier

Polymers 2022, 14(17), 3553; https://doi.org/10.3390/polym14173553 - 29 Aug 2022

Cited by 4 | Viewed by 4317

Abstract

Engineered lattice structures fabricated via additive manufacturing (AM) technologies are of great interest for many applications that require high strength and/or stiffness with minimum mass. This paper studies a novel axial lattice extrusion (ALE) AM technique that greatly enhances mechanical properties of polymeric [...] Read more.

Engineered lattice structures fabricated via additive manufacturing (AM) technologies are of great interest for many applications that require high strength and/or stiffness with minimum mass. This paper studies a novel axial lattice extrusion (ALE) AM technique that greatly enhances mechanical properties of polymeric lattice structures. When the novel ALE process was used to produce 84 mm × 84 mm × 84 mm octet truss lattice samples using fiber reinforced ABS, a total of 219,520 polymer interfaces in the lattice beams were eliminated relative to the conventional 3D printing alternative. Microscopic examination revealed near perfect alignment of the chopped carbon fibers with axes of the cylindrical beams that make up the lattice structure. The greatly enhanced beam quality with fiber reinforcement resulted in excellent mechanical properties. Compression testing yielded an average relative compressive strength of 17.4 MPa and an average modulus of 162.8 MPa. These properties rate very strongly relative to other published work, and indicate that the ALE process shows great potential for fabrication of high-strength, lightweight, large-scale, carbon-fiber composite components. The paper also contributes a modeling approach to finite element analysis (FEA) that captures the highly orthotropic properties of carbon fiber lattice beams. The diagonal shear failure mode predicted via the FEA model was in good agreement with experimentally observed results. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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32 pages, 90212 KiB

Open AccessArticle

Characterization and Multiscale Modeling of the Mechanical Properties for FDM-Printed Copper-Reinforced PLA Composites

by Arda Özen, Gregor Ganzosch, Christina Völlmecke and Dietmar Auhl

Polymers 2022, 14(17), 3512; https://doi.org/10.3390/polym14173512 - 26 Aug 2022

Cited by 8 | Viewed by 2488

Abstract

Additive manufacturing is an emerging technology and provides high design flexibility to customers. Fused deposition modeling (FDM) is an economical and promising additive manufacturing method. Due to its many advantages, FDM received great attention in recent years, and comprehensive studies are being undertaken [...] Read more.

Additive manufacturing is an emerging technology and provides high design flexibility to customers. Fused deposition modeling (FDM) is an economical and promising additive manufacturing method. Due to its many advantages, FDM received great attention in recent years, and comprehensive studies are being undertaken to investigate the properties of FDM-printed polymers and polymer composites. As a result of the manufacturing technology employed in FDM, inner structures are changed with different process parameters, and thus, anisotropic properties are observed. Moreover, composite filaments such as particle- or fiber-reinforced polymers already have anisotropy before FDM printing. In this study, we investigate the effect of different process parameters, namely layer thickness and raster width on FDM-printed copper-reinforced poly(lactic acid) (PLA). Mechanical characterizations with a high-resolution camera are carried out for analyzing the deformation behaviors. Optical microscopy characterizations are performed to observe the mesostructural changes with various process parameters. Scanning electron microscopy (SEM) and an energy-dispersive X-ray spectroscopy (EDS) analysis are conducted for investigating the microstructure, specifically, copper particles in the PLA matrix. A 2D digital image correlation code with a machine learning algorithm is applied to the optical characterization and SEM-EDS images. In this way, micro- and mesostructural features, as well as the porosity ratios of the specimens are investigated. We prepare the multiscale homogenization by finite element method (FEM) simulations to capture the material’s response, both on a microscale and a mesoscale. We determined that the mesostructure and, thereby, the mechanical properties are significantly changed with the aforementioned process parameters. A lower layer thickness and a greater raster width led to a higher elasticity modulus and ultimate tensile strength (UTS). The optical microscopy analysis verified this statement: Decreasing the layer thickness and increasing the raster width result in larger contact lines between adjacent layers and, hence, lower porosity on the mesoscale. Realistic CAD images were prepared regarding the mesostructural differences and porosity ratios. Ultimately, all these changes are accurately modeled with mesoscale and multiscale simulations. The simulation results are validated by laboratory experiments. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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18 pages, 4583 KiB

Open AccessArticle

Development of a Custom-Made 3D Printing Protocol with Commercial Resins for Manufacturing Microfluidic Devices

by Francesc Subirada, Roberto Paoli, Jessica Sierra-Agudelo, Anna Lagunas, Romen Rodriguez-Trujillo and Josep Samitier

Polymers 2022, 14(14), 2955; https://doi.org/10.3390/polym14142955 - 21 Jul 2022

Cited by 12 | Viewed by 2940

Abstract

The combination of microfluidics and photo-polymerization techniques such as stereolithography (SLA) has emerged as a new field which has a lot of potential to influence in such important areas as biological analysis, and chemical detection among others. However, the integration between them is [...] Read more.

The combination of microfluidics and photo-polymerization techniques such as stereolithography (SLA) has emerged as a new field which has a lot of potential to influence in such important areas as biological analysis, and chemical detection among others. However, the integration between them is still at an early stage of development. In this article, after analyzing the resolution of a custom SLA 3D printer with commercial resins, microfluidic devices were manufactured using three different approaches. First, printing a mold with the objective of creating a Polydimethylsiloxane (PDMS) replica with the microfluidic channels; secondly, open channels have been printed and then assembled with a flat cover of the same resin material. Finally, a closed microfluidic device has also been produced in a single process of printing. Important results for 3D printing with commercial resins have been achieved by only printing one layer on top of the channel. All microfluidic devices have been tested successfully for pressure-driven fluid flow. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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27 pages, 12041 KiB

Open AccessArticle

Design and Mechanical Characterization Using Digital Image Correlation of Soft Tissue-Mimicking Polymers

by Oliver Grimaldo Ruiz, Mariana Rodriguez Reinoso, Elena Ingrassia, Federico Vecchio, Filippo Maniero, Vito Burgio, Marco Civera, Ido Bitan, Giuseppe Lacidogna and Cecilia Surace

Polymers 2022, 14(13), 2639; https://doi.org/10.3390/polym14132639 - 28 Jun 2022

Cited by 9 | Viewed by 3904

Abstract

Present and future anatomical models for biomedical applications will need bio-mimicking three-dimensional (3D)-printed tissues. These would enable, for example, the evaluation of the quality-performance of novel devices at an intermediate step between ex-vivo and in-vivo trials. Nowadays, PolyJet technology produces anatomical models with [...] Read more.

Present and future anatomical models for biomedical applications will need bio-mimicking three-dimensional (3D)-printed tissues. These would enable, for example, the evaluation of the quality-performance of novel devices at an intermediate step between ex-vivo and in-vivo trials. Nowadays, PolyJet technology produces anatomical models with varying levels of realism and fidelity to replicate organic tissues. These include anatomical presets set with combinations of multiple materials, transitions, and colors that vary in hardness, flexibility, and density. This study aims to mechanically characterize multi-material specimens designed and fabricated to mimic various bio-inspired hierarchical structures targeted to mimic tendons and ligaments. A Stratasys^® J750™ 3D Printer was used, combining the Agilus30™ material at different hardness levels in the bio-mimicking configurations. Then, the mechanical properties of these different options were tested to evaluate their behavior under uni-axial tensile tests. Digital Image Correlation (DIC) was used to accurately quantify the specimens’ large strains in a non-contact fashion. A difference in the mechanical properties according to pattern type, proposed hardness combinations, and matrix-to-fiber ratio were evidenced. The specimens V, J1, A1, and C were selected as the best for every type of pattern. Specimens V were chosen as the leading combination since they exhibited the best balance of mechanical properties with the higher values of Modulus of elasticity (2.21 ± 0.17 MPa), maximum strain (1.86 ± 0.05 mm/mm), and tensile strength at break (2.11 ± 0.13 MPa). The approach demonstrates the versatility of PolyJet technology that enables core materials to be tailored based on specific needs. These findings will allow the development of more accurate and realistic computational and 3D printed soft tissue anatomical solutions mimicking something much closer to real tissues. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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11 pages, 2070 KiB

Open AccessArticle

3D Printing of Stretchable, Adhesive and Conductive Ti₃C₂T_x-Polyacrylic Acid Hydrogels

by Weijing Zhao, Jie Cao, Fucheng Wang, Fajuan Tian, Wenqian Zheng, Yuqian Bao, Kaiyue Zhang, Zhilin Zhang, Jiawen Yu, Jingkun Xu, Ximei Liu and Baoyang Lu

Polymers 2022, 14(10), 1992; https://doi.org/10.3390/polym14101992 - 13 May 2022

Cited by 12 | Viewed by 3487

Abstract

Stretchable, adhesive, and conductive hydrogels have been regarded as ideal interfacial materials for seamless and biocompatible integration with the human body. However, existing hydrogels can rarely achieve good mechanical, electrical, and adhesive properties simultaneously, as well as limited patterning/manufacturing techniques posing severe challenges [...] Read more.

Stretchable, adhesive, and conductive hydrogels have been regarded as ideal interfacial materials for seamless and biocompatible integration with the human body. However, existing hydrogels can rarely achieve good mechanical, electrical, and adhesive properties simultaneously, as well as limited patterning/manufacturing techniques posing severe challenges to bioelectronic research and their practical applications. Herein, we develop a stretchable, adhesive, and conductive Ti₃C₂T_x-polyacrylic acid hydrogel by a simple pre-crosslinking method followed by successive direct ink writing 3D printing. Pre-polymerization of acrylic acid can be initiated by mechanical mixing with Ti₃C₂T_x nanosheet suspension, leading to the formation of viscous 3D printable ink. Secondary free radical polymerization of the ink patterns via 3D printing can achieve a stretchable, adhesive, and conductive Ti₃C₂T_x-polyacrylic acid hydrogel. The as-formed hydrogel exhibits remarkable stretchability (~622%), high electrical conductivity (5.13 S m⁻¹), and good adhesion strength on varying substrates. We further demonstrate the capability of facilely printing such hydrogels into complex geometries like mesh and rhombus patterns with high resolution and robust integration. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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12 pages, 6665 KiB

Open AccessArticle

Effect of Bio-Inspired Polymer Types on Engineering Characteristics of Cement Composites

by Se-Jin Choi, Sung-Ho Bae, Jae-In Lee, Eun Ji Bang, Hoe Young Choi and Haye Min Ko

Polymers 2022, 14(9), 1808; https://doi.org/10.3390/polym14091808 - 28 Apr 2022

Cited by 6 | Viewed by 2092

Abstract

Cement concrete is the most commonly used building and construction material worldwide because of its many advantages. Over time, however, it develops cracks due to shrinkage and tension, which may lead to premature failure of the entire structure. Recently, the incorporation of polymers [...] Read more.

Cement concrete is the most commonly used building and construction material worldwide because of its many advantages. Over time, however, it develops cracks due to shrinkage and tension, which may lead to premature failure of the entire structure. Recently, the incorporation of polymers has been explored to improve the overall strength and durability of cement concrete. In this study, two types of chitosan-based bio-inspired polymers (a-BIP and b-BIP) were synthesized and mixed with cement mortar in different proportions (5–20%). The fluidity of the resulting mixtures and the properties of the hardened samples, such as the compressive and tensile strengths, drying shrinkage, and carbonation resistance, were evaluated. The characteristics of the polymers were tuned by varying the pH during their syntheses, and their structures were characterized using nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, and ultraviolet-visible spectroscopy. After 28 days of aging, all samples containing BIPs (35.9–41.4 MPa) had noticeably higher compressive strength than the control sample (33.2 MPa). The tensile strength showed a similar improvement (up to 19.1%). Overall, the mechanical properties and durability of the samples were separately dependent on the type and amount of BIP. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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14 pages, 1596 KiB

Open AccessArticle

Effectiveness and Applications of a Metal-Coated HNT/Polylactic Acid Antimicrobial Filtration System

by Antwine W. McFarland, Jr., Anusha Elumalai, Christopher C. Miller, Ahmed Humayun and David K. Mills

Polymers 2022, 14(8), 1603; https://doi.org/10.3390/polym14081603 - 14 Apr 2022

Cited by 11 | Viewed by 2845

Abstract

A broad-spectrum antimicrobial respiration apparatus designed to fight bacteria, viruses, fungi, and other biological agents is critical in halting the current pandemic’s trajectory and containing future outbreaks. We applied a simple and effective electrodeposition method for metal (copper, silver, and zinc) coating the [...] Read more.

A broad-spectrum antimicrobial respiration apparatus designed to fight bacteria, viruses, fungi, and other biological agents is critical in halting the current pandemic’s trajectory and containing future outbreaks. We applied a simple and effective electrodeposition method for metal (copper, silver, and zinc) coating the surface of halloysite nanotubes (HNTs). These nanoparticles are known to possess potent antiviral and antimicrobial properties. Metal-coated HNTs (mHNTs) were then added to polylactic acid (PLA) and extruded to form an mHNT/PLA 3D composite printer filament. Our composite 3D printer filament was then used to fabricate an N95-style mask with an interchangeable/replaceable filter with surfaces designed to inactivate a virus and kill bacteria on contact, thus reducing deadly infections. The filter, made of a multilayered antimicrobial/mHNT blow spun polymer and fabric, is disposable, while the mask can be sanitized and reused. We used several in vitro means of assessing critical clinical features and assessed the bacterial growth inhibition against commonly encountered bacterial strains. These tests demonstrated the capability of our antimicrobial filament to fabricate N95 masks and filters that possessed antibacterial capabilities against both Gram-negative and Gram-positive bacteria. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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18 pages, 4355 KiB

Open AccessArticle

Abrasion-Induced Acceleration of Melt Crystallisation of Wet Comminuted Polybutylene Terephthalate (PBT)

by Florentin Tischer, Björn Düsenberg, Timo Gräser, Joachim Kaschta, Jochen Schmidt and Wolfgang Peukert

Polymers 2022, 14(4), 810; https://doi.org/10.3390/polym14040810 - 19 Feb 2022

Cited by 4 | Viewed by 2793

Abstract

Within this contribution, the effect of grinding media wear on the melt crystallisation of polybutylene terephthalate (PBT) is addressed. PBT was wet ground in a stirred media mill in ethanol using different grinding media beads (silica, chrome steel, cerium-stabilised and yttrium-stabilised zirconia) at [...] Read more.

Within this contribution, the effect of grinding media wear on the melt crystallisation of polybutylene terephthalate (PBT) is addressed. PBT was wet ground in a stirred media mill in ethanol using different grinding media beads (silica, chrome steel, cerium-stabilised and yttrium-stabilised zirconia) at comparable stress energies with the intention to use the obtained particles as feed materials for the production of feedstocks for laser powder bed fusion additive manufacturing (PBF-AM). In PBF‑AM, the feedstock’s optical, rheological and especially thermal properties—including melt crystallisation kinetics—strongly influence the processability and properties of the manufactured parts. The influence of process parameters and used grinding media during wet comminution on the optical properties, crystal structure, molar mass distribution, inorganic content (wear) and thermal properties of the obtained powders is discussed. A grinding media-dependent acceleration of the melt crystallisation could be attributed to wear particles serving as nuclei for heterogeneous crystallisation. Yttrium-stabilised zirconia grinding beads proved to be the most suitable for the production of polymer powders for the PBF process in terms of (fast) comminution kinetics, unchanged optical properties and the least accelerated crystallisation kinetics. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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12 pages, 2300 KiB

Open AccessCommunication

Hydrogel Polyester Scaffolds via Direct-Ink-Writing of Ad Hoc Designed Photocurable Macromonomer

by Tiziana Fuoco, Mo Chen, Shubham Jain, Xi Vincent Wang, Lihui Wang and Anna Finne-Wistrand

Polymers 2022, 14(4), 711; https://doi.org/10.3390/polym14040711 - 12 Feb 2022

Cited by 4 | Viewed by 2121

Abstract

Synthetic, degradable macromonomers have been developed to serve as ink for 3D printing technologies based on direct-ink-writing. The macromonomers are purposely designed to be cross-linkable under the radical mechanism, to impart hydrophilicity to the final material, and to have rheological properties matching the [...] Read more.

Synthetic, degradable macromonomers have been developed to serve as ink for 3D printing technologies based on direct-ink-writing. The macromonomers are purposely designed to be cross-linkable under the radical mechanism, to impart hydrophilicity to the final material, and to have rheological properties matching the printer’s requirements. The suitable viscosity enables the ink to be printed at room temperature, in absence of organic solvents, and to be cross-linked to manufacture soft 3D scaffolds that show no indirect cytotoxicity and have a hydration capacity of up to 100% their mass and a compressive modulus in the range of 0.4–2 MPa. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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12 pages, 3702 KiB

Open AccessArticle

Layer Adhesion Test of Additively Manufactured Pins: A Shear Test

by Márton Tamás Birosz, Mátyás Andó and Ferenc Safranyik

Polymers 2022, 14(1), 55; https://doi.org/10.3390/polym14010055 - 24 Dec 2021

Cited by 3 | Viewed by 2952

Abstract

Additive Manufacturing (AM) became a popular engineering solution not only for Rapid Prototyping (RP) as a part of product development but as an effective solution for producing complex geometries as fully functional components. Even the modern engineering tools, such as the different simulation [...] Read more.

Additive Manufacturing (AM) became a popular engineering solution not only for Rapid Prototyping (RP) as a part of product development but as an effective solution for producing complex geometries as fully functional components. Even the modern engineering tools, such as the different simulation software, have a shape optimization solution especially for parts created by AM. To extend the application of these methods in this work, the failure properties of the 3D-printed parts have been investigated via shear test measurements. The layer adhesion can be calculated based on the results, which can be used later for further numerical modeling. In conclusion, it can be stated that the layer formation and the structure of the infill have a great influence on the mechanical properties. The layers formed following the conventional zig-zag infill style show a random failure, and the layers created via extruded concentric circles show more predictable load resistance. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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Review

Jump to: Research

45 pages, 16750 KiB

Open AccessReview

Influence of Process Parameters on the Characteristics of Additively Manufactured Parts Made from Advanced Biopolymers

by Tomaž Pepelnjak, Josip Stojšić, Luka Sevšek, Dejan Movrin and Mladomir Milutinović

Polymers 2023, 15(3), 716; https://doi.org/10.3390/polym15030716 - 31 Jan 2023

Cited by 21 | Viewed by 3925

Abstract

Over the past few decades, additive manufacturing (AM) has become a reliable tool for prototyping and low-volume production. In recent years, the market share of such products has increased rapidly as these manufacturing concepts allow for greater part complexity compared to conventional manufacturing [...] Read more.

Over the past few decades, additive manufacturing (AM) has become a reliable tool for prototyping and low-volume production. In recent years, the market share of such products has increased rapidly as these manufacturing concepts allow for greater part complexity compared to conventional manufacturing technologies. Furthermore, as recyclability and biocompatibility have become more important in material selection, biopolymers have also become widely used in AM. This article provides an overview of AM with advanced biopolymers in fields from medicine to food packaging. Various AM technologies are presented, focusing on the biopolymers used, selected part fabrication strategies, and influential parameters of the technologies presented. It should be emphasized that inkjet bioprinting, stereolithography, selective laser sintering, fused deposition modeling, extrusion-based bioprinting, and scaffold-free printing are the most commonly used AM technologies for the production of parts from advanced biopolymers. Achievable part complexity will be discussed with emphasis on manufacturable features, layer thickness, production accuracy, materials applied, and part strength in correlation with key AM technologies and their parameters crucial for producing representative examples, anatomical models, specialized medical instruments, medical implants, time-dependent prosthetic features, etc. Future trends of advanced biopolymers focused on establishing target-time-dependent part properties through 4D additive manufacturing are also discussed. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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27 pages, 7978 KiB

Open AccessReview

A Review on Microstructural Formations of Discontinuous Fiber-Reinforced Polymer Composites Prepared via Material Extrusion Additive Manufacturing: Fiber Orientation, Fiber Attrition, and Micro-Voids Distribution

by Zhaogui Wang, Zhenyu Fang, Zhongqi Xie and Douglas E. Smith

Polymers 2022, 14(22), 4941; https://doi.org/10.3390/polym14224941 - 15 Nov 2022

Cited by 14 | Viewed by 3151

Abstract

A discontinuous fiber-reinforced polymer composite (DFRPC) provides superior mechanical performances in material extrusion additive manufacturing (MEAM) parts, and thus promotes their implementations in engineering applications. However, the process-induced structural defects of DFRPCs increase the probability of pre-mature failures as the manufactured parts experience [...] Read more.

A discontinuous fiber-reinforced polymer composite (DFRPC) provides superior mechanical performances in material extrusion additive manufacturing (MEAM) parts, and thus promotes their implementations in engineering applications. However, the process-induced structural defects of DFRPCs increase the probability of pre-mature failures as the manufactured parts experience complicated external loads. In light of this, the meso-structures of the MEAM parts have been discussed previously, while systematic analyses reviewing the studies of the micro-structural formations of the composites are limited. This paper summarizes the current state-of-the-art in exploring the correlations between the MEAM processes and the associated micro-structures of the produced composites. Experimental studies and numerical analyses including fiber orientation, fiber attrition, and micro-voids are collected and discussed. Based on the review and parametric study results, it is considered that the theories and numerical characterizations on fiber length attrition and micro-porosities within the MEAM-produced composites are in high demand, which is a potential topic for further explorations. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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46 pages, 15619 KiB

Open AccessReview

Innovation in Additive Manufacturing Using Polymers: A Survey on the Technological and Material Developments

by Mauricio A. Sarabia-Vallejos, Fernando E. Rodríguez-Umanzor, Carmen M. González-Henríquez and Juan Rodríguez-Hernández

Polymers 2022, 14(7), 1351; https://doi.org/10.3390/polym14071351 - 26 Mar 2022

Cited by 25 | Viewed by 7756

Abstract

This review summarizes the most recent advances from technological and physico-chemical perspectives to improve several remaining issues in polymeric materials’ additive manufacturing (AM). Without a doubt, AM is experimenting with significant progress due to technological innovations that are currently advancing. In this context, [...] Read more.

This review summarizes the most recent advances from technological and physico-chemical perspectives to improve several remaining issues in polymeric materials’ additive manufacturing (AM). Without a doubt, AM is experimenting with significant progress due to technological innovations that are currently advancing. In this context, the state-of-the-art considers both research areas as working separately and contributing to developing the different AM technologies. First, AM techniques’ advantages and current limitations are analyzed and discussed. A detailed overview of the efforts made to improve the two most extensively employed techniques, i.e., material extrusion and VAT-photopolymerization, is presented. Aspects such as the part size, the possibility of producing parts in a continuous process, the improvement of the fabrication time, the reduction of the use of supports, and the fabrication of components using more than one material are analyzed. The last part of this review complements these technological advances with a general overview of the innovations made from a material perspective. The use of reinforced polymers, the preparation of adapted high-temperature materials, or even the fabrication of metallic and ceramic parts using polymers as supports are considered. Finally, the use of smart materials that enable the fabrication of shape-changing 3D objects and sustainable materials will also be explored. Full article

(This article belongs to the Special Issue Structure and Properties of Polymeric Materials in Additive Manufacturing)

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