Mechanical Performance of Polymeric Parts Obtained by Additive Manufacturing

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Processing and Engineering".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 51498

Special Issue Editors


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Guest Editor
Industrial Engineering Department, IQS School of Engineering, Universitat Ramon Llull, 08022 Barcelona, Spain
Interests: additive manufacturing; advanced manufacturing; ball burnishing; fatigue; material characterization; design for manufacturing

E-Mail Website
Guest Editor
Industrial Engineering Department, IQS School of Engineering, Universitat Ramon Llull, 08022 Barcelona, Spain
Interests: experimental mechanics; vibration-based methods; non-destructive evaluation; additive manufacturing; structural assessment

Special Issue Information

Dear Colleagues,

The growing demand for new technologies, in which cost reduction and energy efficiency are paramount, requires the search for multifunctional design solutions. These solutions need to combine various properties such as lightness, rigidity, and the ability to absorb thermal energy or impact, while being viable from a manufacturing point of view. In this sense, additive manufacturing (AM) offers countless benefits over conventional manufacturing methods, expanding the horizons of component design with high geometric complexity and the use of a wide range of different materials. This new era of digital manufacturing has radically transformed how objects are designed and produced, reaching sectors such as the aerospace, automotive, and biomedical industry, which have greatly benefited from these technological advances.

The key to guaranteeing that manufactured elements can respond to their performance lies in the optimization of printing parameters. To cite an example, the handling of the filling density of the printed parts, which allows for a significant reduction in weight and savings in material, is postulated as one of the most significant competitive advantages of additive manufacturing, as opposed to the limitations in mechanical behavior induced by the heterogeneity and anisotropy. These topics are at the core of the research that the AM community is carrying out at the moment, as they are barriers to the complete transfer of these technologies to the industrial sector.

For this reason, this Special Issue compiles the results of the latest studies and analyses of the mechanical behavior of polymeric parts obtained through additive manufacturing. The studies presented will provide the scientific community with relevant information to better manage printing parameters and to optimize the response of printed polymeric parts to the imposed loads.

It is our pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Dr. Giovanni Gómez-Gras
Dr. Marco A. Pérez
Guest Editors

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Keywords

  • additive manufacturing
  • mechanical behavior and characterization
  • numerical simulation
  • fused deposition modeling
  • material jetting manufacturing
  • selective laser sintering
  • multi jet fusion manufacturing
  • stereolithography manufacturing
  • photopolymerization manufacturing
  • 3D/4D printing

Published Papers (14 papers)

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Research

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19 pages, 6787 KiB  
Article
Investigating the Feasibility of Processing Activated Carbon/UHMWPE Polymer Composite Using Laser Powder Bed Fusion
by Yas Khalil, Neil Hopkinson, Adam J. Kowalski and John Patrick A. Fairclough
Polymers 2022, 14(16), 3320; https://doi.org/10.3390/polym14163320 - 15 Aug 2022
Cited by 4 | Viewed by 1854
Abstract
Activated Carbon (AC) is widely available at a relatively low cost, has a high porosity and is commonly used as a filter material for a range of applications. However, it is a brittle and friable material. Ultra-High Molecular Weight Polyethylene (UHMWPE) polymer is [...] Read more.
Activated Carbon (AC) is widely available at a relatively low cost, has a high porosity and is commonly used as a filter material for a range of applications. However, it is a brittle and friable material. Ultra-High Molecular Weight Polyethylene (UHMWPE) polymer is a tough engineering plastic that has been used as a binder. The traditional method used in manufacturing AC/UHMWPE filters involves compressing AC/UHMWPE composite powder during heating in a mould. This process compresses the particles together and the materials undergo sintering. This process results in a low pore interconnectivity, which has a considerable impact on the filter’s efficiency. Selective Laser Sintering is a laser powder bed fusion additive manufacturing technique for polymers. This has a number of advantages compared to the conventional technique and produces a porous structure with improved filtration efficiency. We propose that this is due to the greater pore interconnectivity. In this work, AC/UHMWPE powdered composites were prepared with different AC and UHMWPE ratios. The structure and properties of the AC/UHMWPE composite were investigated and characterised to assess their suitability for selective laser sintering. Particle size and morphology analysis were conducted, as well as density measurements, powder flow, thermal analysis, and crystallinity measurements. The results reveal that the addition of AC improves the UHMWPE flow. The thermal analysis results show that the intrinsic thermal properties of UHMWPE powder are not significantly affected by the introduction of activated carbon. However, thermal gravimetric analysis revealed that the onset of mass loss is considerably shifted (20 °C) to higher temperatures for the AC/UHMWPE composites, which is favourable for laser sintering. Additionally, the change in the composition ratio of untreated composite does not have a significant effect on the degree of crystallinity. Laser-sintered AC/UHMWPE parts were successfully manufactured using a commercial laser-sintering machine. Full article
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12 pages, 416 KiB  
Article
Viscoelastic Characterization of a Thermoplastic Elastomer Processed through Material Extrusion
by Bàrbara Adrover-Monserrat, Silvia García-Vilana, David Sánchez-Molina, Jordi Llumà, Ramón Jerez-Mesa and J. Antonio Travieso-Rodriguez
Polymers 2022, 14(14), 2914; https://doi.org/10.3390/polym14142914 - 18 Jul 2022
Cited by 2 | Viewed by 1721
Abstract
Objective. We aim to characterize the viscoelastic behavior of Polyether-Block-Amide (PEBA 90A), provide reference values for the parameters of a constitutive model for the simulation of mechanical behaviors, and paying attention to the influence of the manufacturing conditions. Methods. Uniaxial relaxation [...] Read more.
Objective. We aim to characterize the viscoelastic behavior of Polyether-Block-Amide (PEBA 90A), provide reference values for the parameters of a constitutive model for the simulation of mechanical behaviors, and paying attention to the influence of the manufacturing conditions. Methods. Uniaxial relaxation tests of filaments of PEBA were used to determine the values of the parameters of a Prony series for a Quasi-Linear Visco-Elastic (QLVE) model. Additional, fast cyclic loading tests were used to corroborate the adequacy of the model under different test criteria in a second test situation. Results. The QLVE model predicts the results of the relaxation tests very accurately. In addition, the behavior inferred from this model fits very well with the measurements of fast cyclic loading tests. The viscoelastic behavior of PEBA under small strain polymer fits very well to a six-parameter QLVE model. Full article
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24 pages, 5415 KiB  
Article
Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing
by Alex Stiles, Thomas-Allan Tison, Liam Pruitt and Uday Vaidya
Polymers 2022, 14(13), 2708; https://doi.org/10.3390/polym14132708 - 1 Jul 2022
Cited by 8 | Viewed by 3101
Abstract
Photopolymers are an attractive option for large-format additive manufacturing (LFAM), because they can be formulated from structural thermosets and cure rapidly in ambient conditions under low-energy ultraviolet light-emitting diode (UV LED) lamps. Photopolymer cure is strongly influenced by the depth penetration of UV [...] Read more.
Photopolymers are an attractive option for large-format additive manufacturing (LFAM), because they can be formulated from structural thermosets and cure rapidly in ambient conditions under low-energy ultraviolet light-emitting diode (UV LED) lamps. Photopolymer cure is strongly influenced by the depth penetration of UV light, which can be limited in the 2–4 mm layer thicknesses typical of LFAM. Photoinitiator (PI) systems that exhibit photobleaching have proven useful in thick-section cure applications, because they generate a photoinitiation wavefront, but this effect is time-dependent. This study investigates the light transmission and through-thickness cure behavior in (meth)acrylate photopolymer formulations with the photobleaching initiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO). Utilizing an optical model developed by Kenning et al., lower concentrations (0.1 wt% to 0.5 wt%) of BAPO were predicted to yield rapid onset of photoinitiation. In situ cure measurements under continuous UV LED irradiation of 380 mW/cm2 showed that a 0.1 wt% concentration of BAPO achieved peak polymerization rate within 2.5 s at a 3-mm depth. With only 1 s of irradiation at 1.7 W/cm2 intensity, the 0.1 wt% BAPO formulation also achieved the highest level of cure of the formulas tested. For an irradiation dose of 5.5 J/cm2 at a duration of 3.7 s, cured polymer specimens achieved a flexural strength of 108 MPa and a flexural modulus of 3.1 GPa. This study demonstrates the utility of optical modeling as a potential screening tool for new photopolymer formulations, primarily in identifying an upper limit to PI concentration for the desired cure depth. The results also show that photobleaching provides only a limited benefit for LFAM applications with short (1.0 s to 3.7 s) UV irradiation times and indicate that excess PI concentration can inhibit light transmission even under extended irradiation times up to 60 s. Full article
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19 pages, 9593 KiB  
Article
Influence of Atmospheric Conditions on Mechanical Properties of Polyamide with Different Content of Recycled Material in Selective Laser Sintering
by Ana Pilipović, Petar Ilinčić, Ante Bakić and Janoš Kodvanj
Polymers 2022, 14(12), 2355; https://doi.org/10.3390/polym14122355 - 10 Jun 2022
Cited by 4 | Viewed by 1657
Abstract
The price of material is an important factor when selecting the additive polymer procedure. In selective laser sintering (SLS), the price can be reduced by the recycling of material, i.e., with different shares of original and recycled material, as well as by the [...] Read more.
The price of material is an important factor when selecting the additive polymer procedure. In selective laser sintering (SLS), the price can be reduced by the recycling of material, i.e., with different shares of original and recycled material, as well as by the orientation of the product during manufacturing. Numerous tests warn that orientation in the direction of z axis should be as low as possible to reduce the total price of the product. The product also has to satisfy the influence of atmospheric conditions to which it is exposed during its lifetime, i.e., UV radiation and humid environment. UV light, with sun being its most common source, and average humidity in different parts of the world can be approximately from 20% to 90%, depending on time, day and geographic location. In this work, the test specimens have been made of original, mixed and 100% recycled material and then exposed to the influences of UV radiation and water absorption. After having been exposed to atmospheric conditions for a longer time, the mechanical properties of the polyamide products made by selective laser sintering were tested. The results show that exposure to UV radiation reduces tensile elongation at all ratios of recycled material and orientation of 70–90% except in the z direction, while in flexural deformation it is the other way around. The effect of water was observed only between the 7th–14th day of absorption with a decrease in strength until the deformation did not change. Full article
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17 pages, 3340 KiB  
Article
Design for 3D Printed Tools: Mechanical Material Properties for Direct Polymer Additive Tooling
by Peter Frohn-Sörensen, Michael Geueke, Bernd Engel, Bernd Löffler, Philipp Bickendorf, Arian Asimi, Georg Bergweiler and Günther Schuh
Polymers 2022, 14(9), 1694; https://doi.org/10.3390/polym14091694 - 21 Apr 2022
Cited by 13 | Viewed by 2587
Abstract
In relation to the fourth industrial revolution, traditional manufacturing methods cannot serve the flexibility demands related to mass customization and small series production. Rapid tooling provided by generative manufacturing has been suggested recently in the context of metal forming. Due to the high [...] Read more.
In relation to the fourth industrial revolution, traditional manufacturing methods cannot serve the flexibility demands related to mass customization and small series production. Rapid tooling provided by generative manufacturing has been suggested recently in the context of metal forming. Due to the high loads applied during processes to such tooling, a purposeful mechanical description of the additively manufactured (AM) materials is crucial. Until now, a comprehensive characterization approach for AM polymers is required to allow a sophisticated layout of rapid tooling. In detail, information on compressive and flexural mechanical properties of solid infilled materials made by additive manufacturing are sparsely available. These elementary mechanical properties are evaluated in the present study. They result from material specimens additively manufactured in the fused filament fabrication (FFF) process. The design of the experiments reveals significant influences of the polymer and the layer height on the resulting flexural and compressive strength and modulus as well as density, hardness, and surface roughness. As a case study, these findings are applied to a cup drawing operation based on the strongest and weakest material and parameter combination. The obtained data and results are intended to guide future applications of direct polymer additive tooling. The presented case study illustrates such an application and shows the range of manufacturing quality achievable within the materials and user settings for 3D printing. Full article
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13 pages, 8316 KiB  
Article
Study of the Influence of the Manufacturing Parameters on Tensile Properties of Thermoplastic Elastomers
by Bàrbara Adrover-Monserrat, Jordi Llumà, Ramón Jerez-Mesa and J. Antonio Travieso-Rodriguez
Polymers 2022, 14(3), 576; https://doi.org/10.3390/polym14030576 - 31 Jan 2022
Cited by 11 | Viewed by 2557
Abstract
Additive manufacturing (AM) has increased its field of application, not only for prototypes but also for final parts. Therefore, the need to study new materials is currently growing. This paper aims to study the effect of the printing parameters used in two different [...] Read more.
Additive manufacturing (AM) has increased its field of application, not only for prototypes but also for final parts. Therefore, the need to study new materials is currently growing. This paper aims to study the effect of the printing parameters used in two different thermoplastic elastomers (PEBA 90A and TPU 98A) subjected to tensile tests, evaluating a competent alternative to the currently most used 3D printed materials. To achieve it, a full factorial design experiment is applied to analyze the influence on the tensile responses of two printing parameters: the layer height and the fill density. In addition, an analysis of variance (ANOVA) is used to describe the relations among the parameters and the mechanical responses obtained. Moreover, assessment of damping properties was done. Results show that each thermoplastic elastomer should be studied separately, although the proposed methodology can be used for each material independently of their nature. Finally, a correlation between the printing parameters and the mechanical behavior of TPU 98A and PEBA 90A was found: the layer height and the infill are statistically influential parameters for both materials. Full article
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13 pages, 36423 KiB  
Article
Accelerated Aging Effect on Mechanical Properties of Common 3D-Printing Polymers
by Catalin Gheorghe Amza, Aurelian Zapciu, Florin Baciu, Mihai Ion Vasile and Adrian Ionut Nicoara
Polymers 2021, 13(23), 4132; https://doi.org/10.3390/polym13234132 - 26 Nov 2021
Cited by 18 | Viewed by 2736
Abstract
In outdoor environments, the action of the Sun through its ultraviolet radiation has a degrading effect on most materials, with polymers being among those affected. In the past few years, 3D printing has seen an increased usage in fabricating parts for functional applications, [...] Read more.
In outdoor environments, the action of the Sun through its ultraviolet radiation has a degrading effect on most materials, with polymers being among those affected. In the past few years, 3D printing has seen an increased usage in fabricating parts for functional applications, including parts destined for outdoor use. This paper analyzes the effect of accelerated aging through prolonged exposure to UV-B on the mechanical properties of parts 3D printed from the commonly used polymers polylactic acid (PLA) and polyethylene terephthalate–glycol (PETG). Samples 3D printed from these materials went through a dry 24 h UV-B exposure aging treatment and were then tested against a control group for changes in mechanical properties. Both the tensile and compressive strengths were determined, as well as changes in material creep characteristics. After irradiation, PLA and PETG parts saw significant decreases in both tensile strength (PLA: −5.3%; PETG: −36%) and compression strength (PLA: −6.3%; PETG: −38.3%). Part stiffness did not change significantly following the UV-B exposure and creep behavior was closely connected to the decrease in mechanical properties. A scanning electron microscopy (SEM) fractographic analysis was carried out to better understand the failure mechanism and material structural changes in tensile loaded, accelerated aged parts. Full article
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17 pages, 5631 KiB  
Article
Mechanical Performance of 3D-Printed Biocompatible Polycarbonate for Biomechanical Applications
by Giovanni Gómez-Gras, Manuel D. Abad and Marco A. Pérez
Polymers 2021, 13(21), 3669; https://doi.org/10.3390/polym13213669 - 25 Oct 2021
Cited by 11 | Viewed by 2465
Abstract
Additive manufacturing has experienced remarkable growth in recent years due to the customisation, precision, and cost savings compared to conventional manufacturing techniques. In parallel, materials with great potential have been developed, such as PC-ISO polycarbonate, which has biocompatibility certifications for use in the [...] Read more.
Additive manufacturing has experienced remarkable growth in recent years due to the customisation, precision, and cost savings compared to conventional manufacturing techniques. In parallel, materials with great potential have been developed, such as PC-ISO polycarbonate, which has biocompatibility certifications for use in the biomedical industry. However, many of these synthetic materials are not capable of meeting the mechanical stresses to which the biological structure of the human body is naturally subjected. In this study, an exhaustive characterisation of the PC-ISO was carried out, including an investigation on the influence of the printing parameters by fused filament fabrication on its mechanical behaviour. It was found that the effect of the combination of the printing parameters does not have a notable impact on the mass, cost, and manufacturing time of the specimens; however, it is relevant when determining the tensile, bending, shear, impact, and fatigue strengths. The best combinations for its application in biomechanics are proposed, and the need to combine PC-ISO with other materials to achieve the necessary strengths for functioning as a bone scaffold is demonstrated. Full article
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26 pages, 10344 KiB  
Article
3D Printing of Thermoplastic Elastomers: Role of the Chemical Composition and Printing Parameters in the Production of Parts with Controlled Energy Absorption and Damping Capacity
by Marina León-Calero, Sara Catherine Reyburn Valés, Ángel Marcos-Fernández and Juan Rodríguez-Hernandez
Polymers 2021, 13(20), 3551; https://doi.org/10.3390/polym13203551 - 15 Oct 2021
Cited by 31 | Viewed by 5281
Abstract
Additive manufacturing (AM) is a disruptive technology that enables one to manufacture complex structures reducing both time and manufacturing cost. Among the materials commonly used for AM, thermoplastic elastomers (TPE) are of high interest due to their energy absorption capacity, energy efficiency, cushion [...] Read more.
Additive manufacturing (AM) is a disruptive technology that enables one to manufacture complex structures reducing both time and manufacturing cost. Among the materials commonly used for AM, thermoplastic elastomers (TPE) are of high interest due to their energy absorption capacity, energy efficiency, cushion factor or damping capacity. Previous investigations have exclusively focused on the optimization of the printing parameters of commercial TPE filaments and the structures to analyse the mechanical properties of the 3D printed parts. In the present paper, the chemical, thermal and mechanical properties for a wide range of commercial thermoplastic polyurethanes (TPU) filaments were investigated. For this purpose, TGA, DSC, 1H-NMR and filament tensile strength experiments were carried out in order to determine the materials characteristics. In addition, compression tests have been carried out to tailor the mechanical properties depending on the 3D printing parameters such as: infill density (10, 20, 50, 80 and 100%) and infill pattern (gyroid, honeycomb and grid). The compression tests were also employed to calculate the specific energy absorption (SEA) and specific damping capacity (SDC) of the materials in order to establish the role of the chemical composition and the geometrical characteristics (infill density and type of infill pattern) on the final properties of the printed part. As a result, optimal SEA and SDC performances were obtained for a honeycomb pattern at a 50% of infill density. Full article
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19 pages, 7547 KiB  
Article
Characterisation and Modelling of PLA Filaments and Evolution with Time
by Jaime Orellana Barrasa, Ana Ferrández-Montero, Begoña Ferrari and José Ygnacio Pastor
Polymers 2021, 13(17), 2899; https://doi.org/10.3390/polym13172899 - 28 Aug 2021
Cited by 17 | Viewed by 3033
Abstract
The properties of polylactic acid (PLA) filaments have not yet been analysed in detail, and they are strongly affected by the extrusion process used in some additive manufacturing systems. Here we present the mechanical, thermal, physical, and fractographical properties of an extruded filament [...] Read more.
The properties of polylactic acid (PLA) filaments have not yet been analysed in detail, and they are strongly affected by the extrusion process used in some additive manufacturing systems. Here we present the mechanical, thermal, physical, and fractographical properties of an extruded filament (not the bulk material or scaffolds), the basic building block of any PLA structure printed via material extrusion. This research aims to create a reference point for the modelisation of additively manufactured structures via extrusion processes, as the main building block is characterised in detail for a deep understanding. Furthermore, we investigated the natural ageing (up to one year), the effect of the printing (extruding) temperature (180 and 190 °C), and the effect of the crosshead speed during the tensile tests (10−1 to 102 mm/min) to provide a deeper analysis of the material. The results showed that the material extruded at 190 °C performed better than the material extruded at 180 °C. However, after one hundred days of natural ageing, both materials behaved similarly. This was related to the flow-induced molecular orientation during the extrusion. The crosshead rate produced a logarithmic increase of the mechanical properties, consistent with the Eyring model. Additionally, the ageing produced significant changes in both the elastic modulus and the yield strength: from 2.4 GPa and 40 MPa, in one-day-aged samples, up to 4 GPa and 62 MPa once entirely aged. Finally, it was observed that the glass transition and the enthalpic relaxation increased with ageing, agreeing with the Kohlraushch–William–Watts model. Full article
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16 pages, 8208 KiB  
Article
Effect of Printing Parameters on the Tensile Properties of 3D-Printed Polylactic Acid (PLA) Based on Fused Deposition Modeling
by Ming-Hsien Hsueh, Chao-Jung Lai, Cheng-Feng Chung, Shi-Hao Wang, Wen-Chen Huang, Chieh-Yu Pan, Yu-Shan Zeng and Chia-Hsin Hsieh
Polymers 2021, 13(14), 2387; https://doi.org/10.3390/polym13142387 - 20 Jul 2021
Cited by 42 | Viewed by 5303
Abstract
In order to optimize the efficiency of the Fused deposition modeling (FDM) process, this study used polylactic acid (PLA) material under different parameters (the printing angle and the raster angle) to fabricate specimens and to explore its tensile properties. The effect of the [...] Read more.
In order to optimize the efficiency of the Fused deposition modeling (FDM) process, this study used polylactic acid (PLA) material under different parameters (the printing angle and the raster angle) to fabricate specimens and to explore its tensile properties. The effect of the ultraviolet (UV) curing process on PLA materials was also investigated. The results showed that the printing and raster angles have a high impact on the tensile properties of PLA materials. The UV curing process enhanced the brittleness and reduced the elongation of PLA material. Different effects were observed on tensile strength and modulus of specimens printed with different parameters after UV curing. The above results will be a great help for researchers who are working to achieve sustainability of PLA materials and FDM technology. Full article
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18 pages, 6874 KiB  
Article
Experimental, Computational, and Dimensional Analysis of the Mechanical Performance of Fused Filament Fabrication Parts
by Iván Rivet, Narges Dialami, Miguel Cervera, Michele Chiumenti, Guillermo Reyes and Marco A. Pérez
Polymers 2021, 13(11), 1766; https://doi.org/10.3390/polym13111766 - 27 May 2021
Cited by 14 | Viewed by 3275
Abstract
Process parameters in Additive Manufacturing (AM) are key factors in the mechanical performance of 3D-printed parts. In order to study their effect, a three-zone model based on the printing pattern was developed. This modelization distinguished three different zones of the 3D-printed part, namely [...] Read more.
Process parameters in Additive Manufacturing (AM) are key factors in the mechanical performance of 3D-printed parts. In order to study their effect, a three-zone model based on the printing pattern was developed. This modelization distinguished three different zones of the 3D-printed part, namely cover, contour, and inner; each zone was treated as a different material. The cover and contour zones were characterized via uniaxial tensile tests and the inner zones via computational homogenization. The model was then validated by means of bending tests and their corresponding computational simulations. To reduce the number of required characterization experiments, a relationship between the raw and 3D-printed material was established by dimensional analysis. This allowed describing the mechanical properties of the printed part with a reduced set of the most influential non-dimensional relationships. The influence on the performance of the parts of inter-layer adhesion was also addressed in this work via the characterization of samples made of Polycarbonate Acrylonitrile Butadiene Styrene (ABS/PC), a polymeric material well known for its poor adhesion strength. It was concluded that by using this approach, the number of required testing configurations could be reduced by two thirds, which implies considerable cost savings. Full article
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16 pages, 20046 KiB  
Article
Experimental Characterization Framework for SLA Additive Manufacturing Materials
by Jordi Martín-Montal, Jesus Pernas-Sánchez and David Varas
Polymers 2021, 13(7), 1147; https://doi.org/10.3390/polym13071147 - 2 Apr 2021
Cited by 37 | Viewed by 4196
Abstract
Additive manufacturing (AM) is driving a change in the industry not only regarding prototyping but due to the ease of including printed parts in final designs. Engineers and designers can go deeper into optimization and improvements of their designs without drawbacks of long [...] Read more.
Additive manufacturing (AM) is driving a change in the industry not only regarding prototyping but due to the ease of including printed parts in final designs. Engineers and designers can go deeper into optimization and improvements of their designs without drawbacks of long manufacturing times. However, some drawbacks such as the limited available materials or uncertainty about mechanical properties and anisotropic behavior of 3D printed parts prevent use in large-scale production. To gain knowledge and confidence about printed materials it is necessary to know how they behave under different stress states and strain-rate regimes, and how some of the printing parameters may affect them. The present work proposes an experimental methodology framework to study and characterize materials printed by stereolithography (SLA) to clarify certain aspects that must be taken into account to broaden the use of this kind of material. To this end, tensile and compression tests at different strain rates were carried out. To study the influence of certain printing parameters on the printed material behavior, samples with different printing angles (θ = [0–90]) and different printing resolution (layer height of 50 and 100 µm) were tested. In addition, the effects of curing time and temperature were also studied. The testing specimens were manufactured in the non-professional SLA machine Form 2 from Formlabs® using resin called Durable. Nevertheless, the proposed experimental methodology could be extended to any other resin. Full article
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Review

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35 pages, 7047 KiB  
Review
Optimisation of Strength Properties of FDM Printed Parts—A Critical Review
by Daniyar Syrlybayev, Beibit Zharylkassyn, Aidana Seisekulova, Mustakhim Akhmetov, Asma Perveen and Didier Talamona
Polymers 2021, 13(10), 1587; https://doi.org/10.3390/polym13101587 - 14 May 2021
Cited by 129 | Viewed by 9976
Abstract
Additive Manufacturing is currently growing fast, especially fused deposition modeling (FDM), also known as fused filament fabrication (FFF). When manufacturing parts use FDM, there are two key parameters—strength of the part and dimensional accuracy—that need to be considered. Although FDM is a popular [...] Read more.
Additive Manufacturing is currently growing fast, especially fused deposition modeling (FDM), also known as fused filament fabrication (FFF). When manufacturing parts use FDM, there are two key parameters—strength of the part and dimensional accuracy—that need to be considered. Although FDM is a popular technology for fabricating prototypes with complex geometry and other part product with reduced cycle time, it is also limited by several drawbacks including inadequate mechanical properties and reduced dimensional accuracy. It is evident that part qualities are greatly influenced by the various process parameters, therefore an extensive review of the effects of the following process parameters was carried out: infill density, infill patterns, extrusion temperature, layer thickness, nozzle diameter, raster angle and build orientation on the mechanical properties. It was found from the literature that layer thickness is the most important factor among the studied ones. Although manipulation of process parameters makes significant differences in the quality and mechanical properties of the printed part, the ideal combination of parameters is challenging to achieve. Hence, this study also includes the influence of pre-processing of the printed part to improve the part strength and new research trends such as, vacuum-assisted FDM that has shown to improve the quality of the printing due to improved bonding between the layers. Advances in materials and technologies that are currently under development are presented. For example, the pre-deposition heating method, using an IR lamp of other technologies, shows a positive impact on the mechanical properties of the printed parts. Full article
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